Synoptic Fall 2010

At 12 UTC Monday, large-scale trough was centered in the western U.S. A surface low was located on the eastern side of this trough at the NE/KS border. The Sutcliffe-Pettersen equation indicated cyclonic vorticity tendency in Iowa, Minnesota, and Wisconsin, which suggests a northeastward track and for the low pressure system. This is corroborated by the 700 mb vorticity and 1000-500 mb thickness plot, where PVA is present to the northeast of the low. From the 500 mb chart, the surface low is located underneath the left exit region of the mid-level jet, which would lead to upward motion and intensification of the low with time.

Low-level winds along the Gulf Coast were southerly to southeasterly, drawing moisture northward. The 850 mb chart indicated a tongue of moisture from the LA coast up through AR and MO. The 285-300K isentropic analyses showed an area of isentropic lift ahead of the cold front in the Central Plains. This, combined with the moisture at 850 mb, will likely result precipitation as the low pressure system moves toward Michigan.

At 18 UTC, the NWS radar mosaic showed convective precipitation in advance of the front. At its current speed, this band of precip should reach Muskegon sometime between 03 and 06 UTC Tuesday. Total amounts are expected to be in the neighborhood of 0.4-0.5 in.

The high temperature will occur earlier in the day on Tuesday before the passage of the cold front, after which temperatures will decrease through the evening. At 18 UTC, Muskegon reported a temperature of 49F with clear skies and winds SE at 14 knots. Surface winds near the low were around 15 knots. Since the low is expected to intensify as it moves to the northeast, peak winds at Muskegon will probably be closer to 20 knots.

Warm advection ahead of the low will increase temperatures, but they will be mitigated by cloud cover associated with the isentropic lift and frontal passage. Highs will be at or slightly above 45F. Surface temperatures behind the cold front at 12 UTC were in the mid- to upper-20s F. Thus, the low in Muskegon will likely be around 25 F toward the end of the forecast period.

Temp: High 45F/ Low 25F
Winds: 20 knots
Precip: 0.43 in.

Surface analysis this afternoon revealed a few interesting features across the G.L. region. Much of southern MI and the OH rvr valley were within the warm sector and strong WAA was noted across this region. The SFC warm front appears to have lifted north into the UP of MI this afternoon. Isentropic ascent along the 300 K theta-sfc was beginning to commence across the lower MS rvr valley per 12Z analysis. Along this same corridor, strong low level moisture advection (per 850mb objective analysis) and strong DVPA in conjunction with the vigorous upper level jet streak appear to have been sufficient forcing for showers and thunderstorms. There appears to be a great deal of anvil debris from ongoing convection across the MO rvr valley per latest visible imagery. Also, advection fog/stratus appears to be moving across the eastern portion of the lower MI peninsula. This corroborates with recent surface observations near MKG. LOT and GRR radars indicate a few echoes across Lake Michigan at this hour. Much of the shower and thunderstorm activity across the central MS rvr valley appears to be in response to a vigorous upper level jet across the central plains per water vapor imagery. The associated vort max appears to be located across eastern NE and western IA, which appears plausible given the position of the vort max at the 12Z analysis (across west central KS into central NE). This vort max will continue to push eastward across the upper MS rvr valley this afternoon and into this evening.

3 hr surface pressure tendencies continue to indicate rapid surface pressure falls across the OH rvr valley at this hour. This leads me to believe that the surface low across the plains will gradually move eastward into the OH rvr valley in response to the falling surface pressures. Trends in WV imagery also suggests that the strong upper tropospheric jet now across southern TX will have its’ nose across the southern MS river valley, placing much of the OH rvr valley beneath the left exit region. Strong ascent should further aid surface pressure falls and induce cyclogenesis. Marine/lake stratus should continue to infiltrate the western portion of the LP of MI. Isentropic ascent and low level WAA will continue across this region and precipitation appears likely. One potential caveat in the precipitation forecast will be to determine how much diabatic cooling is necessary such that precipitation reaches the ground. Also, will diabatic cooling promote a variety of precipitation?
It appears that precipitation will be likely across the western LP of MI…with dewpoints still in the 30s (and temps in the 50s) evaporative cooling will rival any WAA. This could mean that the high temperature will likely occur before precipitation falls tonight. Moreover, WAA and low level stratus should keep temperatures up. Once the precipitation falls, temperatures will gradually fall. The stiff surface pressure gradient should persists and so winds will be rather strong. Given current profiles (though they are relatively cold) a period or two of mixed precipitation or snow will be possible. Finally, the low temperature will likely occur post FROPA. Post frontal mixing will also promote very strong winds, and the strongest winds may occur here.

