Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 211943
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
243 PM CDT Sun May 21 2017

.SHORT TERM...

.TONIGHT and MONDAY...Forecast confidence is Medium.

A midlevel trough will swing through tonight. Behind it the low
levels will start to dry out and clouds will start to break up.
Southwest flow will continue at the surface on Monday as surface low
pressure develops over western Iowa. It will be breezy.

There is a chance for thunderstorms in the afternoon and evening. An
upper low will shift across the upper Great Lakes with warm air
advection at the low levels. Lapse rates will steepen and there will
be surface based CAPE and 30-40 kts of shear. The more conservative
ECMWF shows 400 J. The freezing level is pretty low around 8 kft
so there is a hail threat for any thunderstorm that develop. Meso
models show some activity developing over the region and south
Monday afternoon and evening. SPC has our western forecast area in
a Marginal Risk for severe storms where there is the greatest
instability.

Monday night through Wednesday...Forecast confidence is Medium

A northern stream shortwave over the Upper Mississippi valley sags
slowly southeast into the Western great Lakes Wednesday.

Still around 1000 Joules/kg of CAPE Early Monday evening, with
some hail potential mainly south central, before CAPE values
become elevated and drop to around 125 Joules/kg later Monday
night. Enough CAPE, especially southeast Tuesday for mention of
thunder again. Kept some pops on Wednesday, as low pressure over
the Ohio valley backs toward the northeast bringing precipitation
back into at least far southeast Wisconsin on the GFS. The ECMWF
keeps most of the rain to our south and east.

After milder temperatures it`s back to cooler temperatures
Wednesday.


.LONG TERM...

Thursday through Sunday....Forecast confidence is Medium

An Upper ridge moves across Wisconsin Thursday into Friday,
before another upper trough moves into Wisconsin on Sunday.

Surface high pressure is expected Thursday with the high near the
Upper great lakes into Saturday, before a trough of low pressure
moves into Wisconsin Saturday night or Sunday. Temperatures are
expected to rebound back to around normal to end the work week and
into the weekend.

&&

.AVIATION(21Z TAFS)...

Ceilings of 2-4kft will continue through early evening. Lowest
ceilings will be in the west with mainly VFR ceilings in the east.
Ceilings of 2500-3000 ft at times may move through the east.
Ceilings will become VFR later this evening. Cumulus around 5kft
will likely develop Monday with gusty southwest winds. There is a
chance for showers and thunderstorms in the afternoon and evening.

&&

.MARINE...

Wind gust will diminish this evening but southwest winds of 10-20
knots will continue through the night. Southwest wind gusts will
approach small craft levels again Monday. There is a chance for
showers and thunderstorms Monday afternoon and evening.

&&


.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 9 PM CDT this evening for LMZ643>646.

&&

$$

Tonight/Monday and Aviation/Marine...Marquardt
Monday Night through Sunday...Hentz



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