Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 280945
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
345 AM CST Tue Feb 28 2017

.TODAY AND TONIGHT...Forecast confidence is Medium.

Ongoing showers and isold thunder associated with initial surge of
low level warm air and theta-e advection.  Expect these showers to
wane early as this initial surge moves off to the east.  However
atmosphere already reloading farther southwest for expected second
round of convection later this morning.  GFS and ECMWF show
weakening low level jet carrying across southern WI later this
morning.  Slightly steeper mid-level lapse rates are expected with
this second batch along with NAM MUCape approaching 500 j/kg. Strong
bulk shear can be expected later this morning so not impossible one
or two of these storms may deposit larger hail approaching 1 inch.
Widespread cloud cover should prevent this convection from becoming
surface-base.

Expect a lull in the convection for a time in the afternoon, but
enhanced synoptic scale forcing from left exit region along with
passing low level frontogenetical forcing associated with low
pressure will result in another batch of convection later this
afternoon into the evening.  The best chance for convection will be
in the southeast CWA.  At this point expect activity to remain
elevated, however with warm front flirting with far southeast corner
of WI, possible one or two of the storms could become surface based
and produce some damaging winds along with hail.

Strengthening low pressure will move from IL/WI border into lower
Michigan overnight tonight.  Increasing north winds in its wake
along with amplifying mid-level trof will pull colder air into
southern WI later in the night.  Expect areas of lighter stratiform
precipitation to increase across the area late tonight as mid-level
short wave approaches from the southwest.  Hence northern areas may
experience a changeover to mostly -sn by late tonight with some
minor accumulation.

.WEDNESDAY...Forecast Confidence...Medium to High

A potent shortwave is expected to move through on Wednesday.
Meanwhile, the elongated area of surface circulations will be
consolidating into a single strengthening low, with widespread
snow developing across the forecast area. Should be all snow
northwest at daybreak, with some rain southeast. Precip will
likely transition to all snow southeast by mid morning as colder
air continues to pour in from the northwest. 00Z NAM and ECMWF
really beefed up precip totals, so bumped up forecast as well. Did
not go as high as these two models, given somewhat lower GFS
totals and much lower Canadian totals. Blend of the various
solutions ended up pretty similar to GFS, giving 3-5 inches most
places by the time the snow winds down early evening.

.THURSDAY THOUGH MONDAY...Forecast Confidence...Medium

Still looks like a quick moving wave will pass through the region
on Thursday, bringing some light snow. Models still vary with the
track though, with the ECMWF and Canadian farther south and mainly
dry for southern Wisconsin, while the GFS and NAM take the low and
snow across the forecast area. Left pops at chance for now due to
the uncertainty. Should see temps near normal on Thursday.

High pressure will bring dry weather and some sunshine on Friday,
but temps will likely remain at or even a tad below normal due to
colder temps aloft and snow on the ground.

Warm advection Friday night as the high departs may bring a little
light snow the forecast area.

Milder temperatures are then expected for the weekend under
southerly low level flow. The Canadian is showing a little rain
Sunday, but otherwise it looks dry for the weekend.

Rain chances are likely to return by Monday as low pressure
approaches.

&&

.AVIATION/12Z TAFS/...

Expect cigs to continue to decrease through the early morning as
warm, moist air flows northward into southern Wi, associated with
approaching warm front. Cigs then likely to remain at MVFR levels or
lower much of the day and into tonight, however some breaks in the
low clouds may develop this afternoon in close proximity of warm
front.

&&

.MARINE...

Will post Small Craft Advisory for today, starting with new NSH
issuance.  Today will be a borderline event but thinking more than a
few gusts to 25 knots will affect lake surface today as pressure
gradient tightens.  Low level inversion will be shallow and should
allow those gustier winds to occasionally mix down to surface. With
lake surface temps in the upper 30s to lower 40s, will also have to
watch for dense fog development later today into tonight as warm,
moist air moves northward from the central MS Valley region.  A few
afternoon and evening thunderstorms may also produce some hail.

A strong surge of cold air behind passing low pressure will likely
produce more frequent wind gusts to Small Craft Advisory levels
later tonight into Wednesday.  This surge of colder air will end the
dense fog threat overnight.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 6 PM CST this evening for LMZ643>646.

&&

$$

TODAY/TONIGHT AND AVIATION/MARINE...MBK
Wednesday THROUGH Monday...DDV



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