Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 172029

Area Forecast Discussion
National Weather Service Billings MT
229 PM MDT Fri Mar 17 2017

.SHORT TERM...valid for Sat and Sun...

Approaching upper ridge seen on water vapor will move over the
region tonight through Saturday. Models continued to show some
high elevation moisture over the SW mountains this evening, so
kept some low PoPs in this area. Otherwise, it will be dry through
Saturday. KBHK has been slow to lose the stratus this afternoon,
but visible satellite was showing decreasing clouds, so KBHK
should become mainly clear. RAP and GFS showed moisture developing
in the boundary layer late tonight over KBHK so have added patchy
fog to Fallon County into Sat. morning. Just some mid and high
clouds are expected over the area on Saturday. Deep mixing will
combine with strong downsloping to send temperatures well into the
70s and lower 80s. Expect the four climate stations to exceed
record highs and have highlighted this in the forecast. Mixing
will allow strong winds aloft to reach the surface W of KBIL
around locations like KLVM and Big Timber, so have increased winds
in these areas.

A tight pressure gradient will persist in the western zones Sat.
evening ahead of an approaching cold front, and gusty winds will
continue in the W. Models had the front reaching the eastern
zones by 12Z Sunday under a fast WSW flow. Jet energy N of the
area will bring some lift to the area along with the front.
Moisture will be limited to over and near the western mountains
through 06Z Sun., with limited moisture spreading E through 12Z.
Thus had slight chance PoPs over the far W through 06Z, and higher
PoPs over the W late Sat. night behind the front. Any snowfall
will be limited to the mountains due to the warm airmass.

WSW flow aloft will become W during Sunday. There will be
scattered showers across the area, and the focus for higher PoPs
will gradually shift S as the front slowly moves S through Sun.
night. Low-Level flow will shift E and favor upslope areas in the
foothills as well. It will be breezy and cooler behind the front
on Sunday with highs in the 50s. Expect a mix of rain and snow
showers Sun. night as temperatures fall into the lower 30s/upper
20s. Arthur

.LONG TERM...valid for Mon...Tue...Wed...Thu...Fri...

Monday looks like the chilliest day of the extended period with
temps expected to remain in the 40s, courtesy of a Canadian
surface ridge settled in east of the mountains. Moisture
overrunning baroclinic zone across our south into WY will keep a
chance of precipitation going on Monday, especially across our
southern foothills where some wet snowfall is possible with 850mb
temps near 0C. Mid level warm front will lift north allowing for a
chance of light precipitation across the lower elevations Monday
night into Tuesday, but there remains model uncertainty here with
regard to low level dry air and QPF. Overall, there is confidence
in lowering temps a bit on Monday and raising pops Monday into

Building upper ridge should bring a brief period of dry wx Tuesday
afternoon into Tuesday night. Ridge axis will slide east opening
the door to shortwave energy from the great basin and our next
chance of showers by late Tuesday night and Wednesday. A stronger
trof is expected to move thru the central Rockies by Thursday in
this evolving progressive pattern. Model spread remains high
Thursday, with the 12Z GFS staying south of our cwa and mostly
dry, while the 00Z EC is further north and wet for us. Will keep
pops broadbrushed Wednesday night through Thursday night to cover
this period, and will need to monitor model trends. However you
slice it, without a surge of Canadian air, lower elevation temps
Wednesday to Friday look sufficiently warm to keep p-type as rain,
with high temps mostly in the 50s to lower 60s (Wednesday
probably the warmest day). Expect some high elevation snow with
each of the shortwaves next week.



There is a slight risk of fog at KBHK late tonight and early
Saturday. Otherwise, VFR flight conditions will prevail through
tomorrow as high pressure aloft dominates the region. SW winds
will increase at KLVM, with gusts to 35 kts by late tonight and 45
kts by Saturday afternoon. JKL


    Sat     Sun     Mon     Tue     Wed     Thu     Fri
BIL 039/077 045/057 032/046 032/056 039/062 038/056 036/059
    00/B    14/W    41/E    22/W    22/W    33/W    21/B
LVM 041/074 043/057 031/047 032/058 039/059 035/054 032/057
    00/N    35/W    43/O    32/W    23/W    33/W    32/W
HDN 034/082 043/057 030/049 030/056 034/062 034/056 033/059
    00/B    14/W    41/E    22/W    22/W    23/W    21/B
MLS 034/078 043/057 031/049 031/051 035/059 035/056 032/055
    00/U    13/W    10/B    12/W    21/B    22/W    21/B
4BQ 033/082 043/057 031/048 029/053 033/062 034/055 032/057
    00/U    04/W    42/R    32/W    21/B    23/W    31/B
BHK 029/069 040/054 028/047 025/045 030/057 033/053 030/053
    00/U    03/W    10/B    12/J    31/N    23/W    21/B
SHR 034/079 042/058 031/047 030/056 036/063 034/054 032/057
    00/U    04/W    33/O    32/W    22/W    33/W    21/B




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