Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1239 PM CST Thursday Feb 11 2016
Short term...(today and tonight)
issued at 332 am CST Thursday Feb 11 2016
High pressure will dominate the forecast keeping most of the region
dry and cool with relatively light winds. Later today another band
of light snow is forecast to move across southwest Minnesota...but
this band should be less intense than the one from Wednesday.
It was a chilly night across the region as high pressure...cold
air...and light winds allowed temperatures to fall into the double
digits below zero across areas of western Wisconsin. Meanwhile most
locations in Minnesota were near or below zero as well. Later today
weak pv anomaly currently located over Montana will slide southeast
along the Missouri River basin. Isentropic ascent ahead of this pv
anomaly will lead to another area of light snow similar to what fell
on Wednesday across southwest Minnesota. However...the thermal
gradient is much looser with this system...and the winds are
light...so do not expect as much of a response from the atmosphere
in terms of vertical motion. Forecast soundings support this
claim...and show very weak ascent when compared to Wednesday/S
system. Therefore have lower precipitation chances and snowfall
totals...with generally less than a half an inch expected in the far
southwest part of the forecast area. The snow will end
overnight...and temperatures will fall to near zero for most
Long term...(friday through wednesday)
issued at 332 am CST Thursday Feb 11 2016
The main focus for the long term period continues to be on the
bitter cold Friday night followed by a couple systems to produce
As has been advertised well during the last several days...a
1040-1045 mb high will build south out of the Arctic and settle
over Minnesota Friday night as a deep trough digs into New
England. With the ridge axis directly overhead...think the models
continue to overemphasize the wind over Minnesota. This would allow
temperatures to plummet into the teens and 20s below zero across
the southern half of Minnesota...and 30s below zero over the north half.
Will need to keep an eye on the potential for cirrus streaming in
from the northwest overnight however...which could also have a
significant impact on temperatures. A decent pressure gradient
may keep the wind from fully decoupling over WI...except for the
typically colder sheltered locations. Still believe winds will be
light enough that wind chill headlines won't be necessary although
brief instances of Wind Chill Advisory criteria /-25f/ could be
met at times. The ridge will shift eastward Saturday allowing a
return flow to begin across the plains and western Minnesota. It may hang
on long enough across western WI for temperatures to drop quickly
Saturday evening before clouds and wind increase overnight.
Two somewhat phased disturbances embedded in the west northwest
flow will emerge over the plains Saturday night. One located just
north of the Canadian border and the other over northern Nebraska
will generate two areas of snow. GFS has been phasing these
disturbances the best and has a larger north-south swath of snow
propagating across the upper Mississippi Valley Sunday. The
NAM...Gem...and European model (ecmwf) are not quite as phased and have a greater
emphasis on the southern wave. The southern wave does weaken and
sink southeast with time...so this solution may lead northern and
portions of central Minnesota...and Wisconsin with only minor snow
accumulations. However...all models continue to show potential for
several inches across southern and western Minnesota with between 1/4-1/3 inch of
quantitative precipitation forecast. Increased probability of precipitation to likely or categorical in those areas...and
maintained chance probability of precipitation further north and east.
Northwest flow continues into next week with another wave reaching
the upper Midwest in the Tuesday/Wednesday time frame. European model (ecmwf)
remains the strongest...although not as strong as the 10.00z run.
Nevertheless...could be looking at another accumulating snow
event nearby with that.
Aviation...(for the 18z tafs through 18z Friday afternoon)
issued at 1239 PM CST Thursday Feb 11 2016
Have seen cloud cover expand this morning in warm advection out
ahead of a weak front/surface trough moving across northern Minnesota. The
boundary is moisture starved...so not anticipating any snow...but
it will result in ceilings for much of the night. Lamp guidance and
sref probs support MVFR ceiling restrictions as the boundary
approaches...so continued to advertise a period of MVFR ceilings at Minnesota
terminals. Confidence in seeing MVFR ceilings is highest west and
decreases as you head east...which is why we have kept rnh/eau VFR
for now. Behind this boundary...its a 1045mb Arctic high moving in
and dry air and subsidence with that will clear out the skies to
end the period...though usher in some breezy northwest winds again.
Kmsp...only moderate confidence at best on MVFR ceilings being
observed this evening...may end up being more temporary than taf
implies. Other than that...confidence is high in rest of taf.
/Outlook for kmsp/
Sat...VFR. Wind vrb03kts.
Sun...MVFR/IFR with -sn likely. Wind S 15 knots.
Monday...MVFR/VFR ceilings. Wind west 10 knots.