Area Forecast Discussion
Issued by NWS Twin Cities, MN

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146
FXUS63 KMPX 191801
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
101 PM CDT Sat May 19 2018

.SHORT TERM...(Today and tonight)
Issued at 305 AM CDT Sat May 19 2018

A cold front was moving across the region with north winds and much
cooler temperatures behind it, along with low stratus. These cloud
and the cold air advection behind the front will keep afternoon
highs only in the 60s for most locations today and the
north/northeast winds will make it feel much cooler than the past
few days. There is a chance for a few afternoon showers in western
Wisconsin later this afternoon as the frontal boundary passes
through.

Meanwhile, early morning satellite imagery with Rap13 500mb heights
and winds identified an area of thunderstorms across the Great
Plains. This thunderstorm complex was tied to an upper level wave
upstream, and forecast models bring this upper level shortwave over
Nebraska into Iowa by later this evening. Positive vorticity
advection emanating from this shortwave trough will lead to ascent
and a chance for rain along I-90 Saturday night. There is cold
advection, and no CAPE, so not expecting any thunder.

.LONG TERM...(Sunday through Friday)
Issued at 325 AM CDT Sat May 19 2018

The forecast in the extended outlook has low confidence on any
one day getting any more than isolated/scattered showers/storms
past Monday. However, by late next week there is a slight
increase in rainfall potential as a more pronounced short wave and
cold front move across the Upper Midwest.

Sunday will have a good chance of rainfall along the Iowa border
as the pesky storm system that has plagued the central plains over
the past few days begins to drift northward into Iowa. Rainfall
totals still remain quite low as much drier air continues to
advect southward in the wake of the cold front moving across the
region early this morning.

Return flow develops Monday as high pressure moves off to the
east. Moisture will once again increase, with subtle hints of
another weak disturbance moving southward by midweek. The mean
upper flow remains weak over the Upper Midwest as the split flow
regime dominates the region, and an upper ridge builds back across
the Northern Plains, and parts of southern Canada by midweek. The
only hint of rainfall chances increasing across our region is
related to a low level jet developing Tuesday night/Wednesday
morning. Placement of this low level jet is questionable and even
the models have differences in the location. However, all models
do support some complex of thunderstorms developing along the
nose of this low level jet sometime Tuesday night.

By late next week, models seem to indicate a weakening in the
upper ridge with a stronger short wave moving southeast along the
Canadian border. Thus, as mentioned before, there is a slight
increase in rainfall potential during this time period. By next
weekend, as per the latest model run, much cooler weather will
follow the cold front late next week. In the meantime, other than
this weekend, next week will remain above normal in terms of
temperatures. I wouldn`t be surprised to see highs increasing each
day based on the drier soil moisture levels over the past week.
Even the last couple days, models have been too cool for daytime
highs. Thus, if we don`t get any significant rainfall next week,
highs will likely be 5 to 10 degrees higher than currently forecast.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 101 PM CDT Sat May 19 2018

Satellite shows clouds quickly dissipating as we continue to warm.
Current TAFs were tracking pretty good on improvements to VFR and
continued to run with a blend of the fast to improve HRRR and
slow to improve LAMP. Dry northeast winds will push these clouds
down into Iowa and expect MVFR or lower cigs to only make it about
as far north as I-90 tonight, or south of all MPX terminals.
These dry northeast winds will also keep any rainfall away from
the MPX terminals, with rain currently moving north across Neb/IA
expected to make it about as far north as the I-90 corridor
tonight.

KMSP...CIG heights are starting to trend up and think we`ll be
018 or higher by 1830z, so started MSP off above 017. Looking at
satellite, stratus happens to be thickest from RWF, through the
Twin Cities and off to RNH, so believe what we are seeing with the
NAM/GFS/RAP in that we will not finally lose these clouds until
around 00z. Rest of the period its VFR as we just see mid/high
clouds stream north from activity down across the Plains.

/OUTLOOK FOR KMSP/
MON...MVFR. Chc -SHRA. Wind E 5-10 kt.
TUE...MVFR/chc IFR cigs early, then VFR. Wind SE 5 kts.
WED...VFR. Chc -shra/-tsra. Wind SE 5-10 kts.

&&

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

$$

SHORT TERM...JRB
LONG TERM...JLT
AVIATION...MPG



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