Hi: 50
Lo: 27
Winds: 27 knots
Precip amounts: .40

Today at 12z the current conditions are 48F with a south-southeast wind of 15 knots, the skies are overcast with a chance of rain throughout the day.
The low pressure center is still moving into the area from the west but at a snails pace, the slow progression will allow the cold air to remain in place longer and will also allow for more snow to fall. The large scale wave pattern looks like a wave number 5. The trough over the central US plains is begining to show a negative tilt as a result of the strong jet core.
Once the front is past the area the temperatures will remain the same for the next forcast day. This is due to the overcast skies and the cold air advection in the area. Precip is likely to remain in the area for most of the day, but will most likely be sparatic.

Max Temp: 32
Min Temp: 25
Wind: 14
Precip: 0.01″

Well the folks in the Great Lakes, including Muskegon, MI, will need to bust out their winter coats and gloves, because the first dose of winter is on its way!

The 12Z Monday 500 mb chart shows a fairly broad trough over the western half of the United States with two distinct embedded shortwaves, one centered over northwestern Arizona through Utah and one centered roughly over eastern Colorado into western Nebraska and western South Dakota. The position of the broad trough is bringing southwesterly flow into Muskegon, MI at 500 mb. A look at the vorticity map at 12Z also shows height falls from southwestern Texas all the way to central Illinois and central Minnesota, with the steepest height falls occurring in southwestern Kansas. This, along with the progression of the previous QG Chi and QG Omega maps, suggests that the overall broad trough will dig southward while the embedded shortwave over eastern Colorado and western Nebraska will progress northeastward toward southern Minnesota over the next 24 hours. Water vapor imagery at this time also indicates the presence of this relatively strong upper level cyclone. Both the 12Z 700 mb and 12Z 850 mb charts show a very similar image, with a large trough centered across western Kansas, western Nebraska and central South Dakota that has brought southerly flow at both levels to Muskegon. The 850 mb image also shows moisture being transported northward from the Gulf of Mexico as far north as Missouri by 12Z due to the strong southerly to south-southwesterly flow across the southeastern United States. This moisture return should aid in surface development over that area, which could indeed be seen taking place over eastern Missouri, Illinois and southern Wisconsin at 20Z.

This area of showers and occasional thunderstorms is expected to lift northeast towards Muskegon by late in the day Monday and into the early hours on Tuesday. The 12Z 250 mb chart show a jet streak just south of the base of the 250 mb western U.S. trough, with the jet streak oriented southwest-to-northeast from southwestern Texas up through southeastern Oklahoma. This flow pattern is contributing to west-southwesterly-to-southwesterly flow over Muskegon, which is downstream of the trough at 12Z. A look at the progression of the flow at this level over the past couple of days suggests that this jet streak will progress northeastward directly towards Muskegon over the next 24 hours.

At approximately 20Z, water vapor imagery showed a large amount of upper level moisture being transported northeastward from eastern Missouri and Illinois toward Michigan (very much in association with the previously mentioned surface development over the same areas). Regional satellite also showed fairly dense cloud cover moving into Muskegon from the southwest as well (again very likely in association with the previously mentioned surface development and upper level moisture). The 295K-305K isentropes show some moderate isentropic ascent returning northward from the Gulf of Mexico along and ahead of a cold front oriented across the Central Plains, which also seems to be aiding with the surface development across Missouri and Illinois. At 20Z, Muskegon has a temperature reading of 50 degrees and a dewpoint reading of 32 degrees, with southeasterly winds anywhere from 10-15 knots. Southerly to southeasterly winds are prevailing across Michigan, Ohio, and Indiana as well. The previously mentioned cold front is currently oriented southward and southwestward from western Minnesota all the way back to north central Oklahoma, and some cold air advection south of the 12Z 850 mb trough should help this cold front to continue to progress eastward over the next 24 hours.

