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November 20-21 Early Season Snowstorm

Hoosier

By Hoosier,
in Lakes/Ohio Valley

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HillsdaleMIWeather

HillsdaleMIWeather

Posted
Posted

Final WPC model discussion out, GFS all the way.

..DEEPENING SURFACE LOW/UPPER TROUGH OVER THE MIDWEST/GREAT

LAKES...

PREFERENCE: 00Z GFS

CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS ARE GRADUALLY CLUSTERING AROUND A COMMON SOLUTION WITH

THE EVOLUTION OF SURFACE LOW PRESSURE EJECTING ACROSS THE CENTRAL

PLAINS ON FRI AND THEN MOVING THROUGH THE MID MS VALLEY AND LOWER

GREAT LAKES REGION THROUGH SAT. THE 00Z UKMET AND 00Z CMC HAVE

BOTH TRENDED TOWARD THE LOW TRACK OF THE 00Z GFS...ALTHOUGH THE

00Z GFS CONTINUES TO SUGGEST A DEEPER LOW CENTER WHICH IT HAS BEEN

CONSISTENT IN DOING THE LAST FEW RUNS. THE 00Z NAM IS A TAD SOUTH

OF THE GFS TRACK AS THE SYSTEM APPROACHES THE LOWER GREAT LAKES

REGION. THE 00Z ECMWF HAS TRENDED STRONGER AND A LITTLE FARTHER

NORTH WITH ITS LOW TRACK AND IS NOW VERY CLOSE TO THE NAM.

HOWEVER...THE 00Z GEFS MEAN SUGGESTS THAT THE NAM AND ECMWF MAY

STILL BOTH BE A TAD TOO FAR SOUTH AND A LITTLE WEAK OVERALL...AND

IT TENDS TO SUPPORT THE MORE CONSISTENT GFS. GIVEN THE ENSEMBLE

SUPPORT AND TRENDS OF THE UKMET/CMC AND TO AN EXTENT THE

ECMWF...WILL CONTINUE TO PREFER THE GFS FOR THIS SYSTEM.

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michsnowfreak

michsnowfreak

Posted
Posted

Honestly can't remember a Winter Storm Watch in November before. DTX discussion very reasonable. Definitely riding the line here. 6z NAM was a bit scary but 6z GFS and especially its ensembles with a notable shift east. Fingers crossed.

 

AGGRESSIVE HEIGHT FALLS/MERGING UPPER LEVEL PV WILL CARVE OUT
DIGGING UPPER LEVEL TROUGH OVER THE CENTRAL PLAINS...WITH LEAD SURGE
OF 850-700 MB MOISTURE/THETA-E IMPACTING SOUTHEAST MICHIGAN AFTER
MIDNIGHT...AS ISENTROPIC ASCENT/LOW TO MID LEVEL FGEN EXPECTED TO BE
MOST ACTIVE WITHIN MIDDLE OF THE CWA...OR CLOSE TO THE M-59
CORRIDOR...SUFFICIENT TO GENERATE PRECIPITATION. 1000-850 MB
THICKNESSES BELOW 1290 M POINT TO SNOW...EXCEPT MAYBE DURING THE
ONSET AND TOWARD THE OHIO BORDER...BUT WET BULBING EFFECTS SHOULD
QUICKLY KICK IN TO SUPPORT ALL SNOW...AS TEMPS CRASH TOWARD 30
DEGREES MOST LOCATIONS. ACCUMULATIONS UP TO ONE INCH EXPECTED BEFORE
12Z...AS 3 G/KG OF SPECIFIC HUMIDITY AT 850 MB LIFTS NORTH ACROSS
THE AREA.

