Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 122051

Area Forecast Discussion
National Weather Service Billings MT
251 PM MDT Mon Mar 12 2018

.SHORT TERM...valid for Tue and Wed...

The forecast remains quiet through mid-day on Wednesday. The
ridge will continue to dominate the weather across the Northern
Rockies. The shortwave that was moving through this morning is
currently down into Wyoming and South Dakota, so what cloud cover
there had been this morning as moved out. Given that skies will be
clear overnight cannot rule out some patchy fog especially in the
river valleys east of Billings. Tomorrow will be a little warmer.
Wednesday will likely be the warmest day of the week because by
the afternoon some energy off of a PacNW low will begin to
encroach on the area. This will bring some showers in to the
mountains during the afternoon. These will spread on to the plains
overnight. Given the lower elevations will be fairly warm during
the days with highs into the 50s, this will start out as rain and
will likely mostly stay that way. Reimer

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

Need to stress, large uncertainty when it comes to the forecast
for the end of the week, into next weekend. Models have been
greatly divergent during this time frame, and that has not
changed. Did make a few changes though, as the mid level height
pattern was transitioning to a much more unsettled one, so added
PoPs for most of the periods, to account for this pattern shift.
There are two weather systems of note in the extended period. The
first is in the Thursday through Saturday morning. The second is
early next week.

The models broaden an upper trough over the west on Wednesday and
sends energy out of the trough an into the northern Rockies
Thursday into Friday. How the models handle this energy is vastly
different. The GFS takes the energy and swings it into northern
Montana early Thursday and keeps the forecast area mainly dry. The
ECMWF, on the other hand, cuts a low off over eastern Colorado
and lingers circulation over northern Wyoming for a period of
accumulating snow Thursday night into Friday morning. There are
subtle signs that the GFS was coming around to the EC solution, so
raised PoPs a bit for this. May have to raise PoPs even more
depending on future runs.

The second system has a little more continuity, as both models
were kicking a low across northern Wyoming Sunday in Monday. This
would produce a deep upslope pattern for upwards of a half inch of
QPF, all in cold air, over southern Montana and northern Wyoming.
This could a be a significant accumulating snow event that will
need to be watched closely. Raised PoPs for this.

Otherwise, looks like the moderation in temperatures for mid week
will slowly subside as troughing takes over. This should take the
edge off of any ongoing low land snow melt. TWH



VFR flight conditions and light winds will prevail this afternoon
through tomorrow. Some patch valley fog it possible eas of KBIL
overnight, but will not likely impact any terminals. Reimer



    Tue     Wed     Thu     Fri     Sat     Sun     Mon
BIL 024/045 026/052 032/052 030/049 028/046 026/043 025/044
    00/U    00/U    43/O    44/O    22/O    23/S    32/O
LVM 028/051 030/060 035/055 032/051 031/048 028/044 028/044
    00/U    03/W    52/O    44/O    22/O    23/O    32/O
HDN 019/042 019/050 026/053 025/049 024/046 021/043 019/044
    00/U    00/U    32/O    44/O    22/O    22/S    32/S
MLS 017/035 019/042 024/041 025/040 022/038 019/037 018/035
    00/U    00/U    12/O    43/S    22/S    22/S    33/S
4BQ 021/039 021/050 028/049 029/045 026/044 023/040 021/041
    00/U    00/U    12/O    44/O    32/R    22/S    33/S
BHK 014/038 017/044 024/042 026/041 022/039 020/036 018/036
    00/U    00/U    12/O    22/O    22/S    22/S    33/S
SHR 022/046 022/055 032/056 029/049 027/046 024/042 023/043
    00/U    00/U    22/O    44/O    22/O    23/S    33/S




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