Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 250354
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1054 PM CDT Fri May 24 2019

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Saturday
Issued at 242 PM CDT Fri May 24 2019

Several rounds of showers, and isolated thunderstorms, are
expected late this afternoon and overnight from isentropic lift
north of a warm front surging north through the western Great
Lakes region. Model soundings show the instability to be elevated,
around 1000 J/kg, which could produce some large hail. However
given the steep inversion damaging winds are not anticipated but
wake low winds are not out of the question given the recent
propensity of these types of events.

A cold front will then end the showers later tonight as it moves
into Wisconsin. However the front will stall from central to
northeast Wisconsin before tracking through the rest of the area
Saturday afternoon. Although the previous forecast was dry
Saturday afternoon, there are some hints that there could be
isolated activity along the cold front as it tracks through the
region. Model soundings show a decent amount of bulk shear, on the
order of 50 to 60 knots with the shear being speed and not much
directional shear, as well as MUCAPE values around 1000 J/kg.
This could produce some wind damage if strong storms can develop
Saturday afternoon. Given the front itself is not very dynamic the
chance for this activity will be rather low, therefore will go
with slight chance POPs with the thought that most areas will
likely remain dry. Mostly sunny skies ahead of the cold front
should allow many areas to reach or exceed 80 degrees for the
first time of the year across east-central and northeast Wisconsin
during the afternoon hours.

.LONG TERM...Saturday Night Through Friday
Issued at 242 PM CDT Fri May 24 2019

Focus for the long term will be chances for showers and storms,
chances for severe weather, and if heavy rain potential which
could aggravate flooding concerns.

Saturday night...a few showers or storms will be possible
along/ahead of the cold front during the evening hours across
eastern WI. If storms are around, MUCAPE of 500-1000 J/kg and
bulk shear of up to 50 kts would support a strong storm or two.
But as the evening progresses, instability will wane and the front
will exit the area, ending the shower/storm threat. The rest of
the night is looking dry with weak subsidence and slightly drier
air spreading into the region. Skies look to be mostly clear to
partly cloudy. Most spots will drop into the 40s to around 50, but
would not be surprised to see a few upper 30s in the typical cold
spots across north central WI if skies clear out.

Sunday and Sunday night...a dry day is expected as weak high
pressure slides across the region. A few daytime cumulus clouds
will be possible, along with some mid-high level clouds. It will
be cooler for locations that were ahead of the front on Saturday,
but near or possibly even a couple degrees warmer for locations
across the Northwoods, even as cold air advection will drop 850mb
temps by 5C to 8C and winds will have a more easterly component.
Flow off the chilly bay and lake will bring a significant drop in
temps near Lake Michigan. The dry weather will continue into
Sunday night as the high pressure system drifts east of the
region, but return flow will begin across the Plains and western
Great Lakes which will spread thicker clouds into the area.

Memorial Day...low pressure will eject into the Plains as a warm
front pushes north into southern WI. A large area of showers and
embedded storms is expected to spread across the area through the
day as frontogenetic ascent, approaching shortwave, and a wide
open Gulf provide ample lift and moisture. The rain will be
locally heavy with PWATs between 1.0" and 1.5". Minor urban,
rural, and river flooding will be possible. Prospects for severe
weather remain low as widespread clouds and the warm sector stays
just to our south. Some elevated instability will allow for the
chance for storms. Winds of 40-50 kts are forecast to be between
4000-5000 ft, so if any mixing can occur, gusty winds will be
possible.

Rest of the forecast...models show the warm front making it
northern WI on Tuesday, but confidence on just how far it can
advance is still in question. The front will be close enough to
keep chance POPs in the forecast both Tuesday and Wednesday, with
likely POPs at times as one or two periods of rain/storms look
likely, but just when and where the highest chances end up is
still up in the air. Right now, models focusing on the Tuesday
night period as the best chance, as another trough swings across
the region. Additional heavy rain is possible. Temps will also be
tricky to pin down as clouds, rain, and if/when we will get into
the warm sector remain in question. The end of next week looks a
little quieter, but weak systems in the northwest/west flow will
bring a smaller chances for additional shower and storm activity.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1054 PM CDT Fri May 24 2019

Conditions will deteriorate to solid IFR overnight as
shower/thunderstorm coverage increases near an approaching warm
front. Some LLWS is also possible near and just ahead of the warm
front. Skies will then begin to clear Saturday morning with VFR
conditions and gusty west winds as a cold front sweeps in from the
west. There could be a broken mid ceiling and possibly a few
scattered showers/isolated thunderstorms late morning into early
afternoon. Confidence in this is low at this time, so left this
out of the TAF with this issuance. VFR conditions can then be
expected for Saturday night.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....Kurimski
LONG TERM......Bersch
AVIATION.......Cooley



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