Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 261409
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
909 AM CDT Thu Apr 26 2018

.UPDATE...
The current forecast is in good shape.

&&

.MARINE...
Look for winds to turn onshore, southeast to south later this
morning as the inland areas warm up. Additionally, an approaching
cold front will help to increase those southerly winds.  This
cold front will pass across the near shore waters this evening
causing winds to turn to the north to northwest. A brief burst of
higher winds are expected with gusts possibly reaching 20-22
knots. An isolated gust may reach 25 knots. However will hold off
on Small Craft Advisory for tonight as wave heights are expected
to remain low and short term guidance in disagreement on strength
of winds behind cold front. There is a better chance for gusts
reaching 25 knots behind a passing low pressure system Friday
night into Saturday morning.

&&

.PREV DISCUSSION... (Issued 609 AM CDT Thu Apr 26 2018)

UPDATE...No changes at this time.

AVIATION(12Z TAFS)...Thin cirrus continues to move south across
Wisconsin ahead of approaching weak cold front over the northern
Plains. Low level cold air advection in wake of front may bring a
period of MVFR clouds to eastern areas later tonight. Otherwise,
VFR conditions expected for the majority of the forecast period.

PREV DISCUSSION... (Issued 337 AM CDT Thu Apr 26 2018)

SHORT TERM...

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

Warmer temperatures will return to southern WI today.  A developing
south to southwest breeze in the low levels ahead of an approaching
cold front will result in 925H temps peaking in the 10 to 12C range.
Daytime temperatures should peak in the mid to upper 60s most
locations. Dry conditions are expected for today due to ridging
ahead of approaching weak system.  However, cirrus ahead of this
system will spread across southern WI, but should remain fairly thin
resulting in the warmer temperatures. A fluctuating lake breeze will
keep lakeshore areas a few degrees cooler, but not nearly as cool as
yesterday. The cold front will pass through southern WI during the
evening. Enough of an increase in low to mid level moisture and
synoptic scale lift as it passes through to warrant lower chances
for showers. Instability remains negligible so wl not include
thunder mention. Short term guidance in good agreement on period of
high rh and weak sloping layer frontogenetical forcing sliding
through with front. The shower threat will be brief with dry
conditions returning after midnight due to short wave ridging ahead
of approaching stronger short wave for Friday.

LONG TERM...

Friday through Saturday... Forecast confidence is Medium.

A mid level shortwave trough will barrel through the Upper Great
Lakes Friday afternoon. Timing of this wave is a little uncertain
between the models, but scattered to numerous rain showers are
expected with this potent system, most likely during the afternoon
hours. The trend of the surface low track has been sliding south
which means more of south central and southeast WI is in the area
targeted for widespread showers. Steep low level lapse rates
could lead to a few rumbles of thunder as well, and temperatures
aloft will be quite cold so there may be some graupel or small
hail mixed in.

Precip will exit by mid evening, but low clouds could hang around
through the night. There might be some light snow toward east
central WI as the precip tapers off. The upper trough will linger
over the Great Lakes through Saturday, so expect a few diurnal
cumulus clouds around, especially toward the lakeshore. More
sunshine inland and no lake influence will allow temps to get into
the mid 50s.

Sunday through Monday... Forecast confidence is Medium.

High pressure and increasing southerly flow for the first half of
next week will usher much warmer air into southern Wisconsin.
Sunday will be dry with highs in the 60s inland from the lake.
There will be weak enough flow to allow for a lake breeze. There
is more uncertainty to Monday`s forecast as the ECMWF introduces
rain with a leading shortwave over WI while the GFS keeps the low
layers drier and therefore has a dry forecast for southern WI. I`m
leaning toward the dry forecast since there will be a lot of dry
air to overcome. If we end up with the drier scenario,
temperatures will be even warmer than the forecast lower 70s.

Tuesday and Beyond... Forecast confidence is Medium.

An approaching low pressure system from the Northern Plains will
bring showers and thunderstorms to the Upper Midwest. Depending on
the speed of this next system, Tuesday may remain dry and very
warm with highs in the mid 70s, but dewpoints will be on the rise. There
is better agreement between the models about precip timing Tue afternoon
into Wednesday.

The next system of interest is a large low ejecting from the
Plains and bringing a lot of moisture into southern WI Wednesday
night into Thursday. This system would bring thunderstorms to the
area.

AVIATION(09Z TAFS)...VFR conditions are expected into this
evening. A light shower is possible from some lower VFR clouds
this evening. The main concern is a burst of low level cold air
advection behind a passing cold front. A brief period of MVFR
clouds may accompany the cold air push in the eastern CWA later
tonight.

MARINE...Light offshore winds early this morning will become
southeast later this morning as the land surface rapidly warms
creating a tight temperature gradient at the shore.  Near shore
winds will become more south to southeast this afternoon ahead of
approaching weak cold front.  This cold front will pass across the
near shore waters this evening causing winds to turn to the north to
northwest.  A brief burst of higher winds are expected with gusts
possibly reaching 20-22 knots.  An isolated gust may reach 25 knots.
 However will hold off on Small Craft Advisory for tonight as wave
heights are expected to remain low and short term guidance in
disagreement on strength of winds behind cold front.  There is a
better chance for gusts reaching 25 knots behind a passing low
pressure system Friday night into Saturday morning.

FIRE WEATHER...Warmer temperatures return today with a
developing south to southwest breeze later this morning and
afternoon.  Breezes will likely reach 12-15 mph as temperatures warm
into the mid to upper 60s away from Lake Michigan. Relative
humidities remain tricky today. Atmosphere ahead of approaching
front looks to remain dry so expect dewpoints to fall into the mid
20s to lower 30s across southern WI as moist soil and remaining
snow pile melt having little recent affect on dewpoints. Hence
expect humidity values to fall into the 20 to 30 percent range
later this morning and afternoon. With Fine Fuel Moisture Code
values expected in the 90-92 range, conditions for wildfire
development will be "elevated".

&&

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

$$

Update...Davis
Today/Tonight and Aviation/Marine...MBK
Friday THROUGH Wednesday...Cronce


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