December 3-4 Upper Midwest Snow Event

[A-L-E-K]

Looks like the 12z GFS is gonna be weaker and southeast again. It has shown no consistency with this system.

looks pretty similar if not more amped than it's previous runs, nice hit for N. MO, NW ILL, E. IA and SW WI and IMO it's probably still underdoing cyclogenisis.

[Thundersnow12]

Looks like the 12z GFS is gonna be weaker and southeast again. It has shown no consistency with this system.

Not to me, still a good event from DDC-TOP-DVN

[A-L-E-K]

Not to me, still a good event from DDC-TOP-DVN

i hate these obscure station abbrvs, all i know is DVN.

but yeah, the GFS is slowly coming around and looking at the maps by hr102 or so, you can easily see the potential for much more aggressive cyclogenisis than is being shown.

[wisconsinwx]

i hate these obscure station abbrvs, all i know is DVN.

but yeah, the GFS is slowly coming around and looking at the maps by hr102 or so, you can easily see the potential for much more aggressive cyclogenisis than is being shown.

This particular solution would appear to support advisory-type snows in S Wisconsin (as long as it's mostly snow), and I would even take 2-3 inches with this easily, given it will likely be the first accumulating snow.

[on_wx]

i hate these obscure station abbrvs, all i know is DVN.

Dodge City KS-Topeka KS-Davenport IA?

[Thundersnow12]

NAM showing stronger northern and southern stream waves at 84hr compared to the GFS that are also further east both with a more nuetral tilt to them.

[jhamps10]

Looks interesting, too far SE here, but looks like a watcher for NW Illinois for sure IMO

[BeastFromTheEast]

[A-L-E-K]

NAM showing stronger northern and southern stream waves at 84hr compared to the GFS that are also further east both with a more nuetral tilt to them.

There is promise but it looks like energy hanging back only to be strung out slowly along the positive tilt trough seems to be the consensus right now.

[Geos]

Dodge City KS-Topeka KS-Davenport IA?

Yes!

[Thundersnow12]

sfc a tad too warm at that point probably but quick changeover after this.

[Geos]

This particular solution would appear to support advisory-type snows in S Wisconsin (as long as it's mostly snow), and I would even take 2-3 inches with this easily, given it will likely be the first accumulating snow.

A Dodge City to Davenport line with the snow would mean southern Wisconsin would be next area down that axis to see snow and probably where I'm at also. Might see a mix towards the lake early on, but the air mass sitting in place could be cold enough to dampen the effect of 40-45° lake waters. Most of the time the mix near the lake stays within 5 miles of it, maybe a few more miles in the urban heat island core.

[A-L-E-K]

A Dodge City to Davenport line with the snow would mean southern Wisconsin would be next area down that axis to see snow and probably where I'm at also. Might see a mix towards the lake early on, but the air mass sitting in place could be cold enough to dampen the effect of 40-45° lake waters. Most of the time the mix near the lake stays within 5 miles of it, maybe a few more miles in the urban heat island core.

[wisconsinwx]

A Dodge City to Davenport line with the snow would mean southern Wisconsin would be next area down that axis to see snow and probably where I'm at also. Might see a mix towards the lake early on, but the air mass sitting in place could be cold enough to dampen the effect of 40-45° lake waters. Most of the time the mix near the lake stays within 5 miles of it, maybe a few more miles in the urban heat island core.

I tend to be on the edge in these situations (about 6 miles from the lake, so just close enough that the effects are felt, but I rarely get plain rain in these situations either). How close are you to the shore?

[gosaints]

The NAM extrapolated from hour 84 would seem to want to produce a more powerful storm, but of course it is the NAM at hour 84.

[wisconsinwx]

How about Denver with potentially their third significant winter storm and their fourth winter weather event of the year coming up later this week, and it will barely be December? This is why many are antsy for winter weather in the Great Lakes and Midwest as well.

[A-L-E-K]

The NAM extrapolated from hour 84 would seem to want to produce a more powerful storm, but of course it is the NAM at hour 84.

the NAM is fun to look at but not all the useful at this range, especially extrapolated. I will say it is much faster but still looks like crap at 850. Nice moisture connection at 700 and powerful jet streak would still lead to some decent snows but it's got a long ways to go.

