Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Glasgow Montana
304 am MDT Wednesday Apr 23 2014

Short term...for northeast Montana...today through Friday...
upper trough over Idaho and British Columbia at 09z will move
across Montana today. A cold front ahead of the trough will move
through eastern Montana this morning which will turn the strong
east winds into stronger west winds. An upper low will form along the
upper trough in southern Alberta as it splits away from British Columbia portion
of the trough to the west. At the same time...the surface low in
eastern Montana will become stacked with the Alberta upper low.

At this point...most of the rain is either along the front or within
a 100 miles behind it. As a result...the best chance of rain
today will be as the front moves through the forecast area this
morning and the northeast this afternoon.

After the front moves through northeast Montana...somewhat drier
air moves in. Unstable airmass will allow for some showers this
afternoon possibly a thunderstorm.

The upper low moves across southern Saskatchewan tonight and
Thursday. Northeast Montana will be on the drier south side of the
system and models have diminished the amount of wrap around
moisture associated with the system. Have lower chance of showers
to chance north and slight chance south. Gusty west to northwest
winds will prevail until the low moves to the east Thursday night
and a shortwave ridge builds into eastern Montana.

That ridge will bring dry weather on Friday with temperatures near
normal. East winds will develop during the day ahead of the next
system that will impact the forecast area this weekend. Forrester



Long term...Friday night through Wednesday...

The extended forecast period begins Friday evening with a trough
over the West Coast with its base picking up Pacific moisture off
Southern California. This moisture will be ejected northeast into
Montana beginning Friday night. This trough...and the cold trough
centered over Hudson Bay...will have squeezed up a ridge over
Montana that will swiftly move southeast. This will place the
boundary...separating the northern cold air mass from the southern
air mass...over northeast Montana. The overrunning moisture will
find this boundary as a Focal Point for precipitation into
Saturday and Saturday night. By Sunday morning the trough moves
into Colorado where it stacks up the the surface low to form an
inverted trough over eastern Montana. This will channel more
moisture in from the southeast for wrap-around precipitation
through Sunday...tapering off through Monday. A significant
uncertainty is the precipitation type...with the GFS favoring rain
and the ec favoring snow. Went middle of the Road and kept both
rain and snow in the grids.

The situation becomes even more clouded after Monday when a ridge
begins to build up over the west. The GFS pushes a warm front over
eastern Montana on Tuesday. The ec however keeps the warm air mass
well to the southwest...over California. So...the ec maintains wet
and cool. Thus...there is great uncertainty with temperatures between
the models towards the end of the extended period concerning
northeast Montana.



&&

Aviation...

Showers will affect the terminals today. Lowering ceilings and
periods of heavier showers may cause MVFR conditions through late
morning. Gusty southeast winds will persist through early morning.
Then a wind shift will occur between later this morning as the
front passes and will become westerly at 20-25 kts by 18z. Scattered



&&

Glasgow watches/warnings/advisories...
lake Wind Advisory until 9 PM MDT Thursday for Fort Peck Lake
for central and southeast Phillips...central and southern
valley...Garfield...McCone...Petroleum.

&&

$$

Weather.Gov/Glasgow