Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 221634

Area Forecast Discussion
National Weather Service Billings MT
1034 AM MDT Thu Sep 22 2016


Current analysis shows surface low over northwestern Wyoming with
upper-level low back over western Nevada. Divergence aloft and jet
stream punching around the eastern side of the low is continuing
to generate widespread cloudy and wet conditions over most of
Montana. As was the case yesterday morning, drizzle has continued
through most of the early morning. Expecting this drizzle to clear
and perhaps even a few cracks in the cloud deck to form over Big
Horn county as surface low slides northeastward. Figure enough
breaks in the clouds will warm temperatures into the upper 60s
over Big Horn and eastern Sheridan counties while significant
cloud cover elsewhere will likely keep temps in upper 50s to low
60s. Lowered rain chances across most of the area for this
afternoon. Looks like the main threats will be a passing shower or
a bit of drizzle with a break in the rain as the day wears on. By
early evening a more significant band of rain begins to work in
from the southwest. Isolated thunder will be possible as showers
will be more convective in nature. Most areas should pick up a
quick 0.25-0.50 inches with this round overnight. Walsh


.SHORT TERM...valid for Tdy and Fri...

Damp 3 days ahead for the region as well above normal moisture
content in the airmass will combine with a favorable upper level
flow to produce bursts of moisture into the region. Timing
continues to shift on the heaviest precipitation regarding this
system and latest guidance is decreasing precipitation amounts
today and Friday and shifting the emphasis to Friday night and
Saturday for south central and southeast Montana.

Expect persistent drizzle in a good portion of the region today as
upslope flow continues and guidance shows saturated boundary layer
moisture for most of the day. Expecting showers to move through
the area in southerly flow aloft but this activity appears to be
more hit or miss according to the latest HRRR. All models and HRRR
hint at a broader outbreak of convective activity early this
evening as a 700mb trowal rotates into the area around the
upstream low over southern Idaho.

Friday becomes complex as the upper low shifts towards the area
and generates cyclogenesis over northern Wyoming but this looks to
favor dry slotting for most of the area. There also may be a
subtle downsloping role due to such strong southerly 700mb flow.
Precipitation will increase Friday night as the low tracks into
the area and becomes upslopish at the mid levels for the Beartooth
and Absaroka Mountains with the best moisture spreading from there
into the adjacent plains.

Bottom line its a damp pattern and shower activity is going to
have precipitation amounts be widely varied with the best windows
for moisture this evening and Friday evening in the short term.

.LONG TERM...valid for Sat...Sun...Mon...Tue...Wed...

Little in the way of changes for the extended forecast
period...with bulk of the period under influence of upper level
high pressure. There remains a bit of model uncertainty with the departure of
the upper level low pressure system...but generally agree last
remnant exiting to the east by Sunday evening.

Models indicate a good chance for precip across the bulk of the
region through the day Saturday...with best chances shifting
eastward overnight. Made a few minor adjustments for
timing...generally spreading likely pops back to the west for
Saturday morning...with improved model agreement. Expect outdoor
activities to be impacted from continued wet conditions. Expect
mostly clear conditions across the bulk of the region for last remnants exit east through the
afternoon/evening. Warming trend should begin temps
climb back into the 60s.

Models are in pretty good agreement on a blocking ridge of high
pressure developing over the northeast CONUS by Sunday...which is
then progged to shift eastward through the middle of the work
week. Dry conditions should prevail...with a gradually warming
into the low 70s by the end of the period. AAG


Low CIGS will impact the region and all terminals with a mix of
lifr and ifr currently observed. Brief periods of MVFR/VFR are
possible later this morning and afternoon, and out east, but
expect conditions to deteriorate again later this evening as rain
moves into the region. Dobbs



    Tdy Fri     Sat     Sun     Mon     Tue     Wed
BIL 063 051/058 047/056 044/063 042/065 044/068 046/071
    4/T 95/R    66/W    31/B    01/U    11/U    11/U
LVM 059 046/055 043/054 038/062 039/065 042/070 044/072
    5/R 87/R    73/W    21/B    01/U    11/U    11/U
HDN 069 051/062 047/056 043/064 040/064 043/067 045/070
    5/T 85/R    66/W    31/B    01/U    11/U    11/U
MLS 064 053/063 048/054 042/062 040/063 041/065 044/068
    6/T 96/R    66/W    61/N    11/U    11/U    11/U
4BQ 066 053/070 048/056 041/061 037/061 039/065 042/070
    4/T 64/R    56/W    41/B    11/U    11/U    11/U
BHK 060 049/061 048/054 041/057 039/059 040/061 041/064
    2/T 67/R    65/W    52/W    11/U    11/U    11/U
SHR 070 052/065 045/054 041/060 039/062 040/066 042/070
    5/T 85/R    66/W    31/B    11/U    11/U    11/U




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