Area Forecast Discussion
Issued by NWS Twin Cities, MN

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331
FXUS63 KMPX 210505
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1205 AM CDT Mon Oct 21 2019

.UPDATE...
Issued at 938 PM CDT Sun Oct 20 2019

Couple of updates this evening. First, dry air evident on the 00z
MPX sounding continues to impede the progress of rain moving into
southwest MN (it`s just reaching Sioux Falls, SD as of 9 pm). As a
result, further slowed the northeastward push of PoPs tonight. It
really doesn`t look like this band of rain gets its act together
until after 8z, when the RAP shows a good surge of moisture
transport coming up out of NE IA on the LLJ.

Other change was to add a wind advisory for western into southern
MN Monday night into Tuesday. This is a classic high wind setup
and given how high our confidence is that we will see wind gusts
of at least 50 mph, seems unnecessary to wait another shift to
get this out. Bigger question isn`t whether or not we need an
advisory, but whether or not a warning will be needed. Monday
night, RAP shows h85 winds increasing to over 60 kts on the west
side of the low in a region of CAA. GFS soundings also showing
occasional hours where top of the channel winds from western into
southern MN are up around 55 kts, so big winds are all but a
certainty, it`s just a question of how much of those winds we can
tap into to possibly push us into a warning (50 kt/58 mph gusts or
more).

&&

.SHORT TERM...(This evening through Monday night)
Issued at 332 PM CDT Sun Oct 20 2019

Forecast concerns for the short term are precipitation timing and
extent of convective threat into Monday. Then remain wind becomes
an issue late Monday afternoon/night.

Thicker high clouds moving into the area now, but not fast enough to
hold temperatures from warming through the mid and upper 60s over a
portion of central MN. This should be the last mild day as the next
storm system is poised to affect the region. Slowed the eastward
progression of the precipitation band. It should work into eastern
MN by 12z Monday.  Isentropic lift becomes maximized over eastern MN
08z-12z period. Some threat of thunder with this activity later
tonight. Will hold onto slight chance thunder for now. This works
east during the day Monday as the surface low tracks close to east
central MN. Dry slot may work into southern MN Monday afternoon and
we decreased PoP some to account for this possibility.

As the low lifts east/northeast and occludes over eastern MN late
Monday afternoon, we expect wind to increase over the western CWA
before 00z Tue. Model soundings suggest 45-50kt gust potential from
the northwest over west central MN Monday night. Strong pressure
gradient and CAA should allow winds to reach close to that
potential. We decided to hold off on headlines for the moment. One
more model run to hone in on finer timing details with regards to
surface low.

Colder air moves into the region Monday night, possible cold enough
to mix in some wet snow over the northwest CWA after 06z Wed.
Accumulation isn`t expected.

.LONG TERM...(Tuesday through Sunday)
Issued at 332 PM CDT Sun Oct 20 2019

Unsettled weather continues into the start of the long term period
on Tuesday and Wednesday, and then benign conditions arrive for
the last half of the week.

A very tight surface pressure gradient looks to remain situated
over the area until at least mid-day Tuesday. NAM/GFS Bufkit both
indicate 40-50 knots at the top of the channel through Tuesday
morning, with gradual decrease on Tuesday afternoon as the trough
shifts farther into Ontario and the gradient relaxes. Temperatures
will only moderate a few degrees Tuesday given the low level cold
air advection and cloud cover/showers under the cyclonic flow
regime. Highs will top out in the low/mid 40s, with chilly
apparent temperatures in the 30s.

On Wednesday we quickly shift into westerly large scale flow. GFS
and ECMWF models continue to forecast a weak shortwave/PV feature
sliding from the Plains to MS Valley region as we transition to
an eastern trough/western CONUS ridge pattern. Have included
chance POPS for a rain/snow mix associated with this feature, and
although attendant precip amounts would mostly likely be light,
could envision higher POPs once strength/timing/track details are
more certain. At this point southern areas (along/south of the MN
River Valley) look to be favored.

From Thursday into the first half of the weekend, surface high
pressure dominates the region, and brings a dry forecast with
gradually moderating temperatures. Expect highs in the low/mid 50s
for Saturday.

By Sunday, notable differences in the models evolve with regard to
the large scale pattern, but at this point we look to stay removed
from forcing mechanisms for precipitation.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1204 AM CDT Mon Oct 21 2019

Rain is finally overcoming the dry air and moving into the area.
Previous TAFs already significantly delayed precip onset, so only
minor changes were needed to these TAFs. MKT/MSP/RNH/EAU will see
the dry slot cut off precip tomorrow afternoon, though will have
to watch for thunderstorm development near these terminals in the
afternoon with the steep lapse rates in the dry slot. As surface
low moves across the Twin Cities in the afternoon, strong winds
will develop in western MN, went well above guidance for wind
speeds at the end of the TAF period in MN, getting speeds more in
line with what mixing potential shows from BUFKIT soundings.

KMSP...Main uncertainty with this TAF period is what will happen
when we get into the dry slot. There`s potential to go VFR for a
bit and see scattered thunderstorms as well. For now, stuck with
what a consensus of the short term models has for cigs. Also some
uncertainty with wind direction during the afternoon Monday a the
surface low will be moving overhead. We get into wrap around
precip after 3z Tuesday.

/OUTLOOK FOR KMSP/
Tue...MVFR chc IFR. -SHRA likely. Wind NW at 30G40 kts.
Wed...Chc MVFR. Slight chc -SHRA. Wind NNW at 10-15 kts.
Thu...VFR. Wind NW at 10-15 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Wind Advisory from 10 PM Monday to 4 PM CDT Tuesday for MNZ074-
     075-082-083-091-092.

     Wind Advisory from 7 PM Monday to 4 PM CDT Tuesday for MNZ041-
     042-047>049-054>058-064>067-073.

&&

$$

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



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