Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
607 am CST sun Dec 8 2013
Update...for 12z aviation discussion below
Short term...(today and tonight)
issued at 321 am CST sun Dec 8 2013
Snow will continue expanding across the forecast area today...as a
shortwave visible over southeastern South Dakota on 09z water vapor imagery lifts
across central/southern Minnesota and northern WI. Attendant visibilities
have been consistently lowering to around 2sm as the band works
northeast...which symbolizes the expectation that this will be a
long duration light/fluffy snowfall. Snow ratios of 20:1 or even
pushing 25:1 are likely...which means the expected quantitative precipitation forecast of one to two
tenths of an inch will yield event snowfall accumulations of 3-5
inches in the advisory area of central/south central Minnesota and west
central WI. Amounts will taper off to 1-2 inch totals over west
central Minnesota. The other concern within the short term period is the
return of advisory criteria wind chills tonight into Monday morning
from west central into central Minnesota...as winds pick up again and
temperatures dip below zero yet again. Although it will likely not
occur until between 09z-12z Monday...expect wind chill readings to
lower to between 20 and 30 below. Will therefore issue a Wind Chill
Advisory to the west of the Winter Weather Advisory.
Long term...(monday through saturday)
issued at 321 am CST sun Dec 8 2013
Overall the upper level pattern will continue to be cold for most
of the extended period with some modification by next
weekend...and into the following week. The core of the Arctic air
mass will readjust through Thursday with bouts of very light snow
with each shortwave. One will affect the region Monday
night/Tuesday...with another late Tuesday and Wednesday morning.
Each of these reinforcing shots of Arctic air will generate gusty
winds behind it which will create wind chill values between 25 to
40 below zero during the coldest part of the day. After
Thursday...the core of the Arctic air mass will shift to the
northeast across eastern Canada. Across the Gulf of Alaska which
has been under the influence of an upper level ridge...will
transition to a more progressive pattern. Downstream from this
change...our region will begin to see some modification of
temperatures...but remaining slightly below normal for middle December. Long
range climate models are hinting that the week of December 17-20th
will be warmer than normal with highs back into the 30s. The
pattern will need to change to a more zonal flow for these temperatures to
Aviation...(for the 12z tafs through 12z Monday morning)
issued at 608 am CST sun Dec 8 2013
Snow has ensued across the taf area early this morning...and will
persist through the day. Prevalent visibilities will range between
1 and 3 miles during the event with MVFR ceilings /potentially dipping
just below 1000ft at WI sites /krnh and Keau/ this evening. Total
accumulations ranging from around an inch at axn to 2 to 5 inches
elsewhere /heaviest toward eau/. The snow will come to an end
between 00z and 06z Monday...with VFR ceilings returning Monday.
Kmsp...light snow continues today with visibilities mostly from 1-3sm
and ceilings mainly MVFR this morning. Ceilings are expected to lower to
around 900 feet this afternoon. Conditions improve after 00z as the
snow gradually tapers off...with ceilings also rising to around 1800
feet at the same time. VFR conditions are expected to return
around 15z Monday.
/Outlook for kmsp/
Monday...MVFR possible early...then VFR. Winds west at 15g25kts.
Tuesday...VFR. Winds west 15g25kts.
Wednesday...VFR. Winds west 5-10kts.
Minnesota...Winter Weather Advisory until 6 am CST Monday for mnz060-062-
Wind Chill Advisory from midnight tonight to noon CST Monday for
Winter Weather Advisory until 6 am CST Monday for mnz053-061-063.
WI...Winter Weather Advisory until 6 am CST Monday for wiz024-026.
Winter Weather Advisory until 6 am CST Monday for wiz014>016-023-