FXUS65 KBYZ 242121

Area Forecast Discussion
National Weather Service Billings MT
321 PM MDT Thu May 24 2018

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

Isolated showers and thunderstorms are developing this afternoon
and moving quickly eastward. Thus far, downslope flow has greatly
limited development, and do not expect any severe but could
produce some enhanced wind gusts due to the increased mid level
winds. Activity will diminish after sunset.

Upper level riding will prevail across the region Friday and
Saturday ahead of a developing CA low. southwest flow on back side
of ridge will allow some shortwave activity into mountains and
westernmost zones. The bulk of the cwa should remain dry.

The CA low will push further eastward through the day Saturday,
bringing increasing showers and thunder to the mountains through
the day. At this time, showers and thunder do not appear to spread
into the plains until late Saturday afternoon/evening. Showers
and thunderstorms will spread across the state overnight.

Temperatures will warm into the 80s across the region and around
90 in some locations. We urge everyone to keep a close eye on
rivers and streams affected by the snow melt, especially as we
move into the holiday weekend. AAG

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

Another upper low will develop over the western U.S. this
weekend, bringing another period of showers, thunderstorms (some
strong to severe) and torrential rains.

Difluence from the upper low will continue through Sunday and
into Monday. Precipitable waters are forecast to climb to around
/0.75/ inches W to an inch or higher E during this time. The
highest QPF amounts were progged Sun. afternoon through Sun. night
with convective feedback making it difficult to discern actual
expected QPF amounts. Instability parameters also supported
possible strong to severe storms and heavy rainfall through Sunday

Strong to severe storms potential shift E of KBIL on Monday, with
continued areas of heavy rain across the region. The upper low
continues to be progged to shift E of the area on Tuesday.
Continued with likely PoPs in many areas Sunday afternoon through
Monday, then had chance PoPs Tuesday.

A short period of ridging returns for Wednesday ahead of another
Pacific trof, but quickly transitions eastward, with unsettled
southwest flow returning Wednesday afternoon/evening. This will
bring another chance for showers and thunderstorms, especially for
the mountains. The timing of the trof and associated cold front
pushing eastward varies a bit through the end of the extended
forecast period, so have continued with broadbrush type pops
through the remainder of the period.

Rivers are expected to continue to rise and flow fast, with lots
of bank erosion going on. Please monitor:
water.weather.gov, for the latest on rivers and streams into
early next week. AAG


Isolated showers and thunderstorms are developing this afternoon,
but are expected to clear after sunset. Localized reductions in
flight conditions are possible, but VFR conditions. AAG



Fri Sat Sun Mon Tue Wed Thu
BIL 054/084 057/085 056/070 055/068 053/073 054/078 053/076
21/U 22/B 56/T 76/T 33/T 22/T 23/T
LVM 049/079 050/078 050/066 050/065 048/071 050/073 050/072
22/B 23/T 56/T 66/T 34/T 22/T 24/T
HDN 055/086 058/089 057/073 055/071 054/074 054/079 054/079
21/U 11/U 56/T 76/T 23/T 32/T 22/T
MLS 058/083 060/090 062/077 060/073 057/074 057/078 057/078
10/U 01/U 43/T 66/T 33/T 22/T 22/W
4BQ 057/084 058/090 060/077 058/073 056/073 056/076 055/078
20/U 11/U 24/T 63/T 53/T 22/T 22/T
BHK 056/082 057/088 060/078 058/072 056/072 054/075 054/076
00/U 01/U 23/T 66/T 54/T 32/T 22/B
SHR 052/082 053/087 054/069 052/069 050/070 051/075 051/076
21/U 11/U 46/T 64/T 33/T 32/T 22/T




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