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April 17th-18th Late Season SNOW Event


Powerball

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My latest output pretty much showing a band of 3-5" across W. IA through Northern ILL to S. Wisconsin through the central parts of C. Michigan. have the highest amounts for the first 24 hours across the NE IA to N. ILL areas with 3-4" in that area.

Our office is still calling for an inch for Milwaukee. The question is do I believe the 3-5 inches on your map or do I believe my local weather office?

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Our office is still calling for an inch for Milwaukee. The question is do I believe the 3-5 inches on your map or do I believe my local weather office?

Oh, not going against what they have, they are the subject experts in that area. Guess it will be the case of which one will win out. For city specific, my output for Milwaukee proper is showing 3.8" Guess I will either bust or verify tomorrow.

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000

FXUS63 KDTX 172257

AFDDTX

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI

657 PM EDT SUN APR 17 2011

.AVIATION...

A WEAK RIDGE OF HIGH PRESSURE WILL BUILD INTO SE MICHIGAN DURING THE

EVENING AND BRING AN END TO THE WINDY CONDITIONS. THIS WILL LEAVE

VFR IN PLACE UNTIL THE NEXT LOW PRESSURE SYSTEM MOVES CLOSER TO THE

REGION LATE TONIGHT. THIS SYSTEM IS MOVING QUICKLY THROUGH THE

CENTRAL PLAINS STATES AND WILL INTERACT WITH A FRONTAL BOUNDARY

STALLED ALONG THE OHIO RIVER VALLEY. THE RESULT WILL BE A BURST OF

LATE SEASON SNOW ACCUMULATION MAINLY FROM FLINT SOUTHWARD WITH ONSET

ROUGHLY FROM JUST BEFORE SUNRISE THROUGH ABOUT NOON. THE ZONE OF

HEAVIEST ACCUMULATION REMAINS EXPECTED ROUGHLY ALONG AND SOUTH OF

THE M-59 CORRIDOR DOWN TO ABOUT THE I-94 CORRIDOR WITH 2 TO 4 INCHES

MOST LIKELY AND RESULTING IN IFR/LIFR CONDITIONS DURING THE PEAK OF

THE EVENT. THE HEAVIEST BAND COULD PIVOT NORTH OF METRO AIRPORT

SHORTLY AFTER ONSET, SET UP NEAR PTK, AND THEN MOVE BACK THROUGH DTW

DURING THE MID TO LATE MORNING. HIGH SNOWFALL RATE WILL HELP ENSURE

ACCUMULATION EVEN ON RELATIVELY WARM PAVED SURFACES BEFORE THE SNOW

DIMINISHES AND THEN ENDS BY EARLY MONDAY AFTERNOON. MVFR CONDITIONS

WILL BE LEFT BEHIND FOR THE REST OF THE DAY EXCEPT FROM FNT

NORTHWARD INTO THE SAGINAW VALLEY WHERE IT WILL BE VFR.

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Just look at the radar fellow southern Wisconsinites, this entire part of the state is about to get dumped on. This is an insanely perfect setup for this time of year. I'll go 3-6" for Madison.

I wish I had that much confidence. I had it around noon time today, when most of the models were showing 0.5 inches of QPF or more, but it seems the QPF trends have gone down since then.

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DVN

MID LEVEL SHORTWAVE AND ATTENDANT JET STREAK IS FCST TO PROPAGATE

E/SE AND ACROSS THE MID MISSISSIPPI VALLEY NEXT 12-18 HRS.

