Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 231708

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1208 PM CDT Tue May 23 2017

.SHORT TERM...(Today and tonight)
Issued at 330 AM CDT Tue May 23 2017

Surface analysis early this morning shows a low pressure center
near the MN/WI/IA triple point with a cold front extending
southwest through central IA, southeastern NE into central KS.
Aloft, a large cutoff low is analyzed over central MN within a
large longwave trough encompassing much of the central CONUS. A
potent shortwave axis is rotating southward around the western
periphery of the upper low, and this feature shows up nicely on
both IR and WV imagery, driving nearly due south over the eastern
Dakotas and western MN. Showers currently on KMPX radar are moving
in different directions depending on which part of the coverage
area described: western portions are seeing southeastward-moving
showers while eastern portions are seeing north-northeastward
moving showers. This is owing to the upper level low nearly atop
the coverage area. While the surface low with is associated fronts
are expected to shift slowly off to the south and east, the upper
level low will move nearly due south through MN into IA today and
tonight. While in a deeply moist atmosphere, sporadic rain
showers will rotate through the coverage area all day today then
gradually erode to the east this evening through overnight
tonight. Because of the lack of surface aid to the precipitation
formation, lift will be solely generated by the upper level
feature and, as such, QPF will be reduced to a few hundredths to
possibly a tenth of an inch. Have used coverage wording to
indicate the thinking that showers will come-and-go, rather than
be persistent, and kept pops for most areas capped at 50s percent
to maintain "scattered" wording while far western MN may be more
susceptible to the "numerous" wording with 60 percent pops.
Regardless, showers will be weak and intermittent little rainfall
accumulation. Have also omitted mention of thunder since any
instability will be south and east of the front, thus not
available for this area. That said, a few of the showers could
produce very small hail (i.e. graupel), owing to the cold core
nature of the upper low. The precipitation will come to an end by
daybreak tomorrow morning with mainly cloudy skies in place. As
for temperatures, being behind the front and having cloud/rain
complications underneath the upper level low will promote cooler
conditions than that was experienced yesterday. Highs today will
range 55-60 degrees followed by lows tonight dropping to the low-
mid 40s.

.LONG TERM...(Wednesday through Monday)
Issued at 330 AM CDT Tue May 23 2017

The longer term concerns are timing of the next frontal passage
Thu night/Fri night time frame and development of the long wave
pattern into the holiday weekend.

Initially the upper low pressure trough exits to the east of the
area Wednesday. Drier air and surface ridging moves over the cwa
during the day. This should provide dry conditions along with cool

Timing of the next frontal passage looks to be Friday/Friday night
with initial waa pattern developing into Thursday night over the
west. This will develop a small chance of showers as this upper
trough swings across the Dakotas. As the upper trough moves east,
the front will be driven east Friday/Friday night. Convective
potential appears low at this time the meager moisture and
instability noted on deterministic models. Will hold onto some
slight chance thunder for Friday afternoon/evening to the east.

The GFS and ECMWF diverge some on the overall upper air pattern
over the weekend with the GFS slower and more amplified with the
upper low. We maintained the small chance PoPs for Sunday and
Monday at the moment. Appears temperatures will warm through the
lower to mid 70s into the weekend with a cooling trend into early
next week as the trough exits the area.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1210 PM CDT Tue May 23 2017

VFR, with a brief period of MVFR or IFR is likely this afternoon
as several waves of showers move across central/southern
Minnesota, and west central Wisconsin. Typically, this time of day
cigs begin to rise. But, with ample boundary layer moisture and
several weak waves of energy generating showers, cigs will likely
hold between 3k to 4k. A very brief period of IFR vsby is
possible in south central Minnesota due to a more concentrated
area of showers slowly moving southward. A persistent
north/northeast surface wind will continue as the mean surface low
tracks from southwest Wisconsin, southeast into the Ohio Valley.
MVFR cigs likely will redevelop across northern Wisconsin this
evening, and move southwest across Wisconsin, and the southern
half of Minnesota overnight.


No other changes to aforementioned discussion as mainly VFR
conditions will prevail this afternoon. Only a brief period of
MVFR cigs is possible along with scattered showers thru 02z. MVFR
cigs redevelop after 9z. Northeast wind will prevail thru the taf
period, but remain under 10 kts.


Thu...VFR. Wind SE 5-10 kts.
Fri...VFR. Chc MVFR/-SHRA. Wind SW 5-10 kts.
Sat...VFR. Wind W 5-10 kts.




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