Based on the current progression of both the surface development and upper level moisture, it appears that the clouds that are already approaching Muskegon will be firmly in place by early Monday evening. This should help keep low temperatures from dropping very far, if at all, Monday night. I would expect temperatures to stay in the mid 40’s Monday night. How much Muskegon warms tomorrow before the cold front arrives will depend on how much surface heating occurs in Muskegon during the first half of the day on Tuesday. At 20Z, there is an upper level dry slot along the upper level trough across eastern Nebraska and western Iowa, with some drying also occurring further south across southern Missouri and northwestern Arkansas as well. How close this dry slot comes to Muskegon, as well as when the dry slot interacts with Muskegon, will have a significant impact on high temperatures for Tuesday, since its timing will determine how much surface heating occurs and how long it will last.

Taking all of this into consideration, I believe the dry slot will reach Muskegon by about 18Z, which is 1 p.m. local time in Muskegon. This should allow for a couple of hours of slight warming into the upper 40’s that likely wouldn’t occur if the clouds stayed put during this time. However, as the cold front progresses eastward and eventually reaches Muskegon, thick cloud cover will once again move in, and temperatures will begin to fall into the 30’s as winds pick up to anywhere from 20-25 knots. I expect that the low will be reached at the end of the forecast period, as temperatures should continue to drop up until and past 06Z Wednesday. I expect precipitation in the form of rain to begin before or near the beginning of the forecast period. The 12Z soundings around the Muskegon area show low precipitable water values (approx. 0.21-0.27”), but again, there at least moderate isentropic lift occurring south of Muskegon in the area of the current widespread surface development. Though the very dry atmosphere over Muskegon currently will keep the rain from being very heavy, I still expect just less than a half inch of rain for the Muskegon area with the current surface convection. The timing of the rain-to-snow changeover will be quite tricky and will depend on when the front moves through the area. However, since the coldest conditions are not expected until near the end of the forecast period, I wouldn’t expect the change to snow until the near the end of the period as well, which should have a very minimal impact on the overall measured liquid water precipitation totals.

High: 47 F, Timing: 11/30 ~18Z-20Z

Low: 33 F, Timing: 12/1 ~06Z

Winds: 25 knots

Precip: 0.45 in, Timing: beginning 11/30 ~06Z (probably starting just before forecast period)

Rain-to-snow changeover timing: 12/1 ~03Z-06Z

The 12Z 250mb Northern Hemispheric plot displays a wave number of between 5 and 6, which would suggest a progressive wave train. The existence of a trough in the western United States (over Colorado, Montana, and Wyoming) is producing a southwestern flow over the Central Plains and into Wisconsin and Michigan.

The forecast city for the following two weeks is Muskegon, Michigan. Muskegon is found on the western coast of Michigan on Lake Michigan, which is subjected to challenging forecast conditions due to lake effect snow possibilities.

At 12Z in Muskegon, Michigan, the surface conditions show winds out of the southeast at approximately 10 knots, and a temperature of 32 degrees Fahrenheit. An approaching cold front, associated with the surface low over southeastern Nebraska, is located around central Oklahoma. This surface low was over north/northwestern Kansas 12 hours ago, and has progressed northeastward.

The 925mb 12Z map shows 30 to 40 knot winds coming out of the south from the Mississippi River valley north to Wisconsin and Michigan, pulling moisture from the Gulf of Mexico. The low-pressure center is located in northern Kansas, which is where the surface low is also found. At 12Z, the 850mb map has winds shifting out of the southwest, also pulling moisture out of the Gulf of Mexico into the northern Central Plains to Missouri. There is a small shortwave trough at the base of the longwave trough over western Texas, which could be terrain-induced. Another shortwave is found extending west through southern Colorado to central Arizona. The low-pressure center is more broadly defined: extending from north-central Kansas to North Dakota.

