Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 180347
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1047 PM CDT Tue Oct 17 2017

.UPDATE...
Issued at 1041 PM CDT Tue Oct 17 2017

Updated to include 06z aviation discussion below.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 403 PM CDT Tue Oct 17 2017

The short term concerns are temperature trends and then fire
weather out west Wednesday afternoon.

Continued very warm with afternoon highs overachieving especially
to the lee of the Buffalo Ridge in southwest MN. A few locales
near 80. Expect lows overnight to cool once again but we should
see the boundary layer decouple most areas with more gradient
developing ahead of the incoming front.

This warm trend is expected to continue through Wednesday with
mixing with the fropa yielding at least low to mid 70s across much
of the cwa Wednesday afternoon. There will be a band of mainly mid
or high level clouds associated with the front as it makes
eastward progress. Have increased winds over the west with post
frontal gradient/low level caa giving at least breezy conditions.
Relative humidity will drop off to 25 to 30% in the afternoon to
the southwest as well with the passage of the front. This will
continue to increase the fire weather concerns over the southwest.
Overall fuels still not conducive to significant spread but that
may change in later periods as the warmth continues.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 403 PM CDT Tue Oct 17 2017

Late this week and early next week will offer a rather
interesting contrast of temperatures.

After the frontal passage Wednesday, warm advection begins again
late Wednesday night and really takes hold on Thursday. Some parts
of southwest and west central Minnesota may see 850mb temp rises
of 9C in 18 hours with a ssw wind. Fire weather may become a
concern again Thursday afternoon in our far western counties with
temps exceeding 70, dew points only in the 30s, and RH down to
around 25%

Deep trough moves into the west coast Thursday night with a lead
short wave moving out of the southwest on Thursday. Most models
are not as fast as the GFS, so went with a little slower
progression per model discussion.

Max temps in the 70s will be widespread Friday. Southerly low
level flow will gradually bring moisture into the area, but it
will take a bit of time. Increase of dew points won`t really be
noticeable until Friday, when mid 50s reach west central MN, and
around 50 in west central WI. Short wave arrives late Friday and
this is when precip enters the forecast, with thunderstorms
possible in warm air advection regime. Main upper trough crosses
the plains Saturday night, with more storms possible, especially
Saturday afternoon and evening. Upper trough lags the surface
front by quite a bit, so it may not be a huge precip event.

After the deep trough departs Sunday morning, another upper
trough drops in from the northwest Sunday night and Monday. This
is the one that will introduce much cooler air to the region. By
Tuesday, high temps may only be in the upper 40s or lower 50s, and
this is probably generous. Parts of central MN that will likely
see +18C temps at 850mb this Friday morning may well have below
zero 850 temps by Tuesday morning.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1041 PM CDT Tue Oct 17 2017

VFR throughout with only passing high clouds. Pre-frontal low
level jetting overnight will impact western MN TAF sites with low
level wind shear during the early morning hours. Post-daybreak
mixing should bring some of this down to the surface in the form
of gusts to near 20 knots. Otherwise, winds will shift from SSW to
NW during the day tomorrow in response to a cold frontal passage.

KMSP...Only issue looks to be the timing of the wind shift
tomorrow afternoon with the cold front. Winds will run close to
220 through the morning into the first half of the afternoon until
winds swing around to WNW by the evening push.

/OUTLOOK FOR KMSP/
Thu...VFR. Winds S 5-10 kts.
Fri...VFR. Winds S 10-15G25 kts.
Sat...VFR. Chc TSRA. Winds SSW bcmg W 10-15 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

UPDATE...JPC
SHORT TERM...DWE
LONG TERM...TDK
AVIATION...JPC



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