Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 251837

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
137 PM CDT Sat Mar 25 2017

.Updated for 18Z Aviation Discussion...
Issued at 129 PM CDT Sat Mar 25 2017


.SHORT TERM...(Today and tonight)
Issued at 335 AM CDT Sat Mar 25 2017

Short term concerns are cloud trends today and timing of light rain
chances later this afternoon and overnight.

Low clouds remain over most of the cwa this morning. Moist lower
level flow continues through the day. The HRRR and 0.5km
condensation pressure deficit forecast continues a mostly cloudy
trend for the day. Some indication of some thinning of the moisture
over the northern areas into the afternoon.  We could see some
sunshine develop over that region for a time this afternoon. This
would help temperatures warm close to 50. We will hold onto a more
cloudy trend with temepratures holding mainly in the 40s. Isentropic
forecast at 295K surface shows saturation lifting northwest over the
southeast area of the cwa mainly during the afternoon. Will hold
onto the small chance of light rain for the afternoon there.

The upper circulation  lifts a bit northeast and spreads deeper more
moist early flow over the region. We expect some light rain or
drizzle to work into central MN during the night...with highest pops
in west central Wisconsin. With clouds around again tonight...
lows should remain in the middle 30s.

.LONG TERM...(Sunday through Friday)
Issued at 335 AM CDT Sat Mar 25 2017

Confidence in the model solutions starts high for the Sunday
through Tuesday period, lowers to moderate by midweek and then is
quite low by Friday.

Looking at the big picture, a series of short waves/closed upper
lows will dominate the southern stream during the long term. The
first one will be south of us on Sunday and will lift northeast
across the Great Lakes on Monday. This has been well advertised by
the deterministic solutions with the eastern FA being brushed by
some light rain from Sunday into Monday. Tuesday remains the best
day of the long term as an elongated surface ridge moves through
with plenty of sunshine expected. One concern for Tuesday morning
is the potential for fog, especially eastern areas where it will
have rained. However, lingering mid level cloudiness is
anticipated early on, which should help mitigate the fog

The next short wave/closed upper low will be moving into the
Southern Plains on Wednesday. The GFS still prefers to shear this
system out to the east-northeast while the EC wants to remain more
closed and begin heading our way due to an upstream kicker.
Although the GFS shears out the southern wave, it now has a much
stronger northern stream wave impacting our area. So, either way
we end up with showers, either coming in from the west with the
northern wave, or from the southwest with the southern stream
feature. Much of the rain chances for Wednesday were confined to
western MN with pops spreading east during the night and
continuing on Thursday.

Things totally unwind by the time Friday arrives. The EC continues
to bring the southern stream feature into the Middle MS Valley
with plenty of showers indicated across our area. We would be in a
northeast low level flow pattern with highs from the EC in the
upper 30s to middle 40s. On the other hand, because the GFS had
sheared out this southern wave to the east, it has a new northern
stream wave approaching along with a pretty strong warm front
moving in. Highs from the GFS are progged in the lower to middle
60s. There was discussion from some of the surrounding offices on
lowering highs to be more in line with the EC. However, just
seeing how these waves have been behaving, we kept our highs in
the middle of the two ranges with lower to middle 50s indicated.
Only small chance pops were used as well.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 129 PM CDT Sat Mar 25 2017

Clouds have been slow to lift today, so lowered them slightly from
the previous forecast. Guidance continues to bring down ceilings
again tonight, so expect IFR/LIFR conditions with period of light
drizzle at the eastern Taf sites. Clouds will be very slow to lift
again on Sunday. Winds will be northeast throughout the period.

Ceilings should rise above 1700 feet for a few hours this
afternoon, but expect them to lower again later this evening as
moisture increases with the band of light rain lifting up from the
south. Overnight expect ceilings to drop near or below 700ft, and
remain below 1700 ft through Sunday.

Mon...MVFR early, then VFR. Wind N 5 kts.
Tue...VFR. Wind NE 5 kts.
Wed...VFR. Wind SE at 10kts.




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