Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 211113
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
613 AM CDT Sat Apr 21 2018

.UPDATE...
Issued at 613 AM CDT Sat Apr 21 2018

Updated to include 12Z aviation discussion below.

&&

.SHORT TERM...(Today and tonight)
Issued at 320 AM CDT Sat Apr 21 2018

Early morning infrared imagery and Rap13 500mb surface pressure and
winds showed a storm system across the central Conus with
thunderstorms to the south across Oklahoma and Texas, and high/mid
level clouds to the north across South Dakota, Minnesota, and
Wisconsin. The radar showed echoes across southwest Minnesota, but
there was nothing reaching the ground according to the surface obs.
There is a slight chance for a rain/snow shower through about
sunrise along I-90.

Clouds will hang around most of the day across the south, but areas
to the north should see more sun today. As a result high
temperatures once again are warmer along and north of I-94 than they
are across I-90. Winds will be very light and generally out of the
south. Expect another seasonably cool night, with overnight lows
around 30.

.LONG TERM...(Sunday through Friday)
Issued at 320 AM CDT Sat Apr 21 2018

No significant changes to the longer term forecast. There is still
potential for rain Tuesday and Tuesday night. At the same time, the
uncertainty in the phasing of the northern and southern stream,
together with the lack of deep moisture mentioned in the previous
discussion gives some pause as to increasing the precip chances
beyond the blended guidance.

Temperatures on Sunday and Monday will be the warmest of the year so
far. With that said, the relatively weak H925 winds of only 10 to
15kts will limit the mechanical mixing of the boundary layer and put
a ceiling on the potential for afternoon highs. Should still see
widespread 60s, but as of now it looks like 70s might be a bit of a
reach.

As mentioned earlier, an upper level PV anomaly originating from the
Pacific Northwest will phase together with the northern stream wave
and push a cold front through the region. Showers will develop
along this frontal boundary, but the heaviest precip seems to be
trending along the Missouri River Valley with the vorticity
maxima. The mid levels are pretty much moist adiabatic so there is
little if any CAPE, and this will hold off any chance of thunder,
and produce a near-zero threat for severe weather. It is late
April, so figured mentioning the lack of thermodynamic support for
convection was relevant.

This system will depart to the southeast on Wednesday, but another
northern streams shortwave will follow on its heels for Thursday.
Most of the precipitation associated with this wave will be to the
north along the International border, but it does bring down another
round of arctic air for later next week. Its too early to tell how
cold temperatures will be, but it certainly looks like a return to
below-normal temps is likely for Thursday and Friday, but there
are mixed signals as to how long the cool-down will last. The GEM
21.00 keeps the majority of the cold to the east, while the GFS
and ECMWF are more focused across the Upper Midwest.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 613 AM CDT Sat Apr 21 2018

VFR conditions will prevail through the period as high pressure
centered over the Great Lakes continues to slowly move east.
An upper low over the southern Plains will continue to push some
mid/high clouds into the region today, mainly across the southern
portion of the area.

KMSP...No concerns at this time.

/OUTLOOK FOR KMSP/
Sunday afternoon through Monday night...VFR. Southeast wind less
than 10 kt.
Tuesday...MVFR expected with a chance of rain. Northeast wind 10
to 15 kt.
Tuesday night...MVFR possible early with a chance of rain.
Northeast wind 10 to 15 kt.
Wednesday...VFR. Northeast wind less than 10 kt becoming variable
5 kt or less.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

UPDATE...
SHORT TERM...JRB
LONG TERM...JRB
AVIATION...


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