Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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810
FXUS63 KMKX 210858
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
400 AM CDT MON OCT 21 2019

.SHORT TERM...

TODAY AND TONIGHT - Forecast Confidence...Medium to High.

Decided to extend the Dense Fog Advisory until 7 am given
observations and webcams. Models are in good agreement that
conditions should improve around daybreak.

Didn`t change the forecast much for today. Widespread showers and a
few storms will move through this morning into the afternoon.
Dry air and some clearing is expected behind the front this
afternoon. May see an isolated shower or two towards evening, with a
better chance for showers again later evening into tonight as the
main trough axis moves through. Best chance for showers tonight will
be across the northwest half of the forecast area.

Looks like a couple rounds of gusty winds today. Winds just off the
surface will be very strong ahead of the front, with models showing
around 60 knots at about 925-900 mb. Though conditions won`t be very
good for mixing, it won`t take much to get some higher gusts to the
surface. Showers/storms may help this process as well. Overall
confidence isn`t high in the stronger winds due to the generally
poor mixing, so boosted winds but held off on an advisory for now.
The northeast half of the forecast area has the best chance to
impacted by these winds late morning into early afternoon.

The next round of winds will be behind the front with better mixing
during the mid to late afternoon. Gust potential will be lower with
the strongest winds aloft moving east, but soundings suggest 30 to
35 knots given enough mixing.

Kept the timing and placement of the Lakeshore Flood Advisory. If
anything, confidence has increased in the need for the advisory
given a bump up in forecast winds and waves for today.

Temps today will be stuck in the 50s while the rain is around, but
will have a window of time to rise into the 60s with the clearing
behind the occluded front. Didn`t go quite as high as MOS given the
relative short time to warm up, but low 60s shouldn`t be difficult
to reach. Wouldn`t be surprised by a reading or two in the mid-60s.

TUESDAY THROUGH WEDNESDAY - Forecast Confidence...Medium to
High.

A windy, raw day is expected on Tuesday as deep, cut-off low
pressure moves from northern WI across Lake Superior.  An associated
tight pressure gradient will result in gusty west to southwest winds
with gusts to around 40 mph at times.  Despite the expected cloud
cover, boundary layer mixing to 2K feet will tap into the strong
wind gusts just off the surface.  At this point, thinking gusts will
remain just below Wind Advisory criteria.  However a few gusts may
reach criteria associated with scattered showers that will be moving
through during the day.  These may produce gusts to 40 kts. With the
freezing level only 1.5-2K feet off the ground, may be some snow
pellets mixed in with the heavier rain showers.  High temps on
Tuesday may fail to crack 50F.

The deep low continues to pull away from the area later Tuesday and
Tuesday night allowing the showers to end, along with diminishing
winds.   Chilly conditions will continue through Wednesday.  Breezy
WNW steering winds will usher another weak area of synoptic and
isentropic lift into the area later Wednesday.  Low level
thermodynamic profiles favor liquid Wednesday afternoon, however the
trend has been cooling/downward.  There is a better chance for a
light mix Wednesday evening, but wl hold off on mentioning for now
due to uncertainty.

.LONG TERM...

WEDNESDAY NIGHT THROUGH SUNDAY - Forecast Confidence...Medium to
Low.

A weak mid-level short wave trof and isentropic lift may bring a
period of light rain to southern WI Wednesday evening.  The latest
NAM and GFS are showing slightly cooler low levels, with the
freezing level only about 2K feet off the surface in the northwest
CWA during the evening.  If this trend continues, wl need to add a
mixture into portions of the area Wed eve. The weak lift moves to
the east later in the night ending the light precip threat. Medium
range guidance coming into better agreement on short wave trof
passing to the east of the area on Thu with dry but cool WNW
steering winds settling in. Meanwhile, surface frontal boundary and
inverted surface trof to set up well to the southeast of the area
along with light precipitation. Hence after Wednesday evening,
expecting dry weather into Saturday. Then large discontinuity shows
up for the later periods as ECMWF and GEM showing cut-off low
pressure in the southern Plains moving northeast into the western
Great Lakes Saturday night and Sunday. Meanwhile, the GFS never cuts
off low pressure in the southern Plains and remains with a more
progressive, open trof, and resultant dry conditions over WI.  A few
of the GFS ensembles are showing the cut off low in the area later
in the weekend, and WPC is going with a blend of all the extended
guidance including ECMWF ensembles. For now can not discount small
chances for showers over the weekend, but wl confine chance to
Saturday night.  Temps will be on the upswing over the weekend, but
if the rain threat increases for Sunday, then cooler temps can be
expected.

&&

.AVIATION(09Z TAF UPDATE)...

Fog and low clouds towards Lake Michigan will improve this morning.
Showers and a few storms will then move through southern Wisconsin
this morning into the afternoon, drying out southwest to northeast
by late afternoon. A better chance for showers will return later
evening into tonight, particularly across the northwest half of the
forecast area.

Lower clouds will move through with the showers today, with ceilings
likely returning to VFR behind the front this afternoon as the rain
moves on. Low ceilings will return late evening and overnight as the
trough axis and precip move into the area.

Winds will pick up this morning, with strong winds likely late
morning and afternoon. Breezy conditions will continue tonight. On
the fence with whether to keep low level wind shear in TAFs for
today. Though winds will be strong aloft, they will also be picking
up at the surface.

&&

.MARINE...

Extended the Dense Fog Advisory until 7 am due to latest
observations and webcams in eastern Wisconsin. Conditions should
improve towards daybreak.

A deepening strong low will track from Iowa this morning to Lake
Superior by Tuesday afternoon. The intense low will continue to
track northeast into Canada later Tuesday into Tuesday night.

Southeast winds will pick up today ahead of low...reaching gale
force levels by mid morning. Winds will veer to the southwest later
this afternoon and early evening as a front pushes through.
There may be a brief decrease in winds after the frontal passage,
but gale force winds are expected from later Monday night through
Tuesday night, veering to the west later Tuesday afternoon. Winds
will be a little lighter Wednesday, but will remain gusty and out of
the west.

Decided to start the Gale Warning for the nearshore waters this
morning given increasing confidence in higher winds today.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...

WI...Dense Fog Advisory until 7 AM CDT this morning for WIZ052-060-
     066-071-072.

     Lakeshore Flood Advisory from 10 AM this morning to 10 PM CDT
     this evening for WIZ052-060-066.

LM...Gale Warning from 9 AM this morning to 1 AM CDT Wednesday for
     LMZ080-261-362-364-366-563-565-567-643>646-669-671-673-675-
     777-779-868-870-872-874-876-878.

     Dense Fog Advisory until 7 AM CDT this morning for LMZ643>646.

$$

TODAY AND TONIGHT/AVIATION/MARINE...DDV
TUESDAY THROUGH SUNDAY...MBK



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