Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
345 PM CST Monday Jan 26 2015
Short term...(this evening through tuesday)
issued at 343 PM CST Monday Jan 26 2015
A surface low analyzed by the rap near Duluth this afternoon with a
stalled warm front through extreme western WI...just east of the Minnesota
border. Temperatures west of the front have climbed well into the
40s across most of the region with dew points in the low to middle 30s.
This causes some concern for fog development overnight as a surface
high/ridge axis moves in late tonight and winds go nearly calm. The
tricky part of the forecast is how far west the cloud cover will
extend tonight. Model guidance is quite saturated at 925mb but can
easily impacted by surface moisture. An inversion will develop
after dark and could lock any low cloud cover in place. Confidence
is low in cloud cover across western Minnesota.
In west central Wisconsin...east of the front...temperatures have
held steady in the middle 20s with -fzdz and -sn being reported through
much of the day. Very light and scatter precipitation will continue moving
through this area along the frontal boundary for the next few hours.
Otherwise...cooled temperatures slightly for tomorrow across the east given
lingering cloud cover...and the fact the southerly winds on the back
side of the ridge dont arrive until late in the day.
Long term...(tuesday night through monday)
issued at 343 PM CST Monday Jan 26 2015
A couple chances for light precipitation exist in the extended
period of the forecast...while the cooldown remains on track for the
weekend and into early next week.
Early afternoon watervapor imagery together with GFS 500mb heights
and winds showed a broad area of northeast flow across the central
Continental U.S. Sandwhiched between the negatively tilted ridge along The
Spine of The Rockies...and more notably the negative tilted upper
level trough driving the powerful noreaster over the New England
area. This northwest flow pattern will generally remain in place
across the upper Midwest...with periodic shortwaves bringing
repeated chances for light precipitation.
The first will arrive Wednesday night...and thermal profiles show
the potential for a wintry mix of light snow or freezing drizzle.
Note...wednedays high temperature will depend heavily on cloud
cover...so did not warm temperatures since middle/low level clouds should keep
afternoon highs from warming out of control despite the favorable
timing of the warm air aloft.
High pressure will build in Thursday and Friday...with cold air
advection limiting temperatures to near 30 on Thursday...and 20s on Friday.
Friday night another system will move across the region...but
strength and timing remain uncertain. The GFS is faster and stronger
than the ECMWF/Gem...but neither solution produces significant
precipitation...which will be all snow...across the region. Cold air will
funnel in for the early part of next week...and to echo the thoughts
of the previous forecaster...it appears Monday will have highs in
the single digits...with lows below zero overnight.
Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1154 am CST Monday Jan 26 2015
Warm frontal boundary oriented north-S has reached the Minnesota/WI
border...with clear skies and warm temperatures west of it...and
cold temperatures/-sn/-fzdz east and north of it under low stratus.
Expecting this front to be quasi-stationary so little movement in
the stratus is expected for the remainder of the day. Western Minnesota
will remain mostly clear and expect VFR for the entire period. A
much more complicated scenario in eastern Minnesota...near the boundary
itself. 925 relative humidity fields indicate the potential for low stratus to
get stuck under an inversion tonight...as the cloud cover in
northern Minnesota advects southward through the remainder of the day.
Still...not confident in these high relative humidity levels in the lower levels
actually translating to low ceilings. Significant drying just above
this level /and the inversion/ makes it a tough call from late
tonight through Tuesday morning. Leaned to the optimistic side and
scattered out the low ceilings late tonight...but be aware there
is potential the low ceilings could stick around all night.
Kmsp...VFR initially as we linger near the edge of the cloud deck
to the north and east. Thinking we'll ride the edge for much of
the late afternoon and evening. Went scattered after 07z...but low
confidence in this and will need to continue evaluating ceiling
potential for the overnight period.
/Outlook for kmsp/
Tuesday...VFR. Wind light/variable.
Wednesday...VFR. Chance MVFR. Wind southeast 10 knots.
Thursday...chance MVFR/-sn. Wind northwest 10-20 knots.
WI...Winter Weather Advisory until 6 PM CST this evening for wiz015-