[Geos]

I tend to be on the edge in these situations (about 6 miles from the lake, so just close enough that the effects are felt, but I rarely get plain rain in these situations either). How close are you to the shore?

Yeah the early season storms up until mid December can be tricky. I think once the lake gets down into the mid 30s on average, everyone gets an even distribution of snow from the shore communities inland. Of course there's lake enhancement and effect that changes that equation! A really early storm in late October one year; the lake was still 50°, it wasn't until you got 20 miles inland that you saw snow on the grass.

I'm 4 1/2 miles inland on the edge of farmland vs. built up areas of the county. If the forecast says mix near the lake, little accumulations - it ends up being a mix then eventually does accumulate once winds turn north. A couple inches would be nice to start off the first weekend of December!

[A-L-E-K]

Izzi plays it cool but lays out the players nicely.

BY THIS WEEKEND OUR ATTENTION WILL TURN THE THE VIGOROUS UPPER LOW

THATS CURRENTLY OFF THE BRITISH COLUMBIA COAST. MEDIUM RANGE

GUIDANCE IS IN REMARKABLY GOOD AGREEMENT THROUGH FRIDAY WITH THIS

SYSTEM DROPPING SOUTH AND WITH AN ANOMALOUSLY STRONG UPPER LOW (H5

HEIGHTS 3+ STANDARD DEVIATIONS BELOW AVERAGE) SETTING UP SHOP OVER

THE DESSERT SOUTHWEST BY FRIDAY. MODERATE RIDGING DOWNSTREAM OVER

THE SOUTHEASTERN CONUS SHOULD LEAVE OUR AREA IN A WEST-SOUTHWEST

FLOW ALOFT.

FORECAST CONFIDENCE THIS WEEKEND INTO EARLY NEXT WEEK IS LOW AS

MODELS OFTEN STRUGGLE WITH CUT OFF LOWS. HAVING SAID THAT...IT

APPEARS AS THOUGH THIS FIRST UPPER LOW WILL WEAKEN INTO AN OPEN WAVE

AND RIDE THE SOUTHWEST FLOW ALOFT INTO OUR AREA THIS WEEKEND...WITH

SOME DEGREE OF PHASING WITH A RESULTANT AMPLIFYING NORTHERN

STREAM TROUGH EXPECTED. WHILE DETAILS ARE MURKY...IT WOULD APPEAR

THAT OUR AREA IS IN STORE FOR INCREASINGLY UNSETTLED WEATHER LATE

SATURDAY INTO SUNDAY. WITH VARYING SOLUTIONS ABOUT THE TRACK OF

THE SURFACE SYSTEM AND RESULTANT THERMAL PROFILES IT WOULD BE

ABSURD TRYING TO PINPOINT P-TYPES FOR THE WEEKEND JUST YET.

dvn

THIS WEEKEND...THIS IS WHEN THE FUN REALLY BEGINS WITH POTENTIAL FOR

SIGNIFICANT RAIN AND/OR SNOW. DEEP TROUGH IN THE SOUTHERN ROCKIES WITH

ENERGY DIVING INTO THE NORTHERN ROCKIES AND HOW THEY PHASE WILL PLAY

A BIG ROLE IN PRECIPITATION TYPE. GFS/GEM APPEAR TO KEEP STREAMS

SEPARATE AND NOT AS AMPLIFIED ALLOWING FOR MORE OF COLDER SOLUTION

WITH SIGNIFICANT SNOW OVER MOST OF THE DVN CWA. ON THE OTHER HAND

THE ECM PHASES THE TROUGHS WITH MORE AMPLIFICATION AND BRINGING WARMER

AIR NORTHWARD. THIS WOULD ALLOW FOR A WARMER SOLUTION WITH THE BULK

OF THE PRECIPITATION BEING RAIN...THEN GRADUALLY TURNING TO SNOW.

EITHER WAY A STRENGTHENING LOW LEVEL JET WILL BRING GULF MOISTURE

NORTHWARD WITH POTENTIAL FOR SIGNIFICANT PRECIPITATION. TIMING THE

RAIN OVER TO SNOW AND ACCUMULATIONS REMAIN TO BE DETERMINED.

