Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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024
FXUS63 KMKX 181737 AAB
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1137 AM CST Thu Jan 18 2018

.UPDATE...

No change to the short term forecast.

&&

.AVIATION(18Z TAFS)...

VFR through the TAF period. Patchy drifting snow is possible
through the afternoon, especially on north-south oriented runways.
West/southwest winds will remain elevated today with gusts to 25
kts.

Look for lighter, but still brisk, southwest winds on Friday with
warming temperatures. Expect mid level clouds as well.

&&

.PREV DISCUSSION... (Issued 936 AM CST Thu Jan 18 2018)

UPDATE...

The forecast is on track. Look for gusty west-southwest winds
through late afternoon. This could cause some slick spots on north
to south oriented roads due to blowing snow, especially in rural
areas.

MARINE...

West wind gusts of 20 to 30 knots will continue into the early
afternoon. A Small Craft Advisory is in effect. Winds diminish a
little this afternoon, so for now will not change the end time of
the Small Craft Advisory.

West winds will remain near Small Craft Advisory criteria through
early Friday morning, and will likely reach Small Craft Advisory
criteria again Friday and Friday night.

PREV DISCUSSION... (Issued 514 AM CST Thu Jan 18 2018)

UPDATE...

Continued brisk west winds with gusts of 225 mph with a few 30
mph gusts. A few snow covered and slick stretches of roadways
(especially rural and secondary north south ones) will continue.
Winds will not be quite as strong, and with the continued
compacting of the snow, drifting snow will not be as big a concern
as yesterday.

AVIATION(12Z TAFS)...

VFR through the TAF period with patchy drifting snow into this
afternoon. West/southwest winds will remain elevated today with
gusts to 25 kts, and a few 30 knot gusts.

A period of altocumulus/high clouds expected today.

PREV DISCUSSION... (Issued 318 AM CST Thu Jan 18 2018)

SHORT TERM...

Today And Tonight...Forecast Confidence Is Medium.

Main concern will be the continued brisk west winds with gusts of
20 to 25 mph. Snow covered and slick stretches of roadways
(especially rural and secondary north south ones) will remain.
Winds will not be as strong, and with the continued compacting of
the snow, drifting snow will not be as big a concern as
yesterday.

A fairly strong mid/upper level shortwave moves across the
northern Great Lakes in the northwest upper flow. Low/mid levels
are dry, so only some high altocumulus and upper level clouds with
this feature expected to pass through today.

After a brief period of weak 850 mb cold air advection with the
shortwave, 850 mb temps will resume warming by tonight.

Friday Through Sunday...Forecast Confidence Is Medium.

Models are in good agreement with warm air advection continuing
Friday, with gusty southwest winds. This should continue to bring
milder temperatures into the area, with upper 30s to around 40
expected at this time. Shallow mixing layer below strong inversion
may limit highs from rising much further.

Models are showing a weak cold front sliding east through the area
Friday night, with weak cold air advection lingering into
Saturday. For now, kept highs on Saturday similar to Friday,
though they may need to be a bit lower if more clouds move into
the area.

500 mb flow that was zonal Friday into Saturday then becomes more
southwesterly Saturday night into Sunday, as the main 500 mb low
pushes into the central high Plains area. Focused warm air
advection develops over the area Saturday night into Sunday, along
with some low level frontogenesis into Sunday with the approach
of the warm front from the south.

NAM/GFS forecast soundings are showing potential for light
freezing rain for a time later Saturday night into Sunday morning.
There are no ice crystals present, with a saturated low level area
with temperatures at or below freezing. Thus, added light freezing
rain chances for this period, generally shifting from south to
north across the area.

Chances for rain would then take hold for Sunday, as temperatures
continue to warm above freezing, and the air column slowly
saturates further aloft. This may take some time to saturate
through a deep layer, so there may be some drizzle as well during
this time.

LONG TERM...

Sunday Night Through Wednesday...Forecast Confidence Is Medium.

There is less certainty than yesterday at this time with respect
to the low track for Monday into Monday night across the region.
The models all differ with timing and placement of the low during
this time. The GFS is about 6 to 12 hours quicker and is much
further north than in past runs. It takes the deepening surface
low from south central Iowa across the central Upper Peninsula of
Michigan Sunday night and Monday.

The Canadian model takes a similar track to the GFS, but is
slower and a bit further south. The ECMWF is the furthest south,
taking the low northeast across southern Wisconsin Monday. All of
these are accompanied by a fairly deep 500 mb low, which takes on
a somewhat negatively tilted look as it crosses the region on
Monday.

All of these tracks, despite their differences, would bring the
warm sector into the area Sunday night and into Monday. This would
bring rain to the area, and kept the high PoPs for this period.
There would be a transition back to light snow later Monday into
Monday night, as the colder air shifts into the area after the low
passage.

At this time, it does not look to be much of a snow producer for
southern Wisconsin. This would change if later model runs shift
the low track further south into Illinois. Uncertainty lingers
here, so stay tuned as the forecast gets closer to this time
period. Cooler and perhaps drier conditions may move into the
area after the low moves away Tuesday into Wednesday.

AVIATION(09Z TAFS)...

VFR through the TAF period with patchy drifting snow into this
afternoon. Winds will remain elevated overnight, with low-level
wind shear ending by mid morning.

A period of altocumulus/high clouds expected today.

MARINE...

West wind gusts of 25 to 30 knots will continue this morning and
into the early afternoon. A Small Craft Advisory continues into
this afternoon. Winds diminish a little this afternoon, so for now
will not change the end time of the Small Craft Advisory.

West winds will remain near Small Craft Advisory criteria through
early Friday morning, and will likely reach Small Craft Advisory
criteria again Friday and Friday night.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 3 PM CST this afternoon for
     LMZ643>646.

&&

$$

Update...Cronce
Today/Tonight and Aviation/Marine...Hentz
Friday THROUGH Wednesday...Wood



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