Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Twin Cities/Chanhassen Minnesota
1157 PM CST Monday Dec 9 2013
issued at 559 PM CST Monday Dec 9 2013
Expanded the Wind Chill Advisory from western Wisconsin westward
through central Minnesota due to rapidly falling temperatures this
evening and wind chills that will likely remain near 25 below
through much of tonight. Further south...think temperatures will
begin moderating before the winds increase so did not have enough
confidence to keep it going there. Did lower temperatures this
evening several degrees given current trends. Will also look into
raising probability of precipitation tonight to categorical as the clipper pushes through
and whether advisories will be needed in the Minnesota River Valley due
to blowing snow.
Short term...(this evening through tuesday)
issued at 205 PM CST Monday Dec 9 2013
The big story in the short term is the advancing clipper system
set to move across the forecast area tonight and early Tuesday
morning. The surface low has trended 25-100 miles farther south over
the past 3-5 runs depending on which modeling system you look at
and perhaps even 1-2 mb stronger with the central pressure when it
passes overhead. This means a couple things: 1) central Minnesota should
be more in The Heart of the light snow between midnight and
sunrise and 2) west-SW Minnesota looks like a more favorable location to get
wind gusts to 30-35 kts and the potential for blowing snow. Montana is
already getting gusts between 30-40 kts and there will no doubt be
blizzard conditions in states west of here. In general...we went
with 0.25-1.0" of snow in central Minnesota given the speed of the system
and the lack of moisture. A few locations might end up between
1-2"...but tough to nail that down. We decided to hold off on
issuing a Winter Weather Advisory for blowing snow...but we were
close and right on the fence. It is something to watch with good
mixing to 850 mb and 35-45 kts at the top of the mixed layer. The
strongest core of the wind remains in the Dakotas...but west
central Minnesota and the Minnesota River Valley is right on the fringe.
Forecast soundings are still showing plenty of wind in the
boundary layer. Morning travelers will have to be on the look out
for blowing snow in western and portions of southern Minnesota early
tomorrow morning. The temperature trend is non-diurnal with warm
advection out ahead of the clipper and advancing cloud cover
tonight...followed by another strong cold front during the day
Long term...(tuesday night through monday)
issued at 205 PM CST Monday Dec 9 2013
Only minor adjustment to the longer term...at least initially.
Some models have trended a bit farther south with the snow
potential for Tuesday night. The 12z European model (ecmwf) was more consistent
with keeping potential over the southern half of the County Warning Area then.
Will leave probability of precipitation close to previous forecast for now. Does look like
some light snow accumulation over south central Minnesota during
this period. Colder air drops in behind the system late Tuesday
night into Wednesday. Wind chill issues will continue through
Wednesday night...with northern portions of the area flirting with
warning criteria late Tuesday night into Wednesday. Warm air advection pattern
develops Wednesday night with more light snow possible over the
northeast third of the County Warning Area Wednesday night. Could see
steady/slowly rising temperatures then as warmer air tries to lift
northeast with the next short wave. Will forcing is weaker...and
moisture more limited but may still be able to develop some light
snow with this as well.
Some model discrepancy developing thereafter as longer term models
begin to flatten the upper flow over the area. It appears Minnesota will
be on the edge of the colder air/baroclinic zone/ during this
period. It looked like the allblend was a bit too warm so did
adjust temperatures a bit for next Sunday and Monday.
Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1145 PM CST Monday Dec 9 2013
Light snow will push across Minnesota and WI tonight. It will be fairly
brief...lasting only a few hours...but MVFR and/or IFR conditions
can be expected with the snow. Behind the snow will come gusty
west winds leading to blowing snow...particularly across western and
southern Minnesota late tonight. VFR conditions anticipated for much of
Kmsp...best timing of snow will come between 07-11z. IFR visible
possible at times with the snow...then VFR. Southerly winds will
shift westerly late tonight.
/Outlook for kmsp/
Wednesday...VFR. MVFR and -sn possible Wednesday night. Winds west 5-10kts.
Thursday...VFR. Winds SW 5 kts.
Friday...VFR. MVFR possible. Winds lgt/var.
Minnesota...Winter Weather Advisory until 9 am CST Tuesday for mnz047-048-
Wind Chill Advisory until 6 am CST Tuesday for mnz041>045-
WI...Wind Chill Advisory until 6 am CST Tuesday for wiz014>016-