Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 171955

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

.SHORT TERM...(This evening through Saturday)
Issued at 154 PM CST Fri Nov 17 2017

Early this afternoon, surface low was positioned across eastern
Nebraska with an inverted trough extending into Minnesota.  East of
the trough axis which also corresponds to the 850mb trough,
southerly flow continues providing a continuous supply of saturated
air with dewpoints in the mid 30s. As expected for today,
temperatures warmed above freezing and no icing issues have been
reported.  The moisture currently in place will not move much until
the arrival of the cold front coming down from North Dakota.

As of early this afternoon, the front just went through Alexandria
which noted a complete 180 degree wind direction change from 150
degrees (southeast) to 330 (northwest).  The front will slowly move
through the region tonight, taking until tomorrow morning before
finally moving through the I-90 corridor.  Expect drizzle and low
clouds to continue across the eastern third of Minnesota and all of
western WI.  When the front eventually moves through, the low
stratus will depart but for Saturday we`ll see a mix of sun and mid
and high clouds moving through.

Temperatures will be held in check with persistent northwest flow
tomorrow.  Expect highs of 25 to 35 degrees across the region with
15-20 MPH northwest winds, gusting in the 20-30 MPH range.

.LONG TERM...(Saturday night through Friday)
Issued at 154 PM CST Fri Nov 17 2017

The long term still consists of a roller coaster ride of tempeatures
and little in the way of precipitation.

By tomorrown night, the next feature to watch will be the trough off
the coast of British Columbia because it will quickly lead to
surface cyclogenesis and a strong low pressure system emerging from
the Canadian Rockies by early Monday morning.  We`ll begin to see
the start of the warm air advection wing arrive as south-
southwesterly increase by Sunday afternoon.  This will mostly affect
far western MN as tempertaures Sunday should be about 10 degrees
warmer than Saturday.

As the 988mb surface low moves due east across far southern Canada
through Monday, continued warm air advection will persist through
the day.  High temps across the area look to reach the upper 40s to
lower 50s.  The cold front associated with the strong low in Canada
will move through overnight into Tuesday morning and it looks to
come through with no precip.  It will bring much cooler air in
behind the front, so high temps will be about 20 degrees cooler on
Tuesday as opposed to Monday.  Strong northwest winds will accompany
the arrival of the colder air.

At this point in the forecast, the guidance starts to disagree on
overall timing and evolution of the large trough over the Great
Lakes.  The GFS offers a more amplified patter in which the trough
is deeper and remains in place longer, so it has gone colder for
Thanksgiving Day.  However, the ECMWF remains the more consisten
solution run to run.  The ECMWF indicates a stronger upper level
ridge and pushes the trough northeast of the area, indicating warm
air moving in for Thanksgiving.  The blended forecast indicates
highs near 40, but with more reliance on the ECMWF, we think chances
are better that we will see warmer temperatures than that.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1208 PM CST Fri Nov 17 2017

Low stratus and drizzle across much of eastern MN and western WI
as expected early this afternoon. The incoming cold front is
pushing into extreme western Minnesota as southeast winds have
turned around to northwesterly in that area. An inverted surface
trough axis extending north northeastward from far eastern
Nebraska has been a good dividing line between the low stratus and
drizzle to the east of that line, and mainly passing high clouds
to the west with as the low clouds get scoured out.

So, the guidance may be overly pessimistic today in how far east
the vfr cigs make it. It`s reasonable though to expect the stratus
to halt its progression this evening until the actual cold front
moves through overnight to scour out the moisture. Currently
trending to that forecast for eastern MN and western WI, which
means continued MVFR or even IFR at times through the night, with
improvement tomorrow.

KMSP...Already seeing VFR cigs about 50-75 miles west of MSP, so
it is a bit of a concern that the forecast may be too pessimistic.
Latest satellite trends do show some new formation of stratocu to
the west, and the models would say that trend should continue. For
now, felt this was the most likely scenario but will monitor
closely if conditions change.

Sun...VFR. Wind SW-W 5-10 kts.
Mon...VFR. Wind S 5-10 kts.
Tue...VFR. Wind NW 10-20 kts.




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