Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KMPX 190905

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

.SHORT TERM...(Today and tonight)
Issued at 405 AM CDT Thu Oct 19 2017

The main issue today is near critical fire weather conditions. Dew
points this morning are already quite low in the lower 30s and am not
expecting any recovery until later this afternoon across far
western Minnesota. Deep mixing and dry air aloft will allow dew
points to mix out into the upper 20s or lower across eastern MN
and western WI. While dew points should be a little higher across
western MN, temperatures will also be warmer, possibly in the
lower 80s, which will offset the higher dew points. Min RH values
will fall into the upper teens to mid 20s area wide today, with
stronger winds than observed yesterday. We may have gusts of 30 to
35 mph over western MN. The only question remaining is fuel
quality, which will be assessed this morning for a possible Red
Flag Warning.

Forecasted highs continue to be several degrees above guidance.
Due to favorable mixing, derived high temperatures by mixing to
875 mb. 2 meter and MOS temperatures never seem to capture these
late season warm ups adequately.

Increasing humidity levels and a steady southerly breeze will keep
temperatures from dropping too much below the mid 50s tonight.

.LONG TERM...(Friday through Wednesday)
Issued at 405 AM CDT Thu Oct 19 2017

Confidence remains high for Friday and Saturday forecast as the mean
progressive upper level flow begins to transition to a more
amplified/blocking pattern next week.

First, models have been consistent on the evolution of a long wave
trough moving inland across the Pacific Northwest, Rockies and into
the Plains by Saturday. Embedded short waves, a cold front and
return moisture from the Gulf of Mexico, will lead to an increasing
chance of precipitation Saturday. The increasingly amplified pattern
should also support upper jet energy for widespread precipitation.
Timing is the only factor that remains questionable, but cold
frontal passage should be Saturday afternoon in western Minnesota,
and Saturday evening in eastern Minnesota.

Ahead of this system, and due to the support of jet energy, surface
winds will be strong. Gusts of 30 to 40 mph look reasonable Friday
along with temperatures approaching record highs. Model guidance has
been consistently too cool on the temperatures Friday afternoon, and
even tonights run, guidance readings are 5 degrees too cool. As with
previous forecast, used a mix down process that supports highs in
the upper 70s, to around 80 degrees across the Upper Midwest.

As models converge on this amplified pattern developing, questions
remain on the southern jet core becoming split from the main upper
flow. This allows for a storm system to form in the southern Plains
late in the weekend, and into early next week. Although models
support this split flow regime, consensus on where and how strong
this storm system becomes is low. The EC/GEM/GFS all support a
cutoff upper low forming over the eastern half of the nation next
week, but differences arise on the strength of the surface low and
the depth of the cutoff system. In addition, the northern stream of
the jet core begins to interact with the southern stream. This will
make for a lot of uncertainty in the forecast, and likely
differences from run to run deterministic solutions. The best
scenario is to convey the uncertainty, highlight the potential of a
strong storm system next week, and continue the trend of colder


.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

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.

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.




AVIATION...JPC is the U.S. government's official web portal to all federal, state and local government web resources and services.