Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 172333

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
533 PM CST Fri Feb 17 2017

.SHORT TERM...(This evening through Saturday)
Issued at 345 PM CST Fri Feb 17 2017

The main short term concern remains temperature trends.

Weak surface trough/pacific front moving across eastern MN this
afternoon and responsible for the record warmth over parts of
Minnesota this afternoon. This will shift east this evening and
winds will gradually become light west overnight. We expect lows to
remain above freezing in snow free areas with perhaps a below
freezing temepratures limited to the heavier snow covered areas
along the northeast periphery of the cwa.

Cooler readings are expected into Saturday with afternoon highs
probably some 5 to 10 degrees cooler to the south...but remaining
some 15 to 20 degrees above normal across most of the area. There
does look to be some increasing high clouds from west to east during
the afternoon...which may limit heating somewhat to the west.

.LONG TERM...(Saturday night through Friday)
Issued at 345 PM CST Fri Feb 17 2017


There is literally a little bit of everything in this long term
forecast, so as the overused saying goes, "if you don`t like the
weather, wait 5 minutes."

A high pressure center will slide east to Wisconsin Saturday night
with return flow beginning again across Minnesota. The wind should
be strong enough to keep temperatures above freezing there. 925 mb
temps will rebound back to around +13C across southwestern MN and
+10C across central MN into northern WI. Those are not quite as
warm as today, plus we`ll have quite a few high clouds so not
expecting a complete repeat of today`s temps but they are expected
to still break records.

The system breaking the rest of southern California`s drought
today will eject into the western High Plains Sunday night. The
meridional flow Sunday night and Monday will bring moisture
northward deep from the tropics on a southerly 35-50 kt LLJ. PWATs
are expected to reach nearly 1.2 inches by Monday morning, which
would be over 5 standard deviations above normal, and far
eclipsing the monthly record of 0.87 inches at MPX. Even the
records for the first half of April are around 1.2 inches. With
the increasing moisture and dew points reaching the 50s,
temperatures will hold nearly steady Sunday night in the 50s
across southern and western MN and in the mid to upper 40s north
of I-94. These readings are likely to exceed the warm low monthly
records by several degrees at MSP, STC, and EAU.

Rain will blossom late Sunday night across the eastern Plains as
the system approaches, with that arc of precip reaching MN early
Monday morning and WI by late morning or afternoon. In addition to
the deep moisture, best LIs on the NAM and GFS fall to -4 to -6C
indicating quite a bit of instability. Therefore, increased the
thunder mention. There could be some small hail with the stronger
cells if that magnitude of instability materializes.

Not much cold air follows the early week system. In fact,
thicknesses rise Tuesday again back into the mid 550s DM with 925
mb temps of +9 to +13C, similar to today and Sunday. Currently
calling for highs in the mid 50s to lower 60s, but they may need
to be raised in subsequent forecasts.

Temperatures modify slowly midweek as high pressure to the north
builds south and tightens the baroclinic zone along I-80.
Meanwhile, a potent upper wave crashing ashore central CA Tuesday
night will eject eastward to the central Plains Thursday and begin
to interact with the tightening baroclinicity. There has been
some differences amongst the models with the temporal, spatial,
and strength of the resulting low pressure system. The GFS and the
GEM have been a bit further north than the ECMWF primarily due to
how they handle the interaction between the wave and the northern
stream. The ECMWF has no such interaction, thereby maintaining a
split flow and results in a more easterly propagating low along
the baroclinic zone. The ECMWF track would be a very favorable
path for heavy snow across the entire CWA. Several of the GEFS
members have shown this as well. Only time will tell which
solution wins out. Regardless, the magnitude of the kinematic and
moisture fields with this storm point to the potential for a very
high impact event somewhere nearby. The 2 inches of QPF on the
ECMWF and the 1-2 inches on the GFS would certainly be capable of
12+ inches in a stripe north of the low.

It should be noted...because the QPF is so high and similarly placed
on all the guidance, the model blend we populate with has already
gone with 70-90 PoPs from Thursday through Friday evening.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 533 PM CST Fri Feb 17 2017

A n-s cold front was at STC to start this period and will be working
across the rest of the area over the next few hours, switching
winds around to the west. Only weather concern tonight is the
potential for vis restriction in hz/br, like was seen at AXN last
night. We will have stronger winds than last night, but LAMP
continues to show vis getting down to 1/4sm at AXN in the morning.
For these TAFs, basically followed timing and restrictions that
were observed last night again for tonight. Surface ridge arrives
Saturday, which will cut the winds to basically nil by the
afternoon, though we will have mid/upper cloud cover by then.

KMSP...high confidence in all aspects of TAF.

SUN...VFR. Wind SSE at 5-10 kts.
MON...MVFR with SHRA Likely. ISOLD TSRA. Wind S 10 kts.
Tue...VFR. Wind SW at 5-10 kts.




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