[gosaints]

Thought this was a good write-up from la crosse.

AREA FORECAST DISCUSSIONNATIONAL WEATHER SERVICE LA CROSSE WI300 PM CST TUE NOV 29 2011.SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT300 PM CST TUE NOV 29 2011AT 3 PM...A RIDGE OF HIGH PRESSURE EXTENDED WESTERN AND NORTHERNMINNESOTA SOUTHWEST INTO THE CENTRAL PLAINS. FURTHER TO THEEAST...A SURFACE LOW WAS LOCATED OVER THE WESTERN PORTIONS OF LAKEERIE. THE SURFACE PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS WASPRODUCING SUSTAINED WINDS OF 10 TO 20 MPH WITH WIND GUSTS UP TO30 MPH. AS THE PRESSURE GRADIENT RELAXES LATE THIS AFTERNOON ANDEVENING...THESE WIND SPEEDS WILL RAPIDLY DECREASE TONIGHT.WITH LIGHT WINDS...VERY DRY DEW POINTS...AND CLEAR SKIES TONIGHT...TEMPERATURES SHOULD RAPIDLY FALL TONIGHT. BY MORNING...TEMPERATURES WILL LIKELY RANGE FROM THE TEENS TO AROUND 20.FROM LATE WEDNESDAY NIGHT INTO THURSDAY EVENING...A LONG WAVE INTHE NORTHERN STREAM WILL MOVE SOUTHEAST THROUGH THE FORECAST AREA.MUCH OF THE FORCING ASSOCIATED WITH THIS WAVE WILL BE LOCATEDALONG AND NORTH OF THE INTERSTATE 94 CORRIDOR. DUE TO THIS...THEHIGHEST PRECIPITATION CHANCES WERE PLACED IN THESE LOCATIONS.MODEL SOUNDINGS SUGGEST MAINLY SNOW ACROSS NORTH CENTRAL WISCONSIN...AND SNOW CHANGING TO RAIN ACROSS THE REMAINDER OF THE AREA. SNOWAMOUNTS IN CLARK AND TAYLOR COUNTIES MAY APPROACH A HALF INCH..LONG TERM...FRIDAY THROUGH TUESDAY300 PM CST TUE NOV 29 2011THE MAIN CONCERN WITH THIS PART OF THE FORECAST IS THE POTENTIALWINTER STORM THAT MAY BE IMPACTING THE REGION.WHILE THE 29.12Z OPERATIONAL MODELS ARE CONVERGING ON A SOLUTION FORTHIS WEEKEND. THERE ARE THREE DIFFERENT SCENARIOS THAT ARE SHOWINGUP IN THE ENSEMBLES AND DETERMINISTIC MODELS. THESE COME ABOUT DUE TOTIMING DIFFERENCES IN THE NORTHERN STREAM. WHILE ALL OF THESCENARIOS ARE IN GOOD AGREEMENT THAT A SHORT WAVE TROUGH WILL BEEJECTING OUT OF THE SOUTHWEST UPPER LEVEL LOW. THERE ARE DISTINCTDIFFERENCES ON HOW FAR NORTHWEST THIS WAVE WILL END UP. THISMAINLY DRIVEN BY THE LONG WAVE TROUGH IN THE NORTHERN STREAM.IN SCENARIO 