LONG TERM...SATURDAY THROUGH FRIDAY

 

THE POTENTIAL FOR ACCUMULATING SNOW ON SATURDAY REMAINS FOREFRONT IN
THE FORECAST. THE WATER VAPOR IMAGERY AND 00Z UPPER AIR ANALYSIS
SHOW A 140 KT UPPER JET NOW DIVING INTO THE PACIFIC NORTHWEST. THIS
ENERGY MOVING IN OFF THE PACIFIC WILL PHASE WITH THE NORTHERN STREAM
WAVE NOW DROPPING INTO THE NRN ROCKIES. THE 00Z MODEL SUITE ALL
INDICATE THAT THIS WILL LEAD TO RAPID MID LEVEL TROUGH AMPLIFICATION
ACROSS THE CNTL PLAINS AND MID MISSISSIPPI VALLEY EARLY ON
SATURDAY...WITH THE WAVE THEN TAKING ON A NEGATIVE TILT AS IT
ROTATES ACROSS THE GREAT LAKES LATE SAT AFTERNOON/SAT EVENING. THIS
WILL CAUSE A DEEPENING OF THE ASSOCIATED SURFACE LOW AS IT LIFTS
FROM THE MID MS VALLEY SAT MORNING TO ERN ONTARIO SAT NIGHT.

THE SFC LOW WILL DEEPEN IN RESPONSE TO THE INTENSIFYING LARGE SCALE
DYNAMICS...WHICH INCLUDE STRONG UPPER DIVERGENCE WITHIN THE EXIT
REGION OF A CYCLONICALLY CURVED UPPER JET MAX AND VERY GOOD MID
LEVEL PV ADVECTION/MID LEVEL HEIGHT FALLS. THE STRENGTHENING OF THIS
SYSTEM WILL LEAD TO THE DEVELOPMENT OF A REGION OF GOOD MID LEVEL
DEFORMATION...LIKELY INTENSIFYING OVER SE MI. FAIRLY HIGH STABILITY
EARLY IN THIS SYSTEM MAY LIMIT THE OVERALL INTENSITY OF THE FRONTAL
FORCING. MUCH COLDER AIR ALOFT WILL ARRIVE LATER IN THE DAY
SATURDAY. THIS WILL LEAD TO RAPID MID LEVEL DESTABILIZATION...THE
RESULT OF WHICH WILL LIKELY BE AN INTENSIFICATION OF ASCENT WITHIN
THE MID LEVEL FRONTAL ZONE. THE AIRMASS WHICH CONTINUES TO ADVANCE
ACROSS THE GREAT LAKES IS SUFFICIENTLY COLD FOR SNOW...WITH 850MB
TEMPS DOWN TO AROUND MINUS 7 C. MODEL PLAN VIEWS AND CROSS SECTIONS
CONTINUE TO SUGGEST ADEQUATE MOISTURE QUALITY FOR A WINTER
SYSTEM...WITH 700MB MIXING RATIOS AROUND 2 G/KG. SO OVERALL
CONFIDENCE REMAINS HIGH WITH RESPECT TO SOME ACCUMULATING SNOW ON
SATURDAY.

