251 
FXUS65 KTFX 190618
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1218 AM MDT Thu Oct 19 2017

.UPDATE...

Quick update to include a High wind warning issued for the 
Northern Rocky Mtn Front, where gusts in excess of 75mph are being
reported at several stations along the immediate east slopes. 
Strong winds aloft and favorable conditions for mountain wave 
induced winds will continue through tonight then abate Thursday 
morning. Hoenisch

&&

.SYNOPSIS...

Breezy west to southwest winds will increase late today and tonight 
across North Central Montana with windy and warmer conditions 
returning Thursday. Dry and windy conditions will raise fire 
concerns across Central Montana Thursday. The next front moves 
across the region with showers across Southwest Montana Friday, 
cooler temperatures, and windy conditions through Sunday.

&&

.AVIATION...
Updated 0500Z.

West-Southwest flow aloft gradually backs to Southwesterly over the 
next 24 hrs with VFR conditions prevailing under scattered to 
broken high cloud-cover. Surface wind gusts increase to around 40kts 
in the KCTB vicinity by around 12z and somewhat higher along the 
Rocky Mtn front. Southwest winds increase across all areas Thursday 
afternoon with gusts to 30kts likely across most of the plains as 
well as some SW MT valleys, including the Madison valley and KEKS 
terminal. Hoenisch

&&

.FIRE WEATHER...

Breezy west winds this afternoon will continue into Thursday.
Additionally, afternoon temperatures will warm into the mid/upper
70s with humidity falling into the low teens over the eastern
portions of the region. Thus a Red Flag Warning is in effect for
this region. More seasonable temperatures and slightly higher
humidity move back into the region on Friday. However, it will 
remain windy most days from Friday through early next week.
Brusda

&&

.PREV DISCUSSION...
/ISSUED 844 PM MDT Wed Oct 18 2017/ 

Moist and strong southwest flow aloft will persist across the 
region tonight. As such, the windy conditions will continue across
North Central Montana but models are still indicating that even 
the strongest winds should remain below high wind criteria. 
Combination of downslope winds and cloud cover aloft will also 
prevent temperatures from falling too far. Finally, while 
orographic lift will bring widespread precipitation to northern 
portions of the Continental Divide, the strong downslope winds 
will prevent and showers from moving out over the plains. The 
current forecast package has a very good handle on all these 
variables and, at this time, it appears that no update will be 
required this evening. mpj

.PREV DISCUSSION...
/ISSUED 502 PM MDT Wed Oct 18 2017/

Tonight through Friday...Transient high pressure exits the region 
today with the next upper trough moving from the Gulf of AK toward 
the BC coast. Winds aloft will increase from the SW again later 
today and tonight. Gusty SW winds will persist across North-Central 
MT during the period with the strongest winds along the Rocky Mtn 
Front. Southwesterly flow aloft allows for temperatures to surge 
back to well above average Thursday as well. The upper level trough 
moves inland Thursday night and Friday with a surface front moving 
east across the forecast area by Friday afternoon. Precipitation 
will increase along areas near the Continental Divide Friday with 
showers also possible across Southwest Montana. Temperatures cool 
about 10 to 15 degrees for Friday and Saturday.

Friday night through Wednesday...Look for spotty, light showers to 
persist following the passage of the cold front through the 
overnight hours Friday night and into Saturday. As colder air 
filters in from the north, temperatures will likely continue to 
drop, along with freezing-levels leading to the potential for 
accumulating snow for higher elevations of south-central and 
southwestern MT, especially along the Madison, Bridger and Gallatin 
Ranges. This system will quickly depart early Saturday leaving 
behind clearing skies with cool afternoon highs. However, by 
Saturday night clouds will begin to increase from the west as 
another quick moving system swings across just north of the 
MT/Canadian Border. Behind this system, models continue to 
confidently illustrate the development of a strong jet aloft, which 
will push eastward across the Northern Rockies into the early hours 
on Sunday. This will likely yield yet another high wind event across 
most of the CWA beginning Sunday morning, with the peak of the event 
being in the afternoon hours. Given forecast H7 wind speeds ranging 
between 55-75kts across the Plains, and even higher along the Rocky 
Mountain Front, strong winds aloft will have no trouble transferring 
to the surface via sufficient boundary layer mixing. Having said all 
of that, I have adjusted forecast wind speeds reflect a more 
realistic possibility of high winds following the jet aloft, timed 
with the best diurnal mixing in the afternoon hours. Looking at the 
synoptic pattern as we get into next week, long-range models have 
persistently been advertising the development of a re-enforcing 
ridge across the Southern Pacific coastline, which will reflect 
increasing heights across the majority of the western US. As strong 
ridging amplifies along the entire west coast, this will transition 
the upper-level flow more from the northwest and aid in the 
development of a dominant surface high across the northern Rockies. 
This will likely keep temperatures near, to slightly above normal 
while staying dry through the middle part of next week. KLG
&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  48  58  36  54 /   0  40  10  10 
CTB  42  55  33  51 /   0  10  10  10 
HLN  43  55  35  55 /   0  40  20  10 
BZN  43  58  30  51 /   0  70  40  10 
WEY  33  48  22  38 /   0  70  50  20 
DLN  42  51  28  47 /   0  60  30  10 
HVR  43  62  35  56 /   0  20  10  10 
LWT  45  59  33  51 /   0  40  20  10 

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 AM this morning to 7 PM MDT this 
evening Central and Eastern Lewis and Clark National Forest 
Areas...Chouteau and Fergus Counties...Hill and Blaine Counties.

High Wind Warning until 9 AM MDT this morning Northern Rocky 
Mountain Front.

&&

$$

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