Weather Service Report

FXUS65 KTFX 201611

Area Forecast Discussion
National Weather Service Great Falls MT
1011 AM MDT Fri Oct 20 2017

Windy conditions of late will remain more calm today ahead of the
next system coming from the west late Saturday into Sunday. Expect
winds to become more westerly through the day and a chance of
precipitation along the Continental Divide and Southwest Montana.
Winds look to pick up significantly once again Sunday and thus a
High Wind Watch has been issued for much of Central Montana.



A frontal boundary crosses the region today, bringing a chance 
for showers for the Rocky Mountains and Southwest Montana. Windy 
conditions persist through the weekend with cooler temperatures. 


Updated 1125Z.

Scattered to broken high cloud-cover will prevail overnight. A cold 
front moves through the forecast area by mid-day Friday with winds 
shifting to the west and increasing behind the front. Widespread 
snow and mountain obscurations expected along the Continental Divide 
after 12Z Friday, while isolated to scattered showers accompany 
frontal passage through the plains. VFR conditions expected to 
prevail at all forecast terminals through the period, except for 
brief IFR/MVFR conditions possible in showers. Mountain wave 
turbulence and low level wind shear expected to redevelop in favored 
locations as west winds increase behind frontal passage. mpj/PN


/ISSUED 417 AM MDT Fri Oct 20 2017/

Today through Sunday...Breezy conditions overnight maintained mild
temperatures and remarkably low humidity overnight for much of 
the forecast area. A cold front associated with an Alberta Clipper
system will advance across the area this morning through early 
afternoon. Hence, forecast high temperatures may be reached early 
this morning, with cold advection driving temperatures gradually 
lower through the day. Pressure rises behind the front will 
produce a period of gusty west winds. Wind reports will be 
monitored closely today, but the vertical wind profile does not 
support any more than a few isolated gusts nearing 50 mph. Despite
another breezy day, fire concerns are slightly lower today due to
increasing humidity. Along with these rapid changes in temperature
and winds today, expect rain and mountain snow to develop up to,
and along the Continental Divide, and across southwest Montana
with the passing trough. Sprinkles are possible across the
N-central plains, but otherwise suppressed by the downslope winds.
All this activity tapers downward tonight into Saturday as the
Clipper system pulls further away to the east. A remarkably strong
zonal jet pushes across the PacNW and reaches across the Northern
Rockies Saturday night. Confidence continues to increase that a 
widespread, potentially damaging high wind event could develop
late Saturday night through the day Sunday. A high wind watch is
appropriate for this potential event, but opted to hold off for
now to avoid confusion compared to today's passing front. PN

Sunday night through Thursday...The main concerns during this period 
center around wind and the potential for continued elevated fire 
weather concerns.

An impressive upper level jet and associated moisture/precip aimed 
at the Pacific NW will gradually shift south away from the area 
Sunday night, with precip diminishing in the mountains. NW flow 
takes over aloft as the upper level trough pushes into the central 
US. This is followed by an anomalously strong ridge (for late-
October) TUE/WED which will likely yield a return to above normal 
temps (60s/70s at lower elevations) both days. The models are then 
in very good agreement in bringing a sharp trough SE out of Canada 
later WED into THU. In this transition, another wind event appears 
possible late Tuesday night into Wednesday, especially along the 
Rocky Mtn Front where a 60-80kt mid-level jet and strong pressure 
gradient are forecast to be co-located. Out over the plains, high 
wind criteria may not be met, but as has been seen in previous 
breezy/windy days, relative humidity values may fall low enough to 
warrant elevated to near-critical fire weather concerns. The 
shortwave forecast to dive SE out of Canada will likely be 
accompanied by a strong northerly jet. Where the models differ is 
where the upper jet and coldest air is directed (ie. right over our 
area or further east across eastern MT and the Dakotas). Regardless, 
the mild temps TUE/WED should quickly be replaced by much cooler 
temps late-week. The potential then exists for yet another wind 
event late in the week as well. MARTIN


GTF  60  37  51  45 /  20  10  10  20 
CTB  53  37  48  38 /  10  10  10  20 
HLN  51  35  51  41 /  30  10  20  20 
BZN  59  30  50  38 /  50  30  10  20 
WEY  43  25  35  27 /  90  60  40  60 
DLN  53  28  45  36 /  30  20  20  20 
HVR  61  39  54  36 /  30  20  10  20 
LWT  66  34  49  38 /  20  10   0  20 


High Wind Watch from Sunday morning through Sunday evening 
Blaine...Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Hill...Judith Basin...Liberty...Meagher...Toole.

High Wind Watch from late Saturday night through Sunday evening 
Northern Rocky Mountain Front...Southern Rocky Mountain Front.



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