Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 300104
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
704 PM MDT Sat Apr 29 2017

.UPDATE...

Updated forecast to remove mention of thunder for the early
evening. Still a few light showers showing up on radar from
Wheatland to Musselshell county. This activity should dissipate
with sunset. Otherwise a quiet and mostly clear overnight. A few
areas of fog will be possible with light winds and clearing skies,
especially in areas that still have some snow cover. Chambers

&&

.SHORT TERM...valid for Sun and Mon...

Northern stream trough axis sliding slowly across Montana today
and is generating some convection over the central sections of the
state. This includes the northwest portion of our CWA where some
decent looking scattered to isolated showers are noted on radar
and confirmed on webcams (measurable precipitation reaching
ground). Lightning has been generally north of Lewistown at this
point, but cannot rule out a little thunder with the activity into
the early evening as it shifts east. We expect most of this to
stay north of Billings where there is better forcing and progs
focus CAPE, which reaches up to around 250 J/KG. Southerly flow
off the recent deep snowfall seems to be keeping boundary layer a
little more stable further south. Most of this activity should die
off after sunset with maybe a lingering light shower or sprinkle
to midnight.

After a nice start for Sunday with warmer temperatures near
seasonal averages, we see another unsettled period begin late in
the day through Monday. A fast moving Pacific cold front will race
in from the west spreading showers into our western zones by
afternoon, and through the rest of the CWA during the late
afternoon and evening. CAPE is limited more so than even today,
but with steep lapse rates and a punch of forcing we could get
isolated thunder as this activity quickly moves through. Pressure
change is weak at 4-6 mb/6 hrs. However, GFS 850 winds are 25-35
kts with 700 mb at 30-40 kts. NAM is a little less widespread with
those wind speeds. At any rate, due to steep lapse rates we are
anticipating a blustery period along and behind the front in the
evening. Outdoor activities may be more impacted by the resulting
gusty winds than the fast moving convection.

The flow aloft remains NW through Monday Night. There appears to
be some weak energy within the flow and the usual instability we
see in NW flow. Models suggest periods of scattered showers to
start the work week. The higher terrain may see some snow showers.
Temperatures will be about 5-7 degrees cooler than Sunday. BT

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

Unstable northwest flow will continue across the region on
Tuesday afternoon with widespread showers and an occasional rumble
of thunder possible. With very low freezing levels and enough
instability above this level, definitely could see some graupel
/ice-pellets mix in with any rain showers that form. The mountains
should pick up a few inches of snow. Expect a cool start to the
extended period with highs in the mid 50s on Tuesday.

Low level flow turns westerly as a ridge of high pressure builds
across the region. This will be the beginning of a large warmup
and mostly dry conditions through the end of the work week.
Temperatures on Wednesday will be in the upper 60s and then will
warm into the mid and upper 70s by Thursday and Friday afternoons.
Mid-level temperatures will also be fairly warm so some snow melt
off the mountain foothills and lower elevations is possible.
Widespread flooding is not anticipated at this time, but small
rises along area rivers are possible so folks with plans on the
water should be vigilant along river banks. Some uncertainty in
regards to rain chances and temperatures for late Friday and
through the weekend as an upper level low to our south begins to
affect the region. Left the better rain chances in the western
mountains and foothills for the weekend period. There is also some
uncertainty with temperatures over the weekend so some additional
mountain snow melt is possible over the weekend. Dobbs
&&

.AVIATION...

VFR conditions will prevail through tonight. Isolated light
showers northwest of Billings and in the vicinity of higher
terrain will dissipate with sunset. A few areas of fog will be
possible after about 09z with local IFR conditions possible. Can`t
rule out some of the fog impacting the KBIL, KLVM and KSHR taf
sites around sunrise. Chambers

&&

.PRELIMINARY POINT TEMP/POPS...

    Sun     Mon     Tue     Wed     Thu     Fri     Sat
-----------------------------------------------------------
BIL 037/062 040/057 040/056 039/067 045/076 048/075 045/065
    12/T    43/W    25/W    31/B    00/U    11/U    22/W
LVM 032/058 035/054 034/052 032/064 040/072 044/071 041/062
    13/T    42/W    35/W    20/U    00/U    11/B    22/W
HDN 033/064 040/059 039/057 038/067 042/077 046/077 044/069
    02/W    53/W    25/W    21/B    00/U    11/U    22/W
MLS 034/065 043/059 039/059 040/067 044/076 049/077 047/069
    02/W    43/W    22/W    11/B    00/B    10/U    22/W
4BQ 029/062 040/057 038/057 037/064 041/074 046/077 045/071
    01/U    33/W    24/W    12/W    00/B    00/U    12/W
BHK 030/061 038/055 035/056 034/062 037/071 043/072 043/069
    00/U    34/W    23/W    12/W    00/U    00/U    12/W
SHR 025/055 036/052 036/051 035/061 038/072 040/074 039/067
    01/B    33/W    25/W    31/B    00/U    01/U    12/W

&&

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

&&

$$
weather.gov/billings


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