Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 230024

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
724 PM CDT Tue May 22 2018

Issued at 723 PM CDT Tue May 22 2018

Updated to include 00z aviation discussion below.


.SHORT TERM...(This evening through Wednesday)
Issued at 327 PM CDT Tue May 22 2018

The stratus left behind from the fog this morning was rather slow
to erode today. Extensive cloudiness continues this afternoon from
central Minnesota into western Wisconsin. These clouds are
becoming more diurnally driven, and should largely dissipate after
sunset. Temperatures should rebound quickly late this afternoon
so highs for the rest of the day still appear on track.

Attention then turns to convective trends late tonight. A
developing LLJ over the central Plains this evening will nose
into southwest MN late tonight. Thunderstorms are likely to
develop along or south of the Minnesota river as a response, with
some elevated instability sustaining the activity into early
Wednesday morning. CAMs are in relatively good agreement with the
placement of these storms, but there will ultimately anchor
themselves either, 1) along the surface warm front, or 2) (if they
can develop a good enough cold pool) along the storm induced
outflow boundary. Given the meager instability and wind shear, not
too impressed with the severe potential. The larger threat will
be heavy rainfall given seasonally high PWATS around 1.5 inches
and the risk for some training along the boundary.

These storms will weaken Wednesday morning, and the loss of a LLJ
should allow them to begin lifting northeast across the rest of
the CWA with the surface warm front. Tough to say how warm
temperatures will get tomorrow, especially across the eastern CWA.
Stratus from overnight convection may linger into early afternoon
in those areas, and there is also the possibility of additional
convection firing throughout the day. Areas across western MN
should be able to break into some sun and rise to near 90.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 327 PM CDT Tue May 22 2018


The pattern makes a rather impressive shift into summer mode late
this week into early next week. Southwest flow will prevail
Thursday and Friday, with a short wave passing east across the
region Friday. Scattered thunderstorms are possible in a moist,
unstable environment Wednesday night through Thursday night, with
the best chance occurring with the wave on Friday. A few severe
storms are possible, but the lack of wind shear will greatly limit
the extent of any severe threat. The hot temperatures begin
Thursday and Friday, but convective coverage may temper some areas
from achieving full potential, especially across the east Friday.
925 mb temperatures of +24 to +27C would bring low to mid 90s for
highs in an uncontaminated environment.

From this weekend onward, the ridge continues to build over the
Upper Midwest in response to the potential tropical disturbance
over the southeast and another trough over the southwest. The
storm track shifts north well into Canada making for what looks
like a clean ridge locally. Models continue to trend warmer with
temperatures this holiday weekend, and perhaps have trended too
warm - particularly the GFS. However, given the drier boundary
layer (aided by the lack of significant crop development yet), and
recent dry conditions across central MN eastward into WI, suppose
I cannot completely rule it out. All global guidance brings 925
mb temps into 25-30C range region wide and 850 mb temps into the
low 20s C. This should easily translate to low to mid 90s for
highs through Memorial Day and maybe longer. Records stand the mid
90s which may be challenged on some days.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 723 PM CDT Tue May 22 2018

Remaining mid-level clouds will gradually scatter out, resulting
in mainly high clouds overnight, potentially even clear for a few
hours. Clouds return during the pre-dawn hours, bringing back
mid-level ceilings, as bands of showers/t-storms approach from the
south. Some of this precipitation over southwestern and southern
MN will make a run for east-central MN late morning into the early
afternoon hours, possibly bringing conditions down to MVFR.
Conditions are expected to improve late tomorrow afternoon through
tomorrow evening.

KMSP...Have made few changes from the 22/18z TAF, most notably
being to adjust the PROB30 timing up by an hour to 23/13z to
23/18z. Still looking for mainly MVFR conditions with the
precipitation but cannot rule out IFR conditions, specifically
visibility, should a strong SHRA/TSRA directly impact MSP.

THU...Mainly VFR with -SHRA/TSRA possible late. Wind S 10 kts.
FRI...Mainly VFR with -SHRA/TSRA possible late. Wind SW 5-10 kts.
SAT...VFR. Wind SW 5-10 kts.




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