024
FXUS65 KBYZ 230749
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
149 AM MDT Thu May 23 2024

.DISCUSSION...

Today through Friday night...

...Key Messages...

- Heavy precipitation for lower elevations and heavy snow for
  mountains today lingering early this evening.

- Heavy rain will cause rises on area rivers and streams.

Water vapor imagery was showing a strong upper low over central
Idaho. Models have locked in with the timing and position of this
upper low movement today and tonight. The low tracks across
northern Wyoming, which is a little farther south than previous
tracks. This slides the heaviest precipitation a little farther
south, with the biggest QPF totals generally over the mountains
and foothills of the western and central zones. Strong dynamic
forcing will produce moderate to heavy rainfall today, with the
focus for that over western and central zones through 18z today,
then the eastern parts of central zones (think Sheridan county
into southern Big Horn county and southern Rosebud county east)
and into southeast zones. Amounts along the foothills from say
just south of Columbus to Fort Smith to Lodge Grass and Ashland,
south could pick up 1.5 to 2 inches of rainfall today. NBM was
giving Billings a 70% chance of picking up over 1 inch of rainfall
today, same with Red Lodge and Sheridan. The highest probability
of this (over 80%) was over southern Big Horn county. Sections of
Big Horn county has flood guidance of around 1.5 inches over 6
hours, would be under the forecast amounts in these locations, but
not by a great deal. WPC has placed a marginal risk of flooding
from eastern Yellowstone county eastward, to cover Big Horn
county, Sheridan county, and all of southeast Montana. This seems
reasonable given the dynamics of the system. Will have to keep a
close eye on rain rates today, as heavier amounts might cause very
quick rises on small streams. The Flood Watch for the Little Big
Horn River near Hardin continues from this evening to Saturday
afternoon.

The system was coming in gradually warmer with each passing run
it seems, so the snow threat is mainly for elevations above 6000
feet. Snow levels will fall to around 5000 this morning, so there
will likely be snow this morning over the foothills and higher
hills of western and central zones, but 850mb temperatures stay
above 1c. That and a high sun angle, should keep the snow factor
in these areas brief. Dynamic cooling may play a factor in
changing precipitation over to snow and keeping it as snow longer
than expected. That being said, temperatures were starting out in
the 40s to lower 50s early this morning, so have a ways to go to
get there. Will not issue any additional winter highlights at this
time, given the uncertainty of snow impacts below 5000 feet but
will keep a close eye on radar and webcam trends. NBM
probabilities for 2 inches of snow at Red Lodge was 30%. A quick
Winter Weather Advisory may be needed should rain change to snow
quickly and actually impact road conditions with more than a
dusting of slush. Leaves have come out in full, so this could be a
factor too, but the high sun angle should allow most of the that
to melt off of the trees as falling (unless snowing heavenly for a
few hours straight). Will watch closely as the morning
progresses.

The upper low pulls into the western Dakotas late this afternoon
and early this evening, so will linger high PoPs (60-80%) over the
eastern zones, while tapering back to 20-40% central and west.
The chance of showers will continue to lower through the evening
and overnight hours from west to east tonight as the system pulls
away and zonal flow sets in. Zonal flow will continue into Friday
for generally dry weather. Weak energy will start to move into
western and central zones Friday afternoon and evening, and this
will promote a low chance (20-30%) of showers.

Temperatures will be cool today with showers around. Look for
highs in the upper 40s to lower 50s. Lows tonight will fall into
the 30s most locations with a freeze possible over many western
locations. NBM has a 60-80% chance of western zones having lows
below 32F tonight, with a 10% chance at Billings and a 60% chance
at Sheridan. Warmer weather will return for Friday with high
temperatures in the 60s. TWH

Saturday through Thursday...

An upper trough will move across the region Saturday through
Sunday, bringing an increased chance for precipitation across the
area. See below for a probability table for total precip through
Sunday night.

              >0.10"   >0.25"   >0.50"
---------------------------------------
Livingston     60%      35%      15%
Big Timber     65%      45%      20%
Red Lodge      70%      50%      25%
Billings       60%      40%      20%
Hardin         65%      45%      25%
Sheridan       65%      45%      25%
Forsyth        60%      40%      20%
Miles City     50%      30%      15%
Broadus        50%      30%      20%
Baker          40%      20%      10%

On Monday, upper level ridging will build in, bringing dry
conditions and warmer temperatures into midweek. By Wednesday
afternoon, upper level flow is expected to become southwesterly as
the ridge moves out of the region, leading to a more unsettled
pattern to end the week. Currently, there is a 20-30% chance for
precip Wednesday, increasing to a 30-40% chance Thursday.

High temps will be in the mid 60s to low 70s Saturday before
dipping slightly Sunday into the 60s. Monday will be the start of
the warming trend, with highs in the upper 60s to mid 70s,
increasing to upper 70s to mid 80s by Wednesday. Then, as the
ridge moves out, highs Thursday will drop back into the 70s.
Archer

&&

.AVIATION...

Showers across the area, and rain/snow mix near KLVM and KSHR,
will affect the region this morning through evening. Low ceilings
and pockets of heavy rain will periodically reduce conditions to
IFR/LIFR. Expect mountain obscuration. Winds will gust to 30-35
kts this afternoon and evening. Archer

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Fri     Sat     Sun     Mon     Tue     Wed
-------------------------------------------------------
BIL 052 036/065 042/068 047/067 046/075 049/081 053/082
    +/T 32/W    15/T    65/T    10/U    00/U    12/T
LVM 050 032/062 037/064 041/064 040/073 045/080 050/080
    +/T 12/T    16/T    64/R    10/U    01/U    13/T
HDN 052 034/067 039/070 045/068 043/076 046/082 051/083
    +/T 51/U    13/T    55/T    20/U    00/U    12/T
MLS 053 036/065 040/070 046/068 046/075 047/082 053/084
    9/T 62/W    11/B    35/T    20/U    00/U    11/U
4BQ 059 037/064 040/069 045/066 046/072 047/081 052/084
    9/T 81/U    01/B    35/T    20/U    00/U    01/U
BHK 057 035/062 038/068 042/067 044/072 046/078 049/081
    9/T 81/B    01/U    25/T    21/U    00/U    01/U
SHR 053 031/063 037/066 041/064 040/072 044/079 049/083
    +/T 81/U    03/T    66/T    20/U    00/U    01/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning remains in effect until midnight MDT
      tonight FOR ZONES 67-68.
     Winter Storm Warning in effect until 6 AM MDT Friday FOR ZONE
      171.
WY...Winter Storm Warning in effect until 6 AM MDT Friday FOR ZONE
      198.

&&

$$
weather.gov/billings