The 700mb 12Z map has a similar pattern to the 850mb map, with southwesterly over the Central Plains and southerly flow over Wisconsin and Michigan. The shortwave found over southern Colorado is also seen at 700mb at the same location. This shortwave could help intensify the longwave trough. At 500mb, the low-pressure center can be found from western Kansas into North Dakota. At 300mb, there is a jet flowing south on the west coast and through Arizona, New Mexico, and northeast to Oklahoma, with a jet streak across the US/Mexico border south of Arizona.

Isentropic maps indicate the possibility for lift from the Mississippi River Valley north to Wisconsin on the 300K isentropic map. This is from south/southwesterly winds from the Gulf of Mexico ascending from 850mb to approximately 650mb near Wisconsin. This can also be seen in the 285K, 290K, 295K, 305K, and only slightly in the 310K isentropic maps.

Looking at QG Omega Q-Vector maps, there is an area of significant convergence over southern Wisconsin.

The national radar shows precipitation from northern Louisiana to Illinois and northwest through Wisconsin. At the rate the precipitation is moving, I would forecast rain in Muskegon before the Tuesday forecast period begins. With the progression of the cold front through the Central Plains, it is possible the cold front will hit Muskegon late Tuesday afternoon into the evening, with a possibility of snow after the cold front passes.

Max temperature: 46

Min temperature: 28

Precipitation: 0.6”

Winds: 23 knots

As of 2200 UTC Monday, a strong surface front located from Minnesota into Iowa and the Missouri-Kansas boarder has initiated significant precipitation which is moving steadily eastward. The temperature gradient along the front is 25 degrees F or more. Behind the cold front, temperatures have fallen well below freezing to ~18 degrees F in the Dakotas. Muskegon is currently 50 degrees F with light wind out of the southeast. A surface low in northeast Kansas/southeast Nebraska will move northeastward with time as Q-vector convergence in the lower atmosphere was observed over Iowa. An upper-level ridge, evident from 250 hPa level down to 700 hPa level, to the east of Muskegon will continue to move east. Large height rises over New England, southeast Quebec, New Brunswick, and Nova Scotia, as well as anticyclonic vorticity advection in New England indicate progression of the ridge eastward. Significant height falls over the central plains associated with a broad trough in the Arizona-New Mexico region and strong cyclonic vorticity advection in Oklahoma-Texas-New Mexico-Arizona region also would indicate eastward progression. The associated precipitation with the front should reach Muskegon by later this evening and continue through the night. There will probably be a break in precipitation as a dry slot passes over the region Tuesday morning, but new precipitation will begin around 1800 UTC as the surface low passes through the Great Lakes Region. Temperatures will fall from the mid-40s overnight to 18 F by midday Tuesday, as strong cold air advection behind the front issues in a bitter cold arctic air mass. providing for a good chance of snowfall. Winds will pick up to 20. Expect for the high temperature to occur overnight after 0000 UTC before the cold front moves into the area, with a high temperature of 45. A low of 17 will occur tomorrow evening. Total precipitation amounts (liquid water equivalent) will be around 1″. Total snow fall amounts could be up to 1″. The changeover from rain to snow will occur around 1800 UTC Tuesday as the surface low moves northeast pass  Muskegon. It’s going to get cold and snowy for the next day as old man winter makes himself known in the good ole’ Muskegon area!

