Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 182353
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
653 PM CDT Sun Jun 18 2017

.UPDATE...

&&

.AVIATION(00Z TAFS)...

VFR fcst thru the prd. Low pressure will continue to move away
from WI across sthrn Ontario tonight. This will keep the region
in Wrly flow thru Mon. Pressure gradient diminishes tonight as
low moves away and loss of daytime heating will allow winds to
fall below 10 kts overnight. Wrly winds will gust again Mon but
should not be quite as strong as today. Skies have become fairly
clear late this aftn but occnl VFR scttrd clouds will affect the
terminal thru the night with a gradual increase in cloud cover
after midnight in response to a weak upper level disturbance that
is fcst to pass thru Mon mrng producing isld SHRAs. Addtnl SHRAs
are possible Mon aftn with isld TSTMs also possible. Any rainfall
should should be short lived.

2%

&&

.PREV DISCUSSION... (Issued 236 PM CDT Sun Jun 18 2017)

DISCUSSION...

TONIGHT and MONDAY...Forecast Confidence is Medium...

Surface low pressure will continue to lift northeast across
southeast Canada. The pressure gradient will weaken and with the
loss of daytime heating, winds will be light out of the west
tonight. Mainly dry weather is expected. The latest couple runs of
the HRRR are showing some light showers moving across SW WI early
Monday with a weak shortwave.

High pressure will approach from the southwest on Monday
increasing the pressure gradient. West winds will be gusty, but
not as much as Sunday. An upper low will sit north of the state
with a mid level trough across Wisconsin. The trough axis will
move east of the region during the morning, but flow will still be
diffluent with steep low level lapse rates and cool temperatures
aloft. This could result in a few afternoon showers. Afternoon
Cape is 500-1000 J/kg so will keep mention of thunder during that
time.

Monday night into Tuesday...Forecast confidence medium.

A fast moving mid level wave dives into the area on northwest
flow. The models, in one form or another, bring a cluster of
showers and possible thunderstorms along with it. It looks to
arrive after midnight and exits by around noon on Tuesday. There
isn`t much instability, so mostly showers with a few rumbles
possible.

Tuesday night through Wednesday night...Forecast confidence is
medium.

High pressure builds in for Tuesday night and most of Wednesday.
There is another wave that arrives, mostly reflected in the lower
levels vs up above, generating some decent leading warm air
advection. A surface low and associated cold front reaches our
northwest county warning area toward 12z Thursday. The first of
the showers and possible storms could be reaching areas northwest
of Madison later Wednesday afternoon, but most of the rain will
hit after midnight Wednesday night.

Thursday and Thursday night...Forecast confidence is medium.

The front associated with the passing low is expected to stall
along the WI/IL border area with another low tracking east
northeast along it during this period. The h8 llv jet really
strengthens, producing in impressive moisture surge across the
boundary. The GFS and the EC both bring a wave of precip into
southern Wisconsin...mainly Thursday night...as the low passes by
to the south. This should be a fairly cloudy scenario and we`re on
the colder side of the front, so not much of a concern for strong
storms at this time.

Friday through Sunday...Forecast confidence is medium.

Friday looks dry as the secondary low pulls away, but another low
arrives for the weekend. There of course is model discrepancy that
far out, so we`ll have to see how that plays out. But, right now
it looks like a rainy Saturday with a deepening upper low keeping
it unsettled into Sunday.

AVIATION(21Z TAFS)...
Gusty west winds will diminish this evening. Scattered to broken
mid level clouds are expected this evening and tonight. Scattered
to broken 3000-4500ft cloud bases are expected for Monday. There
is a small chance for a few showers and thunderstorms Monday
afternoon.

MARINE...
A small craft advisory is in effect until 7 pm. Winds will
diminish this evening. West wind gusts of 15-20 knots are expected
on Monday.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 7 PM CDT this evening for LMZ643>646.

&&

$$

Update...BM
Tonight/Monday and Aviation/Marine...BM
Monday Night through Sunday...BM



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