Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 232356

Area Forecast Discussion
National Weather Service Billings MT
Issued by National Weather Service Great Falls MT
550 PM MDT Wed May 23 2018

Aviation Section Updated

.SHORT TERM...valid for Thu and Fri...

Busy day today with heavy rain producing showers and thunderstorms
this morning, adding water to already swollen rivers. Add to that
thunderstorms developing over central and eastern zones with the
capability of producing hail and more heavy rain. There is also a
chance of larger hail, mainly east of Billings, in storms that
develop through the early evening hours.

Upper low has entered south central Montana this afternoon.
Circulation around this low and cold core aloft was combining to
ignite convection. Storms will contain locally heavy rain with
PWATS remaining quite high (around three quarters of an inch).
There could be some stronger storms over southeast Montana where
capes were higher and shortwave energy moving through eastern
Wyoming, gets in there late this afternoon and early this evening.
Will keep the Flood Watch for the western half of the forecast
area going tonight as heavy rain is likely in area storm tonight.
Showers will decrease in coverage and intensity by mid evening.

Ridging builds in for Thursday and Friday which will dry things
out mostly and warm things up. Temperatures will work back into
the 80s these days. Convection should be tied to the terrain on
Thursday. The ridge starts to break down some Friday afternoon and
this may allow for a little more convective development over
western and central zones. Drying things out some will help with
hydrology issues, but warming temperatures will kick mountain snow
melt back into higher gear, so flooding concerns will continue
through the end of the week, through the weekend. TWH

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

No big changes in the extended. By Saturday afternoon the next
trough/cutoff low over the western US will start to influence the
area. Showers and thunderstorms will start to develop over the
mountains during the afternoon and the spread east. Some of the
storms could be quite strong and contain heavy rain. The best
chance of convection looks to be Sunday as the upper low moves
into Utah and sends strong divergent flow and shortwave energy
into the forecast area. PWATs rise above an inch, so heavy rain
will be a legitimate threat, which would be problematic for rivers
and streams. Temperatures will cool down Sunday and Monday as the
upper low moves toward the area. The unsettled weather will
continue into early next week.

Please monitor:, for the latest on rivers and
streams into early next week. Rivers will remain high be flowing
fast and cold, with lots of bank erosion going on. TWH


Main concern is showers/thunderstorms moving from west to east
through the region. Some of the stronger storms will produce large
hail/strong winds. For now the stronger storms should be east of
Billings but will be close to Miles City. Most of the stronger
storms will diminish by 05z. Expect some clearing overnight, with
increasing west winds by morning. Another round of storms will move
into the western sections of the region after 20z Thu. Expect IFR
conditions in/near storms, with mountains obscured at times this
evening and again after 20z Thu. Brusda



    Thu     Fri     Sat     Sun     Mon     Tue     Wed
BIL 053/081 056/086 057/085 056/077 055/073 055/077 055/078
    42/T    21/U    13/T    34/T    65/T    54/T    33/T
LVM 050/077 052/082 050/078 052/071 051/067 048/073 049/075
    63/T    32/T    13/T    37/T    65/T    44/T    34/T
HDN 052/083 055/088 057/089 058/080 056/077 055/080 054/080
    42/T    21/U    12/T    24/T    55/T    54/T    43/T
MLS 056/081 058/087 060/091 062/082 061/080 059/078 058/079
    52/T    10/U    01/U    23/T    54/T    54/T    32/T
4BQ 054/080 057/086 058/092 060/082 058/080 057/077 056/078
    51/B    11/U    01/U    24/T    54/T    54/T    32/T
BHK 054/078 055/084 056/089 059/081 059/079 057/077 054/077
    41/B    10/U    01/U    22/T    54/T    54/T    32/T
SHR 050/078 052/083 052/087 055/076 051/075 051/075 050/076
    42/T    21/U    12/T    25/T    56/T    54/T    43/T


MT...Flood Watch in effect through late tonight FOR ZONES
WY...Flood Watch in effect through late tonight FOR ZONES 98-99.


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