Scientific Forecaster Discussion
fxus65 kggw 280855
Area forecast discussion
National Weather Service Glasgow Montana
255 am MDT sun may 28 2017
Short term...for northeast Montana...today through Tue...
Synoptic setup: a trough runs from the northwest territories down
through the Canadian prairies and into the eastern Dakotas and
upper Mississippi Valley. A ridge runs upward through the
intermountain west into the Pacific northwest and British
Columbia. These two airmasses establish a northern to northwest
flow aloft for eastern Montana.
Today: cold air will drop south in the flow to the east and
intensify the pressure gradient across the region. This will lead
to an increase in winds speeds with nearly 20 to 25 kts sustained
and gusting to nearly 35 kts by the afternoon. In addition...
model data is pushing for min relative humidity around 20 to 25 percent through
the afternoon. However the last 2 days have been almost 5 percent
drier than predicted, and this trend is not expected to change.
So, have shrink-stretched the lowest points down further to below
20 percent. This has lead to both red flag and lake Wind Advisory
criteria for the afternoon. Winds were also switched from the
typical super/consshort to consmos in order to capture the higher
winds in a well mixed atmosphere.
Tonight through monday: as the atmosphere decouples winds will die
off rapidly with sunset with a light northern wind by midnight.
While flow aloft will be strong high pressure forming up north
should cut down some of the gradient mixing down Tuesday with
relatively lighter winds compared Sunday. Gah
Long term...Tue night through sun...
Northwest flow aloft will linger into Tuesday as upper low moves to the
east and upper ridge builds into the forecast area from the west.
Surface high pressure over eastern Montana will allow for dry
weather and light winds over the forecast area.
Upper ridge continues to slide east across Montana Wednesday and
Thursday which will bring warmer temperatures and mainly dry
weather. Models want to bring a shortwave trough/weak frontal
system across eastern Montana Thursday night which could bring a
slight chance of showers and thunderstorms.
Models differ Friday and beyond. European model (ecmwf) brings a shortwave ridge
Friday and Saturday with mainly dry weather while GFS maintains a
quasi- stationary front on northwest flow aloft with chances for showers
and thunderstorms. Will maintain a slight chance of showers and
thunderstorms for now.
Next Sunday, GFS has a ridge while European model (ecmwf) bring a shortwave trough
but keeps precip mainly to the north. Will keep forecast mainly
dry for now.
Flight cat: VFR.
Synopsis: low pressure exiting to the east and high pressure
building to the west will lead to strong winds today which may
generate crosswind concerns for small aircraft.
Wind: northwest at 5 to 15 kts early this morning... increasing
to 20 to 25 kts sustained, gusting 35 kts in the afternoon...
veering to the north and calming to less than 10 kts near
red flag warning from 1 PM this afternoon to 7 PM MDT this
evening for mtz120-122-134-136-137.
Lake Wind Advisory from 10 am this morning to 9 PM MDT this
evening for Fort Peck Lake for central and southeast Phillips...
central and southern valley...Garfield...McCone...Petroleum.