Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 121038

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
538 AM CDT Thu Oct 12 2017


MVFR CIGS will persist through about 06z Friday with VFR CIGS
gradually spreading back into the area late tonight. Some IFR CIGS
will be found mainly southwest of Madison through 15z this
morning along with areas of drizzle. Winds will gradually veer
from east to south today then southwest tonight.


.PREV DISCUSSION... (Issued 309 AM CDT Thu Oct 12 2017)


Today and tonight...Forecast confidence is high.

Surface high pressure will stretch from the western Great Lakes,
northeast into Quebec, Canada today. That ridge will begin to push
east tonight with a trough of low pressure approaching western
Wisconsin by early Friday morning. The clouds will remain locked
under a strong inversion based around 3-4kft into tonight. As the
flow turns more southerly in response to the pattern shift, we may
see some clearing push in later tonight. The moisture is also
pretty deep and it`s possible we could see some spotty drizzle at
times. Highs today will be kept in check due to the low clouds, so
similar to yesterday.


Friday through Saturday... Forecast confidence is high.

Southerly winds on Friday will help temps rise into the mid/upper
60s before the rain gets here. Rain with a few rumbles of thunder
will impact outdoor activities Friday night.

Rain showers and scattered thunderstorms will slide northeast
into south central WI Fri afternoon and into southeast WI by early
evening. This is associated with rising motion due to the upper
jet over the Upper Midwest, fairly deep elevated warm air
advection, and 850mb frontogenesis.

We might see a break in the rain Saturday morning, but models are
trending wetter with this time period. Winds will be increasing
out of the east, but temperatures will remain on the mild side.

The right entrance region of the upper jet will slide into
southern WI on Sat as a mid level trough digs through the central
Rockies. The resultant surface low will slide northeast along the
850mb baroclinic zone and undergo cyclogenesis as it moves through
southern WI Saturday afternoon. The dynamics are very strong with
this system, and moisture content is high with precipitable water
values up to 2 inches which is very high for this time of year.
We will see some thunderstorms Saturday, with the prime time
period during the afternoon and evening when the nose of the very
strong low level jet impinges on southern WI.

The cold front is expected to move southeast through southern WI
around midnight Saturday night. Dry air behind the front will help
us clear out quickly.

Rain amounts will be quite heavy over the weekend. Accum from Fri
afternoon through Sat morning should range from around a quarter
inch toward the Dells to a half or 3/4 inch toward Milwaukee.
Despite the quick-moving system, Sat afternoon and night could
bring a swath of 1.5 to 2 inches through portions of southern WI.

Sunday...Forecast confidence is medium.

Dry and cold air will briefly take hold of WI on Sunday. We should
have mostly sunny skies with some diurnal cumulus, with highs in
the 50s. Clear skies Sunday night should allow temps to drop into
the 30s inland from the Lake, so there is potential for our first
Frost of the season.

Monday through Thursday... Forecast confidence is medium.

The pattern becomes more zonal for the first half of next week
which means more above normal temperatures and fairly dry weather.


Look for primarily MVFR CIGS across the area today, though we
could see some IFR CIGS for a time before 15z this morning. We
should see some VFR cigs push in later tonight as winds turn
southerly and we possibly get into some clearing and drying.


Waves will continue to subside this morning as easterly winds
weaken under high pressure.

Small craft advisory conditions are again possible Saturday night
into Sunday night as strong low pressure moves through the Great




Today/Tonight and Aviation/Marine...Davis
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