WEAK LOWS AT SFC-850 MB WILL PUSH EASTWARD FROM PLAINS TONIGHT

ALONG LOW-MID LEVEL FRONTAL BOUNDARIES/BAROCLINIC ZONES. LOW LEVEL

JET IS FCST TO STRENGTHEN IN RANGE OF 40-50 KTS BY LATE EVE IN

OVERNIGHT WITH STRONG MOISTURE TRANSPORT INITIALLY AIMED AT THE

CWA BEFORE VEERING INTO OHIO VALLEY TOWARD 12Z. MODELS GENERALLY

SHOWING QUITE IMPRESSIVE MID LEVEL FRONTOGENETICAL FORCING AND

ALSO ROBUST ISENTROPIC LIFT DEVELOPING ON NOSE OF JET BETWEEN

03Z-06Z AND CONTINUING OVERNIGHT BEFORE TAPERING AND EXITING THE

FAR EAST BY 12Z-15Z MON. THIS SHOULD RESULT IN WIDESPREAD PCPN

DEVELOPING LATER THIS EVE INTO OVERNIGHT ESPECIALLY ALONG AND

NORTH OF I-80 WHERE BEST FORCING AND CONVERGENCE IS PROGGED. SOME

INDICATIONS OF INSTABILITY WHICH WOULD SUPPORT POTENTIAL

BANDED NATURE OF PCPN WITH ALSO FEW RUMBLES OF THUNDER NOT OUT OF

REALM. CONCERNS ARE WITH DRY/COLD RESERVOIR SITTING IMMEDIATELY TO

OUR NORTH PER 12Z RAOBS AND ANALYSIS... WITH SFC DEWPTS IN THE

20S WITH EVEN SOME TEENS ACROSS PORTIONS OF EASTERN MN AND WESTERN

WI. AS SFC-925 MB FLOW VEERS TO NORTHEAST LATER TNGT IT WILL

CONTINUE TO ADVECT THIS IN RESULTING IN IDEAL EVAPORATIONAL COOLING

SETUP. THIS COUPLED WITH STRONG DYNAMICAL COOLING SHOULD BE

SUFFICIENT TO COOL DOWN COLUMN FOR PCPN TO MIX WITH AND THEN CHANGE

TO SNOW NORTH OF HWY 30. 12Z NAM AND GFS BUFR SOUNDINGS SHOW

CLASSIC HEAVY SNOW WITH DEEP SATURATION AND NEARLY ALL BELOW ZERO

FOR AREAS ESPECIALLY ALONG AND NORTH OF HWY 20. MODELS ALSO SHOWING

IMPRESSIVE OMEGAS IN THE DENDRITIC GROWTH ZONE WHICH COUPLED WITH

MID LEVEL INSTABILITY COULD RESULT IN PERIODS OF MOD/HVY SNOW IN

THE NORTH. DESPITE AIR/GROUND TEMPS GENERALLY ABOVE FREEZING WITH

IT BEING NIGHTFALL AND GIVEN INTENSITY/RATE IT WOULD EASILY OVERWHELM

THIS AND ACCUMULATE. GARCIA METHOD WOULD SUPPORT 4-6 INCH SNOW

ACCUMULATION POTENTIAL FOR 12 HOUR PERIOD OF LIFT. PROBLEMS ARE THIS

WILL BE ABOUT 6-9 HRS AT MOST OF LIFT AND THIS DOES NOT ACCOUNT

FOR MELTING/COMPACTION. BOTTOM LINE... ANTICIPATE A BAND OF SNOW

ACCUMULATION ACROSS THE NORTH... MOST LIKELY VICINITY OF HWY 20 ON

NORTHWARD WHERE 1 TO 3 INCHES APPEARS LIKELY AND COULDN/T RULE OUT

ISOLD AMTS NEAR 4 INCHES VERY FAR NORTHEAST CWA. MOST OF THIS LIKELY

ON GRASSY OR ELEVATED SURFACES... WITH ROADS MAINLY WET OR SLUSHY.

WITH UNCERTAINTIES STILL WITH AMOUNTS AND LOCATION AND IMPACTS... AND

AFTER COORDINATION WITH NEIGHBORING OFFICES... HAVE OPTED TO HOLD OFF

ON ADVISORY ATTIM AND CONTINUE TO HIGHLIGHT IN HWO AND GRAPHICAL WX STORY.

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18z GFS has .80" liquid at DPA in 12hrs with this bullseye..

The bullseye in terms of snow accumulations still looks to be the southern row of counties in Wisconsin into the very northern parts of the northern row of Illinois counties. Basically Rock, Walworth into Racine and Kenosha. DPA may be seeing the QPF bullseye, though if that's what you're talking about.

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The bullseye in terms of snow accumulations still looks to be the southern row of counties in Wisconsin into the very northern parts of the northern row of Illinois counties. Basically Rock, Walworth into Racine and Kenosha. DPA may be seeing the QPF bullseye, though if that's what you're talking about.

I'm well aware of that, but that is some serious lift/ascent taking place and these heavier bands could cool the column faster and allow for some +SN, possibly even TSSN in some areas, a very tricky forecast.

Dynamic cooling is going to work wonders with this one.

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I'm well aware of that, but that is some serious lift/ascent taking place and these heavier bands could cool the column faster and allow for some +SN, possibly even TSSN in some areas, a very tricky forecast.

Dynamic cooling is going to work wonders with this one.

Yeah, you talk about tricky, if the narrow band of heavy precip (likely to be snow) moves just 15 miles north or so, Milwaukee could get 6 inches. As it is, it is more likely to be 2 or 3 inches.

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Yeah, you talk about tricky, if the narrow band of heavy precip (likely to be snow) moves just 15 miles north or so, Milwaukee could get 6 inches. As it is, it is more likely to be 2 or 3 inches.

I've seen events like these produce a half foot of snow in 6 hours, all comes down to how fast the column can cool and if a location can stay under a heavy band for a long period of time.

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This reminds me of an event in I believe either 2006 or 2007 that dropped around 6 inches of snow here. I think it was around April 5 or so and most of the snow came overnight into the morning. We lost power, and a number of spruce trees were toppled way over by the weight of the snow. Here's to tonight setting a new benchmark for late season snows, at least in more recent history.

Was out doing some spring cleaning this afternoon. Got all the tools in for the night and ready for a fresh blanket. If we get to four we are going to get the sleds out early for one last ride. Good stuff.

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I'm well aware of that, but that is some serious lift/ascent taking place and these heavier bands could cool the column faster and allow for some +SN, possibly even TSSN in some areas, a very tricky forecast.

Dynamic cooling is going to work wonders with this one.

Some of that may be "contaminated" by the convective parameterization in the model, but I have little doubt there will be some good forcing in that area.

In that vein, I had noticed that the 12Z 4km WRF wanted to produce some weak updrafts (2-4 m/s) in the precip zone (across some of the same areas outlined by the GFS), which would be more than enough to cause some "snow-island" effects and lightning.The time/height cross sections on the NAM Bufkit had also suggested some weak theta-e folding, suggesting the potential for some weak upright instability or at least some conditional symmetric instability.

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Some of that may be "contaminated" by the convective parameterization in the model, but I have little doubt there will be some good forcing in that area.

In that vein, I had noticed that the 12Z 4km WRF wanted to produce some weak updrafts (2-4 m/s) in the precip zone (across some of the same areas outlined by the GFS), which would be more than enough to cause some "snow-island" effects and lightning.The time/height cross sections on the NAM Bufkit had also suggested some weak theta-e folding, suggesting the potential for some weak upright instability or at least some conditional symmetric instability.

Ya the 12z 4km WRF run was pretty impressive and kept all the heavy precip in northern IL and out of southern WI

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