FXUS65 KTFX 211712
Area Forecast Discussion
National Weather Service Great Falls MT
1112 AM MDT Tue Aug 21 2018
Showers will go on a diminishing trend across central and
southern Montana this morning, with a few areas of patchy fog
also possible. Slightly warmer, yet still below normal,
temperatures along with dry conditions are then expected for the
rest of today. Temperatures begin to warm on Wednesday, with some
scattered chances for showers and thunderstorms across
southwestern portions. Warm temperatures and mainly dry conditions
are then expected for Thursday, with a cold front bringing
chances for precipitation and breezy winds on Friday.
Most of today's forecast remains valid. Just freshened hourly
temperatures, dew points, relative humidity, and apparent
temperatures through noon to better reflect recently observed
Mainly VFR expected next 24-hours as a low pressure trough aloft
moves little over our area. However, periods of MVFR CIGS are
expected into this evening along and south of a KHLN to KLWT line. A
few showers and thunderstorms are possible over SW MT, especially
between 21Z/Tues and 03Z/Wed. Lastly, patchy fog may form between
about 06Z and 15Z/Wed, but confidence remains low.
/ISSUED 405 AM MDT Tue Aug 21 2018/
Today through Thursday...Broad upper level circulation will
continue to influence the weather across the Treasure State for
the next couple of days. Current circulation and increased water
vapor is sandwiched between dry air this morning. The result will
be diminishing chances for showers across central and southern
portions throughout the morning. A few areas of patchy fog are
also possible this morning. Temperatures will then warm slightly
today...but still remain below normal in the 60s and 70s. The
broad circulation will also provide some generally light winds
today...except for terrain induced areas. Smoke may still linger
through today, although impacts may be less than recent days given
the easterly flow. Large circulation then moves through as an
upper level trough on Wednesday. The result will be warmer, near
normal, temperatures moving through the area. Some showers and
thunderstorms may also be found with this feature...mainly across
central and southern portions of the CWA. Weak ridging then builds
in Wednesday night into Thursday, ending chances for
precipitation. Warming temperatures will continue for Thursday.
Expect high temperatures to return into the 80s and 90s for most
areas...with some 70s across the southwest. This heating trend
combined with low RH may bring increased fire weather danger.
Friday through Tuesday...A somewhat active pattern could bring
increased fire danger followed by more chances for showers and
thunderstorms in the long term. Ridge breaks down on
Friday, allowing for a cold front to push across the area. Before
this, warm temperatures, low RH, and breezy winds could bring
increased fire danger. The level of activity with this front is
still uncertain. The best chances for any precip now look to be
found across northern and central portions Friday into Saturday
morning. Cooler and somewhat breezy post frontal conditions will
then be found on Saturday, with generally dry conditions also
expected. Sunday then could see another cold front move across the
area brining more breezy and slightly below normal conditions.
Chances for showers and thunderstorms will also be possible along
this frontal boundary on Sunday. An unsettled pattern then could
set up for Monday and Tuesday. Models indicate a widespread rain
shower event is possible, along with cooler temperatures. Anglin
Increased fire danger concerns are possible to end the work week.
Today through Wednesday will see generally light winds with fair
RH values. Some showers and thunderstorms are possible for
Wednesday across the central and south, while northern areas
remain dry with lowering RH. High pressure ridge then warms
temperatures up Thursday into Friday, also bringing lower RH
values. A cold front could further complicate the fire weather
situation on Friday as it brings increased winds and chances for
showers and thunderstorms. With breezy winds at times and lowering
RH values, some elevated to near critical fire weather danger is
possible on Thursday and Friday.
.PRELIMINARY POINT TEMPS/POPS...
GTF 70 46 85 56 / 10 0 0 10
CTB 73 44 84 53 / 0 0 0 0
HLN 69 47 83 54 / 10 10 10 20
BZN 67 44 80 49 / 10 10 20 30
WEY 68 33 71 38 / 10 10 30 30
DLN 67 41 76 46 / 10 0 20 30
HVR 76 47 85 51 / 0 0 0 10
LWT 66 45 79 52 / 10 10 0 20
FXUS65 KMSO 210919
Area Forecast Discussion
National Weather Service Missoula MT
319 AM MDT Tue Aug 21 2018
.DISCUSSION...A low pressure center continues to circulate over
central Idaho, but rain has mostly ended across the region. Cooler
temperatures will be the most notable result of this area of low
pressure, with values comfortably in the 70s. By Tuesday, temps
will warm into the low 80s. And, while moisture on Monday helped
to rid some of the wildfire smoke across north central Idaho and
west central/southwest Montana, places across northwest Montana
should expect continued impacts from smoke that remains.
Thursday into Saturday, a mostly dry westerly flow will develop
leading to breezy afternoons with temperatures near to slightly
below seasonable levels. There will be a slight chance of
occasional showers and thunderstorms along the Canadian border,
otherwise it will remain dry.
By early next week, forecast models continue to indicate the
potential for a cool and wet weather system settling over the
Northern Rockies. Could we even see light snow on the higher
peaks? It is certainly possible, but details are limited as models
work toward a common solution.
.AVIATION...Smoke will degrade visibility for KGPI today,
otherwise...most other terminals will see a brief reprieve from
smoke impacts. Due to Monday's moisture, a lingering low cloud
deck will hang around KBTM for the first half of today, but will
dissipate as the current low pressure system exits the region.
