Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 202048

Area Forecast Discussion
National Weather Service Billings MT
248 PM MDT Sun May 20 2018

.SHORT TERM...valid for Mon and Tue...

Look for a few showers lingering over the mountains this evening,
but otherwise dry conditions overnight. Flow aloft on Monday will
continue to be out of the southwest. While there are no organized
waves moving through, there are still some weak impulses of
energy embedded in the flow and stretching aloft due to the
relative placement of an upper low over the Great Basin. As a
result, we expect to see an increasing chance of
showers/thunderstorms Monday with some moving out onto the plains.
By Tuesday, that upper low over the Great Basin slowly starts to
drift to the NE and ejects some notable energy toward our region.
At the same time, divergence aloft will be increasing as well.
Therefore, we anticipate a pretty active day of showers and
thunderstorms Tuesday.

Over the next few days a few storms may have some small hail,
however shear remains very weak in the short-term. So widespread
severe storms are not expected.

Temperatures will be in the 70s to around 80 degrees Monday and
Tuesday. BT

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

Active weather coming midweek as an upper trough tracks from
Nevada into our region. This will produce periods of showers and
thunderstorms, especially Wednesday. Shear is on the weak side and
PWATs are relatively high, so look for some heavy rainers. A few
severe storms are possible, mainly near the Dakota borders.

The heavy rain may affect the rise of water levels on area rivers
as well as we start to move toward the peak season for snow melt

The trough lifts north Thursday then moves east Friday and
Saturday, allowing for rising heights and a drying/warming trend
for the end of the week. Cannot rule out diurnal showers/thunderstorms
with weak shortwave energy Thursday and Friday, but Saturday
should be mostly dry.

The extra cloud cover and rainfall may cool things a bit for
Wednesday, but this will be followed by a warming trend for late
week, a scenario agreed upon by GFS/ECMWF ensembles. Some of the
warmest temps we have seen yet this Spring are possible next
weekend. BT



No significant widespread threat to aviation this evening nor
overnight. Expect VFR conditions to prevail with some scattered
evening showers and maybe a thunderstorm over the mountains, some
of which may affect KLVM. Look for an increasing chance of
thunderstorms across the forecast area Monday with occasional
obscuration of mountain tops. BT



    Mon     Tue     Wed     Thu     Fri     Sat     Sun
BIL 050/079 053/076 054/070 054/078 056/081 056/082 056/083
    02/T    25/T    67/T    33/T    32/T    20/U    11/U
LVM 046/074 048/071 050/065 049/074 050/076 050/079 050/078
    24/T    37/T    67/T    44/T    33/T    21/B    12/W
HDN 048/080 053/079 055/072 053/079 055/082 055/083 057/084
    01/U    24/T    67/T    43/T    32/T    20/U    10/U
MLS 049/080 056/080 058/075 056/078 057/081 057/083 057/082
    00/U    23/T    47/T    43/T    21/U    10/U    00/U
4BQ 047/080 054/081 057/074 054/078 056/080 055/081 056/082
    00/U    13/T    56/T    33/T    21/U    10/U    10/U
BHK 045/076 053/078 057/074 055/076 056/078 055/079 054/078
    00/U    14/T    56/T    43/T    22/T    10/U    00/U
SHR 045/076 049/075 052/071 050/076 052/078 051/078 052/081
    02/T    23/T    76/T    43/T    32/T    21/B    11/B




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