Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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947
FXUS63 KMKX 200505
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1105 PM CST Fri Jan 19 2018

.UPDATE...

No changes to the short term forecast.

&&

.AVIATION(06Z TAFS)...

The low level wind shear across the southeast will diminish by
07-08z Saturday. Look for VFR conditions through the day on
Saturday. MVFR then IFR CIGS will quickly spread north into the
area Saturday evening as moisture surges north ahead of an
approaching area of low pressure.

&&

.PREV DISCUSSION... (Issued 842 PM CST Fri Jan 19 2018)

UPDATE...

Winds remain elevated across the southeast, but they`ll be coming
down steadily over the next few hours as the low level jet mix
pushes off to the east. The high clouds and mixing may help to
keep temps up a few degrees vs what we had in the fcst. I`ve
backed off a bit on mins and may have to do it a bit more.
Otherwise, no significant changes needed.

MARINE...

Look for the brisk/gusty southwest winds to steadily diminishing
overnight.

PREV DISCUSSION... (Issued 523 PM CST Fri Jan 19 2018)

UPDATE...

No changes to the overnight forecast.

AVIATION(00Z TAFS)...

A very strong low level jet will pull away to the east very
quickly this evening. Until then, it will result in low level wind
shear through about 06z with 2000ft winds blowing 55-60kts from
the southwest early this evening. Those winds will gradually
subside through the evening. Otherwise, look for VFR conditions
through most of the TAF period. A couple of exceptions. We could
see some light fog around sunrise that could bring some MVFR VSBYS
for a few hours. Then after 00z Sunday, a wall of MVFR/IFR CIGS
will be pushing north into the Great Lakes region. Timing is a big
sketchy right now, but we should turn IFR quickly Saturday night.

PREV DISCUSSION... (Issued 303 PM CST Fri Jan 19 2018)

DISCUSSION...

Tonight and Saturday - Confidence...Medium
Surface low and 500 millibar energy passes to our north this
period. A frontal boundary sags into the area and then essentially
washes out. Overall the surface pressure pattern becomes rather
diffuse. This much less wind on Saturday. Temps remain mild.

Sunday - Confidence...Medium
Warm front starts setting up to our south with some 850 waa taking
hold. Stratus likely to evolve and could set the stage for at
least a brief window for some freezing drizzle Sunday morning.
Models expand the 0.01 qpf across the area most likely reflective
of an expansive area of stratus/fog and possibly some drizzle.
Should see temps modify above freezing as the morning wears along
to reduce the threat of the FZDZ.

Sunday night through Tuesday - Confidence...Medium
Forecast focus continues to be on the low pressure system moving
northeast into the Great Lakes this period. Still looking like a
warm system for us here. The ECMWF is the furthest south solution
and thus the coldest for us. Meanwhile the GEM and GFS continue
to show a solidly warm solution. For now will stay the course on
the warm idea for the bulk of this system. Do think we need to
keep an eye on our northern counties for Sunday night as a
lingering critical thermal field may result in some mixed precip
there for a time. This is most noticeable on the ECMWF and NAM.
Once the cold air sweeps in Monday night there will be a changeover
to snow cwa-wide but accums look to be in the light side.

Wednesday through Friday - Confidence...Medium
Colder air lingers into Wednesday with cold advection in the wake
of the departed low setting up a low level thermal trough. The
high shifts east for Thursday and Friday setting up a return waa
regime. At this time the bulk any waa forcing remains to our
north per GFS/ECMWF with the GEM being the outlier at this point.
All models show an overall mild return flow setting up Thursday
and especially for Friday.

AVIATION(18Z TAFS)...Main concerns will be LLWS tonight. Mid and
high level moisture continues to stream across the area. Decent
pressure gradient has ramped up the southwest winds. Departing
850 speed max combined with some evening dropoff in winds may
result in some LLWS through about 06z or so. As for any stratus or
fog on Saturday have elected to go with the more VFR looking
approach of the GFS rather than the NAM weighted ceiling
solutions. Think stratus and some fog will eventually become an
issue but banking on that arriving more in the Saturday
night/Sunday timeframe as the storm system and better low level
moisture push arrives.

MARINE...The small craft advisory remains in effect until 09z and
this looks reasonable to account for the lingering pressure
gradient ahead of the approaching frontal boundary.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 3 AM CST Saturday for LMZ643>646.

&&

$$

Update...Davis
Tonight/Saturday and Aviation/Marine...Collar
Saturday Night through Friday...Collar



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