Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 220356
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1056 PM CDT Sun May 21 2017

.AVIATION(06Z TAFS)...

Some MVFR CIGS still linger over the area, mainly north of
Milwaukee and Madison now, and they will continue to lift north
tonight. VFR conditions will prevail into the early evening on
Monday. However, a low pressure system and weak frontal boundary
will push in from the west Monday afternoon and evening, bringing
increasing clouds again along with a chance of showers and
thunderstorms toward evening. Look for breezy southwest to west
winds during the afternoon, ahead of the low. As the low moves
overhead Monday night, the weak pressure pattern and increased
moisture may lead to a quick development of MVFR then IFR
CIGS/VSBYS during the late evening and overnight hours.

&&

.PREV DISCUSSION... (Issued 846 PM CDT Sun May 21 2017)

UPDATE...
A decent short wave perturbation rotating around the larger mid
level trough centered over the Upper Midwest/far southern Canada
has kept the clouds and few sprinkles in place this evening. The
sprinkles should diminish over the next hour or so and clearing
will eventually spread in from west to east later tonight. The
forecast is on track.

MARINE...
Will let the small craft advisory expire as winds are gradually
weakening with the surface low lifting off to the north slowly.
Conditions will approach small craft advisory levels again Monday
afternoon into the early evening as southwest to west winds
increase for a time. The highest wave will be farther off shore.

PREV DISCUSSION... (Issued 543 PM CDT Sun May 21 2017)

AVIATION(00Z TAFS)...

MVFR CIGS have pushed into southeast Wisconsin late this
afternoon, but should lift quickly north this evening as some dry
air advects into the area in the wake of departing low pressure.
We will then remain VFR into early Monday evening. There is a
chance of showers and a few storms with a low pressure system and
frontal boundary drifting into the area from the west later
Monday afternoon. We may see MVFR CIGS/VSBYS return later Monday
night under a weak pressure pattern with more moisture in the
area. Winds will be 15 to 25kts Monday afternoon ahead of the
approaching low pressure and frontal boundary...diminishing by
evening.

PREV DISCUSSION... (Issued 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...None.
&&

$$

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



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