Oshkosh, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

042
FXUS63 KGRB 160350 AAA
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1050 PM CDT Thu May 15 2025

.KEY MESSAGES...

- Gusty southwest winds are expected Friday, with highest gusts
  up to 40 mph in the Fox Valley.

- Another period of showers and thunderstorms are expected
  Friday afternoon. Damaging wind gusts may be possible with any
  stronger storm.

&&

.DISCUSSION...

UPDATE...Issued at 936 PM CDT Thu May 15 2025

The line of storms just exited northeast WI. Scattered showers
with a few lightning strikes are still ongoing over north
central WI due to continued vorticity advection with the
spinning closed low that is now over eastern North Dakota.

The southwest winds are gusty upstream with that lobe of
vorticity pushing into central WI, which is due to momentum
transfer. It looks like winds will taper off through the
overnight hours with weaker mixing. But as soon as the sun
rises, expect the gusty winds to kick in once again.

Previous Discussion...Issued at 304 PM CDT Thu May 15 2025

The Rest of this Afternoon through Friday Night:

A broken line of cellular storms has broken out, currently from
Eau Claire down to Madison WI. This is line is expected to
develop further and ramp up in intensity this evening. Hail and
gusty winds are expected, owing to SBCAPE around 2500 J/kg amid
effective shear around 40 knots. A couple tornadoes also look
possible, given effective SRH values around 200 m2/s2 over much
of NE WI, and an effective warm front parked from the Fox
Valley up through Marathon and Lincoln County. The peak timing
for storms looks to be from 5pm through 8pm this evening as the
broken line moves northeast. A Tornado Watch is out from now
through 10pm over much of our CWA.

Storms will quickly move through and a dry punch aloft will
clear out skies fairly quickly behind the storms. There will be
a bit of a lull overnight, but tomorrow, enhanced mixing will
lead to gusty southwest winds with some scattered gusts to 40
mph. A secondary shortwave pivoting around an upper level low
and lingering moisture will squeeze out some more scattered
thunderstorm activity in the afternoon. Very dry low levels and
the high based nature of the storms will cause the potential for
gusty winds with any storms that get established enough in the
environment.

Saturday through Wednesday

The upper low will linger into Saturday. Cooler conditions are
expected due to clouds and the cooler air aloft and highs will
top out in the low to mid 60. Diurnally driven scattered
showers may occur through the day. This upper low should move
east on Sunday, restoring relative high pressure, but clouds
will likely linger along with cooler temperatures as winds will
come around to northeasterly. By late in the extended period, a
large low pressure system is expected to approach the upper
Midwest Monday into Tuesday, bringing a prolonged period of
showery rain and clouds to the area. Winds will remain
northeasterly off of the lake, keeping our CWA cool with highs
in the 50s.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Updated at 1050 PM CDT Thu May 15 2025

While strong thunderstorms have departed late this evening and a
lull in the weather is expected overnight, expect flight conditions
to deteriorate on Friday as low pressure slowly crosses the region.

South to southwest winds will become strong and gusty by mid to late
Friday morning with gusts of 30 to 35 kts likely.  These gusty winds
will diminish on Friday evening.

Low level wind shear will likely develop across the region late
tonight and continue through Friday morning.

Scattered showers and thunderstorms are forecast to develop on
Friday afternoon.  A few strong storms are possible that could
produce wind gusts in excess of 45 kts.

Ceilings are forecast to fall to MVFR on Friday evening with another
round of showers moving across the region.


&&

.MARINE...
Updated at 936 PM CDT Thu May 15 2025

A small craft advisory continues into tonight. The southeast
winds are switching to southwest. There should be a period of
gusty southwest winds overnight, but lower confidence in them
occurring over the lakeshore vs. inland. Therefore, we will
probably allow the Small craft advy expire. We will need another
small craft advisory for tomorrow as gusty southwesterly winds
are expected to become gusty during the daytime hours.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WI...None.
MARINE...Small Craft Advisory until 1 AM CDT Friday for LMZ522.
     Small Craft Advisory until 11 PM CDT this evening for LMZ542-
     543.

&&

$$

DISCUSSION...MRC
AVIATION...MPC
MARINE...MRC