Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 232246
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
446 PM MDT Sun Jul 23 2017

UPDATED AVIATION

...Fire Weather Concerns Continue into Monday, and Possibly
Beyond...

.SYNOPSIS...
A Canadian cold front will move across the plains tonight and result
in cooler and breezy conditions for Monday. Thunderstorm chances
return to start the week especially over central and southwest
Montana. Temperatures will remain slightly above-normal before more
hot weather returns by late week.

&&

.DISCUSSION...

Rest of today through Monday night...Isolated thunderstorms are
developing at this time over the mountains surrounding Ennis and
Bozeman in association with a compact upper low moving through the
area. This evening, a few thunderstorms may develop further north
across parts of central Montana. The threat is conditional on there
being just enough sufficient moisture, as well as the timing of any
lifting mechanism in the form of a shortwave disturbance or possibly
a weak lee-side SFC trough. Over southern Alberta, a SFC low
continues to develop and will push east tonight, sending a cold
front quickly SE across the area. Breezy winds will likely accompany
the front late tonight/early Monday morning across central Montana
and will usher in lower temperatures (ie. about 10 degrees or so
lower than today). While SW MT may see a slight lowering of temps on
Monday, it doesn`t look nearly as breezy as farther north.

On Monday, a s/w moving quickly through the area may kick off a few
thunderstorms, mainly along/south of a Helena to Lewistown line. The
primary threat with any thunderstorm through Monday should be gusty
winds. At this time, severe weather is not anticipated. CC/MARTIN

Tuesday through Sunday...Latest model guidance continues to
illustrate a notable drying trend through the long range. Beginning
with Tuesday and early Wednesday, a closed upper low rotating off
the northern Coast of California will begin to get pulled slowly
northwards in response to weak ridging breaking down in SW Canada.
This shortwave will help feed increasing tropospheric moisture into
the area overnight Tuesday with small, perhaps terrain enhanced
nocturnal clusters of showers and storms making its way as far north
as SW parts of the CWA through daybreak Wednesday. It is looking
like by the daytime hours on Wednesday that most areas will remain
dry as the aforementioned weak ridge holds tight over the majority
of the area. However, by later in the afternoon and evening,
increasing spotty convection area wide will become a good bet, with
a few storms being strong given modest instability across central
and southern areas. Another important note will be lightning
activity as recent drought conditions may enhance the possibility of
new fire starts. Also, breezy conditions are looking possible
Thursday afternoon and evening with the passage of the shortwave
trough that may exacerbate fire weather conditions.

We begin to see a pattern shift beginning on Friday and lasting into
next weekend with the return of the dominant four-corners ridge in
the desert southwest. With good agreement on most long range model
guidance, I`ve started to bump temperatures up enough to reflect
this with highs easily reaching the lower to mid 90s area wide, with
perhaps upper 90`s for some through next weekend. Of course this
will continue to be fine-tuned as we get closer in the week. KLG

&&

.AVIATION...
Updated 2246Z

VFR expected next 24-hours. Southwesterly to westerly flow aloft
will persist as one disturbance exits SW MT this evening and another
dives SE`ward from Central BC/NW AB and skirts North-Central MT
after 06Z/Mon. A surface cold front accompanying the latter
disturbance should advance SE`ward across the Hi-Line between 06Z
and 10Z/Mon and then dissipate before reaching Central MT. A few
showers and thunderstorms are possible over SW MT through 03Z/Mon,
over North-Central MT through 12Z/Mon, and region-wide after 18Z/Mon.
Jaszka

&&

.FIRE WEATHER...
Red Flag Warning continues into this evening as gusty winds and
low humidity. An isolated dry thunderstorm with gusty winds is
also possible later this evening into the overnight. A cold front
will move southward through the region during the overnight hours
tonight. Expect a wind shift to the north over the plains east of
Interstate 15. The winds will be strong/gusty at times
overnight...especially over North Central MT. On Monday expect
breezy west winds to develop by the afternoon hours along with low
humidity, with critical fire weather conditions expected along the
Rocky Mountain Front and along and west of the Big Belt Mountains,
including Helena National Forest and western Lewis and Clark
National Forest. Additionally there is a small chance for a
passing dry thunderstorm, mainly south and east of the Little
Belts. Some storms could produce strong gusty erratic wind gusts.
Brusda/Cassell

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  57  85  51  84 /  20  20  10   0
CTB  51  80  46  81 /  20  10   0   0
HLN  63  91  57  88 /  20  10  10  10
BZN  58  90  52  86 /  10  20  20  10
WEY  49  80  45  77 /  10  20  20  30
DLN  58  87  53  84 /  10  20  20  20
HVR  58  82  51  85 /  20  10  10   0
LWT  63  84  53  82 /  20  20  20   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT this evening Central and Eastern
Lewis and Clark National Forest Areas...Chouteau and Fergus
Counties...Eastern Glacier/Toole/Central/Eastern
Pondera/Liberty...Helena and Townsend Ranger Districts of the
Helena National Forest...Hill and Blaine Counties...Lewis and
Clark National Forest Rocky Mountain District-Rocky Mountain
Front...Lincoln Ranger District of the Helena National Forest.

Red Flag Warning from 1 PM to 9 PM MDT Monday Central and
Eastern Lewis and Clark National Forest Areas...Eastern
Glacier/Toole/Central/Eastern Pondera/Liberty...Helena and
Townsend Ranger Districts of the Helena National Forest...Lewis
and Clark National Forest Rocky Mountain District-Rocky Mountain
Front...Lincoln Ranger District of the Helena National Forest.

Fire Weather Watch from Monday afternoon through Monday evening
Central and Eastern Lewis and Clark National Forest Areas...
Chouteau and Fergus Counties...Eastern
Glacier/Toole/Central/Eastern Pondera/Liberty...Helena and
Townsend Ranger Districts of the Helena National Forest...Hill
and Blaine Counties...Lewis and Clark National Forest Rocky
Mountain District-Rocky Mountain Front...Lincoln Ranger District
of the Helena National Forest.

&&

$$

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