259
FXUS63 KGRB 090346
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1046 PM CDT Tue Oct 8 2024

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Areas of frost will occur north and west of the Fox Valley late
  tonight.

- Low afternoon relative humidities and drought conditions will
  result in elevated fire weather conditions this week, especially
  on Friday, as winds increase in association with a cold front.

- Expect above average temperatures for the rest of the work week. A
  few locations may approach record highs on Friday. Temperatures
  drop to below normal late in the weekend and early next week.

- Next chance of precipitation arrives Saturday night and Sunday.
  Possible first snowfall of the season over the Northwoods early
  next week.

&&

.DISCUSSION...
Issued at 303 PM CDT Tue Oct 8 2024

Short Term...Tonight and Wednesday

The main concerns in the short term will be the potential for
frost tonight followed by another round of low relative humidity
readings in the region tomorrow.

Skies will be mostly clear again tonight, which will allow
temperatures to drop once more across the region. Without any
exchange of airmass and little to no cloud cover would expect to
get back into the lower 30s for much of the areas west and north
of the Fox Valley, which will allow for frost and possible some
patchy ground fog in the coldest areas.

Skies will be sunny again on Wednesday, which should allow for a
fairly rapid warmup across the region. High temperatures tomorrow
will range from the lower 60s across far northern Wisconsin near
the UP border to the upper 60s across central Wisconsin. Dry air
will remain in the region, which means relative humidity readings
in the afternoon will likely once again sit around 30 percent and
create elevated fire weather conditions.

Long Term...Wednesday Night Through Tuesday

Dry conditions expected until later in the weekend, with
temperatures, frost potential and fire weather the main concerns
until then. Also seeing some potential for the first snowfall of
the season in NC WI early next week.

Precipitation Trends: Canadian high pressure will bring dry
conditions through Thursday. A cold front arrives on Friday, but
is moisture-starved and expected to pass through with little or no
rain. A clipper-type low pressure system is expected to phase with
another low arriving from the Central Plains Saturday night, then
rapidly deepen just to our east. This system and an associated
short-wave trough will bring moderate precipitation to most of
the forecast area. Persistent cold NNW flow (with lake-850 mb
delta-t`s of 17-21 C) on the back side of this system will impact
the region from Sunday night through Tuesday, setting the stage
for lake-effect precipitation across northern WI. With H8
temperatures in the -3 to -6 C range and surface temperatures
dropping into the upper 20s and lower 30s in NC WI on Sunday
night and Monday night, expect the rain to mix with or change to
snow during the nighttime hours.

Temperatures: Above normal temperatures are expected for the mid
to late part of the week, with potential for record or near-
record highs in the 70s and lower 80s ahead of the cold front on
Friday. A cool down is anticipated over the weekend, with highs
dropping to below normal from Sunday into Tuesday. Potential
exists for frost development west and north of the Fox Valley
again Wednesday night, though the growing season has already
ended across much of northern WI.

Fire Weather: Continued moderate to severe drought conditions
over northern WI and low relative humidity will support elevated
fire weather conditions through much of the work week. Of
greatest concern is Friday, when enhanced mixing with the cold
front could bring record or near-record highs, southwest winds
gusting to 20 to 30 mph, and low relative humidity. The timing of
the front will be critical, as an earlier arrival time would
result in cooler temperatures.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1046 PM CDT Tue Oct 8 2024

VFR conditions are expected through the TAF period. Only exception
may be some patchy ground/valley fog across north central WI
overnight into Wednesday morning. Confidence remains low regarding
fog development, so will not include, but VSBYs could bounce
around a little bit shortly before dawn through a little after
sunrise, especially at RHI. Better chances for fog look to arrive
late Wednesday evening into early Thursday, but likely holding off
until after 06z. Otherwise, look for mostly clear skies with only
a few high clouds. Winds will remain light.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 9 AM CDT Wednesday for WIZ020-030-031-035-
036-045-073-074.
&&

$$

DISCUSSION.....Uhlmann/Kieckbusch
AVIATION.......Bersch