056
FXUS65 KBYZ 300759
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
159 AM MDT Mon Sep 30 2024

.KEY MESSAGES...

- Cooler conditions with gusty northwest winds today.

- Warmer and dry conditions and breezy in spots for Tuesday and
  Wednesday.

&&

.DISCUSSION...
Today through Tuesday night...

Strong surface cold front was through the forecast area and headed
for KRAP at 0720Z. Pressure rises behind the front were centered
over eastern Big Horn/southern Rosebud Counties per mesoanalysis.
GFS moves the rises out of the area around 09Z. Winds were
gusting into the 30s to lower 40s mph in many places, with K3HT
hitting 47 mph at 1 AM MDT. Earlier line of showers and
thunderstorms over the eastern zones had dissipated. There were
isolated showers near KJDN in area of good vorticity advection,
but not confident those will make it into the forecast area.

Upper trough will continue pushing ESE today and will be E of the
area before 00Z tonight. 850 mb winds at 40 to 45 kt over the E
part of the area per mesoanalysis and NAEFS, will decrease to
30-35 kt by 18Z and then diminish to 20-30 kt by 00Z. Mixing
heights will be around 700 mb late today. Given trends of the wind
speeds in the column and pressure rise trends, have no need for a
wind highlight today. That said, nudged wind speeds up by 50%
toward the NBM 90th percentile through 18Z to capture the higher
winds in the morning and be more in line with the HREF which was
handling the situation well. Wind gusts will be in the 20s/30s kt
into early afternoon, before diminishing from W to E late in the
afternoon through the early evening. High temps will be 30-40
degrees lower than they were yesterday. RH`s will range from the
teens over and near the foothills to the upper 20s in the E.
Fosberg Index decreases through the day and Hot Dry Windy had
nothing over the area, so will continue to highlight FWF with the
cooler and breezy conditions.

NW flow/weak ridging will build over the area tonight through
Tuesday night. Temps tonight will drop into the 30s and the
probability of reaching 32 degrees is 63% at KLVM, 68% at KBHK,
54% at KSHR, 16% at KMLS and 0% at KBIL. Tuesday will be warmer
with temps back up into the 70s, and humidities will be low in the
teens. It will be breezy over portions of the area. Both the
Fosberg and Hot Dry Windy Index showed only spotty areas of
concern over the forecast area, so will keep an eye on this day to
see if fire highlights are needed. There will be poor RH
recoveries due to thermal belts in the foothills Tue. night. It
will be warmer than tonight with lows in the 40s and 50s. Gusty
winds are possible in the gap areas. Arthur

Wednesday through Sunday...

Dry zonal flow over the region into the coming weekend will keep
near to above normal temperatures in the forecast. Highs are
forecast to range from the 70s on Wednesday, to the 60s on
Thursday, warming back into the 70s Friday, through the weekend.
In fact, temperatures into the 80s are possible for some locations
on Saturday. Precipitation chances are low to nonexistent through
the long term. Low PoPs (15%) remain in the forecast over the
mountains on Saturday with some hints of a system, although the
majority of ensemble members point towards a dry forecast at this
time. Winds look to be gusty over portions of the area on
Wednesday and Saturday, and given the lack of rainfall since the
middle of September, fire weather concerns remain present for the
lower elevations. Those getting outdoors to recreate and hunt will
need to be extra cautious with anything that could start a fire
until rainfall arrives, especially on windy days. STP

&&

.AVIATION...

Breezy NW-N winds, gusting 25-40 kts will continue into today,
highest east of a KBIL to KSHR line. Winds are expected to
gradually decrease during the afternoon. In general, VFR will
prevail through the period, although local MVFR reductions due to
smoke from the Elk fire are possible near adjacent to the Bighorn
Mountains. Reductions in slant range visibility are possible as
well. STP
&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Tue     Wed     Thu     Fri     Sat     Sun
-------------------------------------------------------
BIL 061 038/076 051/075 041/065 039/075 050/080 047/074
    0/N 00/U    00/U    00/U    00/U    11/B    00/U
LVM 061 033/078 049/076 036/067 036/079 046/077 042/074
    0/U 00/B    00/N    00/U    00/U    11/B    10/U
HDN 062 033/078 046/075 040/066 036/077 045/081 043/074
    0/U 00/U    00/U    00/U    00/U    11/B    10/U
MLS 060 035/075 050/070 041/063 037/073 047/078 044/070
    0/N 00/U    00/U    10/U    00/U    10/U    00/U
4BQ 060 035/076 049/073 042/066 038/075 049/080 045/072
    0/N 00/B    00/U    10/U    00/U    00/U    00/U
BHK 060 032/074 047/071 038/064 035/072 044/078 040/069
    0/N 00/B    00/U    11/B    00/U    00/U    00/U
SHR 061 031/078 046/078 037/067 035/079 045/084 042/074
    0/N 00/H    00/U    00/U    00/U    01/U    10/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.

&&

$$
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