Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 060744

Area Forecast Discussion
National Weather Service La Crosse WI
245 AM CDT Wed Jul 6 2022

.DISCUSSION...(Today through Tuesday)
Issued at 245 AM CDT Wed Jul 6 2022

Key Messages:

 - Late tonight-Thu...rain chances, mostly south - heavy rain

 - Drier into the weekend, but rain chances Sunday


Bulk of models continue to suggest a southerly sag in the west-east
front - currently laying out *roughly* along the IA/MN border. With
loss of upper level forcing and a shift east/south of the low level
jet, the weakly convergent front will have to rely on itself and
destabilization from daytime heating to kick off any convection.
CAMS models aren`t enthusiastic over these possibilities, and these
chances would still be south of the forecast area. That said, some
hints in the CAMS of remnants from convection over NE could hold
together long enough to shift east and bring some (mainly) shower
chances to parts of SE MN/NE IA and SW WI later this afternoon-
evening. Not a clear signal but will paint small pops in these areas
for the potential.

* TONIGHT/THU: chances for showers/storms, mostly south

The models have been pretty consistent with sparking a convective
complex over the central plains tonight as an upper level shortwave
trough works out of the southern Rockies and the low level
jet/moisture transport noses in. Where this complex moves is where
the models have strayed, and continue to do so. The bulk of the CAMS
drive it east out of NE, working along the boundary as it tracks
across southern IA. GFS favors this too. Most of this pcpn would
hold south of the forecast area. The NAM and EC are shifted farther
north, with rain likely for at least locations south of I-90. With
soaking rains having just occurred in these locations, further heavy
rain could bring some localized flooding concerns. PWS north of 2+
inches and warm cloud depths upwards of 4500 m point to efficient
rain producers.

For now, will lean into the CAMS solutions and trend the higher rain
chances across the south, from overnight into Thu afternoon. While
this scenario would likely shift heavy rain south of the forecast
area, minimizing a flooding threat, if the NAM/EC solutions prove
out, flooding concerns would ramp up.

* WEEKEND INTO NEXT WEEK: dry start, then rain chances

Models remain in good agreement with slowly pushing the upper level
ridge axis from the lee of the rockies to across the plains by Fri.
As it continues to inch east, both the EC and GFS drop a couple
shortwave troughs across the ridge, essentially flattening the ridge
out and carving out more of a trough across the great lakes for
early next week. Good agreement in the SPC clusters with this
scenario, with both the GFS and EC amplifying an upper level ridge
over the west coast as that trough sharpens.

Impacts on temps is generally holding at or perhaps a bit below
normal. EC continues to suggest a bump up around Monday with weak
ridging slipping across the area, but not nearly as enthusiastic as
it was a few days ago.

Precipitation-wise, with the sfc front now well south and a weak sfc
high building across the region, a mostly dry weekend is favored by
the least until Sun aft/evening when that upper level
trough drops in. A few more ripples in the flow then look to slide
through the developing trough,which could continue rain chances for
the start of the new work week.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1018 PM CDT Tue Jul 5 2022

The stratiform rain on the backside of the bow echo should be past,
or nearly past both sites by 06.06Z. As a result, only plan to
include a short VCSH at KLSE. After that, still looking at MVFR,
possibly IFR, ceilings developing overnight for both sites and
persisting for much, if not all of Wednesday. Some improvement to
VFR possible late Wednesday afternoon before the next chance for
rain moves back in later in the evening.





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