Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 140246
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
946 PM CDT Fri Oct 13 2017

.UPDATE...The current batch of rain looks to exit ern WI around
midnight although isolated to sct showers will continue. Another
batch of rain may approach from IL after 08z and affect locations
mainly east and south of Madison through 14z. The HRRR and NAM
show this scenario and it appears to be associated with another
enhancement in the low level jet from ne MO into nrn IL. A stronger
low level jet will then re-develop for Sat aft-eve as
cyclogenesis occurs from IA to Lake Huron. 1-1.5 inches is
expected from the afternoon into the night. How far north the
effective warm front can move into srn WI will likely determine
the eventual severe tstorm threat.


&&

.MARINE...A Gale Watch remains in effect for late Sat nt-Sun aft.
Brisk nwly winds with gale force wind gusts will likely develop in
the wake of low pressure moving newd across central Lake MI. High
waves will develop toward the open waters.


&&

.PREV DISCUSSION... (Issued 711 PM CDT Fri Oct 13 2017)

UPDATE...
The rainfall toward central WI is associated with mid level frontogenesis
while the rain farther south is 925-850 mb frontogenesis. Both
areas of frontogenesis will weaken later this evening but some
rain will likely persist in the south as the low level jet does
not completely veer away from the region. A stronger low level jet
will then re-develop for Sat aft-eve as cyclogenesis occurs from
IA to Lake Huron. 1-1.5 inches is expected from the afternoon into
the night. How far north the effective warm front can move into
srn WI will likely determine the eventual severe tstorm threat.

AVIATION(00Z TAFS)...Periods of rain tnt will eventually result
in the saturation of the low levels with Cigs falling below 1 kft.
The low stratus will then persist for Sat-Sat nt. Overall, vsbys
of 3-5SM BR are forecast but lower vsbys will occur at times in
heavier rain.

PREV DISCUSSION... (Issued 351 PM CDT Fri Oct 13 2017)

DISCUSSION...

Tonight through Sunday...Forecast confidence is medium to high:

Rounds of showers and a few storms are expected this evening
through Saturday night, winding down Sunday morning. A deepening
low pressures system will be moving through with plenty of
moisture to work with, so confidence is high in widespread
rainfall.

The biggest forecast challenge with this system remains the
placement of the warm front and resultant instability. Models are
still not in great agreement with how far north to take the front.
A couple bring it far enough north to bring higher storm chances
into the forecast area...including a severe threat given ample
shear with this system. Other models keep the front and storms
mainly south of the WI/IL border. Temps in the southern half of
the forecast area later Sat into Sat night would be impacted by
the front placement as well.

Showers will exit by mid/late Sunday morning, with decreasing
clouds in the afternoon. High temps will likely be the coolest of
the season thus far and gusty winds will add an extra chill to the
air. Might see some a little frost in spots Sunday night, though
doesn`t look like a widespread event.

Monday through Friday...Forecast confidence is high:

High pressure is expected to bring plenty of sunshine and dry
weather to southern Wisconsin for much of next week. High temps
will likely warm to a few degrees above normal by mid-
week.

AVIATION(21Z TAFS)...

Multiple rounds of showers and a few storms are expected this
afternoon through Saturday. Ceilings will stay in the MVFR range
most places through the evening, with MVFR/IFR likely tonight
into Saturday. Could even see ceilings briefly below 5 kft
tonight/tomorrow. Lower visibilities will be mainly confined to
moderate/heavy rainfall.

MARINE...

Gusty winds are expected later Saturday through Sunday as strong
low pressure moves through the region. Could see a few higher
gusts and waves north of Port Washington tomorrow afternoon and
evening, but the main event should be later Sat night through Sun
afternoon. Have issued a Gale Watch for this period. Winds will
become offshore Saturday night, limiting the highest waves toward
open waters for much of this wind event.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Gale Watch from late Saturday night through Sunday afternoon for
     LMZ643>646.

&&

$$

Update...Gehring
Tonight/Saturday and Aviation/Marine...DDV
Saturday Night through Friday...DDV



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