1...THE NORTHERN STREAM WAVE MOVES RAPIDLY ACROSS THECANADIAN PRAIRIES AND WESTERN ONTARIO...AND BY SUNDAY MORNING THESOUTHERN EXTENT OF THE LONG WAVE TROUGH IS ALREADY LOCATED ACROSSMINNESOTA AND NORTHERN WISCONSIN. THIS WOULD RESULT IN A MUCH FURTHERSOUTHEAST TRACK OF THE SURFACE LOW THROUGH THE MID MISSISSIPPI ANDSOUTHERN GREAT LAKES. WITH THIS TRACK...THE SOUTHERN AND EASTERNPORTIONS OF THE FORECAST AREA WOULD EITHER SEE A BAND OF HEAVYSNOW OR POSSIBLY GET MISSED ALL TOGETHER IF THE SYSTEM TRACK ISEVEN FURTHER SOUTHEAST. THE 29.06Z AND 29.12Z GFS AND TWO-THIRDS OFITS MEMBERS ARE ALSO SHOWING THIS.IN SCENARIO 2...THE NORTHERN STREAM IS JUST A BIT SLOWER AND IT HASTHE SOUTHERN EXTENT OF THIS LONG WAVE TROUGH IS ONLY AS FAR AS EASTAS NORTHWEST MINNESOTA AND EASTERN DAKOTAS BY SUNDAY MORNING.THIS WOULD ALLOW THE LOW PRESSURE SYSTEM TO MOVE FROM THE MIDMISSISSIPPI RIVER VALLEY NORTHEAST INTO THE WESTERN GREAT LAKES.WITH THIS TRACK...THE BAND OF HEAVY SNOW WOULD MOVE ACROSS OURFORECAST AREA. EXACT LOCATIONS WHICH WOULD BE AFFECTED ARE WAYUNCERTAIN TO SPECIFY AT THIS TIME. A THIRD OF THE 29.12Z GFSENSEMBLE FAMILY MEMBERS SUPPORT THIS.IN SCENARIO 3...THE NORTHERN STREAM IS EVEN SLOWER YET AND THESOUTHERN EXTENT OF THIS LONG WAVE TROUGH HAS NOT EVEN REACHEDMINNESOTA YET BY SUNDAY MORNING. THIS WOULD ALLOW THE LOW PRESSURESYSTEM TO MOVE FROM THE CENTRAL PLAINS INTO NORTHWEST WISCONSIN.WITH THIS SCENARIO...THE PRECIPITATION WOULD START OUT AS RAIN ONSATURDAY ACROSS THE FORECAST AREA AND THEN TRANSITION TO SNOW ASCOLDER AIR MOVES INTO THE REGION ON SATURDAY NIGHT. THE LAST THREERUNS OF THE ECMWF AND 29.12Z GEM FAVOR THIS SOLUTION.UNTIL THESE TWO WAVES ENTER THE UPPER AIR NETWORK WHICH WILLLIKELY NOT OCCUR UNTIL THURSDAY...IT IS HARD TO SAY WHICH SCENARIOWILL BE THE MOST PLAUSIBLE. AS A RESULT...JUST RAISED THEPRECIPITATION CHANCES ACROSS THE ENTIRE FORECAST AREA FROM LATEFRIDAY NIGHT INTO SATURDAY NIGHT. THE LARGEST INCREASES IN THEPRECIPITATION CHANCES WERE ACROSS THE EASTERN PORTIONS OFNORTHEAST IOWA...AND IN SOUTHWEST AND CENTRAL WISCONSIN.

