000
FXUS65 KBYZ 140048
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
648 PM MDT Sat Apr 13 2024

.UPDATE...
Weak diurnal convection has developed over and near the
mountains/foothills since mid afternoon, but this activity has
been dying quickly as we are underneath upper ridge axis and
anticyclonic flow aloft. That said, there seem to be hints of a
mid level warm front lifting thru the region, with residual steep
lapse rates, so opportunity for light showers/sprinkles will
linger thru the evening while lifting northward over the west half
of our cwa. Do not see much risk of thunder except for perhaps
along our western foothills (SW flow into south central MT looks a
bit more convective). Locally gusty/erratic winds are likely near
any weak thunderstorms. Have made some pop/wx adjustments and
have scaled back TS wording. The overnight tonight will be dry
with lows in the 40s most places. Sunday will be quite warm,
possibly the warmest day of this short spell, and daily records
will be challenged at each of our climate stations.

SITE        SUN FCST   SUN RECORD
Billings       79       80 (2015)
Livingston     78       79 (1985)
Miles City     82       84 (2015)
Sheridan       81       82 (1963)
Baker          81       80 (2015)

JKL

&&

.DISCUSSION...
This afternoon through Monday night...

Water vapor imagery was showing a flat ridge over the Northern
Rockies with a deep upper low off the California coast. As this
upper low progresses east, the weather will start to turn cooler
and more unsettled once we get into Monday and Tuesday.

For the remainder of the afternoon and tonight, some mid level
moisture was getting drawn into Montana and northern Wyoming.
Models also bring a weak wave across this afternoon and evening
for forcing. Soundings were inverted V with potential for strong
wind gusts. Activity will be isolated to low scattered, so most
people will not experience a shower or thunderstorm, but those who
do, wind gusts of 40-50mph could accompany them.

The ridge will get pushed east into southeast Montana on Sunday,
while the western upper low moves into Nevada. Upper divergence
starts to slide into western zones Sunday afternoon and evening,
and this will be enough to initiate another round of showers and
thunderstorms. The focus for the convection will be over western
and central zones, with the east being protected by the ridge
axis. Temperatures will be warm once again on Sunday with highs in
the upper 70s to lower 80s, which will approach record values.

The upper low moves eastward into Colorado Monday and Monday
night, for increasing upper divergence across the entire area.
Precipitable water values increase to over 8 tenths of an inch
over southeast Montana. A surface trough will slide into the
southeast zones for the focus point for convection. Capes will
rise to around 800j/kg for the potential for strong thunderstorms.
At this time, the Storm Prediction Center slides the marginal
risk of severe weather into southeast Carter county, with the
higher risk over the western Dakotas. Will have to keep an eye on
this and the position of the surface trough for a possible western
shift of this marginal risk. The western and central zones also
have capes above 500j/kg, but will be in the cooler air with
northerly surface winds. That being said, scattered showers and
thunderstorms will be present, and will need to be monitored
closely for small hail, as the upper levels of the atmoshpere
cool. Highs on Monday will range from the upper 60s west, to mid
to upper 70s east. TWH

Tuesday through Saturday...

A cold front will push through the region Tuesday morning,
beginning a period of colder and wetter weather into the weekend.
This front will come from a trof and upper low building into the
region from southern Canada. Highs for Tuesday will be in the mid
50s to mid 60s, with chances for precipitation arriving in the
afternoon out west.

The development and progression of the subsequent pattern,
involving a trof and potentially an upper low, is uncertain as
model ensembles continue to clash. There is some agreement though,
as the GEFS and EC ensembles depict colder air infiltrating the
state Wednesday night and persisting into the weekend. The GEFS
850mb mean temperature anomaly is -9C to -13C, while the EC
ensemble shows an anomaly of -8C to -10C. Along with these
ensembles, the latest NBM forecast has highs in the 40s
Wednesday-Friday, with overnight lows in the 20s to 30s. The
coldest nights will be Thursday night and Friday night.

The GEFS depicts the aforementioned upper low closing off and the
trof deepening over Saskatchewan, Tuesday and Wednesday.
Conversely, the EC ensemble shows a much broader upper low
developing and elongating in SK on Wednesday. As for
precipitation, there is still a lot of disagreement on potential
amounts. The latest EC storm total QPF ranges from 0.1"-0.5" for
lower elevations and up to 1" in the mountains. The latest GEFS
storm total QPF is much wetter, with a range of 0.2"-0.6" in non-
mountain locations, whereas mountains could see QPF amounts up to
2". As mentioned previously, precip chances will begin increasing
from West to East Tuesday afternoon. With the nature of the trof
and low, this looks to be a quick shot for precip totals, through
Wednesday. With surface and mid-level flow out of the WNW, the
west facing mountain slopes have a moderate to high chance of
several inches of snowfall. There are some indications that a
Winter Weather Watch could be needed for the Absaroka/Beartooths,
however it still too soon to make that decision. As the low and
trof move east, probabilities for precip will decrease, remaining
low to moderate, best chances in the higher elevations, for the
rest of the week.

Winds will increase Tuesday and last through Thursday. Winds are
expected to be strongest on Wednesday, with gusts in the 30s-40s
mph range. The higher gusts are anticipated over the far eastern
areas.

Friday and into Saturday, a WNW flow pattern will briefly settle
in before a potential ridge begins to build over the PNW. This
will bring temps back into the mid-40s to 50F on Friday and low-
mid 50s on Saturday.

Matos

&&

.AVIATION...

VFR conditions will prevail through the period. Through 06Z
tonight, expect isolated showers from KBIL to KSHR W. A
thunderstorm or two is also possible, around KLVM, K6S0, the
Crazys, Absarokas and Beartooths. Wind gusts to around 40 kt are
possible with any thunderstorms. Expect localized to areas of
mountain obscuration through 06Z. Isolated to scattered showers
and thunderstorms are possible again after 18Z Sunday W of KBIL.
Arthur

&&

.PRELIMINARY POINT TEMP/POPS...

    Sun     Mon     Tue     Wed     Thu     Fri     Sat
-----------------------------------------------------------
BIL 045/079 048/072 046/063 036/047 031/046 027/047 027/055
    21/U    25/W    32/R    55/S    23/S    12/S    11/B
LVM 043/078 044/065 039/058 032/043 025/043 022/046 024/054
    22/T    35/T    33/R    75/S    23/S    11/B    11/B
HDN 041/080 045/074 046/065 035/049 029/047 025/048 025/056
    21/U    23/W    31/N    55/O    33/S    22/S    11/U
MLS 044/082 046/072 048/062 034/046 028/043 024/046 025/052
    00/U    11/B    21/N    12/S    22/S    11/B    01/U
4BQ 043/083 046/073 047/061 034/047 028/043 024/044 024/052
    00/U    02/T    41/N    13/S    22/S    11/B    11/U
BHK 041/081 044/073 043/059 032/044 024/040 020/041 021/048
    01/U    11/B    42/R    12/S    23/S    11/B    01/B
SHR 040/081 043/069 043/062 032/043 025/042 022/044 022/052
    20/U    03/W    42/R    66/S    33/S    22/S    21/B

&&

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

&&

$$
weather.gov/billings