Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 310358
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1058 PM CDT MON MAY 30 2016

.SHORT TERM...(This evening through Tuesday)
Issued at 258 PM CDT Mon May 30 2016

Several short waves are noted across the Dakotas and Nebraska this
afternoon. These waves will move eastward tonight and be the main
focus for widespread precipitation in Minnesota.

Therefore, categorical pops are noted based on moisture advection
and lift associated with the main short wave moving across the
Dakotas and into the Upper Midwest overnight. The models have slowed
the frontal boundary moving across Minnesota on Tuesday which leads
to a higher chance of thunderstorms in eastern Minnesota and western
Wisconsin Tuesday afternoon. As the main 50H height falls move
across northern Minnesota and boundary layer winds become more south-
southwest Tuesday in eastern Minnesota, I don`t see why the
continuation of showers and thunderstorms for the eastern 1/4 of MPX
forecast area through Tuesday afternoon.

Another aspect on tonight`s forecast is that PWATs values rise to
1.4 inches (95 percentile for Minnesota this time of year), the
probability of heavy rainfall increases. Current QPF amounts of
widespread one half to one inch looks reasonable. So, with a good
probability of thunderstorms, you can increase these values by 3
times in localized areas. So I wouldn`t be surprised to see 1-3
inches of rainfall where thunderstorms begin to train. It was also
noted that some backbuilding of the thunderstorms is possible
based on area soundings, so this increases the chances of
localized flooding where 1-3 inches of rainfall occur. Some of the
CIPS anomalies of 1 or 2 inch rainfall totals in a 12 or 24 hour
period is highlighting areas in eastern Minnesota overnight and
Tuesday.

As for severe thunderstorms, instability remains low (500-1000 J/Kg)
overnight, but shear values (0-3 km) do support organized convection
in western Minnesota this evening. As for Tuesday afternoon on
redevelopment of severe thunderstorms, this will depend on if we can
destabilize during the afternoon. However, shear values are only 20-
25 knots which means mult-cell or less organized convection.

.LONG TERM...(Tuesday night through Monday)
Issued at 258 PM CDT Mon May 30 2016

Wednesday will be cool and blustery with clouds developing by late
morning, and a few afternoon showers scattered across the region.
Drier more seasonable weather will settle in Thursday. On Friday
another system will bring thunderstorm chances across the region,
with slightly drier weather for the weekend.

A strong upper level low will move across the region on Wednesday.
H500 height rises are slow to follow in its wake. The lack of strong
subsidence together with the H850 cold air advection should lead to
a widespread cumulus field by late morning. Forecast soundings
support this idea, and for that reason have increased clouds on
Wednesday. Northwest winds will also be gusting around 20 mph, so
raised wind speeds in the forecast to reflect this. Lastly, a
shallow layer of instability should yield some scattered showers
during the afternoon. Given the combination of the aforementioned
parameters, have lowered high temps on Wednesday below guidance.

Looking ahead, high pressure will build in on Thursday, but the dry
weather is short lived as another system from the northwest will
dive down and bring showers and thunderstorms. The deep layer shear
profile will support organize convection, but forecast soundings
only show around 1000 to 1500 j/kg of cape, so the thermodynamic
environment will be the limiting factor. The cool northwest flow
will keep slight chances for showers and thunderstorms through the
weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1055 PM CDT Mon May 30 2016

Thunderstorms are expanding and impacting portions of central and
southern Minnesota late this evening. KRWF/KAXN are being affected
already. We expect the rain to expand into eastern Minnesota
between 2am and 6am. Overall...the amount of thunder and intensity
of rainfall seems to be trending downward for the morning.

KMSP...

Threat for weak thunderstorms are concern primarily for the
morning rush. We think thunder will be in the vicinity just before
sunrise as the traffic volume increases. Storms will be
approaching from the west-southwest late tonight. Overall...the
amount of thunder looks to be less than what we were thinking
earlier today.

/OUTLOOK FOR KMSP/

WED...VFR. Isolated SHRA/TSRA. West wind 10 to 15 knots.
THR...VFR. West-Northwest wind 5 to 10 knots.
FRI...VFR. Chance of MVFR and thunderstorms. South wind 5 to 10
knots.

&&

.MPX Watches/Warnings/Advisories...
WI...None.
MN...None.
&&

$$

SHORT TERM...CLF
LONG TERM...JRB
AVIATION...CLF



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