A wet period is in store for the Muskegon area followed by a sharp drop in temperatures tomorrow. 00UTC analysis of the hemispheric 500 mb plot showed a wave number of around 6 which would suggest a rather progressive pattern. However, a ridge over the North Atlantic was aiding in slowing down to wave train just a bit. The dominant feature over the United States was a longwave trough with a negative tilt. This negatively tilted trough was contributing to surface pressure falls across the upper Mississippi River Valley. 500 mb analysis of the CONUS showed several shortwave troughs embedded in the longwave trough. 00UTC 250 mb objective analysis showed a 125 knot jet rounding the base of the trough over Northern Texas into Southeastern Oklahoma and Western Arkansas. 00UTC surface analysis showed a 1000 mb low pressure center over Iowa with an associated cold front extending southward into Missouri, Arkansas and Eastern Texas resulting in widespread showers and thunderstorms across the Mississippi River Valley. 00UTC isentropic analysis of the 295K isentrope showed a broad area of ascent over this area with theta-e values exceeding 300K. The 00Z sounding from Green Bay, Wisconsin showed strengthening and veering winds with height, indicative of warm air advection via the thermal wind vector with near saturated conditions up through 750 mb and the precipitable water value was 0.79 inches. Latest water vapor imagery shows a lead shortwave trough over Minnesota with a dry slot advecting northward into Illinois and Wisconsin. Latest radar images show a broad area of precipitation across the Great Lakes region with reflectivity values generally less than 30 dBZ.
As the trough becomes more negatively tilted with time, surface development will spread east and northeast ahead of the current surface low pressure center. As this occurs, the lead shortwave will move off to the northeast and bring the dry slot into the Great Lakes region for a period of time before wrap around precipitation moves in in the wake of the departing shortwave. As the surface low pressure moves northeastward with the surface development, the cold front will move through the Muskegon area and temperatures will fall. Current thinking is dry slot will move in faster than previously thought and result in lower precipitation amounts, both in liquid and ice form. With the anticipated movement of the surface low pressure center into Minnesota and Canada and faster than thought advancement of the dry slot, I have lowered precipitation amounts for the area with a changeover to snow likely happening around 22UTC. The daytime high temperature will be reached fairly early and will be around 46 degrees. The low temperature will be prior to 06UTC thanks to the frontal passage and will be around 33 degrees. Winds behind the front are likely to gust around 20 knots. Precipitation amounts will be around 0.55 inches with only 0.04 inches being in the form of snow.

Today’s weather maps indicate an interesting winter weather setup in the Midwest, and more specifically, in Muskegon, MI.  As of this moment, recent water vapor imagery indicates a strong upper level cyclone is lifting northeastward into southern Minnesota.  This cyclone has been developing surface low pressure systems for the past six hours along the track of the upper level cyclone.  As of the 00 UTC maps this evening, the cyclone has indications that it has propagated eastward, as the center of the cyclone has moved from western South Dakota to western Minnesota.  Currently, rain is falling at KMKG and is being fueled by the warm conveyor belt as seen in the 850 and 700 mb 00 UTC maps.  Along the warm conveyor belt at those two levels is warm air advection, which is helping to force the precipitation along the Mississippi River up into Michigan.  It is clear that from the 00 UTC maps that the precipitation will continue through 06 UTC into tomorrow.

Cold air advection south of the 850 mb 00 UTC low position will continue to move the cold front eastward.  The surface low will continue to shift northeastward via QG forcing and upper level divergence from agestrophic flow of the jet and flow curvature effects.  Such development of the low can be seen in the 05 UTC surface pressure tendency charts, which has a new low forming in central Michigan.    In conjunction with the low’s movement, the main precipitation concern will be with the potential for winter weather as cold Canadian air will enter the KMKG forecast area.  Additionally, the low’s movement will maintain cloud cover across the forecast area and keep temperatures from dropping due to radiational cooling.  In fact, since warm air advection is dominating most of the Midwest, temperatures may continue to rise until the cold front passes as the night goes on.  As the cold front is located along the western border of Illinois as of this moment, it will take some time to make it to KMKG.  Given the current speed of the cold front, I would expect it to arrive at KMKG at approximately 17 UTC tomorrow morning.  Winds ahead and behind the front will likely be very strong, given the strength of the pressure gradient as well as the forecasted further development of the surface low.

