Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 222027

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

.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 18Z TAFS through 18Z Wednesday afternoon)
Issued at 125 PM CDT Tue May 22 2018

Clouds continue to lift and scatter out this afternoon. Diurnal cu
will be left over until sunset and then skies will likely become
clear for a time. Thunderstorms will develop across southwest MN
overnight, spreading mid level clouds eastward overnight. Some
showers and storms will detach from the front over southwest MN
Wednesday morning, lifting northeast across the rest of the area
into the midday hours.

KMSP...Finally VFR, which is expected to continue through the
period. Introduced a PROB30 for TSRA Wednesday morning.

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




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