Severe Thunderstorm Warning 129, NWS Glasgow, MT

Area Forecast Discussion
National Weather Service GLASGOW MT
154 PM MDT SAT JUL 30 2016

.SHORT TERM...for northeast Montana...tonight through Mon...

Upper low over over western Canada is expected to drift east
before lifting into central Canada late Monday. Thunderstorms were
moving east across SW Sask early this afternoon are not expected
to drop into NE MT today. However, southwest flow over central
Montana and an axis of instability could generate a storm or two
that moves into our western zones before sunset. SPC's SSEO has
some winds associated with these storms but nothing severe.

Models take differing approaches on what happens with leftover
storms tonight. GFS has them drifting NE mostly into the northern
zones, less so with the NAM. The ECMWF keeps much of the activity
well north in Canada. Given that the GFS has been too dry/stable
lately, will keep the pops going overnight.

Dry line over central Montana today moves east into the eastern
zones late Sunday. Afternoon convection should fire along and
ahead of it in the late afternoon before moving into North
Dakota. SPC's Severe Thunderstorm outlook with a Marginal area
along the state border and east looks good.

With the upper low moving into the Prairie Provinces Monday, a
drier/slightly cooler airmass moves in. West winds are expected to
remain below Lake Wind Advisory criteria. TFJ

.LONG TERM...Mon night through Sat...

Monday night begins with a hot air-mass over most of the West and
upper troughs over Saskatchewan and near Vancouver Island. This
places Northeast Montana with zonal flow aloft near the boundary
between the two air-masses. Overnight and Tuesday the Saskatchewan
trough lifts into Manitoba and the other trough moves into the
Pac-NW. The movement of the troughs will build up a narrow ridge
over the local area. However by Tuesday evening the trough moves
over the Divide causing local flow aloft to back around to the
southwest, which ejects moisture into the flow.

Late Tuesday night and Wednesday the trough swings across
Northeast Montana sending a cold front that will initially bring
scattered thunderstorms that become more rain showery, mainly
across the northern zones. Brisk winds behind the front could
generate 20kt north to northwest winds. Expect below normal
temperatures for Wednesday and Thursday and near normal for the
weekend.

Made few grid edits since there was uncertainty in timing the
cold front Tuesday night and initiation of precipitation.
Otherwise, grids follow the blended pattern well.

Templer

Previous discussion:
Latest 00z models indicate that an upper ridge over the Northern
High Plains Monday night will shift east into the Dakotas by
Tuesday as a shortwave trough/closed low digs into northwest
Montana. THis will allow for increased chances for showers and
thunderstorms across the CWA. Chances may spill into the midweek,
particularly nearest the Canadian border.

An upper ridge looks to become firmly established late in the week
allowing for large scale subsidence and therefore drier and warmer
temperatures with rising heights. Highs will once more reach the
the 80s to near the 90 degree mark by about Friday. Maliawco

&&

.AVIATION...

A weak upper level ridge moves over Northeast Montana this
afternoon bringing clear skies and dry conditions based on the
northwest flow aloft and the lack of strong convective parameters.
However disturbances in southern areas of the prairie provinces
has initiated scattered thunderstorms that may drift south into
the local area.

So expect limited chances for an isolated thunderstorm to affect
any terminal. Winds will be at 5kt to 15kt from the southeast
today with stronger the winds in the west.

Sunday a broad upper trough pushing through Western Canada will
send a cold front through the local region bringing a better
chance for thunderstorms. Gusty northwest winds of 10kt to 20kt
will develop behind the cold front in the afternoon.

Templer

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

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