Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 232107
AFDGGW

Area Forecast Discussion
National Weather Service GLASGOW MT
307 PM MDT Thu Mar 23 2017

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

Synoptic Setup: Short term with a trough running from Arizona to
southwest Wyoming. North of this flow becomes zonal to slightly
southwest from Northeast Montana to Oregon. Behind the trough a
weak meso-ridge is developing in the flow from southern California
through central Idaho. A much larger synoptic trough lies farther
west from off the coast of California up into Gulf of Alaska.

This afternoon through Tonight: a cold front has barreled through
the northeastern sections of the CWA clipping Sheridan Roosevelt
and Daniels county with a colder airmass. this airmass has rapidly
eaten into and dried out the remaining showers over the
Yellowstone Valley. Low morning cloud cover above this airmass
hints at excess moisture off the deck that could lead to low
stratus and fog tonight across the far northeastern areas with a
stalled boundary likely setting up from Opheim, to Wolf Point, to
Glendive. Near this line is where stratus clouds are most likely
to lead to fog on ground. Fog should clear between 9AM and noon
Friday morning.

Friday though Friday night: Meso-ridge will rapidly amplify
across Montana as the trough to the west steps onshore. With the
Ridge moving across montana Conditions should turn dry and clear
during this time.

Saturday: With the ridge exiting and the new trough over the
Pacific Northwest flow will become Southwestern with Pacific
Moisture being flung up over southeastern Montana. Some of this
may be able to make it up thew Yellowstone Valley for a few rain
showers. Thankfully, there is no Arctic airmass to tap into with
this passage. So, if temperatures reduce or a front does form it
will have minimal impacts over the previous days.    GAH



.LONG TERM...Sat night through Thu...

Chose to update the extended forecast grids to day 7, following
the best model consensus I could find. A few additional waves of
low pressure move through the region with the most impactful being
the Monday night through Wednesday morning period. Granted, the
model agreement is not ideal, but there seems to be at least some
hint of favorable conditions for accumulating rain showers,
especially as advertized by the EC. Other models are not quite as
agressive.

BMickelson


Previous long term discussion: A shortwave trough moves inland
from the Pacific Saturday Night and across Eastern Montana with a
cold front on Sunday. At this point, it looks like the chance for
precipitation will be mainly across the southern zones of the
forecast area.

Shortwave ridge and surface high will allow for mainly dry weather
on Monday.

The next upper trough moves inland from the Pacific on Monday and
splits. The southern branch is forecasted to dig toward the
desert SW Monday Night and Tuesday. A moist southerly or southwest
flow aloft ahead of the trough is expected to extend into Montana
during this period with a good chance of rain for at least parts
of the forecast area for Monday Night, Tuesday and Tuesday Night.

The models have the northern branch trough moving into area
Tuesday Night and Wednesday shifting the moist flow from the
southern branch trough to the east. Expect drier weather to move
in from west to east.

An upper ridge will allow for dry weather Wednesday Night and
Thursday. Then, it looks like the next trough moves into the area
Thursday Night with a chance of rain. Forrester


&&

.AVIATION...
FLIGHT CAT: VFR

SYNOPSIS: Rain showers have cleared out of the Yellowstone valley
this afternoon as a cold front clips the far northeastern corner
of the MT/ND border. The edge of this airmass will generate a
stalled front from Opheim to KOLF to KGDV tonight.

FOG: low stratus and fog in the cold airmass to the east and
north of the front on Satellite this morning points towards excess
moisture which may be able to reform for new low stratus and fog
at KOLF, KSDY, and KGDV. Fog that forms will likely set up around
09Z and last through 15-18Z before clearing out. Confidence is
average.

WIND: West to northwest at 5 to 15 kts this afternoon... becoming
light and variable overnight... then switching to the southeast
at 5 to 15 kts Friday.

GAH


&&

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


&&

$$

weather.gov/glasgow


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