Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 230442

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1142 PM CDT Mon May 22 2017

.AVIATION(06Z TAFS)...Showers and a few t-storms will continue to
affect western CWA next few hours but should start to abate some
as upper level jetlet rotates farther north into central WI. Low
pressure slowly approaching from the west resulting in diminishing
winds with high low level rh lingering over southern WI. Seeing
some increase in sct-bkn MVFR clouds across southern WI so expect
this trend to continue as low edges closer during the late night
into Tuesday morning.


.PREV DISCUSSION... (Issued 923 PM CDT Mon May 22 2017)

UPDATE...Thunderstorms continue to wax and wane but have mostly
lost some of their punch since the early evening. Low level jet
pivoting off to the east contributed to late afternoon convection.
However lingering weak elevated instability and upper level jetlet
rounding the base of the trof and affecting southern WI may
continue to generate showers and a few storms through the late
night. Diminishing winds and increasing low level convergence wl
likely result in low clouds and patchy fog late tonight into

MARINE...Allowed Small Craft Advisory to expire at 02Z. Winds
still gusty over southern zone from Wind Point to Winthrop Harbor
but have diminished to below 22 knots. Racine Reef currently at 18
mph and decreasing. The winds will continue to diminish overnight
to less than 10 knots. Diminishing winds and high low level rh may
allow areas of fog to develop late tonight into Tuesday. The fog
may become dense for a time on Tuesday.

PREV DISCUSSION... (Issued 619 PM CDT Mon May 22 2017)

AVIATION(00Z TAFS)...Scattered convection has spread across
southern portion of CWA last several hours. Strongest storm
deposited dime size hail in/near Monroe around 23Z. That storm has
since weakened. Thinking convection formed due to earlier weak low
level convergence along instability axis. Some weakening of
convection last 30-45 minutes or so. Will need to continue chance
pops at least through the evening due to lingering instability and
nearby frontal boundary. With diminishing winds and high low level
rh, still expect areas of low clouds to develop later tonight into
Tuesday morning.

PREV DISCUSSION... (Issued 344 PM CDT Mon May 22 2017)


Tonight and Tuesday...Forecast confidence medium.

With skies clearing off in the wake of this initial rain area
some buildup of MLCAPE has occurred to our west in Iowa however
low level convergence noted with wind shift and dew point
discontinuity into SW WI. So expecting further development of
shra/tsra into the evening hours esp in the western portion of the
cwa. Meso models have been pretty consistent with this evolution.
The approach of a 250 millibar jet core on eastern side of trough
will be enhancing upper divergence as well. Any tsra expected to
remain below severe levels with better air (instability wise) to
our west. 500 millibar low will continue to drop south into Iowa
through the end of Tuesday. The surface low will evolve well south
with an inverted trough extending into the area. The 500 millibar
low will keep disturbances pivoting in from the southwest as
overall trough axis remains to our west through the end of the
day. So POPS will be on the higher side this period though some
dry times as well.

Tuesday night through Thursday...Forecast confidence medium.

An upper low will drop south from IA to MO Tue nt with
cyclogenesis over the wrn portion of the Ohio River Valley. PVA
from the upper low and an inverted sfc trough extending into srn
WI will continue the light rain into Tue eve before becoming more
spotty. For Wed, the low pressure area will track to IN or Ohio
and then possibly Lower MI for Wed nt. Thus srn WI will be on the
wrn periphery of the low pressure area with small chances of
showers and continued cool temps. The large low pressure area will
finally shift far enough east on Thu for high pressure to build
into the region for the afternoon and night. Therefore, more
sunshine and warmer temps are expected. 0.30-0.60 inches of rain
is forecast from tnt-Wed.

LONG TERM...Friday through Monday...Forecast confidence medium.

Temps will return to near normal for this period although there is
uncertainty on how much cooling may occur with another large upper
trough that may drop into the Great Lakes. The large upper trough
will bring chances of showers and slight chances of tstorms for
the weekend.

AVIATION(18Z TAFS)...With slowly advancing trough axis expect
coverage of shra/isold tsra to be on the increase tonight. Wind
fields will weaken and with an uptick in low level moisture may
see some fog development tonight. Low pressure will continue to
develop to our south Tuesday with inverted trough axis extending
northward into srn WI. MOS guidance showing MVFR cigs evolving
tonight into Tuesday and some lower cigs possible especially with
onshore flow near the Lake. Unsettled pattern with the slowly
developing low pressure and only gradual eastward movement over
the next couple of days.

MARINE...Gusty southwest winds are expected into the early
evening. Gusts up to 25 knots are anticipated, so a Small Craft
Advisory is in effect from until 9 pm. Highest waves will be
toward the open waters.

Will have to watch any fog trends later tonight into Tuesday as
dew points will be up and overall flow is expected to be weaker.

Brisk northeast winds will probably reach small craft advisory
criteria on Wednesday.




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