Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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764
FXUS63 KMKX 211048
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
448 AM CST Wed Feb 21 2018

.UPDATE...

Main issue is with river flooding. The faster response rivers are
falling, but the slower response ones still rising. Several
rivers in Moderate flood.

other issue is remaining standing roads in low areas, along with
freezing of the water with the colder temperatures.

&&

.AVIATION(12Z TAFS)...

Few pockets of MVFR cigs should continue to scatter out. High
clouds should remain. Mid clouds increase again late tonight with
a small chance of light snow toward sunrise Thursday, mainly west
of madison.

&&

.PREV DISCUSSION... (Issued 230 AM CST Wed Feb 21 2018)

DISCUSSION...

Today and Tonight...Forecast Confidence is Medium...

Main issue is with river flooding. The faster response rivers are
falling, but the slower response ones still rising. Several
rivers in Moderate flood.

other issue is remaining standing roads in low areas, along with
freezing of the water with the colder temperatures.

Southern Wisconsin will remain in the right entrance region of a
strong 190 knot 250 mb jet. This results in continued upper
divergence. As a result expect high clouds to be slow to decrease
after the stratocumulus clouds move off with drier low level air.

700 mb upward motion increases tonight, and the mid levels
saturate again. Low levels remain dry, but some very light snow
may reach the ground over south central Wisconsin toward sunrise
Thursday.

Thursday - Confidence...Medium
Initially dominant low level anticyclonic flow gives way to more
of a warm air advection pattern. Progs suggest some light snow
potential across mainly the western cwa. Bufkit soundings show a
much slower erosion of the dry air in the east with better
top/down saturation progression in the west. So will have some
what higher pops there.

Thursday night and Friday - Confidence...Medium
Precip type gets tricky Thursday night as warm layer evolves with
shallow cold air lingering. So have a potpourri of weather types
this period. Less of a warm May see some concerns as it relates
to ice accumulation so may eventually need a headline overnight
and possibly into early Friday morning. The lower level thermal
field modifies during Friday morning so any lingering mixed precip
would become light rain. Overall this is not a strong system with
a ton of moisture with it, but enough forcing and lift combined
with a potentially borderline thermal profile to make for some
slick roads.

Friday night through Saturday night - Confidence...Low to Medium
Surface ridging is expected to linger but there is disagreement
between the GEM and GFS. The ECMWF is old data but sided with the
longer lasting influence of the ridging deep into Friday night and
even into Saturday morning. Meanwhile the GFS is quicker to
spread precip into the area late Friday night and Saturday
morning. Initially the thermal profile supports a period of light
snow then a mix and eventually rain. The GFS is the warmest
solution on this system while the older ECMWF is a compromise
with the more southeast and colder track of the GEM. So pretty
good confidence of higher pops with still some uncertainty out
there on precip type. However consensus of the older ECMWF and
current GFS would suggest more rain with some snow on the back
side. However best shot at any appreciable snow would be well
north.

Sunday through Tuesday - Confidence...Low to Medium
Overall this looks like a quiet period. The GFS is a bit more
robust on the cold advection Sunday into Sunday night. Another
trough/front approaches Tuesday with some rain or a mix arriving
later in the day or into Tuesday night.

AVIATION(09Z TAFS)...MVFR conditions should improve to VFR during
the morning hours. High clouds should remain. Mid clouds increase
again late tonight with a small chance of light snow toward sunrise
Thursday, mainly west of madison.

MARINE...Northwest to north winds will approach small craft advisory
levels this morning. High pressure will then build in this
afternoon and evening with light northeast winds.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

Update...Hentz
Today/Tonight and Aviation/Marine...Hentz
Thursday THROUGH Tuesday...Collar



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