Area Forecast Discussion
Issued by NWS Glasgow, MT
FXUS65 KGGW 310202
Area Forecast Discussion
National Weather Service GLASGOW MT
802 PM MDT TUE AUG 30 2016
.SHORT TERM...for northeast Montana...tonight through Thu...
A few minor updates made to the going forecast. Mainly to increase
chances of thunderstorms overnight in the far northeastern zones
with a shortwave moving into the region that could interact with
the warm front hung up over the region. Overall all other elements
in good shape for this evening. Proton
Previous Discussion...An upper ridge will continue to build along
into the northern and Canadian plains over the next few days. As
the ridge amplifies the hot desert air- mass will filter north
through the local area and into Canada. This will push
temperatures into the 90s for Wednesday and Thursday across most
of the region.
Low level southeast flow is beginning to strengthen across the
plains with higher dew points advecting into southeast Montana.
Some potential for elevated thunderstorms overnight with a weak
wave pushing through the ridge.
Lee trof begins to strengthen on Wednesday to the west, with
increasing easterly winds. Models differing on how far west the
stronger gradient occurs for marginal confidence regarding wind
advisory for the lake for Wednesday afternoon.
Other concern for Wednesday will be high temperatures and low
relative humidity. With the southeast low level flow keeping the
dew points up across the east, expect the areas with the strongest
winds will have the higher humidity.
By Thursday the lee trof will begin to move east pushed by the
upper trof moving into the Pacific Northwest. This front could
provide a focus for thunderstorms. Ebert
.LONG TERM...Thu night through Tue...
Progression of the exit of the ridge has backed up about 24 hours
from Thursday to Friday. This has caused a knock on effect and
slowed down features at range subsequently by roughly 24 hours.
Main area of impact that was Sunday for Rain as a trough dropped
through the area is now on Monday. High PoPs were shifted a day
later and diurnals differences between MaxT and MinT on Sunday
and Monday were renegotiated to attempt to capture this trend with
the latest forecast. GAH
PREVIOUS LONG TERM DISCUSSION:
Look for southwest flow aloft over the forecast area Thursday
Night and Friday as an upper trough moves inland from the Pacific.
A cold front is expected either Friday afternoon or night. While
most of the moisture stays to the north of the forecast area, an
unstable atmosphere may allow for a few thunderstorms.
Expect breezy and cooler weather on Saturday behind cold front.
While upper trough will be over Montana and the Canadian Prairies
on Saturday, models have Montana in a dry slot with most of the
moisture staying to the north. Will maintain a slight chances for
showers and thunderstorms at atmosphere remains somewhat unstable.
The GFS wants to split the trough Saturday Night and keep Eastern
Montana in SW flow aloft between the northern branch trough in
Canada that moves to the east and southern branch trough the forms
over Idaho. The GFS waits until Monday and Tuesday to bring the
southern branch trough through Montana. The ECMWF keeps the trough
as one large system and keeps the forecast area in the trough into
next week. The EC wants to bring shortwaves within the trough through
the forecast area at times. Given the model differences and
tendency to be in some kind of trough, will maintain a chance of
showers possibly thunderstorms most of the timer through the
VFR flight conditions expected.
Isolated showers/thunderstorms along a warm front are possible
near SDY overnight. Otherwise, expect scattered mid and high
clouds elsewhere as an upper ridge shifts over the area.
Wednesday afternoon gusty southeast wind of 20-30kt will develop
as a surface trough pushes through the area. The strongest wind
will affect SDY and GDV. Wind strength will taper off to around