496
FXUS63 KARX 162350
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
650 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 /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 650 PM CDT Thu May 16 2024

VFR conditions are expected through the TAF period with few to sct
middle and high clouds expected. Winds will shift to southerly and
increase during the day tomorrow to around 10 kts. Will still have
to watch for the potential of valley fog at KLSE when considering
the calm winds and clearing skies overnight. However,
confidence for valley fog still remains low at this time.

&&

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

&&

$$

DISCUSSION...Ferguson
AVIATION...Naylor