Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KMPX 251710

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1210 PM CDT Fri May 25 2018

Issued at 1205 AM CDT Fri May 25 2018

Updated to include 18z aviation discussion below.


.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 corridor.

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 18Z TAFS through 18Z Saturday afternoon)
Issued at 1131 AM CDT Fri May 25 2018

Will look for mainly VFR conditions with the caveat the isolated-
scattered convection may put a dent into those plans. Chances are
too low for inclusion at any site other than KEAU at this point
but will monitor radar trends and amend as needed. Best chances
for TSRA will be east of the I-35 corridor this afternoon and
evening. SW winds will be a little gusty this afternoon then
settle down to less than 10 knots this evening through tonight.

KMSP...Will keep MSP dry in the 25/18z TAF but chances are non-
zero that TSRA may impact the terminal. Potential for any
thunderstorms would be late this afternoon into the evening and
the bulk of the activity will be east of MSP. However, cannot rule
out an isolated thunderstorm so will continue to monitor.

SUN...VFR. Wind SW less than 5 kts.
MON...VFR. Slight chc TSRA late. Wind S 5 kts.
TUE...Mainly VFR. Chc -SHRA/-TSRA. Wind SE 5-10 kts.




AVIATION...JPC is the U.S. government's official web portal to all federal, state and local government web resources and services.