Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 152051
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
351 PM CDT Thu Jun 15 2017

.SHORT TERM...(This evening through Friday)
Issued at 350 PM CDT Thu Jun 15 2017

It`s a beautiful day across the Upper MS Valley. As expected, we
have seen deep mixing take hold. The strongest winds, with gusts up
into the 30-35 mph range at times have been observed up in central
MN. In contrast, winds down along I-90 have largely been under 10
mph all day. This wind speed gradient is the result of having a sub
1000mb low in Canada with only a weak pressure gradient from I-80 on
south.

For us, the feature to watch is the 120 kt crashing onshore in the
Pac NW. By Friday afternoon, this jet streak will be into the
Dakotas, putting the upper MS Valley in its exit region. This will
result in a fairly cloudy day Friday as mid level clouds overspread
the area. The question for tomorrow is will we see precip. Forecast
soundings don`t show much of this moisture extending below 10k ft,
so we may just be watching a bunch of virga. We will see another
surge of rich Theta-e air build up into IA, with southern MN getting
on the northern edge of the instability gradient associated with
this airmass. However, the expected mid level clouds will really
hamper our destabilization. On top of that, outside of the broad
diffluence at the nose of the jet streak to our west, we really
don`t have any good upper forcing for precip Friday and at the
surface, we`ll have a baggy pressure gradient and weak convergence
along a moisture gradient that will extend from southwest MN to
northwest WI. The GFS/ECMWF continue to generate some light QPF east
of the gradient, but the NAM/Canadian/MPAS are mainly dry. The CAMs
show scattered activity developing by the late afternoon over
northern IA over into SW WI, mostly missing the MPX area. Given the
uncertainties, stayed pretty close to the existing forecast, with
some 30s by the afternoon around southeast MN, with 20s extending
back west to where the weak moisture gradient is expected to be.
With the better instability to our south, not expecting much of a
severe threat in the MPX area.

.LONG TERM...(Friday night through Thursday)
Issued at 350 PM CDT Thu Jun 15 2017

The exit region of a seasonally strong upper jet will be approaching
the eastern Dakotas Friday evening, generating forcing aloft for
storms ongoing across the mid-Missouri Valley at the start of the
period. NAM is more aggressive with bringing higher instability up
to the Minnesota River valley, but the Euro & GFS look more in
line with limiting the instability and highest severe potential
down into Iowa. Could possibly see 1000 J/kg of MLCAPE sneak up
to the I-90 corridor, which is highlighted under the SPC day 2
Marginal Risk, however the severe threat overall looks low for our
area.

The better chance for widespread precipitation over the area
comes Saturday afternoon & evening as a shortwave digs over
central MN & a surface low begins to deepen over the mid-MO
valley. 12Z models have come into consensus with keeping the
surface warm front & greatest instability over Iowa so any severe
threat should remain well south of our area. Central MN looks to
be stuck in the middle between the area of greatest forcing aloft
over northern MN & highest instability over IA so the forecast
isn`t looking as wet compared to previous days. Regardless we`re
still expecting widespread rainfall amounts of 0.25-0.5" so keep
an eye on the weather for any outdoor activities Saturday. The
system moves out of the area Saturday night with perhaps a few
scattered showers during the day across the northern & eastern
portions of the CWA Sunday as the wrap-around region of the
cyclone lingers over the western Great Lakes. Much cooler air
filters in behind the low with high temperatures only expected to
reach the low 70s Sunday.

Northwest flow on the back side of the trough will lead to a dry &
pleasant day Monday with any precip chances generally remaining east
of the CWA. A building ridge in the desert SW & trough over the
eastern CONUS will keep us in NW flow aloft midweek with another
seasonally strong jet coming onshore in the Pacific NW. Subtle vort
maxes embedded in the strong flow aloft will be enough to kick off at
least some precip chances Tue, Wed, & Thu. Difficult at this time to
improve on a general 20-30% chance across the area with
discrepancies in timing & location of these subtle features.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 106 PM CDT Thu Jun 15 2017

No major changes needed to TAFs for the 18z issuance. Deep mixing
is resulting in rather gusty west winds this afternoon that will
cut off quickly around 00z. We`ll maintain mostly clear skies
through much of the night, but late tonight, the strong jet
currently crashing into the Pac NW will be pushing an area of mid
level clouds across the area Friday. This may result in some
sprinkles/light rain, but forecast soundings remain pretty dry
below 10k feet, so kept terminals dry for now.

KMSP...For now favoring the NAM in keeping MSP dry with cloud
cover moving through tomorrow. Given how dry low levels are, think
the GFS is a little bullish with its precip. We will have no
problem remaining VFR and winds tomorrow will be much weaker than
today. Like the direction trend as well from the LAMP with W today
become SW tonight before veering back to the WSW Friday.

/OUTLOOK FOR KMSP/
Sat...VFR. Chc TSRA/MVFR. Wind W 5-10 kts.
Sun...VFR. Chc SHRA. Wind NW 10-15 kts.
Mon...VFR. Wind NW 5-10 kts.


&&

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

$$

SHORT TERM...MPG
LONG TERM...ETA
AVIATION...MPG



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