Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 201526
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
926 AM MDT Mon Mar 20 2017

.UPDATE...
Moist flow aloft over the area with shortwave tracking over
southern Saskatchewan which is strengthening surface high pressure
over northern Montana. This is enhancing northerly surface flow
which is beginning to shift shower activity southward which hi-
res progs have been advertising. Current forecast looks good
covering these details. Expect precip band to enhance a bit later
tonight and shift back northward as the surface migrates eastward.
Still only expect minor snowfall amounts but taking a look at
southern part of southeast Montana where accumulations could be
greater. borsum

&&

.SHORT TERM...valid for Tdy and Tue...

Scattered showers were continuing across the area this morning,
focused along a band of frontogenesis associated with the cold
front that moved into the region yesterday. Showers will mainly
be focused over the mountains this morning with isolated to
scattered showers over the plains with the frontal boundary
nearly stationary over the area. However, showers will increase
during the afternoon and evening as cold air advection continues
to work in from the north and upslope flow increases. Models
continue to indicate modest omega over the mountains and foothills
this afternoon spreading onto the plains this evening/overnight.
Best precipitation chances will be over the upslope favored areas.

Precipitation begins to shift east tonight as ridging builds in
from the west. Easterly upslope flow and moisture working over the
area will continue to focus showers along the baroclinic zone
associated with the frontal boundary. 850 mb temperatures fall
below 0 degrees C this evening, and a rain/snow mix will
transition over to snowfall over most of the area overnight. Still
looks like in general that an inch or less of snow is possible
across the lower elevations with a couple inches along the
foothills and several more inches in the mountains. Snow will
mainly accumulate on grassy surfaces. Shower chances decrease
through the day Tuesday as ridging builds over the region and
forcing decreases. A warm front associated with the next wave
approaching from the west will lift north through the area Tuesday
night, perhaps producing some showers across the area. Models
differ in precipitation amounts and locations. With the warm front
lifting over cooler temperatures at the surface (near to slightly
below freezing), there is potential for a brief period of
freezing rain/ice pellets across our northeast. Will continue to
monitor the situation.

High temperatures will range from the 40s to near 50 degrees
today, cooling down to the upper 20s to low 30s tonight. Highs on
Tuesday are expected to be in the 40s most places, with 30s across
the far east. STP

.LONG TERM...valid for Wed...Thu...Fri...Sat...Sun...

Two main weather features on the extended forecast will be
Wednesday night and Thursday, and again on Saturday night into
Sunday. Ahead of the first system, Wednesday will be dry and
warmer with downslope winds pushing highs into the mid to upper
60s.

A western upper trough will push into Utah/Nevada early Thursday.
This system will spread upper divergent forcing into northern
Wyoming and southern Montana for ascent. The core of the system
will drive well to the south, but will have adequate moisture
available, and thus models were generating just over a quarter
inch of QPF over parts of southern Montana (at least the ECMWF
was). Have raised PoPs up to likely over most of the area for
Thursday. System was progged to be warm and thus precipitation
should be mainly be in the form of rain.

Next shortwave trough works into Utah/Nevada Saturday night and
shifts across a similar pass to the previous trough for Sunday.
This will likely spread another round of showers across the
forecast area Saturday night into Sunday, so raised PoPs.
Temperatures will be warmest on Wednesday with readings slightly
above seasonal averages the rest of the period. TWH
&&

.AVIATION...

A few light showers will work across southern Montana and
northern Wyoming this morning, but conditions are expected to
remain mainly VFR. Local MVFR conditions can be expected in the
heavier showers, but these conditions will be isolated. A better
chance of showers will roll into the area late this afternoon and
this evening. These showers will drop conditions to MVFR.
Precipitation will likely change to snow during the evening and
this will lower conditions to IFR and local VLIFR. Mountains will
be occasionally obscured today and becoming totally obscured late
this afternoon and tonight. RMS/Borsum

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Tue     Wed     Thu     Fri     Sat     Sun
-------------------------------------------------------
BIL 045 030/047 035/068 040/057 034/059 038/061 038/056
    4/W 63/W    22/W    36/W    20/B    11/E    23/W
LVM 045 029/047 036/064 035/055 028/058 037/058 034/053
    6/W 62/W    32/W    45/W    31/B    23/W    33/W
HDN 050 031/050 032/069 039/058 033/059 034/063 036/058
    5/W 63/W    21/B    36/W    20/B    01/E    23/W
MLS 052 031/043 033/065 039/058 034/057 035/062 037/056
    4/W 43/J    22/W    14/W    20/B    01/B    23/W
4BQ 053 029/041 032/066 039/055 033/056 033/063 036/057
    4/W 74/W    21/B    36/W    40/B    00/B    23/W
BHK 051 025/037 027/056 036/056 030/053 029/056 033/054
    5/W 33/J    22/J    14/W    20/B    00/B    23/W
SHR 051 031/052 035/067 038/054 033/056 033/063 036/055
    6/W 71/E    11/B    46/W    40/B    01/B    23/W

&&

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

&&

$$
weather.gov/billings


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