062
FXUS63 KGRB 081159
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
659 AM CDT Sat Jun 8 2024

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Widespread showers are expected this morning, ending from west
  to east late this morning and early this afternoon. Under 0.25"
  of rain for most spots.

- There is a slight chance of thunderstorms this afternoon, mainly
  across northern Wisconsin. Severe weather is not expected.
  Another slight chance of thunderstorms is forecast Tuesday
  evening.

- Below normal temperatures are forecast through early next week,
  with a possible warm up at the latter half of the week.

&&

.DISCUSSION...
Issued at 422 AM CDT Sat Jun 8 2024

Short Term...Today...Tonight...and Sunday

Main forecast concerns will be timing the arrival/exit of the
precip today, if/where any showers/storms can develop this
afternoon/evening and if any lingering showers impact the north
on Sunday.

Shower/Storm Trends:

Area of light showers and sprinkles early this morning will
transition into a more widespread area of showers through the
morning (with some lulls/breaks expected), as better moisture
arrives ahead of an approaching frontal boundary and shortwave
trough. Some thunder has been observed upstream with very limited
instability (100-200 J/kg) and a little pocket of steeper mid-
level lapse rates, but models all have this instability waning in
the early morning hours, so will keep thunder out of the of the
forecast this morning. Models have come into decent agreement,
bringing the back edge of the rain across eastern WI between
18-20z. Rain totals look to be under 0.25" for most spots. For
this afternoon, instability is forecast to build to between
100-400 J/kg, highest north of Hwy 29, behind the steadier area of
rain. Bulk shear looks to be in the 30-50 kt range, highest over
northern WI, so chances for a few storms is warranted. Weak
surface convergence is expected as the boundary drops across the
area, triggering isolated showers and storms. Better convergence
and higher chances for storms looks to be in the U.P., but have
increased chances over far northeast WI and Door Co. as this
appears to be the area with the highest chance activity in our
area. NAMNest showing a thin line of showers extending all the way
back into central WI, but convergence/moisture concerns will
limit this potential. Severe weather is not expected, but the
inverted-V shown on model soundings could lead to a few higher
wind gusts. Luckily, the 40+ kt winds are over 15,000 ft. A
lingering shower or two may push across parts of central and
northern WI in the evening as another weak shortwave drop into the
state, but this activity should wane as instability fades.

On Sunday, showers will be possible mainly over northern WI as
another weak shortwave drops across the state and temps cool
aloft. Models showing pretty much no instability over northern WI
so will not include any thunder mention.

Temps:

Below normal high temps are expected this weekend. Clouds and rain
will hold temps down this morning, but partial clearing later in
the day will allow a period where temps can climb back into the
upper 60s and low 70s for most locations. Lows tonight look to
fall into the 40s and low 50s. Highs on Sunday will struggle to
get into the 60s over the far north as a push of CAA arrives.
Further south, the CAA should be just delayed enough to allow
highs to climb into the mid 60s to low 70s.

Long Term...Sunday Night Through Friday

Main focus from this forecast period revolves around precipitation
trends from midweek through the end of next week.

Shortwave energy will be departing the region Sunday night and make
way for a ridge of high pressure Monday into Monday night. Dry
conditions and slightly below normal highs (ranging from the
middle 60s to low 70s) under mostly sunny skies will be the result.

The ridge of high pressure will depart on Tuesday and bring the next
chance for showers and storms from a trailing shortwave trough and
surface cold front. The precip should exit the region by Wednesday
morning. The best forcing will coincide with the cold front,
which looks to track across the forecast area Tuesday evening/late
evening, when instability is quickly decreasing. Therefore, do
not anticipate any severe storms, but there will still be a low
chance for general thunderstorms.

Following this shortwave trough, a brief lull in precip is
anticipated Wednesday from a surface ridge, before the next chance
for showers and thunderstorms arrives from another shortwave. Model
guidance is not in agreement with the timing of this shortwave and
has it moving through the area sometime between Wednesday night and
Thursday night. Forecast confidence will remain low with this
shortwave and the rest of the extended until the shortwave timing
window becomes clearer over the next couple of days.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 657 AM CDT Sat Jun 8 2024

Light rain will continue to spread across the area this morning,
ending from west to east in the late morning and afternoon. VFR
conditions will lower to MVFR for a time as the heavier/steadier
rain pushes through. VFR conditions will return this afternoon
into tonight. Isolated showers and possibly a storm is possible
this afternoon and evening, especially across northern WI.

&&

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

&&

$$

DISCUSSION.....Bersch/Kruk
AVIATION.......Bersch