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000
FXUS65 KBYZ 122043
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
243 PM MDT Fri Apr 12 2024

.DISCUSSION...
Tonight through Saturday night...

Areas of cumulus and mid cloud were moving through the region this
afternoon as monsoonal moisture flowed NE into the area under an
upper ridge. It was very warm and breezy from KMLS W where temps
were in the 70s due to good mixing. Raised highs in a few
locations. KLVM had reached its record high and KSHR was
approaching a record high. Temp/dewpoint spreads were large, but
HREF/HRRR do show convection moving in from the W and SW this
afternoon and evening, so had mainly 20% PoPs from Rosebud County
W for late this afternoon and shifted most PoPs N this evening,
which was similar to the previous forecast. Expect threat for
convection to end after 06Z tonight. Another warm day is in store
for Saturday with not as much wind. Models supported another round
of isolated convection spreading W to E through KBIL by 00Z
Sunday. Isolated convection continues in the evening, then
diminishes after 06Z Sunday. Near-record highs are possible on
Sat. at KLVM. Arthur

Sunday through Friday...

A warm Sunday is in store, with high temperatures in the 70s to
low 80s. A 15-35% chance for showers across the west along with
modest instability will allow for a few rumbles of thunder to be
heard.

A pattern change will begin Monday, with cooler temperatures and
wetter conditions expected through the week. A low pressure system
will move in from the West Coast, as to where it goes is unclear
as model ensembles disagree right now. The GEFS shows the low and
associated trough digging into the eastern Sierras to the Wasatch
Range on Monday. This scenario would put our forecast area in a
split flow pattern, resulting in a brief quiet period in the
weather. Going into Tuesday, the GEFS shows the low shooting
through the Central Plains and into the Upper Midwest. As this
takes place, another trough begins to dig into the northern
Rockies from Canada, allowing for cold air and moisture to befall
the region. The GEFS 850mb temperature anomaly is -5C to -12C
Wednesday night into Thursday, as a result, forecasted highs would
drop into the mid 30s to low 40s. The GEFS also depicts a much
wetter period than other ensembles, with total QPF amounts of
0.5-1", Monday through Thursday.

On the other hand, the EC ensemble is much drier and places the
initial low pressure a bit further south and west, then pushing it
into the southern Plains. In this case, a more zonal flow pattern
settles over us. The second low pressure and trough is shown to be
more broad than the GEFS, with it wobbling around in southern
Canada, bringing more NW flow. The total precipitation amounts
from the latest EC ensemble show the stark disagreement with the
GEFS, as only a few hundredths up to 0.3" are displayed. There is
agreement though with colder air infiltrating the region by mid-
week, although the 850mb temperature anomaly isn`t quite as low as
the GEFS, it is around -5C to -10C.

As for what is currently in our forecast, temperatures in the 70s
on Monday, 50s to 60F on Tuesday, and 40s Wednesday-Friday.
Several rounds of precipitation are possible beginning Monday
afternoon and lasting through Thursday. Chances of mountain snow
are moderate to high right now (60-80%), with several inches
possible. As for the foothills and lower elevations, precipitation
type will be rain until Wednesday at the earliest, when
temperatures finally get cool enough (30s with overnight lows) to
transition to a rain/snow mix. There is a lot of uncertainty with
any precip amounts right now, with such warm temperatures this
weekend and the beginning of the week, it would be quite hard to
imagine any falling snow would be able to stick to roads very
well. Snow levels will fall into the 4500ft to 8000ft range on
Tuesday, before falling even further on Wednesday, nearing 2000ft.
Current snow ratios are around 10:1 for non-mtn locations, where
as in the mountains, ratios are in the 15-10:1 range. Any snow
that is able to fall in the lower elevations is expected to be
fairly wet.

Lastly, gusty winds in the 30s to 40 mph are expected to impact
the area, mainly east of Billings, beginning Tuesday and lasting
through Thursday. Along with the winds, there is a low chance (up
to 30%) for blowing snow, especially in the east. Overnight lows
will be in the low 30s Wednesday night and mid to upper 20s
Thursday night. The combination of cold temperatures, blowing
snow, and gusty winds will raise the concern for young livestock
and those who have outdoor plans.

Matos

&&

.AVIATION...

Winds will decrease this afternoon. Isolated showers, and
potentially a few weak thunderstorms, may impact all TAF sites
through this evening. Archer


&&

.PRELIMINARY POINT TEMP/POPS...

    Sat     Sun     Mon     Tue     Wed     Thu     Fri
-----------------------------------------------------------
BIL 047/075 044/078 048/072 045/056 033/044 028/043 025/048
    22/T    21/U    24/R    45/R    56/S    34/S    12/O
LVM 044/073 042/073 043/064 038/050 028/040 022/042 021/048
    22/T    21/U    24/R    46/O    65/S    33/S    11/B
HDN 043/076 043/079 046/073 044/059 033/046 027/045 023/049
    11/U    21/U    23/R    44/R    66/S    44/S    22/O
MLS 044/074 045/079 047/073 046/058 033/043 027/041 023/046
    20/U    10/U    11/B    33/R    35/S    43/S    11/B
4BQ 045/076 044/081 046/072 045/058 032/044 027/040 023/046
    00/U    00/U    02/R    43/R    35/S    33/S    11/B
BHK 043/074 042/077 045/071 044/057 031/041 023/037 020/043
    00/U    01/U    11/B    44/R    35/S    43/S    11/B
SHR 043/076 042/077 043/068 042/056 029/041 022/039 019/046
    21/U    20/U    13/R    44/R    67/S    44/S    22/S

&&

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

&&

$$
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