Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 010200 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
900 PM CDT TUE MAY 31 2016

.UPDATE...

Line of showers and thunderstorms continue to weaken with
increasing stability over region, reflected in most-unstable CAPE
values of 500 J/kg limited to the far southwest and shrinking with
time.

SPC has removed the Marginal risk of severe thunderstorms from
western Wisconsin. Could still see some localized ponding/minor
urban flooding with the heavy downpours associated with the
heavier cells but that threat is lowering with the continuing
weakening of the line.

Have adjusted PoPs for the slow movement and narrow areal coverage
of the line.

&&

.AVIATION/06Z TAFS/...

Expect VFR conditions overall, with some MVFR cigs and vsbys with the
weakening line of showers and thunderstorms moving into far
western sections of the forecast area. No severe as atmosphere
continues to stabilize, but could see some locally heavy downpours
with the stronger cells in the line.

&&

.MARINE...

Winds and waves will remain below small craft advisory levels
through Thursday. Southeast winds will rise to 10 to 20 knots late
tonight into Wednesday morning with the approach of low pressure
and a trailing surface trough, then lower Wednesday afternoon as
the trough approaches and crosses western Lake Michigan, with the
winds shifting west behind the trough. Showers and thunderstorms
are expected with the trough.

&&

.PREV DISCUSSION... /Issued 301 PM CDT TUE MAY 31 2016/

TONIGHT AND WEDNESDAY - Confidence...Medium
500 millibar low center will gradually lift ene to nw of Lake
Superior by the end of the day Wednesday. The associated surface/850
feature will follow along a similar path. This will drag a cold front
through the Upper Midwest and should clear much of southern Wisconsin
by days end on Wednesday. A moist southerly flow ahead of the cold
front combined with weak impulses will result in a good deal of
shra/tsra both ahead of the front in the moist environment and along
the front. So POPS will be on the high side. Decent precipitable water
values advecting into this system. Best instability axis is pooling
a bit further west across ern ia into se mn. Some of this
instability could clip the wrn cwa this eve with some holes
showing up there on vsbl imagery. Later tonight into Wednesday the
jet dynamics associated with this advancing 500 low will wrap in on
the south/southeast periphery of the circulation so the marginal
risk per SPC seems reasonable even though considerable cloud
cover/time of day plays a bit of havoc with instability parameters.
But something to watch if enough instability can crank up ahead of
the front with better jet dynamics arriving.

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

High pressure still looks to maintain control...making this a dry
period. The combo of a mid level short wave moving across and
steep low level lapse rates should result in a bit more cloudiness
on Thursday than what we thought earlier. Still not a bad day with
highs in the 70s.

FRIDAY THROUGH THE WEEKEND...Forecast confidence is high.

All in all, Friday should be a rather decent day with highs in the
70s and clouds increasing from the west. Another low pressure
system will be approaching from the west northwest and we start to
get into some warm advection ahead of it. That forcing could
trigger some showers and storms over mainly the northwest forecast
area Friday afternoon. Then the pattern turns more cloudy and
showery for the weekend. The upper low that approaches on Friday
will move over the western Great Lakes and become a large, closed
upper low overhead by Saturday, lingering into early next week.
So, look for the threat of showers this weekend with the best
chance of thunder on Saturday and just rain on Sunday. High temps
should stay in the 70s.

MONDAY AND TUESDAY...Forecast confidence is medium.

We should see the threat of showers diminish or end by Tuesday as
the upper low finally weakens and pushes off to the east.

AVIATION/00Z TAFS/...Expecting VFR conditions through the TAF
period except for brief MVFR/IFR in scattered showers and
thunderstorms. The coverage of the showers and thunderstorms will
increase as a cold front approaches from the west tonight. Expecting
more shra/tsra on Wednesday as cold front interacts with potentially
unstable airmass before front exits to the east late afternoon or
early evening Wednesday.

MARINE...Light winds and low wave heights are expected to continue
into mid-week. There will be increasing chances of showers
and thunderstorms tonight and Wednesday with passage of a cold front.
Look for winds to turn southeast tonight ahead of the cold front.
Wind speeds will increase tonight, but are expected to remain below
small craft criteria.

&&

.MKX Watches/Warnings/Advisories...
WI...None.
LM...None.
&&

$$

UPDATE...REM
TONIGHT/Wednesday AND AVIATION/MARINE...Collar
Wednesday NIGHT THROUGH Tuesday...Davis



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