Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 291803

Area Forecast Discussion
National Weather Service GLASGOW MT
1203 PM MDT FRI JUL 29 2016

.SHORT TERM...for northeast through Sun...

Additional updates were made since models seem to be underdoing
the instability today. NAM is capturing this better than the GFS,
but still NAM seems a bit too dry and stable compared to current

Instability has reached over 1000 J/kg recently in the CWA so it`s
not out of the question that an SPS or even an isolated Severe
Thunderstorm warning is issued this afternoon. Effective Bulk
Shear of about 30 kts supports this idea. TFJ

847 am update...
Not too many changes were made to going forecast, so mainly
refreshed things.

Fog is lifting across the SE zones with low clouds expected to
linger till about noon. There could be a shower associated with
these clouds in the next few hours before they move into North
Dakota. Otherwise, showers and possibly a thunderstorm have moved
into northern Phillips county. These are expected to move east and
grow a bit, mainly affecting the northern zones this afternoon.

Temperatures today will be below normal. TFJ

Previous Discussion...
A weak upper level disturbance will bring an isolated chance for
showers and thunderstorms across northeast Montana today. Already,
a few lone showers are approaching the western zones very early
this morning. Additional activity is a possibility later in the
day. Aside from that, dew point depressions have narrowed
overnight and some fog/low clouds have developed mainly south and
east of the CWA so far. Will include a patchy mention of fog for
mainly the southeast zones.

Dry weather is anticipated for tonight and early Saturday with an
upper ridge developing. However, a very weak impulse will be
embedded in the flow as it approaches from the west on Saturday.
Thus, will include increasing cloudiness during the day from west
to east. Cannot rule out a lone shower or thunderstorm as well
given this forcing for ascent with the weak vorticity maxima
approaching, though moisture will be limited with best dynamics in
Canada with the upper low/trough.

A more pronounced opportunity will exist for showers and
thunderstorms on Sunday with better instability in the area as the
upper trough pushes east providing diffluent southwest flow aloft
over the area. The trough isn`t very amplified and if anything
activity may develop along the North Dakota Border before pushing
east. Nam/gfs/ecmwf all show some differences in specific
evolution here so things may still change. More confidence will
exist on how things will play out as the system enters the near
term period and mesoscale guidance becomes more available. Do feel
good though about the general idea of convection initiation near
the ND/MT border and then spilling into ND late in the day Sunday
or in the evening hours. Maliawco

.LONG TERM...Sun night through Fri...

Weak westerly flow with embedded shortwaves sliding along the
Canadian border continues through next week. This will result in
the occasional thunderstorm and generally mild temperatures.

Heights lower on Monday with the passage of an upper wave through
the Canadian prairies before another thermal ridge pushes into the
Treasure state on Tuesday. Another shortwave trof pushes through
the region midweek. Models in better agreement with pulling the
wave south of the border and bringing better moisture into the
state to produce thunderstorms with the frontal passage Tuesday
night into Wednesday morning.

Cooler weather follows behind this midweek trof before ridge
begins to rebound over Montana for the end of the week. Ebert



Generally VFR condition are expected. Some low clouds and reduced
visibilities bringing brief IFR and LIFR conditions near and
south of the Yellowstone River valley will shortly rise and
improve as the morning progresses.

To the north and northwest, a few showers are pushing across
north central Montana and could slide east along the hi-line
today with a few brief impacts.





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