Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 072051
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
251 PM CST Wed Dec 7 2016

.TONIGHT AND THURSDAY - Confidence...Medium to High
Water vapor/RAP animation shows large vortex spinning north of Lake
Superior. Models show some fairly weak energy pivoting southeast
into the area and combined with the evolution of some weak surface
east/west troughing there is some potential for flurries or a few
snow showers. POPS will be on the low side though with vry little
showing up in the QPF department. The chilly westerly flow is
maintained into Thursday as pressure gradient looks fairly similar.

.THURSDAY NIGHT THROUGH FRIDAY NIGHT...Forecast confidence is
high.

An arctic ridge will stretch from the northern plains into the
western Great Lakes during this period. We could see some flurries
into Thursday night, squeezed out of a lingering cloud deck with
cold air advection ongoing. Overall, though, it will be a dry and
rather cold period.

.SATURDAY THROUGH MONDAY...Forecast confidence is medium.

This has turned into a very interesting period. The GFS, NAM and
the Canadian are all rather consistent in the handling of the mid
level trough that hits the Pacific Northwest on Friday, pushes
across the northern Rockies and deepens as it reaches the western
Great Lakes Saturday night. The associated sfc cyclogenesis is
quick, developing a low that tracks over far nrn IL early Sunday
morning.

The ECMWF has been fairly benign with the trough through last
night`s model run, keeping it flatter and moving along at a good
clip. However, the new 12z Wed EC has now dramatically changed
that scenario. Now, the Euro is doing something similar to the
others, but digging that mid level trough even deeper and slowing
it down by 18-24hrs. It even goes into a negative tilt as it gets
east of us. So, the GFS/NAM/Canadian have our main snow event
Saturday afternoon through Saturday night, tapering off quickly
Sunday morning. The Euro begins the light snow, well ahead of the
main mid level system, on Saturday, then shows a much stronger and
more southern sfc cyclogenesis that takes the sfc low over nrn
Indiana late Sunday night into Monday morning. The Euro would
have snow falling from Saturday afternoon through Monday morning.

Clearly, there is much uncertainty. What is certain is that the
details of this forecast will change going froward. Keep an open
mind and don`t commit to any solution at this point. The current
thought on snow amounts is in the 4 to 6 inch range.

.TUESDAY AND WEDNESDAY...Forecast confidence is medium.

Surface high pressure should be in control. We are still under a
dominant northwest mid level flow with some short wave energy
sliding through. Those could give us a little light snow or
flurries during this period, but nothing significant right now. If
the Euro verifies with the strong low early next week, we will
likely see a colder intrusion of arctic air by mid week with lows
well below zero. The other model guidance, which is weaker than
the Euro, aren`t quite as cold.

&&

.AVIATION/00Z TAFS/...
Pressure gradient between low pressure north of Lake Superior and
high pressure expanding through the Plains resulting in the cold
westerly flow across the area. Mid level cyclonic flow and low
level thermal trough will keep the potential for MVFR cigs this
period. Attm jet enhanced cirrus across srn WI though some of the
stratus/stratocu just off to our northwest may trend back into the
area tonight/Thursday per increase in LLVL RH progs.

&&

.MARINE...A Small Craft Advisory remains in effect until 6 AM
Friday. A large low pressure area will move across southern Canada
but still bring brisk westerly winds to Lake MI into early Friday
AM. High waves will occur toward the open waters.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...SMALL CRAFT ADVISORY until 6 AM CST Friday for LMZ643>646.

&&

$$

TONIGHT/Thursday AND AVIATION/MARINE...Collar
Thursday NIGHT THROUGH Wednesday...Davis



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