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000
FXUS63 KGRB 142316
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
616 PM CDT Sun Apr 14 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Elevated fire weather conditions are expected again on Monday.
  Mild temperatures, along with relative humidity values of 18 to
  28 percent, are expected during the afternoon and early evening
  hours. Winds will be lighter with gusts only around 15 mph.

- Elevated fire weather conditions will persist into Tuesday
  across northern Wisconsin due to low humidity and increasing
  east winds.

- Showers and a few embedded thunderstorms are expected from
  Tuesday 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 Tuesday into Tuesday
  night, with gusts of 30 to 45 mph. The strongest gusts are
  anticipated across central Wisconsin.

&&

.DISCUSSION...
Issued at 243 PM CDT Sun Apr 14 2024

Short Term...Tonight and Monday

Main forecast issues to be on temperatures and continued fire
weather concerns through Monday.

The 19Z MSAS surface analysis showed a cold front over southern
sections of the Great Lakes and an area of high pressure centered
over the northern Plains. Visible satellite imagery indicated fair
weather high-based cumulus clouds had developed over northeast WI.

The high pressure is expected to build into the western Great
Lakes tonight, bringing clear skies and light/variable wind to
northeast WI. The dry air mass in place will allow for
temperatures to quickly drop tonight with readings reaching the
lower to middle 30s north-central WI, upper 30s to lower 40s
south.

The high pressure slowly drifts east toward the eastern Great
Lakes, but remain our main weather feature through Monday. A weak
shortwave topping an upper ridge over the Upper MS Valley will
bring some high clouds to the forecast area, especially during the
afternoon. 8H temperatures are forecast to be cooler compared to
Sunday, thus temperatures should not be as warm. Look for
readings to range from the lower 60s near Lake MI, lower to middle
60s north and upper 60s to lower 70s south. We will still need to
watch fire weather conditions as afternoon relative humidity
values drop into the 20-30 percent range in the afternoon (away
from the lake). Another special weather statement will be issued
to acknowledge these concerns.

Long Term...Monday Night Through Sunday

The main forecast concerns during the extended forecast will
be widespread shower activity, heavy rainfall, isolated to
scattered thunderstorms, and strong east to southeast winds with
a low pressure system Tuesday into Wednesday.

Canadian high pressure will continue to bring dry conditions
regionwide Monday night, and over much of north central and
northeast WI on Tuesday. Have slowed down the arrival of
precipitation on Tuesday. Elevated fire weather conditions look
likely over northern WI on Tuesday, as RHs drop to around 25
percent and east winds gust to 25 to 30 mph. Will continue to
highlight fire weather concerns in a Special Weather Statement and
the Hazardous Weather Outlook.

Vertically stacked/deep low pressure will move from the Central
Plains to eastern Nebraska IA on Tuesday, then into southeast
MN/northeast IA Tuesday night. A developing 50 kt low-level jet
ahead of this system will bring a surge of moisture into the
forecast area late Tuesday afternoon into Tuesday night, and
generate strong isentropic ascent over a tight baroclinic zone.
Widespread shower activity will overspread the southwest part of
the CWA Tuesday afternoon, and rest of the region Tuesday night.
Showers will continue through Wednesday as the occluding surface
low and strong upper level trough move through WI. Pockets of
heavy rainfall appear likely, with rainfall totals reaching 1 to
2 inches across much of the forecast area. MUCAPE of 500 j/kg or
less move into mainly the south and east parts of the forecast
area Tuesday night into Wednesday. Though widespread severe
weather is not expected, cannot rule out some strong gusts mixing
down with any storms or heavier showers Tuesday night, given
winds of 40-55 knots in the 925-850 mb layer. Strong east to
southeast winds will develop ahead of the low Tuesday into Tuesday
night, with gusts to 30 to 45 mph (strongest in central WI), and
at least a high-end Small Craft Advisory on Lake Michigan.

The remnants of this low lift north into Ontario and eventually
phase with additional energy in central Canada to produce a weak,
slow moving low that tracks well to our north late in the work
week. Suspect most of the precipitation with this system will
remain to our north Thursday into Friday, and the arrival of
a large Canadian high pressure should bring additional dry
weather for the weekend.

Temperatures will start off well above normal for the early to
mid part of the week, then trend closer to normal late in the
week.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 616 PM CDT Sun Apr 14 2024

VFR conditions will prevail through the TAF period as high
pressure moves across the Great Lakes. Any remaining high-based
cumulus clouds will dissipate early this evening, with clear skies
expected tonight. Mid and high clouds will spread into the area on
Monday, especially in the afternoon/evening, ahead of a large,
organizing low pressure system in the Plains.

Winds will diminish around sunset, with light and variable winds
expected tonight. Winds will be little lighter on Monday,
generally out of the north/northwest under 15-20 mph. A lake
breeze will bring onshore winds near Lake Michigan in the late
morning or early afternoon, with winds becoming easterly across
the entire area Monday evening.

&&

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

&&

$$

DISCUSSION.....Kallas/Kieckbusch
AVIATION.......Bersch