FXUS65 KBYZ 211620
Area Forecast Discussion...Updated
National Weather Service Billings MT
1020 AM MDT Tue Aug 21 2018
Made a few changes with this update. Lowered the chance of showers
over much of the area based on latest radar trends and short-term
model data. Also added areas of drizzle to central areas through
about noon MDT. We still have areas of fog over the
Beartooth/Absaroka foothills and in the Bighorn Mountains. Webcams
show that the fog is beginning to lift...so we still think that
the fog should dissipate by noon/early afternoon. Rest of forecast
is on track. RMS
.SHORT TERM...valid for Tdy and Wed...
The Pacific trough that has been bringing the area rain over the
last 24 hours has stalled out along the ID/MT stateline. Most of
the the accent from the wave has pushed into the eastern Montana
overnight shifting the showers and occasional thunderstorms to the
east. Through the morning, expecting the remainder of the precip
to move out of the area. However, with winds out of the northeast
continuing today, the mountains will continue to see a slight
chance for precip even into the afternoon. Temperatures today
will still be on the cool side of normal. Expecting temperatures
to be slightly warmer than yesterday as the smoke is not expected
to be as prevalent. The the HRRR smoke guidance suggests in
generall air quality will be much improved over the past several
days. As such have dropped the areas of smoke from the forecast.
Tomorrow will be warmer with highs approaching normal, up into the
upper 70s and 80s. By afternoon however, as the Pacific trough
starts to track east showers and some isolated thunderstorms will
spread east across the area through the afternoon and evening.
.LONG TERM...valid for Thu...Fri...Sat...Sun...Mon...
GEFS and ECMWF ensembles both showed uncertainty with the Pacific
trough that moves into the Pacific NW during the extended period.
The GFS and ECMWF deterministic models also showed differences
with resolving this pattern. The above pattern uncertainty will
likely result in forecast changes as the pattern becomes more
certain with time.
There was better forecast confidence early in the period. On
Thursday, the upper low will move E out of MT into the Dakotas.
Expect isolated to scattered showers and a slight chance of
thunderstorms over most of the area in the morning, then just a
slight chance of precipitation over SE MT and the NE Bighorns in
the afternoon. Temperatures will reach the 80s as skies clear out
behind the system. Upper ridging and dry weather will follow the
low for Thu. night, then the flow becomes either zonal or SW
ahead of the next Pacific system on Friday. Both models remained
dry, but the ECMWF was a little cooler than the GFS. Model blends
gave highs in the mid 80s to low 90s. The same flow patterns
continued on Saturday with dry weather and cooler conditions. On
Sunday, the GFS pushes the upper trough toward the area, while the
ECMWF has the system over W. Canada. Both models were dry with
seasonable highs. The models bring a trough into the area Monday
through Tuesday and had increasing chances for precipitaton as
well as cooler conditions. Again, with the uncertainty noted
above, the pattern will have to be watched for changes. Arthur
MVFR to IFR ceilings will occur from KBIL to KSHR W this morning
with low clouds and areas of fog, then gradually improve to VFR by
early afternoon. Localized MVFR is possible in showers E of KBIL
to KSHR this morning. VFR will prevail this afternoon and tonight.
Mountains will be obscured, with some improvement expected this
.PRELIMINARY POINT TEMP/POPS...
Tdy Wed Thu Fri Sat Sun Mon
BIL 064 052/082 058/085 057/086 055/078 054/085 055/078
3/W 01/U 22/T 00/U 00/U 00/U 00/B
LVM 062 046/081 050/083 049/085 046/081 047/084 049/076
2/W 13/T 41/N 00/U 00/U 00/U 02/T
HDN 069 050/083 056/085 054/088 053/080 052/087 054/081
2/W 01/U 22/T 00/U 00/U 00/U 00/B
MLS 071 052/085 058/086 056/091 056/081 056/089 056/083
2/W 00/U 22/T 00/U 11/U 00/U 00/U
4BQ 070 050/085 057/083 054/089 055/083 054/089 055/086
2/W 00/U 22/T 00/U 00/U 00/U 00/U
BHK 071 049/083 056/083 052/089 055/081 052/089 053/084
1/B 00/U 24/T 10/U 01/U 10/U 00/U
SHR 070 050/084 053/082 052/088 052/082 051/089 053/083
2/W 12/T 32/T 00/U 00/U 00/U 00/U
FXUS65 KGGW 211503 AAA
Area Forecast Discussion...UPDATED
National Weather Service Glasgow MT
903 AM MDT Tue Aug 21 2018
Sent an update this morning to represent the fog along the river
valleys. Rest of the day looks very similar to the previous
forecast. Sunny and clear skies except for just a little bit of
upper level smoke from western states fires. There may be a
resurgence of smoke from the south up through central Montana
tonight and tomorrow, but expecting generally clear skies for NE
Montana. Winds will be light and variable early, then set up
generally from the south up to 10 mph through the day.
Previous discussion: Elongated trof stretching from western
Montana into northern California will slip southward today, and
clear the moisture and showers out of southern Montana. Northerly
flow into this trof will continue to keep much of the smoke out of
northeast Montana for another day.
Over the next few days the upper trof will form a semi-closed low
and drift eastward across Montana. Rising temperatures expected as
the upper flow shifts to the south and west. Moisture limited to
the southern side of the low, with showers mostly likely across
southern Montana on Thursday. The shift in the flow also has the
potential to bring more widespread smoke from the western
wildfires back into the region by Friday if not earlier.
A shortwave moving across western Canada late in the week will
push a cold front into the state. A few showers are possible with
the front on Friday night.
Model continue to suggest a large trof digging into the Pacific
Northwest early next week. This could bring some widespread rain
to the region, but still some significant model differences. Ebert
Generally VFR conditions are expected through the TAF period.
Clouds and showers across southern Montana will be moving out of
the region this morning. Much of the smoke has also cleared out
due to northerly flow aloft.