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000
FXUS63 KGRB 171949
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
249 PM CDT Wed Apr 17 2024

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Showers and a few thunderstorms this afternoon. Stronger showers
  and storms could produce wind gusts over 40 mph. Locally heavy
  rain is possible in any of the stronger thunderstorms.

- Break in rain by late this evening, but more showers return late
  tonight into Thursday, mainly south of highway 29.

- Friday looking windy with westerly winds gusting to 30 to 40
  mph, especially central and southern areas.

&&

.DISCUSSION...
Issued at 249 PM CDT Wed Apr 17 2024

Short Term...Tonight and Thursday

 Radar and water vapor imagery are showing a low pressure system
slowly tracking northeast across northeast WI this afternoon
keeping scattered rain showers across the region. These light to
moderate showers will continue through the rest of this
afternoon. Mesoanalysis shows an area of weak surface CAPE (100-
400 J/kg) and increasing surface to 1.5 km lapse rates of 7-
7.5 C/km across the Fox Valley that may support a few weak
surface based thunderstorms later this afternoon, but severe
weather is not anticipated.

As the aforementioned low pressure system tracks northeast out of
the region this evening expect rain shower activity to come to an
end shortly after sunset. Gusty northwest winds will be possible
this evening on the backside of the low with a few gusts to 25-
35 mph possible, strongest across central WI. A weak ridge moving
across the area overnight should keep conditions dry. Dry air
aloft may lead to some brief clearing early Thursday morning, but
skies are expected to quickly fill back in ahead of a compact mid-
level low developing across the Northern Plains. Low temperatures
tonight are expected to drop into the mid 30s to low 40s region
wide.

Another round of rain is expected to arrive Thursday morning as
the previously mentioned mid-level low and a 100-110kt upper
level jet track into the western Great Lakes. Don`t expect much
in the way of thunderstorms Thursday with almost no instability
and meager mid-level lapse rates. High temperatures Thursday are
expected to reach the low to mid 50s in most location.

Long Term...Thursday Night Through Wednesday

Precipitation...A few showers may clip east-central WI on Thursday
evening. These will be occurring along southern edge of upper
level jet and to the north of weak low pressure wave crossing the
western Ohio Valley. Majority of deeper moisture shifts east
overnight as a leading cold front moves through, taking any lingering
showers out of the area. Upstream is a large deep upper trough
that will be settling east- southeast by Friday morning. Main sfc
low tied to the trough will be well to the north of Lake Superior,
if not to James Bay, so in general ascent for precip over our
area Friday will be limited. May be just enough low-level moisture
and cold air advection for a few rain and snow showers over far
northern WI, though westerly flow will not be favorable for much
precip. Winds veering to northwest Friday night with continued
cold air advection in the deeper trough may result in increasing
snow showers, especially for Vilas County. A touch of late season
snow accumulation could result, though the somewhat higher
probabilities from the NBM of 0.5 inch or more of snow along the
WI/Upper MI border seen overnight have come down some compared to
previous runs. NW flow persists on Saturday and Saturday morning
is when the lowest H85 temps of -8c to -10c are seen into northern
WI. Net result will be continued chance of some light snow
showers Saturday morning along with good deal of lingering clouds,
even away from northern WI.

Otherwise, the weekend will be mainly dry as high pressure slides
across. The next chance for precip looks to arrive late Monday
into Tuesday. Temps look warm enough for just rain this time
around. Still have to nail down details though.

Winds...Westerly winds will increase on Friday due to strong
winds (35 to 45 kts) in the low to mid levels to the south of the
main low pressure system. Soundings show steep low-level lapse
rates, deep mixing will tap into these stronger winds. Good
landing point now is west wind gusts 30-40 mph over especially
central and southern areas. If cloud cover is not as robust on
Friday for these southern areas, could even see a few locations
reaching near advisory level gusts of 45-50 mph. Weakening low-level
lapse rates will allow the winds/gusts to diminish on Friday night.

Temperatures...Following a lead cold front that moves through on
Thursday night, below normal temperatures are expected Friday and
Saturday. The largest departures for high temps will be from central
to north-central WI with readings 7-10 degrees below normal. Departures
will not be as significant from the Fox Valley to the lakeshore.
Temps will then rise to normal or slightly above normal for Sunday
into early next week, with highs mainly in the 50s, though some
readings in the 60s will make an appearance on Monday.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1227 PM CDT Wed Apr 17 2024

Rain showers and LIFR/IFR/MVFR cigs will continue across the
region this afternoon as a low pressure system works it way
across northeast WI. Didn`t not include any thunderstorms at any
of the TAF sites this afternoon, but weak surface instability
could lead to a few rumbles of thunder. Winds have already stared
to pivot around to the southwest across central this morning as
low center moves across the region. Winds will continue to veer
to the west and finely northwest by tonight. Stronger wind gusts
will also be possible late this afternoon and evening on the back
side of the low with a few gusts reaching 25-30 knots. Rain
showers are forecast to come to an end at all TAF sites this
evening with dry conditions expected overnight, however, MVFR
cigs may linger into early Thursday morning before rising to VFR.
Another chance for rain is expected to arrive mid-Thursday
morning, but no thunder is expected at this time.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION.....GK/JLA
AVIATION.......GK