Area Forecast Discussion
Issued by NWS Glasgow, MT
FXUS65 KGGW 300225
Area Forecast Discussion
National Weather Service GLASGOW MT
825 PM MDT THU SEP 29 2016
.SHORT TERM...for northeast Montana...tonight through Sat...
The upper flow has turned more into the southwest this evening for
the region. This is bringing some high clouds and very light
showers to central and southern Montana. This will slowly work
it`s way into the far southwestern and southeastern areas
overnight. Little change to the ongoing forecast tonight. Proton
Upper Ridge was centered to our east allowing for a weak
southwest flow over Montana. Some moisture has pushed into the
state with an increase in clouds. Instability has also increased
as evident by developing thunderstorms in eastern Idaho and
Associated upper disturbance with the said thunderstorms will move
into central and eastern Montana tonight. But coverage and
intensity should be diminished. Isolated showers are expected.
Upper trough off the Pacific Northwest coast will move inland by
Saturday. Until then for Northeast Montana, warm and mostly dry
conditions will be the rule through Saturday. Nighttime lows will
continue to challenge records.
More active conditions are expected beyond this period. TFJ
.LONG TERM...Sat night through Thu...
Inherited forecast elements remain largely on track. The latest
model consensus continues to depict an initial round of light rain
showers over the region Saturday night into early Sunday. At this
point amounts should remain less than one tenth of an inch.
Models are still showing quite a bit of run to run variability
into next week, but are beginning to come into better agreement
for the eastern zones. Thus, this is where the greatest confidence
currently exists for the highest rainfall amounts. The progression
of the upper trough is expected to be rather slow, but details are
still uncertain and therefore it is difficult to determine precise
rainfall totals at this time. Nevertheless, many locations can
expect wetting rains, and pockets of up to one inch of weekly
accumulated rainfall are possible.
Other changes included populating winds and temperatures with
latest consensus blends. Overall, forecast was kept fairly in line
with previous shift thinking. Maliawco
Previous Long Term Forecast Discussion...
Synoptic setup: long range begins with a ridge running northward
from the southern high Plains through the Dakotas and southern
Saskatchewan and Manitoba. A large trough sets over the coast of
northern California and The Pacific Northwest and moves inland
over British Columbia and western Alberta. An equal amplitude
ridge is directly behind that over the Gulf of Alaska moving up
through the state of Alaska and into the Arctic.
Saturday night through Sunday: a Shortwave will move through the
area bringing a brief burst of precipitation. Current best
guesses set around a couple hundredths to a quarter inch. directly
behind it will be a weak shortwave ridge with about 6 to 12 hours
of dry conditions before the next wave.
Sunday night through Tuesday: Trough to the west moves inland and
places northeast montana under a southern to southwest flow
pattern with multiple jet streaks and a tap on baja moisture. PoPs
are getting kicked up rapidly here as this system looks to produce
more moisture than the previous wave and may have a few
significant bursts similar to last week. temperatures will also
be reduced during this time with some models showing a canadian
tap late in the event.
Tuesday night onward: confidence in these periods has raised
slightly with the big three having a more fuzzy agreement than
previous. These periods will likely begin with colder temperatures
than those prior but weak ridging may move back in by late in the
week slowly ticking temps up. GAH
VFR conditions will continue overnight with high cloudiness
increasing across the area. East or southeast winds of 10 to 15 kts
are expected overnight.
A passing isolated rain shower is possible on Friday, but
confidence is too low at this time to include it in the TAFs.