Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1145 am CST sun Nov 23 2014
issued at 1132 am CST sun Nov 23 2014
Just extended the dense fog advisory for areas east of I-35 through
00z. At the moment...a cold front extends more or less down
I-35...fog east of it and much improved conditions and a band of
deformation rain to the west. A quick Tours of webcams across the
cities shows quite the impressive gradient in conditions...with
494 going from 1/4sm visibility at Minnesota-5 to just hazy conditions at
Minnesota-77 along I-94 we are seeing the same thing...with good
visibilities in Minneapolis...but dense fog in St. Paul...with
Minnesota-280 acting as the delineation line at this point.
With the hrrr showing low visbys remaining across western WI through
at least 00z...decided to extend the advisory through then. We will
reassess the advisory later this afternoon to probably knock of a few
of the counties on the west side and decide if we need to go any
longer into the night of the far eastern mpx County Warning Area counties.
Short term...(today and tonight)
issued at 400 am CST sun Nov 23 2014
The surface trough nosing into the forecast area will continue to
Foster areas of dense fog for areas generally north of Interstate
94 this morning north of the warm front that/S bisecting the
forecast area. Have extended the dense fog advisory through the
morning hours...with little improvement in visibility expected
The aforementioned warm front will continue to lift north across
the area today...with ongoing light precipitation possible through
the day. The good news is that temperatures have climbed above the
freezing mark across the entire forecast area...therefore
minimizing the concern for freezing precipitation during the
This evening...as colder air infiltrates the air in relation to the
passing cold front...should see the precipitation type transition
to all snow. Winds behind the front will be significant...with
sustained speeds across west central Minnesota between 25 miles per hour and 30 miles per hour
with gusts to around 30 miles per hour. Blowing snow concerns have diminished
a bit given the affects the antecedent precipitation and snowmelt.
Long term...(monday through saturday)
issued at 400 am CST sun Nov 23 2014
Only a few minor changes in the extended period with the cold than
normal conds continuing with small chance/S of snow.
Overall...the mean upper flow remains from the north/northwest this week.
The 5-day 500 mb mean /GFS/Gem/ec/ is consistent with the upper low
parked north of Hudson Bay through this week. The biggest change is
associated with the break down of the upper ridge across the
west...which may lead to a more progressive/zonal flow by the week
of December 1st. Temperatures will be coldest Monday through Thursday...with
some modifications next weekend.
Monday will be windy with some patchy blowing snow where winds gusts
in the 30 to 40 miles per hour range. However...snowfall will be limited in the
typical areas of wc/SW/SC Minnesota Monday with only a light dusting
expected. Plus warm temperatures over the past 24 to 36 hours has allowed a
crest to form on the snow cover...limiting blowing snow potential.
For precipitation related changes next week...a fast moving shortwave and
associated surface low will move across the plains/Midwest Wednesday. There
remains a fairly strong jet streak with this system...leading to an
enhanced area of large scale lift in the exit region of this jet in
the upper Midwest. Moisture levels remain limited...so heavier
snowfall amts will be based on the location of the surface low and middle
level frontogenesis. Have increased to 50% for Wednesday based on
the stronger jet streak and surface low location.
Aviation...(for the 12z tafs through 12z Monday morning)
issued at 700 am CST sun Nov 23 2014
MVFR ceilings/visibilities will persist this morning as a warm front lifts
across the area. The worst conditions /and lowest ceilings and vsys/
will occur north of the taf sites...but an improvement should be
seen this afternoon at the Minnesota sites. A cold front works across the
area this evening...with gusty northwest winds developing in its wake.
Reas of drizzle/rain over WI sites/primarily Keau/ will transition
to snow after sunset...with kmsp on the western edge of the snow/precip.
visibilities should remain around 5-6sm with areas of fog through the
morning. Tough call on the timing for VFR ceilings...if anything
expect the taf is too optimistic in going to VFR by 14z. Frontal passage
occurs this afternoon with winds shifting to the northwest around
21z...and gusts into the middle/upper 20s developing this evening and
persisting into Sunday...with sub-1800 feet ceilings returing.
/Outlook for kmsp/
Monday...MVFR/IFR ceilings chance -sn. Winds northwest 20g30 knots.
Tuesday...VFR. Winds west 5-10 knots.
Wednesday...MVFR/IFR chance -sn. Winds northwest 10kts.
Minnesota...dense fog advisory until 6 PM CST this evening for mnz053-
WI...dense fog advisory until 6 PM CST this evening for wiz014>016-