Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Glasgow Montana
436 am MST Thursday Jan 29 2015
Short term...for northeast Montana...today through Saturday...
With a ridge over western Canada and an Arctic low centered over
Hudson Bay flow aloft for northeast Montana will continue from the
northwest today and Friday. Nemont will remain on the warm side of
the stationary boundary through Friday afternoon. So expect
conditions to continue running warmer than normal...anywhere from
10f to 15f degrees above seasonal norms.
Patchy freezing fog developed over much of the region early this
morning. Continued the fog through 15z.
Conditions change Friday evening when the Arctic low sends a wave
around the west side of Hudson Bay that brings a backdoor cold
front into the local region in coincidence with a short-wave
clipper. The front quickly drops south of the international
border overnight. Overrunning Pacific moisture spreads across
British Columbia and the prairie provinces following the frontal
boundary. Expect light snow to fall mainly north of the Missouri
River after midnight. Snow becomes more widespread Saturday
morning and begins to taper off from the north Saturday afternoon
to become flurries. Cold air advection from the north and northeast will limit
highs very close to seasonal norms...which is in the teens in the
north and lower 30s in the south.
The main challenge for now is quantitative precipitation forecast. All precipitation Friday night
and Saturday will be snow...with increasing snow ratios. So far
quantitative precipitation forecast limits snow amounts to 1 to 2 inches...and maybe up to 3
inches north of the hi-line. Wind will be brisk from the northeast
with a limited chance for blsn. So added patchy blsn to areas of
strongest wind. Scattered
Long term...Saturday night through Thursday...
persistent West Coast ridge together with Hudson Bay low leaves
region beneath northwest flow aloft through period. Upper ridge
retrogresses Saturday night as Hudson Bay low deepens allowing colder
Canadian air to push into Montana from the northeast. Several
short wave disturbances rotate around low bringing increased moisture
at low and middle levels through remainder of weekend and next week.
GFS and European model (ecmwf) differ slightly in placement and timing of these
disturbances...so will simply go with slight chance showers
through period. Temperatures will remain near or slightly below
normal for the entire extended forecast period. Surface pressure
gradients do not support generation of strong winds...so expect
only occasionally breezy winds over northeast Montana. Britton
flight category: MVFR...becoming VFR from west to east after 15z
Ceilings and vsby: MVFR with some IFR ceilings at Wolf Point and
Sydney aerodromes expected to dissipate between 15z and 18z.
Wind: light winds will pick up a bit this afternoon from the
south but speeds will generally remain less than 10 kts.
due to the recent record setting warm temperatures some of the
creeks and small streams are running. Minor flooding was reported at
7 mile creek near Glendive and Beaver Creek near Wibaux...which
prompted the issuance of a small stream Flood Advisory through
Temperatures are expected remain above average today and Friday.
Then on Saturday temperatures will return to normal...which will
begin to limit any further flooding. Scattered