Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 190322
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1022 PM CDT Wed Oct 18 2017

.UPDATE...
Issued at 1020 PM CDT Wed Oct 18 2017

Updated to include 06z aviation discussion below.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 245 PM CDT Wed Oct 18 2017

The quiet weather will continue through the short term, with the
only concerns surrounding fire weather.

Cold front continues to make steady progress across MN this
afternoon. Not much of a temperature drop in the MPX area behind
the front (that`s up in North Dakota), but we are seeing a good
dewpoint drop, with several sites seeing dewpoints in the 20s. As
a result we are seeing borderline critical fire conditions with
sustained NW winds up in the ballpark of 20 mph and humidities in
the 20-25% range. Given the borderline nature of both the weather
and fuel conditions, held off on issuing any red flag warnings.
Cirrus came in a bit thicker today than anticipated, which kept
temperatures from getting quite as warm as we had forecast, but
airmass is still plenty warm enough to allow for highs today to be
a good 10 to 15 degrees above normal.

Tonight, though we are not expecting the boundary layer to
completely decouple, winds will calm down to around 5 mph or less
and those light winds with the dry air coming in along with clear
skies will allow for efficient radiational cooling, so did go on
the lower side of the guidance envelope for lows tonight.

Also happening tonight, winds will turn back out of the south as a
warm front moves back across the area. We will see 925mb temps
warm to around 15c for Thursday, which will again allow for highs
to get into the low/mid 70s along/south of I-94. We should over
achieve against guidance by a couple of degrees (as we have been
doing this entire fall in patterns like this), so continued to go
at the top end of the model envelop for highs tomorrow.

For fire weather conditions, south winds will be increasing during
the day, with sustained speeds similar to what we are seeing today
expected out in western/central MN once again. The question for
tomorrow is how quickly does the moisture return. The NAM brings
it back pretty fast, and holds humidities up in the 30s, the GFS
is much slower and shows potential for another day with minimum
humidities in the 20-25% range out in western MN. Again, both
fuels and weather conditions look borderline from the red flag
perspective, so will again advertise the elevated fire weather
condition threat for Thursday in the FWF and HWO, but hold off on
any headlines.

.LONG TERM...(Thursday night through Wednesday)
Issued at 245 PM CDT Wed Oct 18 2017

The forecast concerns for the longer term remain temperature
trends and thunder threat for Saturday.

Friday looks to be breezy and warm ahead of the Dakotas cold
front. We may see some increase in high level clouds as well which
may limit significant warming. Tempered highs some with an overall
blend of previous/super and mix down tool. This did continue to
yield highs in the 70s most areas.

Low level flow increases Friday night and we could see some
showers/isold thunder develop later in the night. Timing of the
cold front should bring it through eastern MN by 00Z Sunday. We
will trail pops off from west to east Sunday night. Thunder
threat does develop into Saturday with some forcing along the
front/upper trough and instability increases with the GFS a little
more unstable than the ECMWF. Still should see MUCAPE 500-1000
J/kg lift out ahead of the front with mid level lapse rates around
7. The 00Z GEFS standardized anomaly was indicating PW`s some 2
to 3 standard deviations above normal with the system. This should
give some heavier rains across the eastern cwa. We have QPF of
one quarter to one half inch so far.

The front exits to the east through Saturday night. We left a
small PoP to the east early Sunday but believe we had some model
issues with the GEM developing a closed low over Great Lakes and
affecting model blend PoPs. Both the 12Z GFS and ECMWF are
faster/more progressive with the trough.

After that, an overall cooling trend develops through midweek
with what appears to be the coldest air of the season dropping
into the region as an eastern CONUS trough develops. This should
drop in some colder Canadian air over the Great Lakes. It doesnt
appear to be really below normal however, with overall
temperatures trending closer to seasonal averages. Some small
chances for precipitation into the midweek as well, as a secondary
cold front drops southeast and some possible light QPF affecting
mainly the eastern cwa into midweek.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1020 PM CDT Wed Oct 18 2017

High confidence in VFR conditions throughout this TAF set with
only passing high clouds, if anything at all. Main issue will be
wind directions with the departing front followed by warm
sectoring ahead of the next front for Saturday. Will look for
winds to remain WNW into the overnight hours then back to
southerly by daybreak tomorrow then have breezy speeds tomorrow
afternoon.

KMSP...No significant issues outside of the wind directions. Could
see some winds near 220 with speeds in the 4-5 kt area during the
morning push tomorrow but winds will mainly be light/variable
before becoming solidly southerly by midday.

/OUTLOOK FOR KMSP/
Fri...VFR. Winds S 10-15G25 kts.
Sat...Mainly VFR. Chance of TSRA/MVFR in aftn. Winds S bcmg W
10-15 kts.
Sun...VFR. Winds W 5-10 kts.

&&

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

$$

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



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