Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 051221

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
621 AM CST Mon Dec 5 2016

Issued at 528 AM CST Mon Dec 5 2016

Updated to include 12z aviation discussion below.


.SHORT TERM...(Today and tonight)
Issued at 435 AM CST Mon Dec 5 2016

Surface analysis this morning indicates high pressure centered
over the Ohio Valley, helping to push away the trough which
brought early morning snowfall this time yesterday. A more
organized cold front is lingering over the Dakotas through WY/UT
and it is this feature which will be watched today for possibly
some -RA/-SN showers later today into tonight along with its
associated warm front which may bring a spike in temperatures.
Low level flow in advance of the approaching cold front are taking
a more southerly than southwest orientation but it is still
nevertheless capable of bringing in even a modified portion of
925mb temps a few degrees over 0 deg C. Clouds will not be
entirely solid throughout the day, making for a mix with some
sunshine. Depending on how far north the warm front can punch into
the area, highs hitting the lower 40s and possibly middle 40s are
entirely reasonable for southwestern and south-central portions of
MN. As the day progresses, isolated -RA/-SN showers look to break
out over eastern portions, mainly in response to the warm front,
while isolated -SN showers develop in western MN due to the cold
front. The front looks to pass over the area in the 06/03z-06/06z
time frame this evening, changing any -RA over to -SN but only a
dusting at best accumulation is expected. The main change will be
the start of prolonged cold air advection which will last through
the rest of the week. As alluded to earlier, highs will hit the
mid-upper 30s in northern and eastern portions of the coverage
area with the low-mid 40s in southwestern and south-central
portions. This will be followed by lows tonight near 20 in western
MN to the upper 20s in western WI but also with breezy NW winds.

.LONG TERM...(Tuesday through Sunday)
Issued at 435 AM CST Mon Dec 5 2016

By tomorrow morning, a 993mb surface low will be near Lake Of The
Woods, with strong cold air advection ongoing across the state. By
this time 850mb temperatures look to fall to -10C to -12C. In
this post front state, temperatures tomorrow will not rise through
the daytime hours as they normally would. Hence, the high for the
day may occur tomorrow morning. The core of the cold will be yet
to come, but west winds will increase to 15-25 MPH, with gusts in
western MN of 30-35 MPH. Light snow will be possible especially
across central MN as we remain under the influence of the low
pressure system providing the region with ample moisture, cyclonic
flow, and cold air advection. We do not expect much in terms of
accumulation at this time, less than an inch.

The cooling trend continues as the large upper level trough
dictates a northwesterly jet across the western CONUS that dives
well south of us, allowing cold air to pour in from the north.
Highs on Wednesday through Friday will mostly be in the teens,
well below normal for the first half of December. A secondary
trough will rotate through Wednesday into Thursday and bring snow
showers to the region under continued low level moisture and
cyclonic flow. Again, not expecting much in terms of accumulation.

The jet looks to become more zonal toward the weekend, hence
somewhat warmer temperatures in the forecast.  The guidance
indicates an upper trough will move through the upper midwest with
a low level baroclinic zone moving through the area which led to
the widespread pops this weekend for light snow. It`s much too
early to discuss amounts at this point in time.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 528 AM CST Mon Dec 5 2016

Incoming high clouds evident on overnight IR satellite imagery
along with upstream observations have helped mitigated more
widespread fog development. Only areas experiencing it at
initialization time this morning are satellite MSP-area airports
and the WI sites. Light winds plus higher low-level moisture
levels due to snowfall from yesterday are contributing factors.
Beyond daybreak, any fog issues will abate and will no longer be a
concern. Clouds will then steadily lower and thicken as the day
progresses with the approach and passage of a warm front and
following cold front this afternoon and this evening,
respectively. Very little chance for precipitation with the
frontal passages, potentially low-end chance over WI this evening
so have only included VCSH at KEAU later. Otherwise, winds will
veer and increase in speed while ceilings drop to MVFR levels.
Only other concern is that model soundings are indicating the
potential for strong low level winds this afternoon and evening,
increasing to SW in the 35-40kt area. Confidence not great in this
thinking due to poor initialization with the KMPX RAOB this
morning and that it is mainly a speed shear issue with less than
30 degree directional difference. As such, have omitted any
mention of LLWS, going more the thinking of "low level
turbulence," if it even develops at all.

KMSP...VFR conditions expected through the day today with high
clouds moving in from the west and increasing in coverage.
Ceilings look to drop to MVFR at the tail end of the evening rush
and remain there through daybreak Tuesday morning. Not looking for
any precipitation, with -RA/-SN east of MSP this afternoon then
-SHSN west of MSP overnight. Winds will steadily swing from SE to
S today then continue veering to SW overnight. Speeds will
increase to around 10 knots with some gusts in the 15-20kt range
later today and tonight.

Wed...MVFR. Wind WNW 15g25kts.
Thu...MVFR. Chc -SN. Wind WNW 15g25kts.
Fri...VFR. Wind NW 5-10 kts...becoming S.




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