Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Glasgow Montana
920 am MDT Wednesday Aug 20 2014
Short term...for northeast Montana...today through Friday...
southwest flow aloft is helping to produce some showers this morning
but any are light. It/S expected to remain that way today with the
best chances for showers confined to the the northeast zones for
late this afternoon. Overall...forecast appeared to be in good
upper trough extending from the Canadian rockies through the Great
Basin expected to deepen through the end of the week...with a
closed low forming over the Pacific northwest by the weekend.
Moisture spreading into the state with the southwest flow aloft
and as shortwave energy begins lifting out of the trough and across
Montana...expect periods of showers along with a few
First wave already lifting across Wyoming and into southern
Montana this morning...and showers expected to continue developing
northward today. Next shortwave pushes out of the northern rockies
on Thursday morning...and crosses northeast Montana as it lifts into
southern Saskatchewan. This wave expected to provide the most
extensive and heaviest rainfall during the short term period.
More widespread and less convectively driven rain expected to
begin to spread out of southwest Montana late on Friday as upper
low swings through the northern rockies.
Long term...Friday night through Wednesday...
the extended period begins on Friday night with the large trough
across the western U.S. Pushing southwest flow aloft over
northeast Montana. Abundant moisture and plenty of upper level
dynamic support will lend to periods of rain continuing through
Saturday with perhaps some embedded thunder. Wrap-around shower
activity will continue...especially east...into Sunday as well as
surface low tracks into southern Manitoba. In fact...guidance is
has trended toward a solution with a slower progression of this
event. As the storm system becomes vertically stacked over
southern Manitoba on Monday...isolated showers may still be
possible across northeast Montana. By the time all is said and
done...widespread wetting rains are likely. Specific timing and
details are still somewhat uncertain. The trough in place will
also mean relatively low 500-1000 mb thicknesses across Montana.
Therefore...temperatures will be well below average through early
Tuesday Onward...ensemble of 500mb heights begin to show
increasingly larger spread...lending to lowering confidence. The
20/00z European model (ecmwf) and GFS each show the potential for ridging across
the region toward the middle or end of next week.
However...differences in timing/evolution/characteristics of
synoptic features are large enough this far out that it is
difficult to add much insight as to what precipitation chances may
result. For now will trend probability of precipitation to near climatology for the end of the
long range. As at least the potential exists for ridging once the
large trough loses influence on the County Warning Area...will gradually trend
temperatures upward as well for the middle of next week. Maliawco
In general expect VFR conditions to prevail...although scattered
showers and perhaps a thunderstorm may cause brief restricted
visibilities across the taf sites as the day progresses. Ceilings
will lower to about 5000 feet late in the afternoon. Expect winds
to become northwest at 10-15 kts. Maliawco