National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KGRB 161114
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
614 AM CDT Tue Apr 16 2024

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Elevated fire weather conditions will persist today across
  northern Wisconsin due to low relative humidity and increasing
  easterly winds.

- Showers and a few embedded thunderstorms are expected from this
  afternoon into Wednesday. Widespread severe weather is not
  expected, but strong winds aloft could mix to the surface with
  any storms or heavier showers. Heavy rainfall will be likely
  regionwide.

- Strong east to southeast winds are expected this afternoon into
  tonight, with gusts of 30 to 50 mph. The strongest gusts are
  anticipated across central, east-central, and portions of north-
  central Wisconsin, where a Wind Advisory has been issued.

&&

.DISCUSSION...
Issued at 407 AM CDT Tue Apr 16 2024

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

Synopsis:

A strong low pressure system, currently analyzed over western
Nebraska at 991 mb, will track east towards the Missouri Valley
today, then the upper Mississippi Valley tonight, and the
Wisconsin/Michigan border on Wednesday.

Surface Winds:

As the low approaches the area, the pressure gradient will tighten
precipitously across the western Great Lakes region. Very gusty
easterly winds are expected across central Wisconsin around
midday and across the rest of the area later this afternoon and
into the evening hours. Probabilistic model data indicates a high
probability (70-90 percent) of hitting 45 mph or greater across
much of central, east-central, and portions of north-central
Wisconsin this afternoon into the early overnight hours. Winds
will slacken off a bit late tonight into Wednesday morning as the
surface low approaches and eventually tracks through northeast
Wisconsin later on Wednesday. Given the relatively high
probabilities of hitting Wind Advisory criteria as the low
approaches the region, will issue a Wind Advisory for central,
east-central, and portions of north-central Wisconsin from this
afternoon through early Wednesday morning.

Precipitation:

A band of precipitation ahead of the main low, associated with
isentropic lift and strong mid level frontogenesis, will lift
northeast through Wisconsin today and through northeast Wisconsin
later this afternoon and this evening. Abundant dry air ahead of
these rain showers, as evidenced by the very low dew points across
the region, will stall the onset of the precipitation from the
previous forecast by a few hours.

There will be some modest elevated instability in place across
the area with MUCAPE values of 300 to 600 J/kg. However, model
soundings indicate there will be a substantial temperature
inversion in place around 850 mb; therefore, the high winds speeds
of 60 to 70 knots at this layer are not expected to reach the
ground. It would not be surprising if a vigorous shower or
thunderstorm brings down winds of 40 to 50 knots, which wouldn`t
be that much higher than the synoptic winds that will be in place
across the region during this activity.

A second band of rain showers is then expected to lift northeast
associated with the main low and mid level trough with attendant
shortwaves late tonight/early Wednesday morning and track through
the area throughout the morning. These showers will also have
embedded elevated thunderstorms with continued MUCAPE values of
300 to 600 J/kg and a continued steep inversion in place around
900 mb.

Lingering showers and a few thunderstorms will then be possible
behind the main low lifting northeast as daytime heating builds
modest SBCAPE values of 100-300 J/kg. Although these thunderstorms
will be surface based, the meager instability values indicate this
activity will be generic non-severe thunderstorms.

Long Term...Wednesday Night Through Monday

Precipitation...Light rain showers will be on their way out of the
region to the northeast Wednesday evening, as the surface low
departs. Models are struggling with the details for the next chance
for precip possibly on Thursday. All models indicate a system
passing to the south of the forecast area on Thursday, and some have
a secondary surface low developing over northern WI/Upper MI. The
models that have a stronger surface low developing over northern
WI/Upper MI have a surface boundary generating rain showers over
portions of the forecast area on Thursday. Since not all models are
in agreement with this occurring, kept the blend of models slight
chance PoPs across the north and chance PoPs across central and east-
central WI. By early Friday, an upper-level low will slide over
western Ontario and bring cyclonic flow and CAA over the region. As
the low shifts further east, a shortwave/trough looks to generate
some light precip over the northern portion of the forecast area
sometime Friday afternoon/evening. With the cooler air over the
region, the light precip may fall as a mix of rain and snow, and
possibly all snow into the evening as boundary layer temps fall
below freezing. Dry conditions are anticipated for the weekend as
the low shifts northeast of the region and surface high pressure
moves into the area.

Temperatures...Thursday`s temperatures will be tricky to nail down
given the potential for a frontal passage with precip. For now,
leaning towards temperatures to be above normal by a few degrees in
the middle 50s to low 60s, but given the uncertainty would not be
surprised to see values decrease in later forecasts. Temperatures
will then dip below normal for Friday and Saturday with the
prevailing CAA. Have highs ranging from the middle 40s to low 50s
for both days. Temperatures then return to normal or slightly above
normal (highs mainly in the middle to upper 50s) for Sunday and
Monday with high pressure building into the area.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 614 AM CDT Tue Apr 16 2024

VFR conditions will prevail this morning with only some mid and
high clouds across the region. Flying conditions will deteriorate
from southwest to northeast this afternoon and evening as a
strong low pressure system tracks towards the state. Look for low
clouds and a large area of rain to spread into the area. Some
embedded thunderstorms are also expected, especially across
central and eastern WI. MVFR conditions look to arrive after 7-8pm
with IFR conditions holding off until closer to midnight, with
some LIFR possible Wednesday morning.

East surface winds will increase this morning, becoming gusty by
mid-morning. Gusts will increase through the day, peaking in the
afternoon/evening in the 30-40 kt range. Locally higher gusts are
possible.

LLWS looks likely this evening as winds aloft increase significantly,
reaching 50-60 kts at 2000 ft.

&&

.MARINE...
Issued at 407 AM CDT Tue Apr 16 2024

A tightening surface pressure gradient will cause easterly winds
to increase to small craft criteria early this afternoon then to
gale force late this afternoon into early this evening. Gale force
gusts to 40 knots will continue tonight until winds slowly subside
Wednesday morning into Wednesday afternoon. Small craft
conditions will likely persist into much of Wednesday as winds and
waves slowly subside.

Given the fairly high confidence in reaching Gale Warning criteria
will upgrade the Gale Watch to a Gale Warning with a preceding
Small Craft Advisory this afternoon.

&&

.FIRE WEATHER...
Issued at 407 AM CDT Tue Apr 16 2024

Very dry air in place across the region today will cause afternoon
RH values to plummet to the upper teens to lower 20s across
northern Wisconsin. In addition, very gusty easterly winds of 25
to 40 mph are expected across this region with temperatures in the
upper 50s. Precipitation approaching from the southwest is not
expected to make it to northern Wisconsin until late this
afternoon or early this evening. The low RH values and gusty winds
will cause elevated fire weather conditions across northern
Wisconsin today until relief arrives with the approaching rain
showers from the southwest. Therefore, will issue an SPS to
highlight these conditions across the area.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 4 PM this afternoon to 4 AM CDT Wednesday for
WIZ018-019-031-037>040-048>050.

Wind Advisory from 1 PM this afternoon to 4 AM CDT Wednesday for
WIZ030-035-036-045.
&&

$$

DISCUSSION.....Kurimski/Kruk
AVIATION.......Kurimski
MARINE.........Kurimski
FIRE WEATHER...Kurimski