Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
312 am CST Sat Jan 31 2015
Short term...(today and tonight)
issued at 313 am CST Sat Jan 31 2015
A very potent storm system will begin to organize across the central
Continental U.S. Over the next 24-36 hours. The main concern in Minnesota is whether the
much drier air from Canada will suppress the deeper moisture to our
south...leading to only flurries across southern and central
Minnesota...with the bulk of any measurable precipitation along and south
of the Iowa/Minnesota border.
Although short term models have done a good job with the spread of
precipitation across KS/NE...the cold front that was moving across
southern Minnesota early this morning has brought much drier air into
northern Minnesota. Regional satellite imagery noted this much drier air
eroding the cloud cover across the far northwest corner of Minnesota. Usually
models have a hard time spreading too much moisture northward in
this type of scenario with a cold/dry north/NE flow developing.
Especially considering wind spds will increase during the
aftn/evening...leading to further drying in the low levels. With
this in mind...there will be a very sharp cutoff on measurable
precipitation...to flurries at best from south to north. Considering
quantitative precipitation forecast amts along the Minnesota/Iowa border and the amount of forcing expected late
tonight and into Sunday morning...there could be a period of
moderate snowfall along the Iowa/Minnesota border. Current grids have
snowfall amts of 3-5 inches in the far southern tier of mpx County Warning Area.
This is taking into account the drier air and snowfall ratios vs.
Quantitative precipitation forecast amts. Later shifts could issue a Winter Weather Advisory for far
southern Minnesota...but the uncertainty of the amount of dry air vs. Forcing
remains low. No other concerns through Sunday morning as the storm
system begins to move off to the east/southeast into the Ohio Valley.
Long term...(sunday through friday)
issued at 313 am CST Sat Jan 31 2015
Long term forecast concerns are rather minimal...and primarily
revolve around snowfall chances on Tuesday along with the cold
start to February.
In the wake of the system on Sunday...semi-zonal middle level flow
will develop into the beginning of next week. At the
surface...the high pressure area of Arctic origin will yield
temperatures ranging from 5 to 15 degrees below climatological
On Monday...the aforementioned surface high slips off to the
southeast as another clipper-like system approaches from the
northwest. Low level warm air advection ahead of the associated
trough will initiate a weak moderation in temperatures on
Tuesday...with highs sneaking closer to normal...but still
slightly below with readings ranging from around 20 to 25
degrees. While we could see snow develop as early as Monday
evening as a weak potential vorticity element passes over...the
better forcing and moisture advection arrive as the trough passes
on Tuesday. Accumulations in the half inch to 2 inch range appear
After Tuesday...the remainder of the work week looks to be dry
overall...with temperatures warming back to near or above normal
values for next weekend.
Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1129 PM CST Friday Jan 30 2015
Current MVFR ceilings on track to spread S/southeast across mpx County Warning Area by
12z. There may be a delay of an hour or two in the southern part of
mpx County Warning Area...but still have high confidence of the continued trend.
Upstream across south central Canada...strong evidents of drier
air moving southward which means the MVFR ceilings will likely begin
to break up or dissipate by middle/late morning across central
Minnesota. How far south the drier air will spread is the main
concern...especially for krwf/Keau where MVFR may continue through
the taf period. The worse conds will occur after 06z/01...but enough
confidence to introduce -sn at krwf by 3z. Winds will shift to the
north/NE today with gusty winds developing Saturday afternoon/evening from
High confidence of VFR conds through 12z...with ceilings lowering to MVFR
by 12-14z. Timing is the main issue but current trends seem
reasonable of VFR through 12z. MVFR ceilings may continue through the afternoon
before drier air filters in from the N/NE. Confidence remains low
on when the MVFR ceilings dissipate or continue based on the strength
of the drier air. Have introduced -sn after 9z as a storm system
across the plains brushes the southern part of mpx County Warning Area. Winds will
shift to the north by 10-12z...then more NE and increasing during
the afternoon/evening with gusty winds.
/Outlook for kmsp/
Sun...MVFR ceilings/visibilities early with -sn. North wind 10 to 15 knots.
Sun night...VFR. North wind becoming SW 5-10 knots.
Monday...VFR. Southwest wind 5 to 10 knots.
Monday night...MVFR ceilings possible. Southwest wind 5 to 10 knots.
Tuesday...MVFR ceilings/visibilities in -sn possibly IFR at times. Wind becoming
north around 10 knots.