Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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 232020

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
320 PM CDT MON MAY 23 2016

.SHORT TERM...(This evening through Tuesday)
Issued at 319 PM CDT Mon May 23 2016

A moist and unstable corridor has developed today from eastern
Nebraska on northeast into central Minnesota. PWAT values by this
evening are progged to be well above the 90th percentile across
southern MN and actually just about a tenth of an inch below the
daily max of 1.64 inches.

The CAMS have been back and forth today on the initiation of the
afternoon convection across southern MN and points northeast. It
appears now that by around 4 pm there should be some scattered
storms from near Redwood Falls to north of the Twin Cities metro.
The kicker for this activity is a short wave over eastern Nebraska
that will drive northeast this evening. Hence, likely to categorical
pops remain in place from south central through east central MN and
west central WI for a time tonight. The better showers and
thunderstorms will be capable of brief heavy downpours due to the
high PWAT values. There remains some concern for severe storms
through this evening, but the low level wind field is weak and
rather unorganized at this point. Still, a few storms with wind
gusts to 35 knots and small hail can`t be ruled out.

Another concern overnight is the potential for extensive stratus and
fog in the wake of the showers and thunderstorms. This is due to the
weak wind field and clearing expected overnight along with a nearly
vertical hydrolapse. Areas of eastern/southern MN and west central
WI are most vulnerable.

Tuesday still looks like a mostly dry day although a few random
showers can`t be ruled out across central MN and west central WI. It
should be a warm day across central and southern MN with 850mb
temperatures climbing to around 16 deg C here in the Twin Cities to
around 18 deg C at the western border. Mix-down from 750mb yields
highs in the middle to upper 80s from the Twin Cities on west.

.LONG TERM...(Tuesday night through Monday)
Issued at 319 PM CDT Mon May 23 2016

An active long term forecast period will ensue as active southwest
mid level flow prevails through the Memorial Day weekend. Expect
several bouts of widespread showers and thunderstorms through then,
with several inches of rain expected. Temperatures will be
slightly above normal /5-10 degrees/ through Friday, and then
retreat back closer to normal for the weekend.

Confidence in the shift to a more active pattern as described
above is high, although timing of the precipitation rounds will be
a bit tricky due to them being a product of rather weak shortwaves
in the southwest flow. That being said, it does appear that
Tuesday evening will be a dry window of time, and then soggy
weather arrives for Wednesday as a shortwave and warm front lift across
the area. The next break appears to arrive Wednesday night into
Thursday, although given the variability in models, there is at
least a 30 percent chance Thursday into Friday. The next stronger
wave and surface trough are progged for late Friday and Saturday,
so 50-60 percent chances for showers and thunderstorms were
justified during that time frame.

So, in summary, Wednesday and Saturday look to have the highest
potential to have widespread showers and thunderstorms, with more
fleeting and less concentrated activity possible on the other
days. Although severe weather cannot be ruled out for any of those
days at this point, it would more likely occur in conjunction with
the surface lows...currently progged for Wednesday/Saturday.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1215 pm CDT Mon May 23 2016

SHRA/TSRA will become widespread by mid afternoon from southwest
through east central MN. The storms will progress slowly eastward
through the late afternoon and evening across western WI. The
terminals that will be primarily affected this afternoon and early
tonight include KMSP...KRNH and KEAU. Outside of the TSRA chances,
there are two concerns going forward. The first is the threat for
MVFR ceilings to develop this afternoon due to the very moist low
level conditions developing. This is echoed in the 0.5 deg
condensation pressure deficits from the RAP. LAMP indicates
little to no chance so will keep the MVFR to the tempo groups. The
second concern is mvfr or lower conditions with fog after midnight
tonight through daybreak Tuesday across eastern MN and western WI
where the SHRA/TSRA occur this afternoon and evening. NAM Bufkit
hydrolapse profiles are either vertical or increasing with height
for the aforementioned areas. Hence, included low MVFR/IFR

KMSP...latest short term guidance indicates storms could develop
just west and north of the airfield in the 19z-20z time frame and
then progress slowly across the Twin Cities through 00z-01z. Used
a four hour tempo group from 20-24z to indicate this threat as
there is some uncertainty on the exact time of initiation. A few
of the storms could produce wind gusts to 35 knots. Confidence is
high on the mvfr ceilings and vsbys late tonight in the wake of
the afternoon and evening SHRA/TSRA.

TUE...MVFR/IFR early...then VFR. Wind S 5 kts.
WED...Mainly VFR. TSRA/MVFR Likely. Wind light and variable.
THU...Mainly VFR. CHC TSRA/MVFR. Wind south-southwest 5 kts.


.MPX Watches/Warnings/Advisories...


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