NWS-La Crosse Forecast Discussion

 

						FXUS63 KARX 171125
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
625 AM CDT Tue Jul 17 2018

.SHORT TERM...(Today and tonight)
Issued at 258 AM CDT Tue Jul 17 2018

Early this morning, watching an area of convection across central
NE. These storms will continue to drift south and east through
12Z with the primary impact to the local area being some
convective debris clouds. There is another narrow area of
altocumulus across central MN into central WI associated with some
850 to 700 hPa frontogenesis and these clouds could linger across
the region for much of the day. Otherwise, expect partly cloudy
to mostly sunny skies as surface high pressure continues to
dominate the regional weather pattern. Slightly cooler 925 hPa
temperatures compared to yesterday will result in afternoon highs
from the mid 70s to lower 80s.

Mostly clear, dry conditions will continue tonight with lows
ranging from around 50 degrees across north central WI to the
lower 60s across parts of northeast IA into far southwest WI.

.LONG TERM...(Wednesday through Monday)
Issued at 258 AM CDT Tue Jul 17 2018

High clouds will slowly increase from west to east Wednesday
ahead of the next Pacific wave aloft, but much of the day will
remain dry as surface high pressure holds tough across the
region. Only late in the evening/overnight will rain chances
gradually increase with the approaching wave.

There continue to be differences in model solutions with the
timing/strength/track of Thursday's short-wave. The GFS/ECMWF are
stronger, closing off the 500 hPa trough across central MN
Thursday afternoon, whereas the NAM is a bit slower and keeps it
an open wave. Compared to model runs 24 hours ago, there also
appears to be a slight northward shift in the surface low track.
This favors higher instability/shear farther north within the
moist sector. The forecast area also looks to be in a more
favorable location for the left exit region of the 60 kt 500 hPa
jet steak. Still uncertainty in just how much instability will be
able to build north into the forecast area, but some stronger
storms are at least possible with the primary threats being gusty
winds and hail. This idea matches well with the SPC Day 3 Outlook
highlighting a marginal risk for areas west of the Mississippi
River. Will need to continue to monitor the track of this system
as models converge on a solution. Either way, POPs in the 60 to 70
percent range for much of Thursday seem reasonable.

Some additional showers/storms are possible on the backside of the
departing low on Friday, but the weekend into early next week is
still looking mostly dry as a 500 hPa short-wave ridge builds
across the region. Afternoon highs in the mid 70s to lower 80s
will continue to be the rule through Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 625 AM CDT Tue Jul 17 2018

VFR conditions will continue as high pressure drifts south
towards the western Great Lakes through Wednesday morning with
winds less than 10 kts and a few patches of mid/high clouds at
times. Some patchy fog could develop in valleys near the end of
the period, but confidence was not high enough to include at KLSE
at this time.

&&

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

$$

SHORT TERM...Rogers
LONG TERM...Rogers
AVIATION...JM