Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 192116

Area Forecast Discussion
National Weather Service Billings MT
316 PM MDT Thu Apr 19 2018

.SHORT TERM...valid for Fri and Sat...

Upper low, seen on water vapor imagery this afternoon, moving E
into the four-corners region, will move slowly E through the
four-corners region through Friday night. Jet divergence with the
system will affect SE MT late tonight through Friday, otherwise a
few spokes of vorticity will cross the area through the period.
Moisture will be confined to the southern mountains tonight for
just a slight chance of snow showers. Winds will remain gusty E of
KBIL through the evening. Moisture will move into the SE part of
the area during Friday, but models differed in the amount of
moisture, with the GFS being the most aggressive of the models.
The GFS remained the wettest model in the SE Fri. night. Given the
discrepancies, blended the model solutions for a chance of showers
over the far southern and SE tier of the area with slight chances
a bit further N. Highs on Fri. will range from the upper 40s SE to
the lower 60s central and W. Winds will not be as strong as they
were today.

The upper low will move into the southern plains on Saturday, and
a shortwave N of the Canadian border will push a cold front SE
toward the area. While it will be warm ahead of the front, all
ensemble guidance has trended lower with high temperatures and
downslope flow was not overly strong. Thus, lowered the highs a
couple of degrees. The cold front will drop S through the region
Sat. night with limited moisture. Kept a slight chance of showers
from KBIL W and S into the NE Bighorns in the evening, then had a
chance of rain/snow showers over the higher elevation of the SW
late Sat. night. Gusty northerly winds will accompany the frontal
passage Sat. night. Arthur

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

Little in the way of changes for the extended forecast period,
with good consistency through Tuesday, followed by poor agreement

Cooler temperatures move in Sunday behind the cool front crossing
the region Saturday night, with highs mainly in the 50s, and a
few low 60s.

A disturbance will begin to move into western Montana Sunday
night, with rain showers overspreading the region through Monday.
Still plenty of uncertainty with this system but model trends have
been upward trend for precipitation amounts. This system looks
like mainly rain for the early morning and much of Monday, but
cannot rule out some snow or rain snow mix in higher hills,
foothills and mountains. Expect more of a rain/snow mix Monday
evening/night. A switch to all snow is possible Monday night, so
cannot rule out the possibility of accumulating snow. That said,
the heaviest precip looks to fall through the daylight hours
Monday. This system moves out of the region early Tuesday morning
leaving much cooler temperatures in the region for the afternoon.

Models diverge fairly quickly from this point onward, with the
GFS keeping an active and cooler pattern in place while the Euro
solution brings warmer and drier conditions back into the region.
Have generally kept middle of the road temps in place, and held
slight pops in the high terrain to end the period. AAG



VFR conditions will prevail through the TAF period. East and
southeast winds continue for all routes, with gusts of 20-30kts
common across much of the region. Strongest gusts, around 35kts,
have been reported in KSHR. Winds will diminish from west to east
overnight. AAG



    Fri     Sat     Sun     Mon     Tue     Wed     Thu
BIL 037/062 036/072 037/058 036/048 029/057 034/064 034/062
    11/B    00/U    20/B    46/W    21/U    12/W    32/W
LVM 031/061 033/070 035/062 036/047 025/059 032/062 031/062
    10/U    00/U    21/B    58/W    21/U    13/W    22/W
HDN 036/061 035/073 036/058 035/048 028/057 032/065 032/062
    01/B    10/U    10/B    36/W    31/U    12/W    22/W
MLS 039/060 035/070 037/058 035/047 031/057 034/063 032/062
    11/B    10/U    10/B    27/W    20/U    00/U    21/U
4BQ 037/055 035/067 037/057 036/049 030/056 033/062 032/060
    12/W    21/U    10/B    36/W    51/U    01/B    21/B
BHK 034/052 035/064 036/055 036/047 029/050 031/058 034/057
    12/W    21/U    10/B    26/W    40/U    00/U    20/U
SHR 036/055 033/069 034/063 035/052 027/060 031/065 031/061
    13/W    20/U    10/U    26/W    41/U    12/W    22/W




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