Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
512 am CST Sat Dec 7 2013
Update...for 12z aviation discussion below
Short term...(today and tonight)
issued at 407 am CST Sat Dec 7 2013
Very cold temperatures this morning with many readings between 10 and 20
below zero as of 230 am. The coldest areas were located in Morrison
County where deeper snow exists and winds are less. Even with a
5 to 10 miles per hour wind...wind chill values have averaged between 20 and 35
below zero...with the coldest readings in west central/central Minnesota.
Regional satellite imagery is showing many clear skies overhead with
the next storm system expected to produce more snowfall by late
tonight...affecting the Great Basin of Nevada/Utah. Through this
evening...no weather problems will occur with the exception of cold wind
chills. Will continue with the wind chill warning/advisory through noon
due to the very cold temperatures and winds still averaging close to 10 miles per hour
through the morning. Late tonight...and with the combination of rapid
return of middle level moisture and the influx of upper level energy
associated with the shortwave across the Great Basin...should induce a
broad area of light snow across the plains of Nebraska/Iowa/SD. As
with any Arctic air mass...it will take some time to saturate the
lower levels of the atmosphere which may delay the onset of -sn by
Sunday morning. However...short term models are showing a strong
upglide of adiabatic Omega or isentropic lift across southern Minnesota
starting 6z-12z/8. Even some of the local models reflectivity output
is showing a broad area of -sn spreading across far SW Minnesota after
6z...and across most of southern Minnesota by 12z. Will continue the same
forecast with the bulk of the quantitative precipitation forecast and -sn across SW/SC Minnesota during the
overnight hours. The intensify and coverage should expand on Sunday as
the system moves further to the E/NE.
Long term...(sunday through friday)
issued at 407 am CST Sat Dec 7 2013
Things are right on track for the next bout of measurable snowfall
to arrive on Sunday...as the surface high shifts east and a
midlevel trough lifts northeast from The Four Corners region to
Lake Michigan. Expect snow to begin by daybreak Sunday...as modest
/but deep/ isentropic lift expands north and east across the area.
Quantitative precipitation forecast amounts remain on the modest side...but snow ratios
/approximately 20-25 to 1/ should help plowable snowfall amounts
to come to fruition. Expect this to be especially true from south
central Minnesota northeast to east central Minnesota and west central
WI...where a solid swath of 3-5 inches is expected between 09z
Sunday and 09z Monday. Given the long duration of a light/fluffy
snow event /without intense bursts of heavier snow/...and the
absence of Stout winds...the need for an advisory appears somewhat
borderline at this point. We will see winds pick up on Monday
however...which will likely yield blowing and drifting snow...and
another brush with Wind Chill Advisory criteria across west
central Minnesota. Highs on Monday will struggle to rise above zero
degrees across west central Minnesota...with single digits expected area-
On Monday night into Tuesday...a northern stream wave is slated to
dive southeast across the area from Canada...and bring a quick
shot of light snow to central Minnesota and northern WI. As typical of
clipper systems...snow accumulations around one inch would be
common with this feature. A reinforcement of the cold air
infiltrates the area in the wake of clipper...with 5 below to 15
below lows on Wednesday morning...and yet another potential for 25
below to 30 below wind chills.
There are indications that some relief from the bitter cold will
arrive late next week...as low/middle level heights rise slightly. By
Friday...highs in 20s appear possible across much of the area.
Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 511 am CST Sat Dec 7 2013
VFR conds through 00z/08 with winds generally from the west/west-northwest around 8-10
kts...becoming light and variable by sunset. Krwf will begin to see
-sn after 3z...with MVFR/IFR conds becoming likely after 6z.
Elsewhere...VFR conds should prevail with some -sn possible by the
end of the taf period. Winds overnight will remain light...but
become more se/ESE.
VFR conds through 6z/08 with winds west-northwest around 8-10 kts...becoming light
and variable by 00z...then southeast/east-southeast after 6z/8. Clouds will begin to
increase and lower after 6z...with -sn becoming likely toward 12z. A
period of MVFR/IFR visibilities are likely after 12z with ceilings slowly
lowering. Winds will generally hold near the southeast/east-southeast under 10 kts after
12z/08. Confidence is high for VFR conds through 6z...with low
confidence of IFR visibilities after 12z.
/Outlook for kmsp/
Sun afternoon...MVFR/IFR with snow. Winds east-southeast at 5-10kts.
Monday...MVFR/-sn ending early...then VFR. Winds west at 15g25kts.
Tuesday...VFR. Winds west-northwest 15g25kts.
Minnesota...Wind Chill Advisory until noon CST today for mnz045-052-053-
Wind chill warning until noon CST today for mnz041>044-047>051-
WI...Wind Chill Advisory until noon CST today for wiz014>016-023>028.