947
FXUS63 KARX 050349
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1049 PM CDT Fri Oct 4 2024

.KEY MESSAGES...

- Windy conditions Saturday afternoon with potential (30-80%
  chance) for a 40 mph wind gust, particularly west of the
  Mississippi Valley.

- Showers and thunderstorms possible Saturday evening, mainly
  east of the Mississippi River. A severe wind gust could (5 to
  15%) occur if thunderstorms develop.

- Temperatures creep back up above normal Monday through Friday

&&

.DISCUSSION...
Issued at 208 PM CDT Fri Oct 4 2024

Windy Saturday with evening showers and storms

Saturday, an upper wave looks to advance from over the Pacific
Northwest to over the Upper Midwest. With high pressure aloft
remaining in place over the SE CONUS, winds from the surface through
the mid-levels will be on the increase as gradient tightens. Mixing
should be able to tap into some of these stronger winds, resulting
in some 20-25 mph sustained winds and gusts around 35 mph west of
the Mississippi River. Have leaned winds toward the strong side and
dewpoints toward the dry side of consensus blends due to the
potential for efficient mixing during the daytime hours. 04.12z
probabilities from NBM and HREF suggest a slightly lower top end
wind gust potential compared to guidance from yesterday, a result
that seems reasonable considering the potential for some midday mid-
level clouds. Have thus continued to hold off on a Wind Advisory for
Saturday.

Moving ahead to the precipitation potential, am still inclined to
believe at least our northeastern counties should see rain given the
impressive dynamics with the approaching upper wave. Uncertainty
remains high elsewhere as the aforementioned potential efficient
mixing leads to concerns about having sufficient moisture.
Additionally, relatively warm air in the 500-600mb layer may prevent
nascent updrafts from surviving, particularly in the western half of
the forecast area. Have therefore attempted to tighten the gradient
in PoPs from southwest to northeast using consensus of short term
guidance. As for hazards, aside from lightning, showers and storms
Saturday evening would have very high cloud bases atop a well-mixed
boundary layer and thus have the potential to produce dry
microbursts. Indeed, 04.12z guidance suggests around 1000-1500 J/kg
of DCAPE will be present. Will thus need to remain alert for
potential sporadic, localized severe wind gusts with any convection
that does develop.

Slowly warming Monday through Thursday

Little change to the extended forecast...west-northwesterly flow
aloft looks to be predominant, offering little opportunity for
appreciable moisture to return to our area. With high pressure
slowly building over the south central Plains, the net result should
be a slow warming trend to above normal temperatures with little to
no chance for rain.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1100 PM CDT Fri Oct 4 2024

While VFR is expected across the forecast area from northeast
Iowa, southeast Minnesota, and western into central Wisconsin,
increased winds will be a concern for much of the weekend.
Initial southeast winds will increase shortly after TAF (06.06Z)
issuance as the pressure gradient tightens ahead of an incoming
trough. There will be less dependence on diurnal heating to
initiate winds. Therefore, expect gusts above 20kts near
sunrise primarily in wind prone areas west of the Mississippi
River Valley. Daytime mixing will exacerbate these increased winds,
rotating clockwise through the afternoon to southwesterly,
gusting above 30kts by late afternoon. The surface front passage
will further rotate winds to northwest late Saturday night.
Cold air advection into early Sunday morning expected to persist
stronger winds potentially through the overnight hours.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.

&&

$$

DISCUSSION...Ferguson
AVIATION...JAR