Area Forecast Discussion
Issued by NWS Twin Cities, MN

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647
FXUS63 KMPX 281640
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1140 AM CDT Tue Mar 28 2017

.UPDATE...For 18z Aviation discussion below

&&

.SHORT TERM...(Today and tonight)
Issued at 330 AM CDT Tue Mar 28 2017

There are three concerns for the short term. The first is
additional fog development early this morning, high temperatures
today and the chance of rain late tonight.

A surface ridge stretches north to south along the western spine of
MN early this morning. Widespread dense fog has formed in eastern ND
and is pushing slowly southward into northeast SD. Short term
guidance keeps this just to our west through daybreak and no
headline is expected at this time. Farther east, areas of fog were
common over south central MN on northeast through west central WI.
So far, only isolated spots of dense fog are noted, with one being
at the KEAU airfield, which is typical in this pattern. There has
been an increase in mid level clouds across west central and
southwest MN, ahead of a mid level trough that stretches west to
east across central MN and WI. In addition there are also some high
level clouds streaming across the southern third of MN. Current
thinking is that any dense fog will likely be confined from near
KAEL to KEAU. Will continue to monitor for a dense fog advisory, but
not planning one at this time.

Once the H7 trough moves south of us by mid morning we will be
looking at a good deal of sunshine for the rest of the day. The 925-
850mb column is a degree or two warmer over that on Monday. Hence,
highs should be at or above what we experienced, which got out of
control in the Twin Cities with lower 60s. Mix-down from 850mb
supports 60-65 from the Twin Cities on WNW through KRWF, KBDH and
KAXN. Readings to the east and south are more in the 55 to 60 degree
range. Guidance used to make the thermal gradient sharper included
an equal blend of BC ADJMET, BC GFS and BC CONSRAW.

The surface ridge will move off to the east of the FA early tonight
with increasing SE low level flow. It will be a warmer night with
lows in the upper 30s from the Twin Cities on WNW with 30-35 to the
north, east and south of KMSP. The third in a series of a strong
upper low in the southern stream will advance into the central and
southern Plains overnight. The CAMS keep the leading edge of the
light rain almost entirely out of our FA until after 12z Wednesday.
Therefore, only slight chance pops reach SW Martin county
through 11z.

.LONG TERM...(Wednesday through Monday)
Issued at 330 AM CDT Tue Mar 28 2017

The longer term concern remains the coverage of light rain
spreading over the southern third of Minnesota into west central
WIsconsin Wednesday into Thursday.

The deterministic models have pretty much come to a consensus of
drawing moisture into at least the southern third of Minnesota
during the day Wednesday...and then moving it east as the northern
and southern stream phase enough to generate enough moisture
transport into the region. The 290k isentropic forecast actually
draws lower level saturation central Minnesota and west central
Wisconsin Wednesday night and actually drops a couple hundredths
of an inch of liquid in this region. It still remains a question
of how far north and west this will develop...and we did draw PoPs
a bit farther north into east central Minnesota. Temperatures are
forecast to drop off into the mid 30s and thickness and lower
level boundary layer temepratures may get cool enough for at least
a rain/snow mix to the southeast late Wednesday night. Little or
no accumulation is expected however.

Following this system...drier air returns to the region as the
upper flow pattern remains split. Models still draw a waves in the
northern stream across the region during the Saturday/Saturday
night time frame. There is a wide spread in strength and how much
moisture will be available. We retained the small PoP for parts
of the cwa.

Models diverge further into early next week...with an increasing
threat of more widespread precipitation developing into early
next week. There remains a phasing issue with the western conus
trough and its counterpart to the north...so overall timing will
continue to be a problem. Overall...temperatures should remain
above normal through the period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1140 AM CDT Tue Mar 28 2017

Light winds and only a few high clouds will be found through
tonight. Therefore have high confidence in VFR through then, with
the exception of the potential for patchy fog redevelopment near
KRNH and KEAU toward daybreak Wednesday. Otherwise, will see and
increase/thickening of mid level clouds throughout Wednesday, with
-RA inching up toward sites from southern MN during the afternoon
hours. Winds will be east/southeast through the period at speeds
of 4-8kts.

KMSP...
High confidence in VFR through the period with an increase in
mid/high clouds on Wednesday. Rain chances hold off until after
00z Thursday.

/OUTLOOK FOR KMSP/
Wed ngt...VFR. Chc -RA. Wind ESE at 7-10kts.
Thu...VFR. Chc -RA. Wind E at 8-10kts.
Fri...VFR. Wind NE 4-8kts.

&&

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

$$

SHORT TERM...RAH
LONG TERM...DWE
AVIATION...LS



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