Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 250314

Area Forecast Discussion
National Weather Service Glasgow MT
914 PM MDT Mon Jul 24 2017

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

Changes to the forecast were mostly focused on getting the latest
mesoscale wind field data into the grids for the next 6 to 12
hours. Outside of this radar echos are being monitored over Golden
Valley and Fergus County for their lightning chance and
directional bearing. Currently there was a single strike over
high terrain in the last hours with the hope that this will
dissipate as it moves over the high plains of Petroleum and
Garfield county. Upper level moisture around 700 mb is evident on
GOES 13/15 IR and in most models with limited thin CAPE, but thus
far there has been no lift trigger present to set off thunder
leading to reduced chances as the night continues. GAH

An upper level low pressure system is moving eastward across
Saskatchewan this afternoon. This is the same system that has
dragged the cold front across the region today, which brought a
wind shift to the northwest and gusty winds to northeast Montana.

With a return to northwest flow, dry weather will continue across
northeast Montana. As the upper low continues east dragging the
front along, a shortwave disturbance will move into the region
from upstream in the flow. These features will provide enough lift
to produce a few high- based thunderstorms this evening and
tonight. Although most of this activity will be to our south,
there is a chance that this will impact our southern zones. Again,
these will produce little to no precipitation, and lightning and
gusty winds will accompany any storms that develop. With a
prominent inverted-V sounding, downburst and strong outflow winds
will be an issue with any thunderstorm, as will be the potential
for lightning sparked wildfires.

Tuesday: By around 12z Tuesday morning, the system will have
exited the area, leading to sunny to partly cloudy skies.


.LONG TERM...Wed night through Mon...
Tuesday night, the storm system in Canada will move far enough
east that the northerly wind will begin to veer to the east
overnight. Upper flow begins zonal, but off to the west another
upper-level ridge begins to amplify. The weak frontal boundary
stretched across Northeast Montana will become a diffuse warm
front Wednesday allowing warmer air to drift into the area again.
Temperatures for the forecast area will begin to rise into the
mid 80s in the northeast and near 90s in the west. As the front
moves east it will be the focus of weak disturbances that could
initiate isolated thunderstorms through Wednesday night.

Thursday, the ridge peaks over the forecast area, driving most
most highs into at least the lower 90s. The result will be
western areas seeing upper flow back to the southwest and more
weak disturbances drifting in, which could initiate more
thunderstorms through Thursday night into Friday. The storms
Thursday afternoon/night could become strong with hail and very
gusty wind, based on a very unstable environment. Because of
moisture from the southwest flow aloft, any storm that gets going
could dump localized rain.

Friday and Saturday the ridge firmly reestablishes itself, with
temperatures again drifting into the mid to upper 90s. During this
period models are generating isolated to scattered thunderstorms
as weak disturbances drift through the region. Monday and beyond,
model agreement evaporates.

Grid edits were done with FB, paying closer attention to pop/wx
grids. Guidance probably underestimates maximum temperatures next
week, but with little agreement. Except for tweaking RHs down a
bit, went with the blends.

Overall, expect temperatures to again run in the 90s, with low
RHs, no strong wind, although from Wednesday night on southeast
winds may become gusty at around 15 kt. Models indicate the
possibility of nuisance thunderstorms with no real wetting rains
expected. This will be mainly a fire wx concern.


Tuesday night into Wednesday night: Ridge will redevelop and
strengthen to the west stabilizing the profile and creating clear
to partly cloudy skies and dry conditions.

Thursday through Friday: Ridge will further strengthen and move
across northeast Montana. Temperates could begin pushing the
upper 90s to 100s with very low RH and surprisingly gusty winds.
This will be a group of periods to monitor for critical fire
weather conditions.

Friday night through Sunday night: Canadian breaks away from the
rest of the ensembled models leading to decreased confidence from
here onward. While the ridge axis crests over Montana, a shortwave
is expected to to move across the canadian prairies which will
blunt the ridge over northern Montana and may bring a light dry
cold front or at least partially cooler conditions initially. By
the end of these periods the ridge could easily rebound.

Monday onward: Chaos takes hold here onward with GFS/EC suggesting
another light frontal passage to the north blunting the ridge yet
again, yet these two models are also beginning to lose phase as
well. GAH



Flight Category: VFR today, tonight and Tuesday, although smoke
from the Lodgepole Complex fires may cause unpredictable

Today, GOES satellite imagery shows a stacked up low pressure
system in central Alberta moving into the middle of Saskatchewan
at noon today. By 6 AM Tuesday the center of the storm will have
moved into central Manitoba. A cold front associated with this
storm system kicked off a few thunderstorms this morning, which
are expected to move east out of the area this afternoon. The
other main effect will be the associated gusty northwest wind of
15-25G35KT. This wind is expected to diminish to less than 20KT
late this afternoon.

Tonight, another disturbance is expected to focus along the
frontal boundary and initiate thunderstorms south of the Missouri
River. Some of these thunderstorms may move through the
Yellowstone River area, affecting KGDV, and possibly KSDY for
temporary reductions to the flight category and gusty wind. Wind
overall will be northeasterly at less than 10 KT.

Tuesday, mild conditions with FEW to SCT clouds return with a
light northerly breeze of around 10 KT.



Red Flag Warning until 9 AM MDT Tuesday for MTZ122-135>137.

Dense Smoke Advisory until 9 PM MDT Tuesday for Garfield.


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