Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 251105

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
605 AM CDT Fri May 25 2018

.SHORT TERM...(Today and tonight)
Issued at 425 AM CDT Fri May 25 2018

There is very little change in the airmass for today, with a cold
front still bisecting the forecast area. Early morning water
vapor imagery shows an upstream shortwave trough over North Dakota
and southern Manitoba that will supply extra support for
convective re-initiation today. The first area of concern will be
along/ahead of the cold front as diurnal heating induces
destabilization. While layer shear is again weak, lapse rates and
instability (dewpoints in the lower 60s and MLCAPE values of 1500
J/KG) could prove sufficient for a widely scattered severe storms
this afternoon/evening along and east of the Interstate 35

The other area of potential convective development is back to the
west over west central MN, where weak shortwave energy could be
sufficient to initiate some regeneration of widely scattered
showers and thunderstorms this afternoon. Several of the hi-res
models are picking up on this scenario, so have included chance
POPS for the entire area.

High temperatures will be a bit tricky given the potential for
convective debris clouds and re-development, but generally think
readings should be within a few degrees of Thursday`s highs.
Expect 85-95 degrees from west central WI to west central MN,

Showers look a bit lackadaisical in clearing tonight, so have
included low POPS in west central WI until 09Z.

.LONG TERM...(Saturday through Thursday)
Issued at 425 AM CDT Fri May 25 2018

The main change in the long term forecast period was to insert low
POPs for Memorial Day, with less confidence that the mid-level
ridge will be robust enough to entirely inhibit convection. The
GFS has been consistent in showing the potential for widely
scattered activity, and the ECMWF is now hinting at that potential
as well. Kept Sunday dry for now, but I wouldn`t be surprised to
see a few pop-up showers/storms develop then as well.

Temperatures will be the other concern, with hot and humid
conditions expected both Saturday and Sunday. Current forecast
temps/dewpoints do not yield heat index values quite high enough
to warrant a heat advisory at this point. However, given winds
will be light and skies will be mostly sunny, the Wet Bulb Globe
Temperature (WBGT) is a much better indicator of the potential for
heat risk for those who will be active outdoors. WBGT values in
the 75-80 degree range are expected Saturday, and even higher
values in the lower 80s are forecast for Sunday. These values
indicate discretion is suggested for outdoor exercise/activities,
especially those of an intense or prolonged nature. More frequent
rest breaks are also recommended.

Models eject the western trough across the area in the Tuesday-
Wednesday time frame, so shower and thunderstorm chances and a
trend toward more seasonal temperatures were included.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 600 AM CDT Fri May 25 2018

Thunderstorms continue to weaken this morning while continuing to
travel eastward to the east of RWF and RNH. EAU can expect TSRA
through the remainder of the mid-morning. Otherwise, winds this
morning will become predominately west-southwesterly and increase
with daytime heating. Gusts near 20-25 kts will be possible
during Friday afternoon. Scattered thunderstorm chances return by
late Friday afternoon with the best chances being around and East
of MSP and MKT. Dry conditions are expected to resume overnight
into Saturday.

KMSP...VFR conditions are expected for most of the TAF period.
The main concern is the possibility for thunderstorm development
Friday afternoon and evening.

SAT Night...VFR. Wind WNW 5-10 kts.
SUN...VFR. Wind light/variable winds.
MON...VFR. Slight chc TSRA late. Wind S 5 kts.




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