312
FXUS63 KGRB 112354
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
654 PM CDT Sun Aug 11 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Showers and a few scattered, non-severe thunderstorms are
possible (15% to 25% chance) this evening, tomorrow and Tuesday
afternoon/evenings, mainly in northern WI.

 - Widespread precipitation becoming likely (40 to 60% chance)
Thursday into Saturday, but low confidence on exact timing and
magnitude of precipitation at this time. Heavy Rainfall cannot be
ruled out during this period.

&&

.DISCUSSION...
Issued at 259 PM CDT Sun Aug 11 2024

Our weather pattern will be fairly  for the next few days.
Similar to yesterday (Saturday) afternoon, widespread cu/sc
establishes itself across northern/north-central WI under WNW
flow. Scattered pockets of 850 moisture flux convergence phased
with pockets of 950mb frontogenetical forcing will be a
sufficient catalyst for a few of these SC/CU clouds to grow tall
enough to produce a few scattered showers. With a few hundred
joules of CAPE available during peak daytime heating, a few
rumbles of thunder are possible. However, the severe weather
parameter space is not supportive of severe weather at this time.

Temperature-wise, highs for the next few days should be within a few
degrees of normal for this time of year, with lows around 50
degrees, and highs in the upper 70s.

Heading into the Thursday - Saturday timeperiod, a nearly vertically-
stacked low is slated to establish itself near NE Iowa/SW Minnesota.
Overall progression with this system is slated to move very slowly.
The instability and shear parameter space doesn`t reflect anything
notable for severe potential with this setup, so focus will be on
locally heavy rains, especially given the slow movement of this
system. The GFS ensemble runs have been much more bullish with this
system than the ECMWF. Overall, the GFS family does seem slightly
more plausible, so will initially lean some more towards it.

If the GFS pans out, am at least slightly concerned about the
potential for heavy rainfall. PWATs approach 2 inches, and the
forecast vertical sounding profile looks to suggest efficient
rainfall... as supported by 0-6 km mixing ratios of 8 g/kg & a wide
swath of warm cloud depths 4.0-4.5km at times.. Even the less-
bullish EC ensemble moisture parameters are anomalously high based
on mid August climatology with 925/850mb specific humidities and
precipitable water values in the upper 90th percentiles.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 653 PM CDT Sun Aug 11 2024

Scattered light showers over central Wisconsin should dissipate
this evening after sunset. Otherwise, VFR conditions are expected
tonight and Monday. There is a slight chance of showers again late
Monday afternoon and early evening in central and east central
Wisconsin.

&&

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

&&

$$

DISCUSSION.....Kotenberg
AVIATION.......RDM