Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Glasgow Montana
335 am MST Monday Nov 30 2015
Short term...for northeast Montana...today through Wednesday...
the primary forecast challenge in the near term will surround
dense freezing fog across portions of the County Warning Area...mainly having
developed off of Fort Peck Lake and spread across portions of
valley and western Roosevelt County. Given visibility below one
quarter mile at times...will have a dense freezing fog advisory in
effect until 11 am.
The question remains as to how much improvement there will be
during the day and the next shift will need to closely assess the
environment. Synoptically speaking there is not much that can
really mix out the inversion with the overall closed upper low
remaining in place. Thus...during the daytime the areal coverage
may shrink and/or visibilities may rise from their lows...but
confidence is low as to timing and/or the amount of recovery.
For tonight...high resolution models differ on whether or not
there will be a return of fog conditions. Given low confidence
included patchy fog for tonight.
For Tuesday and Wednesday...the upper low will push east and an
upper ridge over the Pacific coast will begin to push east and
spread rising heights across the region. This should allow dry
weather to continue and temperatures to modify. Maliawco
Long term...Wednesday night through Monday...
pattern trending back to warmer and dry weather for most of the
extended period as an upper ridge builds over The Rockies and
into the plains.
High pressure developing west of The Divide will lead to
development of Chinook winds across the Front Range spreading
warmer air eastward. A shortwave trough sliding across the top of
the upper ridge will bring a weak cold front out of the north late
Wednesday. The main impact from this front should be an slight
increase in winds and better mixing Wednesday night.
After midweek as another upper trough approaches the West Coast and
upper flow turns south...even warmer air spreads north into the
state on Thursday. This trough pushes a stronger cold front across
the region on Friday...but any potential drop in temperatures will
be offset by very good mixing with increasing west winds.
Precipitation signature is very weak with limited moisture making
it across The Divide so will keep the forecast dry for now
following this feature. Ebert
VFR condition expected across much of the region even as a large
upper low moves from Wyoming into the northern plains. The
exception is around kggw and possibly kolf where moisture off of
Fort Peck Lake will be trapped under the shallow inversion and
produce IFR or vlifr conditions with dense fog and low clouds
periodically through the next 24 hours.
freezing fog advisory until 11 am MST this morning for central
and southern valley...northern valley...western Roosevelt.