580
FXUS63 KGRB 070327
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1027 PM CDT Tue May 6 2025

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Minimal chances for rainfall the next week. Highest chances
  (less than 20 percent) are Friday night and next Tuesday.

- Low temperatures in the lower to middle 30s Wednesday night and
  Thursday night. Frost advisories may be needed for portions of
  central, northeast and east-central WI where the frost/freeze
  program has started for the season.

- Low relative humidity this afternoon and again Thursday through
  Saturday away from Lake Michigan and the Bay of Green Bay.
  Strongest winds this week will be on Wednesday, but RH values
  will be slightly higher. Watching Sunday into early next week
  for next potential of near critical fire weather due to low RH
  values, gusty south to southwest winds and temperatures warming
  to around 80 inland from Lake Michigan.

&&

.DISCUSSION...
Issued at 222 PM CDT Tue May 6 2025

Dry weather prevails through early next week with a couple of
minor exceptions. Temps and fire weather will be the primary
concerns.

Upper level low bringing rain as close as lower Michigan this
afternoon shifts east through Wednesday. This is in response to
shortwave trough dropping through in northwest flow over the
central Great Lakes. This feature will push a backdoor cold front
north to south across the area late tonight, leading to breezy
and cooler conditions on Wednesday. It earlier looked like there
could be sprinkles as the front moved through on Wednesday, but
soundings look awfully dry and models have trended that way as
well. Ridging brings dry weather late this week, then another
weak and moisture starved cold front could bring a few showers
on Friday night.

The next very small chance of rain does not return until next
Tuesday as warmer and slightly more unstable air works its way in
from the plains ahead of low pressure system.

Temperatures: After the early summer-like temperatures occurring
today with some places topping out near 80, readings cool toward
normal Wednesday and Thursday behind the cold front with highs
reaching the upper 50s to mid-upper 60s, warmest over central WI.
Coolest conditions will be with the onshore flow near the bay and
the lake. Couple of chilly nights expected Wednesday night and
Thursday night. NBM probabilities of lows <35F are over 60% on
Wednesday night, highest in the north where frost/freeze program
has not started yet. On Thursday night though, the higher probabilities
of lows < 35F (50-75%) impact more of the area. So long as winds
are light, could see either or both of these nights having the
potential for frost advisory headlines.

Warming back above normal Friday and Saturday, then another surge
of early summer-like warmth returns with highs upper 70s to lower
80s Sunday through Tuesday, though it will be locally cooler by
the lake where winds will be more sse versus ssw.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1021 PM CDT Tue May 6 2025

Patchy mid-level clouds were observed across the forecast area
late this evening, and a cold front was dropping south through
northern WI.

A back door cold front will continue to move through the forecast
area early in the new TAF period. SCT-BKN cloud cover is expected
later tonight into Wednesday morning, followed by a clearing
trend from north to south during the afternoon. While most
locations will remain VFR, it is possible that MVFR ceilings may
impact the far north (near the U.P. border) early in the day.

N-NE winds will pick up after the cold front passes through
overnight, with blustery conditions expected during the day on
Wednesday. The winds should be strongest in the Fox Valley and
lakeshore areas, where gusts to 20 to 25 kts are likely.

&&

.FIRE WEATHER...
Issued at 222 PM CDT Tue May 6 2025

Minimal rainfall and fuels approaching critical levels will keep
fire weather as the primary issue through at least early next
week. Very low RH values this afternoon down to as low as 15-20
percent over northern WI will moderate into the 30-35 percent
range on Wednesday in wake of a cold front. Increased winds/gusts
a bit, but if these end up even higher, then we would be into
elevated conditions even with the higher RH values. Thursday
through Saturday will be similar to today, with light winds but
lower RH values. Attention then turns to Sunday and into early
next week as increasing south-southwest winds and warming temps
will combine with dry conditions and low RH values to lead to
potentially near critical fire weather conditions.

&&

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

&&

$$

DISCUSSION.....JLA
AVIATION.......Kieckbusch
FIRE WEATHER...JLA