Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 240250 AAA

Area Forecast Discussion...UPDATED
National Weather Service Glasgow MT
850 PM MDT Sat Sep 23 2017

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

Based on observations of our eastern and southeastern locations,
felt it was warranted to increase PoPs there to reflect current
rainfall actually reaching the ground. This slow-moving upper-
level trough is expected to keep rain showers there and only
gradually move them eastward through tomorrow. Tried to blend the
best and latest hourly model consensus I could find.


Previous short term discussion: Upper level low pressure trough
to our west will shift slightly eastward over eastern Montana over
the next few days. This pattern will bring cool conditions with
temperatures in the upper 40s and 50s Sunday, warming into 50s to
lower 60s Monday as skies begin to clear from the west.

Light showers will lift across McCone, Richland, Dawson, Prairie,
and Wibaux counties as a weather disturbance moves NE along and a
head of the upper low pressure trough moving from the east.
Heaviest rain is expected to remain in the Dakotas as a weak 700mb
low lifting across southeast Montana tonight could bring some
higher qpf amounts on the east side of the Yellowstone River
overnight. Rain is forecast to diminish Sunday afternoon and
evening. Some instability showers will be possible Monday
afternoon over McCone, Richland, Dawson, Prairie, and Wibaux


.LONG TERM...Sun night through Sat...

Little change was made to the inherited long term forecast other
than to trend toward 12z model consensus blends. Expecting a large
upper trough over the western U.S. with axis across eastern
Montana Sunday night to gradually lift northeast through the week.
All the meanwhile, an upper ridge will become established across
the Pacific Northwest by the midweek and advance eastward for the
second half of next week. This will bring large scale subsidence
and associated height rises to the CWA late in the week with dry
weather and warmer temperatures.

Previous Long Term Discussion:

Beginning Sunday night, the slow-moving, main low pressure trough
axis will finally be moving through eastern Montana, which will push
the chances for any remaining organized rain showers further
east, in that SW flow aloft, which will have been impacting our
SE zones for a few days.

Monday evening through Tuesday night, the trough closes off a bit
into a weak upper low center up and through our CWA. But, due to
the lack of available moisture and any significant forcing for
ascent, any precipitation will be scattered and light at best -
hardly impactful.

Beginning late Tuesday night, general NW aloft returns to the
region, with some minor model precip discrepancies appearing,
which in turn, lower overall forecast confidence.

Thursday night and beyond, another ridge of high pressure builds
into the region from the west, with higher confidence in a warmer
and drier forecast through the early part of next weekend.




Synopsis: With lingering low pressure in the area, low-level
ceilings persist. Rain showers continue to be directed up the
lee side of the trough.

Flight conditions: VFR for KGGW; VFR with vicinity rain showers
for KOLF; and MVFR expected for KSDY and KGDV with ceilings as low
as 2000 feet at times. Toward the end of the TAF cycle, expect
conditions to gradually improve to higher VFR.

Winds: Light and variable.





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