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FXUS63 KARX 280719

Area Forecast Discussion
National Weather Service La Crosse WI
219 AM CDT Mon May 28 2018

.SHORT TERM...(Today through Wednesday) 
Issued at 219 AM CDT Mon May 28 2018

Today looks to be the last really warm day before a gradual
cooling trend sets in for Tuesday and Wednesday. Temperatures at
925mb top out around 28C Sunday and are expected to do so again
today before dropping back to 24-25C Tuesday and down to 20-21C
for Wednesday. Underneath these temperatures aloft, surface
readings today should again reach the middle to upper 90s, with
upper 80s to lower 90s Tuesday and then lower to middle 80s for
Wednesday. Dew points today should be slightly higher than Sunday
and push the heat index into the upper 90s to around 100. Even
though some spots may exceed advisory criteria for a short period
this afternoon, not planning to issue an advisory as these values
should not be very widespread. Also concerned that dew points
could mix out again this afternoon as they did Sunday afternoon,
but with light winds through much of the boundary layer,
confidence in this occurring is not very high. There could also be
more cloud cover around if convection develops that would hold air

Speaking of convection developing, the HRRR and CR-HRRR have been
consistent for a few runs showing activity developing over
portions of northeast Iowa into southeast Minnesota this
afternoon. Looking through the 28.00Z models and the 28.05Z RAP,
tough to find much of a trigger for this development other than
being on the eastern edge of a weak moisture transport axis that
develops from southern Illinois northwest into western Minnesota.
The RAP also wants to push a weak surface boundary into the
Interstate 90 corridor with some weak convergence along this. Not
sure if this will be enough to get some convection going, but
given the subtle boundaries that have sparked activity around the
region the last couple of days, it possibly could be and plan to
leave the small chances going for the afternoon. The focus for
convection for this evening into tonight should then shift farther
north as another short wave trough runs up the backside of the
upper level ridge with the models showing development over central
Minnesota that then moves into northern Wisconsin. With this in
mind, trended toward a dry forecast for the overnight hours.

Tuesday looks to be very similar to today with no clear cut
signals to force convection to go in the afternoon and will just
have some low rain chances to cover any subtle boundaries that may
be in place.

The models are still in flux on their solutions for Wednesday with
the remains of the upper level low coming out of the Rockies and
the remains of Alberto working north from the mid-Mississippi
River Valley into the Great Lakes. There is now better agreement
on the remains of the upper level low tracking across the Dakotas,
northern Minnesota before heading east across Lake Superior where
it may or may not be absorbed into the remains of Alberto. This 
does not look to provide a lot of forcing to the area with only 
some weak pv advection in the 500-300 mb layer moving across. 
Enough warm air advection to produce 1-2 ubar/s of up glide on the
305K surface and with the increase in moisture from Alberto it 
should be enough to generate showers with some embedded thunder.

.LONG TERM...(Wednesday night through Sunday) 
Issued at 219 AM CDT Mon May 28 2018

Some activity from the passage of the upper level low and Alberto
will linger into Wednesday night across the eastern sections 
before possibly increasing in coverage Thursday afternoon 
northeast of Interstate 94 as the remains of the upper level low 
swings across the Great Lakes on the backside of Alberto. After 
that, it looks dry into the start of the weekend before a trough 
moves across the Upper Midwest for another chance of rain Saturday
night into Sunday.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1142 PM CDT Sun May 27 2018

An area of thunderstorms across northern MN will move eastward 
overnight, potentially expanding across northern portions of WI. 
These storms are expected to remain north of TAF airfields with 
the primary impact being blow off cirrus. Additional showers and 
thunderstorms are possible Monday afternoon into the early 
evening, but a weak flow regime and poor agreement between 
forecast guidance precludes mention at this time. Away from any 
thunderstorms, VFR conditions and light winds will be the rule. 
Expect light southeast wind overnight, becoming more south- 
southwesterly through Monday. 




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