Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 261144
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
644 AM CDT Tue Mar 26 2024

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Rain continues this morning, then changes over to light snow
  this afternoon/evening. Minor snow accumulations are possible,
  but with little to no impacts.

- Blustery conditions are expected, mainly over eastern Wisconsin
  this morning, then across the entire area tonight into
  Wednesday. Gusts to 30-35 mph, locally higher at times.

- Slight chance for thunderstorms over eastern Wisconsin late
  this morning and early afternoon. If storms develop, gusty winds
  to 45 mph and small hail would be possible.

- Several chances for precip through the weekend into early next
  week. First round of wintry precip likely Friday afternoon
  through Saturday with some snow and freezing rain possible
  across the north. Another wintry mix possible Sunday evening
  into Tuesday, although details are uncertain this far out.

&&

.DISCUSSION...
Issued at 355 AM CDT Tue Mar 26 2024

Short Term...Today...Tonight...and Wednesday

Precip / Thunder Chances / Clouds:

First large area of soaking rain is exiting very early this
morning, with an additional area pushing in from the south/west,
as surface low pressure slides into the western U.P., as we
remain within the warm conveyor belt ahead of the low. As the
rain ends from south to north this morning, some brief breaks in
the overcast are possible, but any breaks will be short-lived and
quick moving. Models still showing modest 200-400 J/kg MUCAPE
across eastern WI later this morning, with mid-level lapse rates
approaching 7.5 C/km. Any breaks in the clouds would allow low-
level to steepen as well. This instability, combined with a weak
shortwave lifting through the area, approaching cold front and
pocket of deeper moisture will produce isolated to scattered
showers from mid-late morning into the afternoon. A few
thunderstorms can`t be ruled out, so will add thunder to much of
eastern WI. Any stronger shower or storm could bring down some of
the stronger winds aloft, up to 45 mph, and some small hail.

As CAA pushes west to east this afternoon behind the advancing
cold front, boundary layer temps will cool sufficiently to switch
the rain over to snow showers. The better moisture and lift will
have exited the region, so only looking for minor snow amounts up
to an inch, highest over north-central WI. As cyclonic flow
prevails tonight into Wednesday, snow showers could linger over
the far north, but accumulations will be very minor. Clouds look
to hang tough for much/all of tonight into Wednesday, with only
partial clearing possible over parts of central and eastern WI.

Winds / Fog / Temps:

Winds were slow to pick up early this morning, with the strongest
winds remaining aloft and/or to our east. This allowed patchy
dense fog to develop across parts of the area late last evening
into the early morning hours. Some fog could linger into the
morning hours, especially over central and north-central WI where
the snowpack is the thickest and where the gradient will be the
weakest the longest (near the low track). Some fog could linger
in/near Lake Michigan and the Bay as well. Any remaining fog
should mix out as winds turn westerly this afternoon.

Stronger winds aloft (~50 kts around 2500 ft) and a tightening
pressure gradient will allow winds across eastern WI to continue
to increase early this morning. HREF still showing high
probabilities (over 80%) of 35+ mph wind gusts from 4-5am through
late morning. A few higher gusts will be possible, mainly confined
to far eastern WI. Winds will shift to the west this
afternoon/evening as the pushes into Lake Superior. Soundings show
gusts to 25-35 mph for most spots, with mixing aided by the
better CAA. Continued CAA and fairly tight pressure gradient will
keep winds gusting tonight into Wednesday, up to around 30 mph.

While precip and clouds will hinder temps climbing this morning, a
warm start to the day across eastern WI (temps only falling in the
upper 40s to around 50) should allow highs to climb into the 50s,
with a 60 not out of the question, especially if we can get a few
breaks in the clouds. Highs in the 40s are expected the further
west you go, closer to the low pressure track and approaching
cold front. Look for morning highs over central and north-central
WI and early afternoon highs in the east as the front progresses
east. CAA continues tonight with lows dropping to between 10-25,
coldest across north-central WI. Wind chills will drop to around
zero late tonight. It will be colder on Wednesday, with highs
ranging from the upper 20s in north-central WI to the 30s to near
40 across eastern WI, with winds chills in the teens and 20s.

Long Term...Wednesday Night Through Monday

The influence of surface high pressure to our south and west
combined with upper-level ridging should keep the forecast area
mostly dry through Friday afternoon. A slightly more active
pattern is then expected to set up this weekend through early next
week as several shortwaves bring chances for precip to the
western Great Lakes. Precip chances are expected to arrive in two
waves: the first Friday afternoon through Saturday and the second
Sunday evening through Tuesday.

Weekend precip chances... A closed low spinning off the west coast
is progged to eject a shallow, transient shortwave across the
central US and through Wisconsin Saturday morning as jet energy
builds into the Midwest. Favorable synoptic setup will result in
the placement of a weak surface low and attendant warm front
across the Wisconsin/Illinois border. Warm air advection precip
will then begin to lift north across Wisconsin Friday afternoon
with some assistance from isentropic ascent ahead of the front.
Dominant precip type should be rain as post-frontal temperatures
warm to the mid 40s across central Wisconsin. However, some snow
or freezing rain mixing in across the north is not out of the
question as winds veer to northerly and colder Canadian air digs
down into the upper Midwest. Models seem to be targeting central
Wisconsin for highest QPF amounts of around 0.25 to 0.3". Deep
Gulf moisture behind the front suggests that QPF values may trend
on the higher end of what current ensemble guidance is showing.

Early week precip chances... Much more uncertainty with early week
precip chances given model disagreement about timing and intensity
of the driving shortwave. Temperature profiles suggest that this
may be a mixed precip event, with rain, snow, and freezing rain
all within the realm of possibility. Pinpointing the transition
from frozen to liquid precip as well as exact amounts/accumulations
is not yet possible with this suite of model runs.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 644 AM CDT Tue Mar 26 2024

Poor flying conditions continue today as low pressure tracks
towards Lake Superior. Look for a large area of rain to push south
to north through the area early this morning, with more isolated
to scattered activity later this morning and afternoon. As a cold
front pushes west to east across the area this afternoon, any rain
shower activity will transition to a rain/snow mix then to all
snow. Snow accumulations look to be minor, highest at RHI. A
thunderstorm can`t be ruled out, mainly across eastern WI, late
this morning and afternoon ahead of the cold front. Confidence
remains too low in this occurring, so continued to exclude
mention of thunder in this TAF package.

Gusty southeast to south winds will veer to the west this
afternoon/evening. Gusts to 20-30 kts are expected, with a few
locally higher gusts possible.

&&

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

&&

$$

DISCUSSION.....Bersch/Goodin
AVIATION.......Bersch


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