Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
349 am CST Thursday Jan 29 2015
Short term...(today and tonight)
issued at 349 am CST Thursday Jan 29 2015
Short term concerns are headlines early this morning. Then overall
improving trend and turning colder.
Radar continues to show some light intensity echoes moving across
east central Minnesota. Water vapor imagery showing secondary trough
moving into western Minnesota now. The trend on the rap has been
generating some light quantitative precipitation forecast into south central Minnesota through about 14z.
Nothing too dramatic on radar...although surface observation continue to
show some visibility reduction in br and occasionally some -sn or up.
Will continue the Freezing Rain Advisory through 12z. Will word
that precipitation should be ending this morning.
The other concern is the wind advection to the southwest. Winds have been
increasing to the west overnight as the pressure gradient increases
with the cold front moving through. This should continue through at
least middle morning as the greatest pressure rise moves through the
area. Have included a couple more counties in west central Minnesota as
Winds are expected to diminish overall after 18z and become light
into tonight. Clouds will this as well with temperatures dropping
through the single digits and teens for lows tonight.
Long term...(friday through wednesday)
issued at 349 am CST Thursday Jan 29 2015
West/northwest flow will prevail through the majority of the long
term forecast period...with only minor/fleeting chances for
precipitation foreseen into early next week.
Friday will be a tale of two stories within the forecast area...as
the departing surface high yields temperatures around 5 to 10 degrees
below normal in the east over Wisconsin...and low level warm air
advection over the west brings highs from 5 to 10 degrees above
normal to west central and southwestern Minnesota. Expect high
temperatures to range from 15 to 20 degrees over west central WI...to the
lower 30s along the Minnesota River Valley.
On Saturday...the GFS and European model (ecmwf) models are sticking to their GUNS
in progging the bulk of the precipitation to pass south of the
forecast area...as an incoming Arctic high suppresses the system
lifting out of the southwestern Continental U.S.. could see a light round of
snowfall with inch or so accumulations on Saturday night ahead of
the approaching high...but the main /southern stream/ system
should stay well south of the area.
The Arctic high will inevitably be accompanied by a notable
reduction in temperatures...with highs from 5 to 15 degrees on
Sunday...and sub-zero lows occurring nearly area-wide on Sunday
night. Associated winds will be rather light...so do not currently
expect wind chills to dip lower than -15 to -20 on Sunday night
and Monday morning.
As the high slips off to the southeast...temperatures will
gradually moderate back to normal as a surface trough approaches
from the northern rockies. This feature may bring a light round of
snow on Monday night into Tuesday morning...during which 20-30
probability of precipitation have been included.
Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1127 PM CST Wednesday Jan 28 2015
Large area of -fzdz slowly eroding away to the east as cold front makes
progress through the County warning forecast area. This is allowing western Minnesota to have ceilings
rise from IFR range to MVFR range while visibility increases to VFR. This
trend will continue eastward slowly through the early morning hours. In
conjunction with the clearing will be a strong surge in wind
speeds in the wake of the cold front. Northwest winds will increase to 15-25
knots with higher gusts during the early morning hours...lasting through Thursday
afternoon before speeds dissipate Thursday evening. The increases in wind speeds
will help scour out near-surface moisture...allowing visibilities to quickly
increases but the low stratus will linger for much of the day. By late
afternoon...any lingering low stratus will scatter out...resulting in
VFR conds by late Thursday afternoon into Thursday evening.
Kmsp...have initialized with IFR conds but as the cold front continues
to shift east across the area...visibility will quickly improve between 06z-
08z to VFR conds. Ceilings will be slow to follow by am expecting ceilings
to rise into MVFR range by 08z. Still some question as to how
quickly ceilings rise about the 1700 feet threshold...and if anything...
the timing may be later than the 14z timeframe currently
advertised. Otherwise...conds are on track to reach VFR levels by
late Thursday afternoon with continued improvement through Thursday night.
/Outlook for kmsp/
Friday...VFR. Wind S 5 knots.
Sat...mainly VFR...chance MVFR cigs/-sn. Wind north 5-10 knots.
Sun...mainly VFR...chance MVFR ceilings. Wind north 10 knots.
Minnesota...Freezing Rain Advisory until 6 am CST early this morning for
Wind Advisory until 9 am CST this morning for mnz047-048-054>057-
WI...Freezing Rain Advisory until 6 am CST early this morning for