Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 201925

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
225 PM CDT Wed Sep 20 2017

.SHORT TERM...(This evening through Thursday)
Issued at 225 PM CDT Wed Sep 20 2017

The main forecast concern in the near term is temperature trend.

The cold front has exited the far eastern area of the cwa late this
afternoon. High pressure will builds southeast over the area during
the night. With light wind and a clear sky, some threat of patchy
fog developing under the ridge considering last nights rain. We
expect temperatures to cool through the lower 50s in the south with
some upper 40s in the northeast cwa closer to the surface ridge.

The front will drop into Iowa overnight and as the ridge exits to
the east, we will see the front lift back north into southern
Minnesota as a warm front by late Thursday afternoon. We should
remain dry through the day, but instability increases in the
vicinity of the front as dewpoints rise into the 60s once again. We
also expect some cumulus to form as the moisture begins to return to
the area. Temperatures should warm through the lower 80s along and
south of the front with 70s to the north.

.LONG TERM...(Thursday night through Wednesday)
Issued at 225 PM CDT Wed Sep 20 2017

The numerical guidance is in fairly good agreement on the
evolution of the large scale pattern during the Friday through
Wednesday period. The western trough looks to remain in place
through the weekend, with southwest flow and warm temperatures
over our area. However, the trough looks to move east Monday
through Wednesday, albeit slowly, bringing cooler temperatures
(and eventually, drier weather) into the area. We still look to
have a prolonged period of precipitation chances from Friday into
early next week as the aforementioned trough and associated
surface frontal boundary slowly push eastward.

We could see some elevated convection over the area Thursday night
with warm advection and an increasing low level jet, but the best
chance of activity looks to be north of I-94. Things look to be
capped across our area on Friday, with sunshine likely making it
our warmest day during a stretch of above normal days. Continued
to go a bit above guidance given recent overachievement on warmer
days and an overall favorable pattern for near record highs.
Frontal boundary to our west on Friday will ever so slowly push
east, and find its into the west Friday night. SPC has outlooked
the western portion of the area for day 3, mainly due to
convective potential Friday night ahead of the frontal boundary.
We will then likely see rounds of showers and thunderstorms
Saturday into Monday, with the boundary not making much in the way
of eastward progress until the Sunday night/Monday time frame. So,
it still appears that we`ll have a prolonged period of rainfall
potential (oriented southwest to northeast) from Friday night
through Sunday night in roughly the same area, which could lead to
some significant rainfall totals and potential flooding. The main
area of concern still looks to be near and north/west of a line
from Redwood Falls to Mora, but we could certainly see that shift
some depending on what convective outflows do to the baroclinic
zone, and the eventual position/timing of shortwave troughs
embedded in the southwest flow. We will begin cooling down from
northwest to southeast on Sunday, but much more so Monday and
Tuesday, with things eventually drying out from west to east
Tuesday and Tuesday night.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1153 AM CDT Wed Sep 20 2017

Some mvfr cigs to the east early then becoming skc by 00z. Expect
w-nw winds through the afternoon some gusts to 18kts possible
mainly east after fropa. Could still see a -shra isold -tsra near
KEAU through about 21z but coverage should be low enough to
exclude in taf for now. Increasing se winds into Thu afternoon
with some stratocu developing ahead of warm front to the south.

KMSP...Becoming SKC with nw-w winds becoming light se into
tonight. Some cu developing out ahead of incoming warm front to
the south Thu afternoon.

Thu night...VFR. Winds SE 10 kts.
Fri...VFR. Winds S 10-15 kts.
Sat...Mainly VFR. Chance MVFR/TSRA. Winds SW 5-10 kts.




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