Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 191539
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
939 AM CST Fri Jan 19 2018

.UPDATE...No changes planned to forecast at this time.

PC

&&

.MARINE...Small Craft Advisory still looks good. Southwest winds
ramping up.

PC

&&

.PREV DISCUSSION... (Issued 558 AM CST Fri Jan 19 2018)

UPDATE...

Milder air will continue to spread into southern WI on brisk
southwest winds. Some locations could hit 40. High clouds are
expected. We should see a burst of gusts of 25 to 30 mph by
afternoon.

AVIATION(12Z TAFS)...

VFR is expected through the period. Gusty southwest winds 15 to 25
knots today, with LLWS again by evening as surface winds weaken.
Cirrus today.

PREV DISCUSSION... (Issued 326 AM CST Fri Jan 19 2018)

SHORT TERM...

Today And Tonight...Forecast Confidence Is Medium.

Milder air will continue to spread into southern WI on steady
southwest winds. Some locations could hit 40. Mid and high clouds
are expected. We should see a burst of gustier southwest winds by
afternoon into the evening, with the passage of a surface trough
stemming from low pressure crossing southern Ontario.

The upper level flow become more zonal, with a 150 knot 250 mb
jet max moving across the Lake Superior region. This results in
the mid level shortwave and weak 700 mb upward motion. As a
result, expect some high level clouds. Low levels are still dry.

850 mb warm air advection continues today, with weak cooling
tonight behind the Upper Great Lakes shortwave.

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

Weak warm air advection lingers into Saturday, as low clouds move
into the area under the strong inversion. Mild temperatures are
expected to linger, with upper 30s in most areas.

Models then show the warm front approaching the area from the
south Saturday night into Sunday. Subsequent low level
frontogenesis response pushes into the area mainly Sunday
afternoon. There is weak 850 mb convergence in the area Saturday
night into Sunday morning, before warm air advection develops
later in the day.

Thus, the upward vertical motion Saturday night into Sunday
morning is rather weak, before increasing later in the day.
Surface temperatures remain below freezing later Saturday night,
before increasing gradually Sunday morning. Given the relatively
shallow saturation up to around 800 mb, continued mention for
light freezing rain for this period.

Chances for light rain is then forecast for the rest of the day,
as temperatures warm above freezing. Given the weak upward
vertical motion, this may end up being freezing drizzle/drizzle
Saturday night into Sunday.

Warm air advection then becomes more robust Sunday night, with the
closed 500 mb low approaching the region from the southwest. The
area gets into the warm sector airmass with this system, and this
will bring rain to the area. Some fog is expected as well.
Forecast soundings were showing very weak elevated CAPE, but will
not mention thunder at this time.

LONG TERM...

Monday Through Thursday...Forecast Confidence Is Medium.

Models have trended into somewhat better agreement with the
occluding low track across the area Monday into Monday night.
They are generally now taking the low northeastward through
southern and east central Wisconsin. The ECMWF is a bit further to
the south and keeps it in far northern Illinois, with the GFS and
Canadian further north.

Still, the consensus is for the warm sector to remain in the area
into Monday, which will keep the rain going. The colder air then
pushes into the area Monday night and Tuesday. This will bring a
change to snow Monday night before tapering off Tuesday morning.
At this time, is does not appear to bring much in the way of
snowfall.

The deep 500 mb low should depart the region Tuesday, with
northwest flow lingering into the rest of the week. Quiet weather
and more seasonable temperatures are anticipated at this time.

AVIATION(09Z TAFS)...

VFR is expected through the period. LLWS tonight will give way to
a period of gusty winds during the day Friday, with LLWS
increasing again by evening. Surface winds will be from the
southwest, and increase to 15 to 25 knots this afternoon.

MARINE...

Small Craft Advisory is now in effect from 9 AM until late Friday
night, with southwest winds expected to gust to near 30 kt during
the afternoon and evening.

Winds will increase again from the east and southeast, ahead of
an approaching storm system Saturday and Sunday. This will lead
to higher waves across the nearshore waters, and likely Small
Craft Advisories.

&&

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

&&

$$
Today/Tonight and Aviation/Marine...Hentz
Saturday THROUGH Thursday...Wood



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