Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 110426
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1126 PM CDT Tue Oct 10 2017

.AVIATION(06Z TAFS)...Ceilings have been slow to lower, most
likely due to the northeast low level feed of slightly drier air.
However trend still slowly downward as more widespread rain
spreads across the area, so expect most areas across southern CWA
to lower to IFR in next several hours. IFR cigs may not stick
around quite as long on Wednesday.

&&

.PREV DISCUSSION... (Issued 937 PM CDT Tue Oct 10 2017)

UPDATE...Onset of showers caused temperatures to fall to the
wet-bulb temperature early in the evening, which was lower than
the expected minimum overnight temperature. The temperature has
since leveled off but needed to lower numerous locations several
degrees. Otherwise, showers continues to spread back into southern
Wisconsin as upper low passes by to the south and low to mid
level deformation sets up across southern WI. Still expect
widespread rainfall between about four tenths to over an inch in
some southern locations.

MARINE...Increasing potential for ENE wind gusts to 35 knots
later tonight into early Wednesday in southern marine area due to
tightening pressure gradient north of passing low pressure moving
from central IL towards the OH Valley. Hence upgraded Small Craft
Advisory to Gale Warning for LMZ646, from Wind Point to Winthrop
Harbor for late tonight. Small Craft Advisory remains in effect
elsewhere until 21Z Wednesday. Possible the SCY may need to be
extended into Wednesday night due to lingering high waves.

PREV DISCUSSION... (Issued 648 PM CDT Tue Oct 10 2017)

UPDATE...Showers have spread across almost all of southern Wi,
just now getting to the Fond du Lac and Sheboygan areas. Temporary
back edge of the showers from KEFT to KMRJ but more upstream
showers over eastern IA and northwest IL spreading north. As upper
level circulation moves mostly east across northern IL overnight,
expect periods of showers and light rain to affect the CWA,
tapering off from west to east, mostly from after midnight
through the early morning.

AVIATION(00Z TAFS)...Moist ENE flow and periods of showers will
result in lowering cigs through 06z. Expect most areas to drop to
between 500 and 1500 ft AGL.

PREV DISCUSSION... (Issued 321 PM CDT Tue Oct 10 2017)

DISCUSSION...

Tonight And Wednesday...Forecast Confidence Is High.

Models are in good agreement with the 500 mb shortwave trough
sliding east northeast toward the area into this evening, then
eastward later tonight into Wednesday. Robust differential
cyclonic vorticity advection, along with low and mid level
frontogenesis response, will continue to bring the rain showers
north northeastward into this evening.

The low level jet will also aid in maintaining deep moisture
transport into the area tonight. The showers will linger later
tonight, before tapering off from northwest to southeast across
the area on Wednesday. Continued with high PoPs across the area
into tonight, tapering off gradually on Wednesday from northwest
to southeast.

Gusty northeast winds are expected into this evening, with a
tight pressure gradient. The winds will veer eastward later
tonight into Wednesday.

Temperatures should only fall into the upper 40s to middle 50s
northwest to southeast across the area tonight, with highs only
reaching the lower 60s on Wednesday. They may not rise even that
high, with the clouds and rain showers over the area. Low clouds
should linger after the showers exit the area Wednesday afternoon.

Thursday - Confidence...Medium
Strong southwest mid level flow with lingering influence of
departing surface high noted. The return flow with some moisture
advection suggests low cloud cover may be in place. Not ready to
go with drizzle at this point, though low ceilings proggd by the
NAM MOS suggest some spotty drizzle would be possible. However,
GFS a little more optimistic. Will leave drizzle out of forecast
at this time but will go with a good deal of cloud cover.

Friday - Confidence...Medium
The high moves away with a cold front shifting through WI. Models
are showing various solutions with respect to the speed of this
boundary. There will be some showers along this feature with the
better chances in western and northern WI. The GFS shows 925 temps
well into the teens celsius with the other models a smidge cooler.
The NAM is hinting at stratus potential in this warm sector while
the GFS less so. However LLVL RH progs cast some doubt on the
degree of sun available to really boost the temps, so confidence
not overwhelming on the warm temps forecast at this time.

Friday night through Sunday - Confidence...Medium to High
Decent confidence for some additional rainfall. Surface/850 low
approaches Saturday with a good moisture push ahead of it. The low
then tracks through the Saturday night into Sunday with more
rains expected with the help of the 500 millibar wave and some
right rear divergence from the 200-300 jet core. So POPS are high
this period with potential for some appreciable rainfall.

Monday and Tuesday - Confidence...Medium
Low level thermal trough will be across the area on Monday with
some chilly 850 temps down to near zero c. The cool airmass gets
whisked off to the east pretty quick as 850/925 west or southwest
winds pull warmer air right back into southern WI for Tuesday.

AVIATION(21Z TAFS)...Rain showers will continue to move north
northeastward into the area into this evening. They will linger
tonight into Wednesday, ending from northwest to southeast across
the area during the late morning and early afternoon.

Gusty northeast winds are expected into this evening, veering
east and remaining gusty later tonight, lingering into Wednesday.
The gusts should weaken somewhat on Wednesday, except near Lake
Michigan.

Ceilings should drop to MVFR category by late afternoon or early
evening, and IFR later this evening and into Wednesday morning.
Ceilings will remain MVFR category into Wednesday afternoon.
Visibility values should be MVFR category with the showers, with
some IFR expected at times.

MARINE...The Small Craft Advisory remains in effect until 4 PM CDT
Wednesday across the nearshore waters of Lake Michigan. A tight
pressure gradient will linger over the region during this period.
Northeast winds of 15 to 25 knots, with frequent gusts to 30
knots, are expected into this evening. These gusty winds should
veer to the east later tonight and linger into Wednesday.

These winds will bring waves of 4 to 8 feet into tonight, then
slowly subsiding on Wednesday. The waves may linger above 4 feet
south of North Point Lighthouse late Wednesday afternoon. Winds
and waves should fall below Small Craft Advisory levels by
Wednesday evening.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until midnight CDT tonight for LMZ646.

     Small Craft Advisory from 7 AM to 4 PM CDT Wednesday for LMZ646.

     Gale Warning until 7 AM CDT Wednesday for LMZ646.

     Small Craft Advisory until 4 PM CDT Wednesday for LMZ643>645.

&&

$$

Update/Aviation..MBK
Tonight/Wednesday and Aviation/Marine...Collar
Wednesday Night through Tuesday...Wood



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