Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1007 PM CST Thursday Feb 26 2015
Update...for 06z aviation discussion below
Short term...(this evening through friday)
issued at 400 PM CST Thursday Feb 26 2015
Minimal sensible weather highlights in the short term period other
than the low temperatures tonight. High pressure will build across
the region...and clear skies with light winds will promote
radiational cooling. Therefore felt confident using bias corrected
guidance to highlight the typical cold spots across the County Warning Area...and
then adjusted temperatures down along the Minnesota valley where the fresh snow
fell yesterday. Winds will be light...so no Wind Chill Advisory was
deemed necessary...although air temperatures will start the morning at -15
to -20 for most locations outside the city limits. Friday temperatures will
rebound into the teens with clear skies and light west southwest
winds. There is zero chance for measurable precipitation.
Long term...(friday night through thursday)
issued at 400 PM CST Thursday Feb 26 2015
Starting off Friday night...quiet weather expected with the
surface high over the southern Great Lakes. The dry air mass in
place will keep the region dry and partly cloudy into Saturday.
Southerly winds will pick up Saturday and warm temperatures into
the upper teens and lower 20s. Meanwhile a positively tilted
trough will be deepening across the West Coast. As this
occurs...the upper jet across the southern Continental U.S. Will begin
lifting north...and warm air advection in the low levels will
ensue across the Great Plains and Midwest. Accumulating snow is
expected to our south as that area will see the strongest lift
paired with saturation. With the forcing limited in our area...as
well as moisture...expecting there will be potential to see some
light snow in our south...but generally less than an inch
expected Saturday night into Sunday.
Focus turns to early next week when the aforementioned trough
pivots to the east and Lee side cyclogenesis occurs. The surface
low is projected to eject east-northeast through the Midwest
toward the Great Lakes. The ec/GFS indicate the potential for
measurable snowfall especially across southern Minnesota from late Monday
night through late Tuesday night. Being 5 days away its much too
early to talk specifics with this system and there remains plenty
of spread in the ensemble solutions. This system will have a
tight thermal gradient with Gulf moisture being pulled up from the
south...and another Arctic surge on the northwestern flank to
follow. With the GFS/ec solutions indicating a similar surface
low track...did increase probability of precipitation into the likely category for
southern Minnesota and west central WI. At this time indicated snow as
the only p-type but much of a shift north from the current GFS
solution would cause p-type concerns for our area. Much of how
this system develops will depend on a northern stream wave
advancing southeast from western Canada.
After this system moves through Midwest...another Arctic surge
will follow with much below normal temperatures looking more and
more likely. However...the GFS/ec both indicate the western Continental U.S.
Ridge pushing east and warming US up around next weekend...so will
see if this trend continues.
Aviation...(for the 06z tafs through 06z Friday night)
issued at 1007 PM CST Thursday Feb 26 2015
Mostly clear skies with high confidence in VFR conditions through
the period. Cumulus development just east of the taf area is possible
on Friday afternoon...so have included a few030 group at Keau.
Clear skies will prevail for the rest of the sites. Northwest
winds below 10 kts overnight gradually back to the west/southwest
by midday Friday...then to the south by 00z Sat.
high confidence in VFR through the period with winds below 10
kts. Directional component will be from the northwest overnight...back
to around 250 degrees by 15z Friday...200 degrees by 00z Sat...then
170 degrees by 09z Sat.
/Outlook for kmsp/
Sat...VFR.MVFR/-sn possible late. Winds S at 15 kts.
Sun...VFR. Winds west at 10 kts.
Monday...VFR with MVFR/IFR snow likely late. Winds southeast at 10kts.