Area Forecast Discussion
Issued by NWS Glasgow, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS65 KGGW 270328 AAA

Area Forecast Discussion...UPDATED
National Weather Service Glasgow MT
928 PM MDT Wed Jul 26 2017

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

Sent an update tonight to try and blend the latest and best near-
short-term model consensus I could find. A few isolated rain
showers are starting to emerge over NE Montana and based on this
consensus, the coverage of this precipitation should become more
widespread through most of the day on Thursday. There seems to be
enough precipitable water in the atmosphere that dry lightning may
not be as much of a threat compared to earlier this week. Granted,
most of this will still be thunderstorms, but they will probably
be more efficient rain producers as well.


Previous short term discussion: A surface high pressure system
over eastern Saskatchewan will continue to push eastward into
Manitoba tonight as an upper level ridge builds over the region. A
weak surface low is expected to develop just to our south and
west, which will mean easterly winds overnight. This could bring
an isolated shower or thunderstorm tonight and into early Thursday
morning, but currently this disturbance looks as if it may weaken
even further as it moves across northeast Montana overnight.

Thursday looks to be more of the same. The upper ridge will
continue to build over the region, bringing hot weather over our
CWA with high temperatures expected to be in the 90s at nearly all
locations. Another disturbance will develop just to the west and
will move across northeast Montana Thursday afternoon and evening.
With the positioning of the upper ridge and surface disturbance,
there will be a pretty good pull of monsoonal moisture from the
southwestern US. The big question is how much of that moisture
northeast Montana will see. Models do not really agree very well
on this, although they do suggest any precipitation will be much
more isolated during the morning Thursday than in the afternoon
and evening. If it does reach this far north, any thunderstorms
that develop have a chance of rain to go along with them, although
widespread precipitation is not anticipated.


.LONG TERM...Fri night through Wed...

Conditional instability will be a main player with the early
portion of this period as upper vort maxes round the crest of the
ridge. It looks like Thursday evening will be stormy in parts of
the area. Storms look to contain brief heavy rainfall, cloud to
ground lightning and gusty winds. With Precipitable Waters over
an inch Thursday Night and Friday, dry lightning does not look
very likely. Winds and humidity for the most part do not look
concerning at this time for the entire period.


Previous Discussion...
The general story of the extended forecast period is
characterized by trying to discern and time the various subtle
embedded short-wave disturbances that will ride across the top of
the high-pressure ridge which continues to dominate much of the
inter-mountain west and high plains regions.

The problem with this messy flow pattern and its storm track is
that the various deterministic models have a difficult time
resolving the placement and intensity of any storm which may form
in these scenarios. At best, the chances for any storms in the
extended period could be described as scattered or slight chance
of rain showers with some isolated thunderstorms possible. Any
further attempts at specifics would be pre-mature at this point,
and to mention just one variable, could depend on the
atmosphere`s varying content of smoke aerosols from local and
regional wildfires.

Tried to blend the best model agreement I could find which places
the best chances for precipitation over our central and eastern
zones leading into and persisting through the weekend, especially
each afternoon and evening.

Expect daily high temperatures from near 90 to 95 and daily low
temperatures from the low to mid 60s. A frontal system seems
evident in the model data with no apparent change in temperature,
and may simply be the passage of a surface pressure trough and
would be the focus for any developing thunderstorms. Otherwise,
expect winds to be rather benign.




Flight Conditions: VFR, with MVFR possible with increased
thunderstorm coverage through Thursday evening.

Synopsis: High pressure will dominate the weather pattern over
the region for the next 24 hours, but small, embedded disturbances
could easily set of some scattered thunderstorms over the next few

Winds: From the southeast at 10 to 15 mph, then more from the east
overnight tonight with a few higher gusts, especially near any
stronger storms.




Surface high pressure will continue to slide to the east, with
winds shifting out of the east tonight and then from the
southeast by Thursday morning. This will bring some slight
increase in low level moisture northward across the high plains.
Therefore, dry lightning will probably not be as much of a threat.

With an upper ridge building into the region, will see an increase
in temperatures. Weak disturbances will begin moving through the
ridge by this evening, and could initiate a few isolated
thunderstorms. The best potential for thunderstorms will be with a
stronger disturbance through most of the day on Thursday, but an
isolated storm may show up as early as tonight. These storms are
expected to move fairly slowly, so some rainfall is possible along
with erratic gusty winds and lightning.

Otherwise, expect a return to hot and dry conditions late in the





$$ is the U.S. government's official web portal to all federal, state and local government web resources and services.