Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 170921
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
421 AM CDT Wed Jul 17 2019

.SHORT TERM...

Today And Tonight...Forecast Confidence Is High.

This morning should be mostly dry to start with clouds pushing
out. This should allow us to warm up to the mid to upper 80s
during the day. There will be a slight chance for a few weak
storms to develop in the afternoon along the lake breeze, but
generally it should remain dry during this period.

Into the evening and especially the overnight period we will
likely see some storms, with a few possibly becoming severe.
However, the timing and available CAPE may limit this risk
somewhat. During this period, storms will develop along the warm
front being aided by strong WAA from the fairly strong LLJ just
off to the west. Storms will move east/southeast across
southwestern Wisconsin with 2000-3000 J/kg of MUCAPE and upwards
of 40 kts of 0-6 km bulk shear. This would be enough for a few
severe storms with hail and wind the main threats.

In addition to the severe threat, there will be concerns for
training convection and thus some flooding, primarily across
southwest Wisconsin. While there remains uncertainty with this
system, PWATs look to be around 2 inches, with storms likely to
propagate southwest along the warm front. CAMs seem to support
the idea of training storms, though the better flooding potential
will be further west, given the better timing for storms pushing
through.

Thursday Through Friday Night...Forecast Confidence Is High.

Enough confidence with temperatures and heat index values from
midday Thursday through Friday evening to issue a Heat Advisory
for the entire forecast area.

There is still some uncertainty with how long any clouds will
linger from the exiting convection Thursday morning. However, it
won`t take much sun to quickly warm up temperatures, even if it
does not occur until midday. So, felt confident enough to issue
the Heat Advisory starting at noon CDT Thursday.

925 mb temperatures from models, as well as looking at model
certainty trends, suggest highs in the lower 90s for Thursday, and
middle to upper 90s for Friday. Gusty southwest winds are expected
each day, which may lower dew points a little from currently
forecast. However, still expect heat index values to reach 100 to
106 Thursday afternoon, and 103 to 110 Friday afternoon. Given
these values, Friday will have the bigger impact. Record highs at
Milwaukee and Madison may be reached on Friday. Record high
minimums may be reached as well.

Mainly small chances for showers and storms remain Thursday
afternoon and night, as the low level jet remains pointed into the
area. Anything that develops would be elevated, and there is
decent elevated CAPE with decent deep layer bulk shear. SPC
marginal risk lingers Thursday afternoon into Thursday night, and
again mainly Friday night across the area. Friday night may see
showers and storms approach from the northwest, as a cold front
moves toward the area. Area may be capped, so some uncertainty on
how widespread any showers and storms will be Friday night.

.LONG TERM...

Saturday Through Sunday...Forecast Confidence Is Low.

A fair amount of uncertainty lingers for this period. The models
are having a tough time finding agreement on trends. Generally
speaking, the cold front may stall over or near the area Saturday
into Saturday night, before a low pressure system moves across
southern Wisconsin or northern Illinois Sunday. The timing and
placement of these features remains in flux, so will maintain
blended model PoPs and temperatures for now.

This uncertainty also leads to less confidence with heat concerns
for Saturday, as clouds and possible convection may limit highs
quite a bit. Lowered highs a little for now, which keeps heat
index values remaining in the middle to upper 90s. Cooler highs in
the 80s for Sunday with the passing low and precipitation look
reasonable.

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

Models are in decent agreement with showing cold air advection
later Sunday into Sunday night/Monday, which should bring back
more seasonable temperatures to the region. High pressure should
then bring quiet weather for the first part of next week.

&&

.AVIATION(09Z TAF UPDATES)...

There may be some patchy fog this morning, though VSBYS are not
expected to be impacted much. VFR conditions are expected
throughout the day today, with light and variable winds this
morning turning southerly by the afternoon. Into the evening and
overnight hours storms are expected to push in from the west,
bringing potential for temporary VSBY restrictions and some lower
clouds. The best chances for stronger storms will be further west.

&&

.MARINE...

Dense Fog Advisory remains in effect over the lake, with some
dense fog expected to persist through much of the morning hours
before dissipating. Winds will remain fairly light and variable
throughout the day, with winds turning to the south by the
afternoon and strengthening a bit, especially in the northern
half of the lake where gusts could reach 20-25 kts. Otherwise,
showers/storms are expected primarily across the southern half of
the lake by the early morning hours on Thursday, possibly
bringing some stronger gusts.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Heat Advisory from noon Thursday to 11 PM CDT Friday for WIZ046-
     047-051-052-056>060-062>072.

LM...Dense Fog Advisory until 1 PM CDT this afternoon for LMZ080-261-
     362-364-366-563-565-567-643>646-669-671-673-675-777-779-868-
     870-872-874-876-878.

&&

$$

Today/Tonight and Aviation/Marine...ARK
Thursday through Tuesday...Wood


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