Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Glasgow Montana
338 am MDT sun Apr 19 2015
Short term...for northeast Montana...today through Tuesday...
a look at 500mb heights for today shows a ridge building across
the western Continental U.S. And extending north into British Columbia.
Meanwhile a trough/closed low feature exists over central and
south Manitoba. In between will lie upper level northwest flow
riding across the northern High Plains. The latest 00z model
guidance continues to place very light quantitative precipitation forecast over the North Dakota
border region for today on the backside of that system as it
departs to the east...and reflectivity echoes are in fact present
early this morning on Canadian radar. While much of this may occur
as virga...enough guidance support exists for a slight chance
mention of showers.
Also...with high pressure building in from the west...the County Warning Area
will also remain within a fairly tight pressure gradient allowing
for gusty northwest winds to develop. Already at 3 am wind speeds
were around 14 miles per hour near The Fort Peck dam. Expect that wind speeds
near 20 miles per hour will develop quite easily with vertical mixing
today...and gusts to near 35 miles per hour. Will therefore have no problems
hoisting the lake Wind Advisory for today to alert those
recreating this weekend. The strongest winds will be near the dam
and lighter winds are expected further west. Despite conditions
more marginal on the west end of the lake decided to play it safe
and include them in the advisory for now. Winds will relax this
An upper level ridge will translate east over the region for
Monday and Tuesday. This has excellent support from the 00z
European model (ecmwf)/GFS and latest CMC and NAM solutions. Therefore...expect a
drying trend and a gradual warm up through Tuesday. In fact...much
of northeast Montana may experience temperatures above
climatological normals by Tuesday afternoon...well in the 60s. The
new European model (ecmwf) has 850mb temperatures by 00z Wednesday near +3c along
the Canadian border...and +6c to +12c over the central and
southern zones. If decent boundary layer mixing can result...a few
locations in the southwest portions of the County Warning Area may see highs near
70. The better odds for that will be in southwest Phillips County
as well as Petroleum and western Garfield counties. Maliawco
Long term...Tuesday night through Sunday...
models have diverged from earlier runs on their solutions for the
extended period. They both start the extended period Tuesday night
and Wednesday with northwest flow aloft over the forecast area between an
upper ridge to the west (western montana) and deep upper low to the east.
The GFS barely moves the ridge during the entire forecast period
and generally keeps it in Montana and Alberta with a surface
nearby to the east and the upper low to the east remaining quasi-
stationary over Ontario. This would keep northeast Montana dry for
the most part with temperatures either near normal or slight
cooler than normal. The GFS does bring a wave through the Pacific
northwest next weekend and through western Montana and Wyoming that could
bring a chance of showers to the southwest part of the forecast area.
Meanwhile...the European model (ecmwf) tries to be more progressive and slowly
moves the upper low to the east which in turn nudges the ridge
east to the Dakotas by next weekend. The ec even has a shortwave
trough undercutting the ridge across southern Alberta and
Saskatchewan Thursday and Friday which would bring enough moisture
into the forecast area for a chance of showers. Then the ec brings
an upper trough and cold front through eastern Montana next
weekend for another chance of showers.
At this point... it looks like the GFS has more run to run
consistency and will lean towards its forecast for now. Forrester
VFR most of the time. Ceilings may drop to MVFR levels at times with
low clouds today.
Clouds: a deck of low clouds will move south into northeast
Montana from Saskatchewan this morning. Ceilings may drop as low
as 2500 feet this morning. Isolated showers are possible today.
Some middle and high level clouds are expected tonight.
Winds: west to northwest at 5-15 knots this morning then increasing to
about 20-25 knots by this afternoon. Northwest winds will diminish to 5-10
knots around sunset this evening.
lake Wind Advisory from 8 am this morning to 10 PM MDT this
evening for Fort Peck Lake for central and southeast Phillips...
central and southern valley...Garfield...McCone...Petroleum.