Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 200816

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
316 AM CDT Tue Mar 20 2018

.TODAY AND TONIGHT - Confidence...Medium to High.

Main concern this forecast period is lake effect clouds. Persistent
northeast flow will continue this period, pulling colder air into
the area.  85H temps fall to between -6 to -8C today resulting in
delta-T values around 10 degrees as lake temp hovering around 35 per
latest GOES-16 imagery.  Low level flow will vary from ENE to more
NE over the next 24 hours.  While dewpoints are currently in the mid
20s south of KSBM, upstream dewpoints fall off into the teens. The
mid 20 dewpoints have contributed to some patchy lower clouds
developing downwind of Lake Michigan from KMKE south and west.
NAMnest doing the best with these lower ceilings early this morning
and other short term guidance showing periods of lower clouds
affecting eastern areas through tonight.  Otherwise, periods of mid-
high clouds will affect rest of CWA as upstream inverted trof
weakens as it moves east and runs into short wave ridging and drier
air.  Blustery northeast winds to continue today, especially in
eastern areas.  Colder low level air has settled into southern WI so
daytime temperatures should be 5 to 10 degrees cooler than yesterday.

.Wednesday through Friday - Confidence...High

The pressure gradient will weaken as low pressure moves east of
the Appalachians. Northeast winds will remain slightly elevated
near Lake Michigan keeping temperatures down. There could be some
scattered low level clouds, otherwise we should see some sun. An
inverted trough, associated with the high over Hudson Bay, will
move through Wednesday night brining light winds. Quiet weather
will dominate through Friday afternoon due to the lingering
influence of the high to the north. Northwest flow will dominate
at the mid levels as a ridge builds across the plains.

.Friday Night and Saturday - Confidence...Low

There continues to be a lot of uncertainty during this period.
Low pressure will be moving south of the state bringing some
precipitation to southern Wisconsin. Models differ on how much of
the state gets clipped and on temperatures, and as a result,
precipitation type. The ECMWF continues to show a few or more
inches of snow. The GFS has most of the precip staying to the
south and west with southwest Wisconsin seeing some rain or snow.
The Canadian has the rain/snow line right through southern
Wisconsin with some snow accumulation possible. The ECMWF lingers
precip into Sunday. So, will have to keep an eye on this system
as it develops.

.Sunday through Tuesday - Confidence...Medium

The GFS and ECMWF are showing an upper trough or closed low
approaching the region bringing precip chances on Monday. Pops are low
as this system may lift north. This also creates some
uncertainty with temperatures during this time.


Low level winds will vary from more east to northeast to
northeast over the next 24 hours. Low level moisture will remain
sparse, however short term bufkit soundings in agreement on
shallow layer of rh persisting over eastern CWA through the period
with occasional weak low level convergence. 850H temps will fall
to between -6 to -8C today and persist through tonight, resulting
in delta-T around 10 degrees. Some short term guidance showing
periods of MVFR ceilings affecting eastern areas through the
forecast period. MVFR ceilings have already developed from KMKE to
KBUU. Currently being handled best by NAMnest guidance. Will
introduce several periods of lower clouds into eastern TAF sites
through tonight as can`t ignore ingredients coming together. Will
hold off on any flurry mention as moisture remains shallow. MVFR
cigs will occasional affect some inland areas, but should thin
farther west toward south central WI.


Persistent gusty northeast winds will continue today
into tonight due to moderate pressure gradient over the Great
Lakes as low pressure moves across the southeast and east central
CONUS. Lake surface temp around 35 degrees per latest GOES-16 skin
temperature measurements. The winds will gradually abate tonight
into Wednesday as the pressure gradient weakens. However the
elevated wave heights will be slow to fall due to persistent
onshore flow. Hence will extend current Small Craft expires to 18Z


LM...Small Craft Advisory until 1 PM CDT Wednesday for LMZ643>646.



Today/Tonight and Aviation/Marine...MBK
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