756
FXUS63 KGRB 300347
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1047 PM CDT Sun Sep 29 2024

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Gusty winds and high waves expected Monday night into Tuesday
  morning and again on Wednesday.

- Well above normal temperatures on Monday. A strong cold front
  will bring windy conditions and much cooler temperatures on
  Tuesday. A frost is likely Tuesday night, mainly across northern
  WI.

- Warmer and windy conditions return on Wednesday, which could
  lead to some elevated fire weather concerns.

&&

.DISCUSSION...
Issued at 256 PM CDT Sun Sep 29 2024

Short Term...Tonight and Monday

Another warm late September afternoon with temperatures in the
middle 70s to lower 80s under sunny skies. Persistent and gusty
northeast winds were continuing along the Lake Michigan shoreline
resulting in an increased risk of rip currents in Kewaunee and
Manitowoc counties.

For tonight, clear skies will prevail with some patchy fog
possible after midnight. Did not stray far from the previous
forecast for lows. The high waves and increased risk of rip
currents will come to an end later this evening.

On Monday, any linger fog should burn off by 9 am. Sunny skies
should prevail with another warm day on tap with highs in the
middle 70s to lower 80s. Southerly winds should be on the
increase with gusts of 15 to 25 mph during the afternoon. The
highest wind gusts will be north and west of the Fox Valley.

Long Term...Monday Night Through Sunday

Drought conditions will worsen this week with widespread
appreciable rain not expected. Only small/brief chances for rain
are expected late Monday into early Tuesday and again late in the
week. Fire weather concerns need to be monitored mid-week as low
relative humidity and gusty winds are expected. Temps return to
near normal on Tuesday, then warm back up mid-week.

Shower/Storm Chances: A dynamic, quick-moving trough and cold
front will swing across the region late Monday into early Tuesday,
bringing a chance (25-40%) for sprinkles/showers, highest across
northern WI. Models continue to really struggle generating
measurable rain, with amounts limited to 0.1" or less, due to the
quick moving nature of this system and lack of deep layer
moisture. A ribbon of mainly elevated instability (MUCAPE up to
~300 J/kg and steep mid-level lapse rates to ~7.5 C/km) could be
enough to produce a storm or two, but continued to keep thunder
out of the forecast. Another small chance (10-15%) for showers
arrives late Thursday into Friday as another quick-moving
trough/front push across the Great Lakes. Any precip looks to be
pretty spotty/light. The lack of any appreciable rain will worsen
the drought conditions.

Winds: South winds will shift to the northwest Monday night into
Tuesday behind the cold front. While mixing will be reduced at
night, still expected gusts to ~20 mph Monday night. Then on
Tuesday, gusts of 20-30 mph are expected as there will be better
mixing after sunrise, but winds aloft start to decrease in the mid
to late morning. The CAA over the relatively warmer waters of the
bay and lake could create hazardous conditions for small craft
overnight into Tuesday morning. Winds turn southwest on Wednesday,
with some 20-35 mph gusts possible as soundings indicating strong
winds aloft (~40 kts at 3000 ft) mixing down, highest across
north central WI. Models have slowed down the arrive of the
stronger winds a little, so gusts may hold off until later in the
day over the south/east.

Temperatures: The stretch of above normal temps come to an end
Tuesday as 850mb temps drop from around 14-15C to 1-4C with the
passage of the cold front. Expect highs holding mainly the 60s,
with some upper 50s possible over far north central WI. Continued
to lean toward the colder guidance for Tuesday night, but some
mid-high clouds will limit how much temps tank. Still think lows
in the 30s will produce some frost across the colder spots of
northern WI, with lows in the low and mid 40s further south/east.
850mb quickly jump back to between 9-13C on Wednesday. While we
probably won`t mix all the way to 850mb, highs look to climb into
the mid 60s to low 70s. Near/above normal temps look to continue
through Saturday.

Fire Weather Concerns: A surge of dry air will arrive behind the
front, with relative humidity values dropping into the upper 20s
and 30s, but fire concerns will likely be held in check due to the
cooler temps. Even drier air with relative humidity values as low
as 20 percent, stronger winds and warmer temps on Wednesday could
led to elevated fire weather concerns, especially with the
extended period of dry weather the area has seen.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1041 PM CDT Sun Sep 29 2024

Clear skies and VFR conditions overnight with only a slight increase
of high clouds on Monday. The only exception to VFR conditions will
be from 08z to 13z Monday with possible patchy ground fog from north-
central to east-central Wisconsin with IFR/MVFR conditions are possible.
Mid clouds will slowly increase from the west on Monday night with small
chances for rain showers, mainly over northern WI.

Winds are expected to veer to the southeast or south on Monday,
with gusts of 15 to 25 knots Monday afternoon. Highest wind gusts
will be across central and north-central Wisconsin.

&&

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

&&

$$

DISCUSSION.....Eckberg/Bersch
AVIATION.......JLA