After the cold front passes, there will be a small window of no precipitation for the 06 UTC Tuesday to 06 UTC Wednesday time frame.  As mentioned previously, precipitation after the cold front passage will likely be of a winter weather type (SNOW) due to cold air advection throughout the lower to mid levels.  Given that the cyclone will continue to develop, there is a chance of snow showers given the moisture that will wrap around the western side of the cyclone.  00 UTC soundings (i.e. ABR) behind the cold front indicate a vertical profile prime for snow, with a large part of the surface to middle troposphere saturated and well below freezing.  This precipitation will likely be forced by warm air advection occurring north and west of the cyclone.  As the cyclone exits the Midwest, there will be a chance for scattered snowfall at Muskegon.

Given that the forecast will consist of mostly cloudy conditions through the forecast period, it may seem that the temperature max/min spread is not expected to be very large; however low level temperature advection patterns will significantly alter the forecast period’s max/min temperatures.  Given the precipitation and warm air advection, temperatures will rise into the lower 50s tonight and into the mid 50s tomorrow afternoon.  Once the cold front passes, temperatures should drop.  Precipitation will be light and the largest amounts will be constrained to the first rainfall event due to the higher certainty of the event and liquid nature of it.  Snowfall amounts will be limited and will likely contribute less (approximately .05 inches) to the overall precipitation forecast.

Max: 55 F

Min: 33 F

Winds: 20 knots

Precipitation: .4 inches

Also, considering the recent events in Mississippi and Louisiana, I highly encourage people in the southeast U.S. to stay alert to weather conditions for today and tomorrow!

Don’t get used to the recent warm air Muskegon, MI because a cold front is on its way into the Great Lakes region. A large-scale trough with several embedded shortwaves was situated in the western Central Plains as of Monday morning. An associated surface low over Nebraska and the Dakotas was moving northeast as the larger trough progressed eastward on Monday and is expected to be in the Muskegon area by tomorrow morning. This is helped by a fairly progressive planetary wave pattern (wave number ~5-6). A large ridge currently over the east coast slowly moving out to the ENE, though a low to the north was slowing its progression slightly today. This semi-blocking low is expected to retrograde towards the WNW, which will allow the east coast ridge to continue moving out. Another fairly strong ridge is moving in from the west coast as well. This is helping to push the Central Plains low into the Great Lakes region by tomorrow.

Coupling of frontal dynamics and isentropic lift has helped generate a wide band of showers and thunderstorms ahead of the cold front. Stretching from Iowa down into Louisiana around 18Z (as seen by radar and satellite imagery), this band of cloud cover and precipitation will likely reach Muskegon late tonight into Tuesday morning. Increasing cloud cover Monday evening will help keep temperatures up overnight as well. Some rain showers, up to about a quarter of an inch, will be possible early in the morning before the associated broad dry-slot moves over the region around mid-day. This dry-slot is not the end though because strong westerly winds behind the front will bring the chance for scattered snow showers tomorrow afternoon and evening. These snow showers are expected to be fairly light, but may be locally heavier in certain terrain pools with most regions possibly seeing over an inch by late Tuesday night. Recent warm conditions will increase the chance for snowmelt, which may help reduce overall accumulation totals.

Gusty winds following the front are expected to be mostly out of the west of about 20 mph. Also, a jet streak associated with the large-scale trough will also be over the Muskegon region during this event. Though it was situated south of Arizona today, it is very likely that it will intersect the surface cold front and increase precipitation chances (and gusty conditions) during the day tomorrow. Temperatures will be fairly mild (in the mid 40s to near 50) until the main dry slot passes and the stronger cold air advection reaches the region. Upper moisture associated with the 700 mb low may help to keep clouds over the region, and thus temperatures slightly warmer, until Wednesday morning when lows will really start falling into the 20s.

In summary:

Max: ~48 (Tuesday morning or with the dry slot)

Min: ~25 (Wednesday morning)

Winds: 15-25 (with gusts to 30+ mph)

Precipitation: Rain in the morning (~0.25”) followed by scattered snow showers in the late afternoon/evening hours (~1+” in some areas) by Wednesday morning.