Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 200021

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
721 PM CDT Thu Oct 19 2017

.SHORT TERM...(This evening through Friday)
Issued at 330 PM CDT Thu Oct 19 2017

We have one more day of mild and dry weather coming Friday as upper
ridging continues to build across the central CONUS. Today will be
the last day where fire weather issues are a concern though, as an
expected increase in dewpoints overnight will help keep humidities
up in the 30s/40s Friday. This increase in dewpoints overnight,
along with south winds staying up in the 5-10mph range will result
in very mild lows overnight, with much of the area staying in the
50s. Did warm the forecast overnight closer to a blend of the raw
deterministic models.

For Friday, the gradient kicks up over what we have today as low
pressure deepens over the western Dakotas as the strong wave moving
into the Pac NW moves over the northern Rockies Friday. In addition
h85 winds will be picking up to around 50kts. Both mean wind speeds
tomorrow will be up 5-10 mph than what we are seeing today. Looking
at forecast soundings, we should have no problem getting gusts to 35
mph out in western MN, with some gusts up around 40 mph not out of
the question. For temperatures, we did knock our highs back a couple
of degrees. Mixing down our 925mb temps of around 18c supports highs
in the mid/upper 70s, so did nudge forecast highs down a couple of
degrees from what we had. This still keeps us around 5 degrees above
the blended guidance, so even though we did cut back on
temperatures, we are still keeping the trend of keeping highs
several degrees above what guidance gives us.

.LONG TERM...(Friday night through Thursday)
Issued at 330 PM CDT Thu Oct 19 2017

The long term period will feature three significant troughs
moving through the area. The first one will be associated with
thunderstorms Friday night through Saturday night, the next one
Monday will bring in much cooler air with showers, then another
one Thursday will bring showers and another surge of cool air.

The upper high that has brought such mild weather will be in the
eastern states Friday evening, and moisture will have surged
northward and will continue to do so Friday night and Saturday. By
Saturday morning, dew points should be in the upper 50s across much
of our MN area, and lower 50s in Wisconsin.  There will be a lead
short wave arriving Friday evening associated with the main western
trough, and Friday evening is when the first showers will be
possible. A strong low level jet around 50 knots and continuing
instability will keep the potential for storms late Friday night and
Saturday morning, even though there is no obvious embedded upper
wave. But the full latitude trough begins moving in Saturday
afternoon, and so storms should become abundant Saturday afternoon
and continue into the evening. The GFS remains the fastest of the
main models, and it seems likely to be too fast. Storms should exit
MN early Saturday evening, and end in Wisconsin later in the

The next significant trough arrives Monday, and it will deepen, with
an upper low developing in Wisconsin Tuesday morning. It will be a
significant contrast in temperatures, with 850 mb temps Tuesday
morning around -4C. Which compares to +18C or so later today. A
rather healthy cooldown indeed. Cool temps and showery conditions
will be widespread.  After that goes by, there will be a brief
warmup before the next trough arrives Thursday with another surge of
cool air. Quite the push pull pattern right now.


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 720 PM CDT Thu Oct 19 2017

Winds will become less gusty tonight but remain out of the south
around 10 kts. Winds will become gusty again by late tomorrow
morning, with southerly winds gusting up to 25-30 kts. VFR
conditions will prevail with cirrus will become more widespread
towards evening.

Expect winds to gust 5-10 kts higher tomorrow vs. this afternoon.
Gusts out of the SSW around 25 kts expected to pick up by 17z

Sat...Chc MVFR. Aftn SHRA/CHC TSRA. Winds S bcmg W 10-15 kts.
Sun...VFR. Winds WSW 5-10 kts.
Mon...VFR. Winds W 5-10 kts.



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