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Area forecast discussion 
National Weather Service Great Falls Montana
401 am MDT Thu Aug 21 2014

Discussion...
today through Saturday...an upper level low pressure system is
slowly moving through the region...while a Canadian cold front has
pushed southward through the County Warning Area. The end result is scattered
showers and isolated thunderstorms will continue to move through
the region today. The precipitation has not been as widespread as
previously thought over north central Montana so far. However...because
humidities are so high...passing areas of precipitation are
possible in most areas today. Thus pops remain high for
today...even though overall quantitative precipitation forecast amounts will generally not be
significant today...and a widespread all day rain is not expected
either. The scattered precip continues tonight...again with high
pops mainly for the event. On Friday...as the upper level trof
comes close to central Montana...and a surface low develops over the
central rockies...better upslope conditions are expected to
develop over central/north central Montana. Thus Friday night through
Saturday...a band of widespread precipitation is expected to move
through the region. The heaviest precip is expected over the
Rocky Mountain front and the Central Mountain ranges...with 1.50
to 2.50 inches possible in the mountains...at lower elevations
1.00 to 1.50 inches will be possible. Precip amounts will
generally be less than 1.00 inches in southwest Montana. In terms of
snow...the latest forecast models indicate snow levels should
generally be above 7500 feet in the Glacier park region. For
now...I will leave the snow level down to the currently forecasted
snow level near 6500 feet in case latter model runs bring down
some colder air. In either case...snow accumulations of 1 to 2
inches will be possible at mountain peaks over Glacier park Friday
into Saturday. In terms of temperatures...well below normal
temperatures are expected through Saturday. There is the
potential that temperatures could be a few degrees cooler than
forecasted highs should clouds/precip continue for several hours
during the afternoon hours. Brusda

Saturday night through Thursday...a slow moving upper level trough
will remain over the region through the weekend until at least
Tuesday. Models are in decent agreement on details through Monday
morning keeping a good likelihood of precipitation over the region
Saturday evening then a chance of showers into Monday. Solutions
once again diverge as a jet streak moves over the ridge in the Gulf
of Alaska and moves south along the British Columbia coast. The
European model (ecmwf) depicts a stronger and faster jet thereby digging further
south along the West Coast and elongating the trough southwestward
while the GFS reinforces the trough over the northern rockies. GFS
solution drives the trough eastward and places Montana into a
generally dry northwest to westerly flow aloft. Meanwhile, the European model (ecmwf)
develops a closed low over the West Coast then drifts this feature
eastward through the Great Basin and Wyoming with wrap around
moisture being advected into southwest Montana. At this time the GFS
is more in keeping with previous forecasts so have continued to
trend the forecast towards a warmer and dryer solution. Mpj

&&

Aviation...
updated 0450z.
Scattered -shra continue to move through parts of central Montana this
evening ahead of an approaching upper-level trough and surface cold
front. At 0430z the front was just north of kgtf and is expected to
make slow progress southward through the overnight period.
Precipitation should become more isolated after 06z but then
redevelop behind the front vcnty kctb/khvr around 09-10z, with the
coverage of showers expanding south toward kgtf/khln/klwt on thurs
morning. Ceilings should generally remain VFR tonight, with some
brief MVFR conditions possible under any moderate showers. As the
rain develops tomorrow morning, ceilings will gradually trend
downward to 3000-5000 ft, with better chance for MVFR ceilings from
midday Onward as rain becomes more widespread.
Waranauskas

&&

Preliminary point temps/pops...
gtf 64 51 64 52 / 70 60 90 100
ctb 61 49 58 49 / 70 60 90 90
hln 68 53 65 52 / 60 60 90 100
bzn 69 51 67 49 / 50 60 80 80
wey 60 45 61 40 / 40 40 50 40
dln 69 48 65 45 / 40 50 80 70
hvr 66 55 66 55 / 70 50 80 80
lwt 62 50 60 51 / 70 60 80 90

&&

Tfx watches/warnings/advisories...
none.

&&

$$

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