Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 230819
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
319 AM CDT MON MAY 23 2016

.SHORT TERM...(Today and tonight)
Issued at 319 AM CDT Mon May 23 2016

Latest water vapor satellite imagery shows upper level trough over
the southern Canadian Rockies and the northern United States Rockies
and upper level ridge over the Upper Great Lakes Region. Several
shortwave troughs wrapping around the upper level trough are
producing showers and thunderstorms from the Northern Plains to the
High Plains.

Main forecast concerns are precipitation chances today into tonight.
The 23.00z GFS/NAM are in good agreement in breaking down upper
level ridge over the Great Lakes Region and developing southwesterly
flow aloft over the central United States. The 23.00z GFS/NAM are in
good agreement in weakening ongoing convection in association with
first impulse over the Northern Plains...as instability weakens out
of ahead of the convection. Second piece of energy embedded in
southwesterly flow aloft pushes into the Upper Great Lakes region
late this afternoon and tonight. The 23.00z GFS/NAM/ECMWF indicate
moisture transport/convection and lift in association with this
piece of energy. However...the models show some weakening of the
moisture transport/convergence and focus this across the far
northern and southern sections of the forecast area. This is
evident...as the hi-resolution/CAMS models indicate redevelopment
convection to form across the far northern/southern sections of
the forecast area late this afternoon. Continued trend of higher
chances of showers and thunderstorms over these areas.

Confidence in severe potential remains very low...as the 23.00z
GFS/NAM continue indicate 20-25 knots of 0-3 km shear and up to
1000 J/kg of CAPE. Not anticipating any severe weather with the
thunderstorms.

.LONG TERM...(Tuesday through Sunday)
Issued at 319 AM CDT Mon May 23 2016

Unsettled weather pattern continues Tuesday into Wednesday
night...as the 23.00z GFS/NAM/ECMWF eject a couple of shortwave
troughs out of the upper level trough over the western United States
into the Upper Great Lakes Region. Differences occur between the
models on timing/placement of the shortwave troughs. The 23.00z
GFS/NAM/ECMWF hint at focusing the stronger moisture
transport/convergence and placement of surface front south of the
forecast area Tuesday night into Wednesday. This would result in
developing stronger convection south of the forecast area.
However...if the forecast area builds enough instability and given
the wind shear at 0-3km of 20 to 30 knots...some of the
thunderstorms could be strong with gusty winds and hail.

Main forecast concerns Thursday into Sunday continue to be
precipitation chances across the forecast area...as the 23.00z
GFS/ECMWF/GEM show southwesterly flow aloft and embedded
shortwave troughs tracking into the Upper Great Lakes Region.
Timing and placement of individual shortwave troughs continue to
be the main issues between the long range models. Will continue
with trend of shower and thunderstorm chances across the forecast
area through the period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1148 PM CDT Sun May 22 2016

Cirrus will slowly push eastward overnight, but bigger impact will
be strengthening winds aloft. Kept wind shear component at KRST
through 23.13Z, and also added one at KLSE with surface winds
dropping below 5 kts and winds at 2000 ft agl around 35 kts.

Removed VCSH at KRST Monday morning as latest guidance now shows
convective activity currently across the eastern Dakotas
completely falling apart before reaching the Upper Mississippi
River Valley. In fact, low confidence in timing and coverage of
additional thunderstorms later in the period, so kept TAFs
thunder-free at this time. Will add details as convective
evolution becomes clearer. Unless a thunderstorm moves directly
over a TAF site, expect VFR ceilings/visibility through the
period.

Expect gusty southerly winds mid Monday morning and through the
afternoon with frequent gusts into the mid to upper 20 kt range at
both TAF sites. Would not be surprised to see some gusts topping
30 kts at KRST.


&&

.ARX Watches/Warnings/Advisories...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...ROGERS



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