Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 200330

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1030 PM CDT Thu Oct 19 2017

Issued at 1026 PM CDT Thu Oct 19 2017

Updated to include 06z aviation discussion below.


.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 Pacific 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 evening.

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 06Z TAFS through 06Z Friday night)
Issued at 1026 PM CDT Thu Oct 19 2017

VFR conditions will continue through this TAF set though upper
level clouds will fill in, developing high ceilings during the
day, then gradually lowering late day tomorrow through tomorrow
night. Winds will remain out of the south around 10 kts then
increase to around 15 knots tomorrow, gusting up to around 25 kts.

KMSP...Expect winds to gust 5-10 kts higher Friday afternoon
compared to Thursday afternoon. Gusts out of the SSW around 25 kts
expected to pick up by 17z Friday.

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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