[afterimage]

This has IWX interest

"WITH THE INCOMING SHORTWAVE ON SATURDAY...HAVE INCREASED POP TO MORE CLOSELY MATCH SURROUNDING OFFICES AND WOULD EXPECT TO SEE ANOTHER

ACCUMULATING SNOWFALL DURING THE PERIOD."

[A-L-E-K]

This has IWX interest

"WITH THE INCOMING SHORTWAVE ON SATURDAY...HAVE INCREASED POP TO MORE CLOSELY MATCH SURROUNDING OFFICES AND WOULD EXPECT TO SEE ANOTHER

ACCUMULATING SNOWFALL DURING THE PERIOD."

bold

[Thundersnow12]

the NAM is fun to look at but not all the useful at this range, especially extrapolated. I will say it is much faster but still looks like crap at 850. Nice moisture connection at 700 and powerful jet streak would still lead to some decent snows but it's got a long ways to go.

Would probably go west of us with a good amount of WAA already taking place and good moisture feed as you said, seen by the explosion of precip at 84hr.

[Geos]

Informative AFD's.

Here's MKX's discussion from 2:53pm

.SATURDAY THROUGH SUNDAY...FORECAST CONFIDENCE IS MEDIUM. THE ECMWF HAS BEEN STEADY EDDIE WITH THE NEXT SYSTEM KICKING OUT OF THE SOUTHWEST U.S. THIS WEEKEND. A TIGHTENING H8 BAROCLINIC ZONE IS FORECAST TO SET UP FROM WISCONSIN BACK INTO OKLAHOMA AND TEXAS FRIDAY NIGHT AND SATURDAY. THE ECMWF/GFS/GEM ALL KICK OUT A PIECE OF ENERGY FROM THE CUT OFF UPPER LOW SOUTH OF THE 4-CORNERS AREA. IT THEN RACES NORTHEAST INTO THE WESTERN GREAT LAKES BY SUNDAY. THE LOWER LEVELS RESPOND WITH A DEVELOPING LOW PRESSURE SYSTEM...NOTHING MAJOR...BUT ENOUGH TO PULL UP A DECENT SURGE OF MOISTURE...ABOUT 3G/KG AT 750-700MB. CONDENSATION PRESSURE DEFICITS TANK TO THE LOWER SINGLE DIGITS. IT/S LOOKING MORE LIKELY WE WILL GET SOME PRECIP SATURDAY NIGHT INTO SUNDAY. THE ECMWF/GFS/GEM ALL HAVE SOME PRECIP ACROSS THE AREA DURING THIS TIME. THE BIGGEST QUESTION WILL BE WHAT TYPE. THE GFS IS COLD AND WOULD SUPPORT A MORE SNOWY SCENARIO...WHILE THE ECMWF IS WARMER WITH A RAIN OR RAIN/SNOW MIX TO START...CHANGING OVER TO LIGHT SNOW LATER SATURDAY NIGHT. THE GEM LOOKS TO BE SOMEWHERE IN THE MIDDLE. SO...CONFIDENCE IS HIGH WE/LL GET PRECIP...BUT LOW ON THE TYPE AND WHAT IMPACTS MAY RESULT. IF THE GFS VERIFIES...WE/D LIKELY BE LOOKING AT AN SNOW ADVISORY FOR AT LEAST THE CENTRAL AND NORTHWEST PORTION OF THE FORECAST AREA. STAY TUNED.

[Thundersnow12]

18z GFS warmer here with the best band further west.

[A-L-E-K]

18z GFS warmer here with the best band further west.

Consensus isn't there, but like I said earlier, I anticipate further stronger/nw shifts.

[Geos]

18z GFS warmer here with the best band further west.

Still about 100 hours out. Lots of time for things to change. The NAM went too far NW with this current storm. I wonder if it will do it again with this storm coming. By Thursday morning there should be a good idea on the track. Local newscasters are being cautious with the NE Illinois forecast - generally saying rain and snow potential there.

[wisconsinwx]

Consensus isn't there, but like I said earlier, I anticipate further stronger/nw shifts.

Normally, I would say, and it is still the most likely scenario. However, in playing devil's advocate, we really haven't seen a NW trend in the short term before storms in the past month or two. In fact, they have held pretty steady. Take the November 9-10 storm in the Upper Midwest as an example. That one actually shifted SE toward the end, so it's far from a foregone conclusion. Obviously I still like Des Moines (or NW) to LaCrosse to GRB, though, as the Euro is steadfast with a NW solution.

[Thundersnow12]

Normally, I would say, and it is still the most likely scenario. However, in playing devil's advocate, we really haven't seen a NW trend in the short term before storms in the past month or two. In fact, they have held pretty steady. Take the November 9-10 storm in the Upper Midwest as an example. That one actually shifted SE toward the end, so it's far from a foregone conclusion. Obviously I still like Des Moines (or NW) to LaCrosse to GRB, though, as the Euro is steadfast with a NW solution.

you say it like were supposed to see nw trends...

Every system has to be looked at differently and they will do what they want with models handling certain situations differently.

[cyclone77]

I'm not really sure what to think about this system. The Euro and GEM have remained pretty consistent over the last few days. The GFS seems to be coming around to the Euro/GEM, and has adjusted a bit NW with the 18z. Think we'll see a few more adjustments NW on future GFS runs. Still looks like Omaha to Green Bay are the best locations to pick up some snow. As Alek noted earlier, that makes sense based on typical early Dec climo with SW flow storm systems. What could really change things though is how strong the southern vort ends up being. Right now most of the models really show it crapping the bed as it ejects out across the Plains. Of course, if it ends up being stronger it would probably pull further NW and be more of a threat to the Dakotas and Minnesota.