208
FXUS63 KARX 170337
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1037 PM CDT Thu May 16 2024

.KEY MESSAGES...

- While a couple thunderstorms may develop in the far eastern
  portions of southwestern and west central Wisconsin this
  afternoon, this threat is expected to end over the next couple
  hours with severe thunderstorms no longer expected.

- A chance (20-30%) for thunderstorms returns Saturday afternoon and
evening. If thunderstorms develop, a stray severe thunderstorm
cannot be ruled out.

- Next week features repeat chances for showers and thunderstorms.
Currently, confidence in timing is low, so these chances are spread
over many more periods than will ultimately be affected. Additional
refinements will occur in the coming days.

&&

.DISCUSSION...
Issued at 437 AM CDT Thu May 16 2024

This afternoon:

19z WV satellite shows a weak shortwave over Black River Falls with
visible and IR channels showing a field of cumulus largely with
little vertical extent, with the exception of couple small storms
around Baraboo/Madison. This largely comports with non-NAM guidance,
which suggests warm temperatures around 750mb are preventing deep
convection from developing and will continue to do so this
afternoon. As the aforementioned shortwave exits to the east in
the next couple hours, the chance for additional rain will end.

Saturday thunderstorms:

Saturday, upper low looks to advance from North Dakota to Montana
with an associated weak surface front progged to sweep eastward
through Minnesota with a narrow axis of moisture advecting
northeastward ahead of this feature. Model guidance suggests around
1000 J/kg of MLCAPE could build by late afternoon. As the front
arrives, a few showers and thunderstorms could develop, particularly
if the front arrives before surface heating is lost. While best
upper level winds and thus deep shear remain displaced well to our
north and west, if thunderstorms do develop, some severe hail could
occur given aforementioned instability and 700-500mb lapse rates
favored to be around 7.5 C/km.

Sunday night through Thursday precip:

Next week brings an extended period with west-southwesterly to
southwesterly flow aloft. Guidance depicts a variety of shortwaves
ejecting downstream in this flow with a variety of exact timings.
Thus, while NBM PoPs were allowed to remain in the forecast, expect
the periods with likely showers and thunderstorms to eventually
focus on shorter time periods once details become clearer.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1037 PM CDT Thu May 16 2024

Weak surface ridge builds into eastern Minnesota/western Wisconsin
tonight into Friday. Subsidence underneath ridge will allow for
mostly clear skies tonight into Friday morning. Some mid to high
clouds are expected to drift over the area Friday
afternoon/evening. However...ceilings should remain VFR through
the taf period at both RST/LSE taf sites. Pressure gradient
tightens on backside of surface ridge Friday afternoon/evening.
Wind speeds will be 10 to 15 knots with gust to around 20 knots
by 18z Friday especially west of the Mississippi River.

&&

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

&&

$$

DISCUSSION...Ferguson
AVIATION...DTJ