755
FXUS63 KGRB 270801
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
301 AM CDT Mon May 27 2024

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- There will be additional rounds of showers and a few
  thunderstorms across the region today through Tuesday. Severe
  weather is not anticipated.

- A few rivers across central and eastern Wisconsin are expected
  to surpass minor flood stage early this week.

- Areas of patchy frost are possible Wednesday night into early
  Thursday morning across far northern Wisconsin.

&&

.DISCUSSION...
Issued at 301 AM CDT Mon May 27 2024

Short Term...Today...Tonight...and Tuesday

A low pressure system, seen spinning just off the coast of
Manitowoc on satellite and and radar imagery, will continue to
slowly move east towards lower Michigan this morning. Since the
low is moving slowly, rain showers will continue through much of
the morning across northeast Wisconsin and the lakeshore counties.
Additional rainfall amounts across this area could reach one half
up to an inch this morning, with the highest amounts across Door
County where rain will linger the longest. This additional
rainfall may cause localized flooding; however, the rain is more
light to moderate versus heavy which should help mitigate flash
flooding.

Meanwhile, a weak shortwave will track through the upper
Mississippi Valley this afternoon around a larger upper low
situated across southern Canada. This will bring the chance for
showers and a few thunderstorms to much of the area this afternoon
and this evening. MUCAPEs of only a few hundred J/kg will mean
non-severe thunderstorms are expected with this activity.

A more substantial mid level positively tilted trough and vigorous
shortwave will approach northern Minnesota late tonight and slowly
dig across the western Great Lakes region on Tuesday as it spins
off from the main low. This will bring the chance for showers
across north-central Wisconsin late tonight and across the rest
of the region on Tuesday. Modest MUCAPEs of a few hundred J/kg
will once again mean non-severe thunderstorms will be possible as
this trough tracks through the area.

Abundant cloud cover will keep temperatures below normal today,
with highs mainly in the 60s. Lows tonight are expected to range
from the upper 40s across the north to the lower 50s across
east-central Wisconsin. Highs on Tuesday will once again be cool
given the abundant cloud cover and rain expected during the day,
with temperatures ranging from around 60 across the north to the
middle 60s across east-central Wisconsin.

Long Term...Tuesday Night Through Sunday

An upper ridge is forecast to move from the northern Plains into
the Great Lakes region during the Wednesday-Friday time frame and
provide for a much needed break from the rain. This ridge shifts
east and weakens, allowing for a return of gulf moisture and an
eastward moving shortwave trough to move into WI with our next
chance for showers Friday night through Saturday night.
Temperatures will continue below normal through mid-week, then
become closer to normal late week.

Tuesday night and Wednesday...
Light showers look to carry over into Tuesday evening, mainly over
central/east-central WI as the shortwave trough to still be in the
process of exiting the area. High pressure stretching from western
Ontario through the Upper MS Valley will begin to build into WI
later Tuesday night bringing a decrease in clouds. Min
temperatures to range from the middle to upper 30s north-central
WI, to the middle to upper 40s over east-central WI. Perhaps a
little patchy frost over the colder locations of the Northwoods.
This ridge of high pressure moves into the western Great Lakes on
Wednesday and should bring mostly sunny skies and a north wind at
5 to 10 mph. Air mass aloft is still a bit on the cool side (8H
temperatures around +5C), thus expect max temperatures to be in
the lower 60s near Lake MI, middle 60s to around 70 degrees
inland.

Wednesday night and Thursday...
Models hardly move this high pressure through Wednesday night. The
combination of cool air aloft, a dry air mass in place and light
winds will allow temperatures to quickly fall through the night.
Parts of northern WI could see min temperatures in the lower to
middle 30s and the possibility of frost developing. Central and
east-central WI are expected to stay frost-free with temperatures
falling into the lower to middle 40s. As the high pressure starts
to slowly shift east on Thursday, winds will turn to the south-
southeast by the afternoon and begin to tap slightly warmer air. A
dry air mass overhead will help temperatures recover despite the
cool start to the day. Look for max temperatures in the middle 60s
near Lake MI, mainly lower to middle 70s inland.

Thursday night and Friday...
The high pressure moves toward the eastern Great Lakes by Friday,
while an upper ridge moves into the western Great Lakes. Even with
a push of WAA, the air mass over northeast WI remains too dry to
support any precipitation, thus dry conditions should continue
through Friday. Do anticipate some increase in clouds by Friday
afternoon between the persistent WAA, a gradual increase in
moisture and a mid-level shortwave trough that will push into the
northern Plains. Max temperatures on Friday to be in the upper 60s
near Lake MI, lower to middle 70s north and middle to upper 70s
south.

Friday night and Saturday...
Questions remain as to how soon to bring precipitation chances
back to northeast WI as models continue to disagree on timing/
movement of the shortwave trough, as well as how fast can the
atmosphere saturate. Models tend to underestimate the lingering
dry air and send precipitation too far to the east. That being
said, do expect to see a band of showers move across the Upper MS
Valley into at least western WI Friday night, then sweep across
the rest of WI on Saturday as the shortwave trough arrives and a
weak cold front traverses the area. Max temperatures Saturday to
be in the upper 60s lakeside, around 70 degrees north-central WI
and lower to middle 70s elsewhere.

Saturday night and Sunday...
Uncertainty persists going into the latter part of the weekend as
models differ on the strength of the shortwave trough. A weaker,
progressive trough would exit Saturday night with a dry Sunday. A
stronger, slower moving trough would keep precipitation in the
forecast through Sunday. Have followed the model blend which does
keep a mention of showers on Sunday.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1048 PM CDT Sun May 26 2024

Widespread moderate to locally heavy showers will slowly lift
north through NE WI overnight, and exit by early Monday morning.
Not sure if low clouds will fill in over NC WI overnight, but will
hedge that direction due to guidance trends. Elsewhere, expect
MVFR/IFR ceilings to persist into Monday morning before lifting
to VFR in the early to mid afternoon. A short-wave trough will
bring a chance of showers and storms to mainly the southwest part
of the CWA Monday afternoon and early evening, but confidence is
not high enough to mention storms at any of the TAF sites.

LLWS will occur in parts of the CWA overnight. Gusty surface
winds from the NE will back to the NW late tonight into Monday.

&&

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

&&

$$

DISCUSSION.....Kurimski/Kallas
AVIATION.......Kieckbusch