Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 201945

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
245 PM CDT Wed Sep 20 2017


Tonight - Confidence...Medium
Convection firing from ne IA into SW WI ahead of low level
frontal boundary. Airmass is very unstable with MLCAPE values
reaching 3000 j/kg into sw WI. Dynamics proggd to ride to our
north so lower level forcing to be the primary forcing mechanism.
Mid level lapse rates not favorable though some higher 0-6km
shear sneaking into the cwa, upwards of 30 to 35 knots. Best combo
of forcing and instability looks to be lined up in SC WI where
meso progs show convection at its peak very late in the afternoon
through about 02z or 03z. So have highest pops in that area and
this is also where SPC has the SLight Risk placed and that looks
fine. Coverage of any shra/tsra proggd to diminish with time
overnight with decreasing instability. Depending on degree of
clearing fog may set up once again with the lighter winds
associated with weak winds in vicinity of the boundary.

Thursday - Confidence...Medium
The front is then proggd to lift back to the north. The GFS is
most aggressive with developing some shra/tsra. Mid level flow is
southwest with a broad anticyclonic look and building heights. 850
LLJ is also proggd to remain to our west, so forcing looks again
to be in the lower levels. 925 temps bounce back into the low or
mid 20s celsius so toasty temps and high dew points expected once

Thursday night through Sunday...Forecast confidence high.

An upper ridge will hold from the ern Great Lakes to E TX through
this period with a longwave upper trough over the wrn USA. S WI
will experience sly flow and very warm and humid conditions. Heat
index values will reach the upper 80s to lower 90s through the
weekend with cooler conditions near Lake MI via sely flow.

.LONG TERM...Monday through Wednesday...Forecast confidence

The upper trough over the wrn USA will slowly progress ewd during
this period. Thus the sfc trough/cold front will eventually move
into the region. Chances of showers and tstorms return for Mon-Tue
with temps gradually cooling, but still mild for this time of


.AVIATION(18Z TAFS)...Main story will be arriving shra/tsra with
approaching trough/wind shift into srn WI this evening. Still
expect potential for some stronger storms esp into sc WI where
frontal forcing will interact with peak instability. Meso models
decrease precip coverage overnight as instability wanes and better
dynamics ride to our north. Will have to watch for fog
development later tonight with lighter wind regime and lingering
low level moisture with higher dew points still in place.


.MARINE...Small Craft Advisory continues into this evening due to
a gusty southeast wind and higher waves which have built highest
towards Sheboygan. No changes planned.


.BEACHES...Breezy south to southeast winds have built waves
around 4 feet at beaches in Sheboygan and Ozaukee counties, thus a
Beach Hazard Statement remains in effect. The highest waves and
strongest currents are expected into the evening.


WI...Beach Hazards Statement until 9 PM CDT this evening for WIZ052-

LM...Small Craft Advisory until 9 PM CDT this evening for LMZ643.


Thursday Night through Wednesday...Gehring is the U.S. government's official web portal to all federal, state and local government web resources and services.