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Area forecast discussion
National Weather Service Glasgow Montana
821 PM MDT Wednesday Apr 16 2014
Short term...for northeast Montana...tonight through Friday...
didn/T make too many changes to going forecast for tonight...but did
lower probability of precipitation for Thursday.
Atmosphere a bit unstable and this should keep cloudiness around
tonight but little precipitation is expected. Going forecast has this
Moisture looks to move out of the area tomorrow and current chances
for precipitation do not look justified. Rest of forecast looked
Previous short term discussion...
upper level low pressure trough over northern plains continues to
move eastward during period winding up over Great Lakes region by
Friday afternoon. The upper ridge over the Pacific northwest today
will slide over northeast Montana Thursday night. Ahead of the
ridge ggw County Warning Area will be under a northwest flow aloft...and behind
the ridge a southwest flow aloft.
Several weak short wave disturbances sweep through flow during
period accompanied by ample moisture at low- and mid-levels.
These factors produce rain and snow showers during much of the
period...except for a brief respite overnight Thursday night when
the upper ridge axis is overhead. Temperatures will remain at or
below climatological normals. A quasi-stationary front stretches
across the state from northwest to southeast resulting in easterly
winds 10-20 miles per hour throughout period. Britton
Long term...Friday night through Wednesday...
Friday night begins with a stacked-up low moving east across the
southern portions of the prairie provinces. This will direct the
jet over northeast Montana to bring about a good chance for rain
before midnight and a slight chance after. The trough departs east
Saturday morning to first bring westerly flow aloft that veers to
the northwest during the day. Then Saturday night and Sunday an
upper ridge will bring about warmer and milder conditions. Then
late Sunday afternoon and night another disturbance treks east
across the prairie provinces...but should be far enough north to
bring about generally zonal flow aloft. This pattern will bring
about a warming trend to send temperatures warmer than normal into
Tuesday. Any precipitation that falls in the extended period will
likely fall as rain.
A big change comes about over the west early next week when a
large split trough forms up along the West Coast. The base of this
trough will pick up Pacific moisture off Southern California to
send a significant amount of moisture into the central and
northern rockies and across The Divide into the High Plains.
Naturally this far out the models have not yet aligned with each
other but the large features are there. This large system will
lift through Montana on its way into Canada around mid-week. The
GFS is already indicating strong convective parameters...generally
south of nemont. For now there is a potential for a strong Spring
storm that could produce a significant amount of moisture through
late next week. Thunder is also a possibility.
synoptic set up...a weak ridge extends from the southern US High
Plains up through the Dakotas while a Second Ridge runs up the
coast of California...the Pacific northwest...and British
Columbia. A weak trough lies between these two features over
Montana and the High Plains of Alberta. Farther west...a large
trough exists over the bearing sea and is ejecting into the Gulf
Friday night...the trough aloft will form a surface low over
Alberta and move it east into Saskatchewan. A cold front
extending down with Pacific moisture will quickly exit the area
but not before leaving rain showers behind that evening.
Saturday through Monday night...coastal ridge will move into the
area and dry conditions out with weak down-sloping effect in the
surface layer through Saturday. Then the ridge will flatten
slightly allowing for the warmer side of zonal flow and slightly
unstable afternoons. High temperatures will rise into the 60s and
70s helping to destabilize the surface layer a bit more.
Tuesday Onward...surprisingly...models seem to be holding together
during these periods with fairly well matched synoptic features
from run to run and model to model. The main player is the large
trough over the bearing sea and Gulf of Alaska dropping down over
the western third of the Continental U.S.. models have not resolved the
base/southern component of this trough...however they do appear to
break the trough into a northern and southern component with the
northern component bringing increased chances for precipitation to
northeast Montana in multiple models. For this reason...raised
probability of precipitation considerably above the normal climatology of 15 to 20 percent
during these periods. Gah
flight category: high MVFR to VFR.
Synopsis: a line of high MVFR clouds above 2kft has overspread
across the terminals from southern Saskatchewan into North Dakota.
This cloud deck is anticipated to remain almost in place with a
slow creep to back to the east through around 18z. At which point
clearing is anticipated to accelerate.
Snow showers: a slight chance for snow showers exists at all
terminals but chances are too low to include directly in the
tafs. If snow does occur it could bring ceilings into fuel
loading conditions below 2kft but would be very brief. MVFR
visibilities would also be possible with snow showers.
Area winds: out of the east around 10 to 15 kts through 18z...
then veering slightly to southeast and increasing to 15 to 20 kts.