THERE DOES REMAIN SOME MODEL SPREAD WITH RESPECT TO THE TRACK OF THE
SURFACE LOW. THIS UNFORTUNATELY WILL HAVE LARGE IMPACTS ON POTENTIAL
SNOWFALL ACCUMULATIONS ACROSS SE MI. THE DETERMINISTIC GFS REMAINS
STRONGEST AND FARTHEST WEST OF THE 00Z MODEL SUITE. THE MAJORITY OF
ITS ENSEMBLE MEMBERS SUGGEST A WEAKER AND FARTHER EAST SFC LOW
/TRACKING ACROSS NRN OHIO AND LAKE ERIE/. THERE HAS HOWEVER BEEN A
NOTED TREND AMONG THE NAM AND ECMWF OF A SLIGHTLY STRONGER SYSTEM.
THIS RAISES ENOUGH CONFIDENCE TO SUGGEST A SWATH OF ACCUMULATING
SNOW ACROSS SE MI. GIVEN THE FORCING AND FAIRLY FAST SPEED OF THE
SYSTEM...QPF IN THE .4 TO .6 INCH RANGE SEEMS REASONABLE. EVEN WITH
FAIRLY LOW LIQUID TO SNOW RATIOS...THIS WILL HAVE THE POTENTIAL TO
PRODUCE SNOW TOTALS OF 3 TO 7 INCHES. THE MAIN UNCERTAINTY IS JUST
WHERE THE STRONGEST MID LEVEL DEFORMATION WILL SET UP. A FARTHER
WEST TRACK /LIKE THE GFS/ WOULD PLACE THE HIGHER SNOWFALL TOTALS
ACROSS THE SAGINAW VALLEY AND THUMB AND EVEN SUGGESTS A PERIOD OF
RAIN IN THE SOUTH WHERE WARMER AIR GETS ADVECTED INTO THE BOUNDARY
LAYER. A FARTHER EAST SOLUTION WOULD PLACE THE AXIS OF HIGHEST
SNOWFALL TOTALS ACROSS THE SOUTHERN AND EASTERN PORTIONS OF THE
FORECAST AREA. GIVEN THIS UNCERTAINTY...A WINTER STORM WATCH IS
BEING ISSUED FOR THE ENTIRE CWA WITH THE EXPECTATION THAT PORTIONS
OF THE WATCH WILL EITHER BE DOWNGRADED TO AN ADVISORY OR UPGRADED TO
A WARNING IN LATER FORECAST CYCLES. WHILE SNOW WILL OVERSPREAD THE
AREA DURING THE FIRST HALF OF THE DAY SAT...IT MAY STRUGGLE TO
ACCUMULATE. THE STRONGEST FORCING AND THUS BETTER SNOWFALL RATES AND
POTENTIAL ACCUMULATIONS ON THE ROADS WILL BE LATE SAT AFTERNOON AND
EVENING.

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michsnowfreak

michsnowfreak

Posted
Posted

Going to be a weird shock to the system after the warm Fall we have had. Really cannot remember the last November synoptic storm to hit Detroit area honestly

We have had a handful of 2-3" type November snowfalls, but yes, I cannot remember a true winter storm such as this. My biggest single November snowfall since I have began keeping records was 3.4" on Nov 23, 2005 (LES the next day brought the 24-hour total to 4.0" but the depth never exceeded 3"). Also....in 1996, 1997, and 2014, we had the very, very rare for November "snow on snow" phenomenon where light snow fell atop snowcover. But each time the systems were of the 1-3" variety.

 

As stated yesterday, the last official 4"+ November storm at DTW was 1984, the last 5"+ was 1977, and the last 6"+ was 1966!

 

I definitely know my location in SE MI will mean I wont jackpot, but I will enjoy regardless because this could be a hell of a storm for November. IF there is some ungodly cutoff, I will simply take a nice trip to a park near Ann Arbor on Sunday, when highs will remain in the 20s.

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A-L-E-K

A-L-E-K

Posted
Posted

Looking for positives here and low level flow looks to be relatively favorable for minimizing marine impacts downtown, at least relative to other early season events. Low level winds over the area should remain relatively strong out of the wnw until around 18z. After 18z, it looks like we'll see 7-8 hrs of weak flow during saturation and before on-shore flow ramps up. This plus the diurnally favorable timing of onset give the lakefront areas a chance to get off to a decent start if we can get under an early weenie band (which currently looks to set up just north). That said, It's really hard to bet against a strong marine influence during an early season event with a lake this warm.

 

Picture becomes much more murky during the height of the storm around 12-15z Saturday with strong NE flow off the warm lake.

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RyanDe680

RyanDe680

Posted
Posted

Looking for positives here and low level flow looks to be relatively favorable for minimizing marine impacts downtown, at least relative to other early season events. Low level winds over the area should remain relatively strong out of the wnw until around 18z. After 18z, it looks like we'll see 7-8 hrs of weak flow during saturation and before on-shore flow ramps up. This plus the diurnally favorable timing of onset give the lakefront areas a chance to get off to a decent start if we can get under an early weenie band (which currently looks to set up just north). That said, It's really hard to bet against a strong marine influence during an early season event with a lake this warm.

 

Picture becomes much more murky during the height of the storm around 12-15z Saturday with strong NE flow off the warm lake.

 

Lake water still around 50F

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