Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 281144

Area Forecast Discussion
National Weather Service Great Falls MT
544 AM MDT Wed Jun 28 2017

...Update to Aviation...


Upper level low pressure system will bring scattered showers and
thunderstorms to Montana Wednesday through Thursday but drier
conditions should return Friday. Seasonable temperatures on
Wednesday will cool 5 to 10 degrees Thursday as a surface cool front
pushes through the region. Building high pressure aloft brings
warming temperatures Friday through the weekend.



Today through Friday...An upper level low pressure system remains
over central Alberta/Saskatchewan today. Unsettled westerly flow
aloft over Montana will bring variable clouds along with scattered
showers and thunderstorms to southwest Montana while only isolated
afternoon and evening showers will affect north central portions
of the state. The upper low drops southward and opens into a
positive-tilt trough across Montana Thursday before sliding
eastward into the northern Great Plains on Friday. This system
will help push a Canadian cold front into Montana for cooler
temperatures and a continued chance for precipitation Thursday.
Building high pressure along the West Coast edges eastward into
western Montana on Friday allowing temperatures to warm back up to
seasonable temperatures with mostly dry conditions over the plains
and isolated PoPs over the mountains. mpj

Friday night through Tuesday night...a progressive upper level
pattern best describes the long term once again, with very quick
transient ridging and shortwaves moving across the Northern Rockies
and Northern High Plains. A quick moving shortwave will translate
from the Intermountain West Saturday morning and across the Northern
Rockies through the remainder of the day. This shortwave should
spark off scattered showers and thunderstorms off of the higher
terrain of North Central and Southwest Montana by the afternoon
hours on Saturday, with any shower/storm then moving from west to
east. Thunderstorms on Saturday are expected to be of the garden
variety type, with a few storms possibly producing some breezy winds
and small hail. Both GFS and EC guidance have continued to trend up
with high temperatures through Monday, so felt comfortable in
raising temperatures further. For the day on Monday, upper level
ridging will begin to break down, with H500 flow becoming southwest
to westerly. H850 temperatures will soar into the mid 20C to low
30C. This should translate to high temperatures in the mid 80s to
mid 90s across the CWA. These warm/hot temperatures, combined with
dry/breezy downsloping winds and low afternoon relative humidity
values, will lead to heightened fire weather concerns for the day on
Monday. Given the ongoing dry conditions across our far eastern
zones, am growing concerned about the potential for grassland fire
spread given the aforementioned weather conditions. Finally, an
early look at Independence Day reveals highs potentially being just
as warm as Monday, with continued dry and breezy winds. Am not as
confident in temperatures being as warm on Tuesday (with respect to
Monday) given a broad trough moving into the region. However, given
the expected breezy winds and antecedent dry conditions, fire
weather concerns will once again linger for the day on Tuesday. -


Updated 1144Z

Upper level low will remain over central Alberta/Saskatchewan with a
moist and somewhat unstable westerly flow aloft over the forecast
area today. Scattered showers and thunderstorms will affect
southwest Montana but only isolated precipitation is expected in
north central Montana through 03Z. VFR conditions will prevail
except for brief MVFR conditions in precipitation through this
evening. After 03Z Thursday, a Canadian cold front will push
southward with scattered to numerous showers developing along with
lowering ceilings for MVFR/low VFR conditions overnight. mpj


GTF  80  49  70  48 /  10  30  40  10
CTB  77  48  69  47 /  10  30  20  10
HLN  82  52  74  51 /  10  20  30  10
BZN  75  46  71  45 /  30  30  20  10
WEY  63  37  65  36 /  60  50  10  10
DLN  70  44  71  45 /  40  20  20  10
HVR  81  52  72  46 /  10  20  30  10
LWT  75  47  68  44 /  10  20  30  10



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