Area Forecast Discussion
Issued by NWS Billings, MT

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598
FXUS65 KBYZ 230912
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
312 AM MDT Wed May 23 2018

.SHORT TERM...valid for Tdy and Thu...

Water vapor imagery shows strong diffluence over the region as
shortwave lifts through central WY, associated with broad upper
low over the intermountain west. Areas of rain since yesterday
evening have been moderate to heavy mostly in our central cwa to
this point. Atmospheric moisture is quite high...see 00z raobs
showing precipitable water of just under an inch at GGW and RAP,
and over an inch at BIS. We`ve seen reports of 1-2 inches since
Tuesday evening, and Billings has received about a quarter inch of
rain as of this writing. Rain will continue and should become
enhanced as vorticity axis lifts into our cwa early this morning.
This includes our east which has been mostly dry so far but should
see a period of showers/t-storms during the early morning hours.

As shortwave continues to lift northward, a mid level low will
deepen a bit west of Billings. This will result in a westward
shift in the heavier precip. Our western cwa will see anywhere
from 0.50-1.50 inches of rain today. Eastern parts will see
decreasing showers from south to north through the morning. Will
make no changes to the Flood Watch that is in effect for Roundup-
Billings-Sheridan westward.

Other concern today is severe weather across our east. Decreasing
cloud cover after early morning showers will allow for quick
warming and destabilization. Initially, we will see dry slotting
and descent in our far east, but there is an axis of convergence
on NW side of surface trof (i.e. near places like Forsyth and
Miles City) that should allow convection to fire by early-mid
afternoon. By evening, as upper low tracks slowly east and a
weaker wave lifts through eastern WY, there is risk of strong to
severe storms across southeast MT. Hail and wind are the primary
threats with any severe weather today.

Weather will quiet down tonight as trof lifts to the northeast.
We`ll see some breezy westerly winds and just isolated coverage
of mainly diurnal showers/t-storms on Thursday. None of the storms
on Thursday will be severe.

Temperatures today will ary quite a bit, ranging from the upper
50s in our far west to lower 80s in our far east. We should see
mid 70s to mid 80s everywhere on Thursday as ridge begins to build
back in, along with the drier west winds.

JKL

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

No big changes in the extended. Friday will be the best chance for
a dry day as ridging builds in. 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. More
shortwaves will move through the area through Wednesday. The
biggest concerns with these storms will be the high moisture
content with this system producing heavy rainfall. This will
continue the risk of flooding as rivers will be nearing the peak
of snowmelt runoff season.

Please monitor water.weather.gov for the latest on our streams
into early next week. The main spring runoff will likely be upon
us later this week through the holiday weekend and will need to be
closely monitored for potential flooding. Reimer

&&

.AVIATION...

Expect showers and isolated thunderstorms to continue to most of
the day. Flight conditions will be MVFR to IFR from KBIL west,
with localized LIFR in heavier showers. Conditions will begin to
improve from towards 00Z. Reimer
&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Thu     Fri     Sat     Sun     Mon     Tue
-------------------------------------------------------
BIL 066 053/081 055/086 056/087 056/080 056/077 055/077
    +/T 42/T    11/U    12/T    23/T    55/T    54/T
LVM 058 048/077 049/082 050/082 051/074 051/072 050/074
    +/T 63/T    22/T    12/T    36/T    65/T    44/T
HDN 072 051/083 054/088 057/091 057/083 057/081 055/080
    9/T 42/T    11/U    11/U    23/T    55/T    54/T
MLS 078 056/080 058/087 060/090 061/085 061/083 060/081
    9/T 52/T    10/U    00/U    33/T    54/T    53/T
4BQ 081 054/080 057/086 058/090 060/085 059/082 057/079
    5/T 31/B    11/U    00/U    14/T    55/T    54/T
BHK 080 054/077 055/084 056/088 058/084 058/081 056/078
    8/T 41/B    10/U    01/U    23/T    44/T    54/T
SHR 075 050/079 052/083 053/087 055/079 053/077 051/075
    4/T 42/T    21/U    11/U    24/T    56/T    54/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Flood Watch in effect through late tonight FOR ZONES
      28-29-34-35-38>42-56-57-63>68.
WY...Flood Watch in effect through late tonight FOR ZONES 98-99.

&&

$$
weather.gov/billings



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