Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 141726

Area Forecast Discussion
National Weather Service Billings MT
1026 AM MST Tue Feb 14 2017


No update to inherited forecast this morning. AAG


.SHORT TERM...valid for Tdy and Wed...

A strong upper ridge was positioned over Idaho this morning and
will provide dry and mild weather through the short term. The
ridge is progged to slide into western Montana and become
positively tilted this afternoon. The ridge will then get
suppressed south on Wednesday with energy streaming over the top
into Canada. This whole process will provide mild temperatures. In
fact, high temperatures will approach 60 degrees Wednesday with
increased downslope flow. Will have to monitor rivers for
potentially increased ice jam activity with warmer weather, along
with lingering low land snow melt.

Winds will increase over the western valleys tonight and continue
through Wednesday night as a lee trough forms and deepens. Models
have sped up the onset of potentially advisory level winds to
Wednesday morning with these level winds continuing into the day
Thursday. Gradient does tighten up during the period, but 700mb
winds were a little slower to increase until Wednesday afternoon.
Bumped winds up a little more and pushed them closer to advisory
level Wednesday morning with the thought the strongest, and more
prolonged event, will be Wednesday night into early Thursday. Will
let the day crew evaluate further with the aid of a couple more
model runs. TWH

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

A more active period was in store for the extended forecast, but
the ECMWF ensembles showed pattern uncertainty through much of the
period. The deterministic GFS/ECMWF did not agree on the pattern

On Thursday, the upper ridge that was anchored over the area
during the short-term period will slide E, allowed a more active
SW flow to overtake the region Thu. night. Thursday will be
another warm day with 850 mb temperatures reaching +8 to +12
degrees c, resulting in highs in the 50s to 60s. The pressure
gradient supported Advisory criteria wind speeds in the gap flow
areas. Moisture spreads into the area Thu. night, combining with
lift to support isolated to scattered rain and snow showers. Winds
in the gap flow areas will fall below Advisory speeds. A shortwave
was progged to move NE through the area on Friday. Models differed
on the moisture amounts so kept the slight chance across the area
in the morning. Fri. will be a little cooler with highs in the
50s. Shortwave ridging will be over the area Fri. night and Sat.
with limited moisture. Kept the forecast mostly dry. Highs will be
in the upper 40s on Saturday. Active SW flow returns to the area
Sat. night through Sun. with moisture confined mainly to the
western part of the area. Mild weather will continue with Sun.
highs in the 50s.

The northern part of a splitting trough was forecast to move into
the area Sun. night with timing of the trough`s departure
differing between models for Monday. Moisture differed between the
models so had low PoPs across the entire area through Monday. 850
mb temperatures fall below zero degrees C on Mon. on the GFS, but
stay around +4 degrees C on the ECMWF. Blended guidance gave highs
in the 40s. Weak ridging returns for the end of the period with
differences in model details. Had some PoPs in the W with highs
in the 40s on Tuesday. Arthur



VFR conditions will prevail today and tonight across the area. W
to SW surface winds will increase over KLVM and Big Timber
tonight, with gusts of 40 to 45 kt expect late tonight. Arthur


    Tdy Wed     Thu     Fri     Sat     Sun     Mon
BIL 053 030/058 036/057 035/052 027/050 033/054 033/048
    0/U 00/N    00/N    22/W    11/B    12/W    32/W
LVM 052 032/056 037/054 033/049 024/049 031/050 028/044
    0/U 00/N    01/N    33/W    12/W    22/W    22/W
HDN 049 024/056 024/056 029/052 022/048 028/052 028/047
    0/U 00/U    00/U    32/W    11/B    12/W    22/W
MLS 046 025/054 028/053 030/050 025/048 028/049 028/043
    0/U 00/U    00/U    12/W    11/U    11/B    22/W
4BQ 048 025/055 031/057 028/052 025/051 032/054 031/047
    0/U 00/U    00/U    02/W    11/B    11/B    22/W
BHK 044 023/052 027/053 030/049 025/048 030/052 030/042
    0/U 00/U    00/U    02/W    11/B    11/B    22/W
SHR 048 020/058 024/058 028/052 022/049 029/054 029/048
    0/U 00/U    00/U    12/J    11/B    11/B    22/W




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