Area Forecast Discussion
Issued by NWS Twin Cities, MN
FXUS63 KMPX 061023
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
423 AM CST Tue Dec 6 2016
.SHORT TERM...(Today and tonight)
Issued at 335 AM CST Tue Dec 6 2016
Surface analysis this morning shows a large rotating low over
northwestern MN while its main cold front is well out in advance
of the center, draped over western WI southward through the Mid-
Mississippi River Valley. Aloft, a deep upper level low is nearly
atop the surface feature, showing up nicely on WV satellite
imagery. Otherwise, much of the northern-central plains
east southeast into the Ohio Valley is under generally zonal
flow, which will make for a progressive nature of the deep low
pressure center. It is expected to drift eastward through the day
into tonight, moving over Lake Superior by daybreak Wednesday
morning. It will slightly deepen as it shifts east, expanding its
range into central Minnesota later today. In addition, a much
tightened pressure gradient on the backside of the low will
develop, in response to dense arctic high pressure arriving from
northwestern Canada. Thus, the passage of this system will contain
multiple impacts in that it will signal and end to temperatures
above freezing, it will bring in strong westerly winds and it will
bring light snow accumulations for west-central Minnesota. Given
the timing of the increase in winds with the incoming snowfall,
event light snowfall acumulations of 1-2" will be enough to reduce
visibility in west-central Minnesota, mainly affecting I-94.
Therefore, have opted to issue a Snow and Blowing Snow Advisory
for a handful of counties out in western MN. With the wind speeds
still an issue going into southwestern MN, have also issued a
Windy Advisory since the winds will still be in the 25-35 mph
range but just without the snow/visibility restriction. Both
impacts look to subside this evening with breezy conditions
thereafter and little/no additional falling snow. As for
temperatures, CAA is certainly ongoing as temperatures in western
MN have dropped to the teens while temperatures in western WI are
still holding in the lower 30s. In fact, today may well be one of
those days where highs are reported at midnight with
steady/falling temperatures for much of the day.
.LONG TERM...(Wednesday through Monday)
Issued at 405 AM CST Tue Dec 6 2016
The long term forecast has changed very little over the past few
days and that trend continued. By tomorrow morning, the longwave
trough will still be in place across central North America with a
strong low pressure system just north of Lake Superior. Strong
cyclonic flow from this system will continue helping drive cold
air from the north down into the CONUS.
The coldest temperatures of the season so far are set to arrive
with the Wednesday-Friday period being the particularly coolest
part of the forecast. And with the aforementioned strong low
pressure system slowly departing to the northeast during this
timeframe, the atmosphere will remain ripe for snow showers and
flurries, especially Wednesday through Thursday owing to the ample
moisture, cyclonic flow and persistent cold air advection.
Continued to nudge pops and winds up above the blend of the model
guidance for this time period. Blended winds just look to low
especially across western MN knowing the persistent cold air
advection should efficiently tap into above ground winds and mix
those directly to the ground. The guidance is trying to indicate
there could be some snow showers during this period, but is not
aggressive enough. We feel snow showers Wed night/Thu especially
are a good bet.
Pops come back into the forecast Saturday-Sunday with a separate
shortwave potentially affecting the area, but the long term
guidance disagrees on how this system will be handled and the
evolution of the overall pattern. The GFS/EC at least both agree
on a warm air advection band of snow moving through as the system
approaches, so included at least chance wording in the forecast.
At this point, QPF is not impressive for this period. Looking
ahead to next week, the guidance is indicating the arctic air
really gathering in Canada and advancing south toward the USA
border hence the Climate Prediction Centers 8-14 day outlook
calling for below normal temperatures.
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1017 PM CST Mon Dec 5 2016
No significant changes to the previous forecast, with updates
mainly to reflect observed trends. Cold front continues to push
across the area, with some light precipitation now confined to the
eastern part of the area. Winds shifting westerly behind the
front, will strengthen and be gusty Tuesday into Tuesday night.
Lower ceilings associated with cold air stratocumulus will
predominate, with some snow showers Tuesday, particularly north,
owing to some instability with good lapse rates in place.
Overall, appears to be mainly MVFR conditions, although some IFR
can`t be ruled out, especially during any periods of snowfall.
KMSP...Main uncertainties are with timing of the intial arrival of
lower ceilings and with any visibility restrictions owing to
snowfall on Tuesday.
/OUTLOOK FOR KMSP/
Wednesday...MVFR expected at times with a chance of snow
showers/flurries. West to west-northwest wind 15 to 25 kt.
Wednesday night through Thursday...MVFR expected at times with
scattered snow showers. Northwest wind 15 to 25 kt.
Thursday night...MVFR possible early with a chance of snow
showers/flurries. Northwest wind 10 to 20 kt becoming west around
Friday...VFR. West wind less than 10 kt becoming south.
MN...Winter Weather Advisory from 9 AM this morning to 9 PM CST this
evening for MNZ041-042-047>049-055.
Wind Advisory from 9 AM this morning to 9 PM CST this evening