Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 212135

Area Forecast Discussion
National Weather Service Billings MT
335 PM MDT THU JUL 21 2016

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

Cumulus was starting to develop over portions of the area this
afternoon as monsoonal moisture was advecting north through the
central Rockies. An isolated thunderstorm or two will be possible
over the southwest mountains and Big Horn Mountains late this
afternoon and evening. High temperatures are expected to top out
in the 90s to low 100s across the area this afternoon.

A surface low will begin to lift north and east out of central
Wyoming this evening, with some warm air advection lifting north
through eastern areas. This may provide enough forcing for
isolated showers and thunderstorms across eastern areas later
tonight. On Friday, the aforementioned surface low will continue
to lift north and east, eventually merging over central Montana with
another surface low associated with an approaching shortwave from
the northwest. Increasing instability and moisture will be
advected around this area of merging low pressure at the surface
into areas of central and eastern Montana. Showers and
thunderstorms will develop across south central and southeast
Montana during the afternoon and evening hours, gradually
decreasing overnight. MUCAPE values of 1000 to 1500 j/kg, deep
layer shear of 30 to 50 kts, and theta-e advection will lead to a
few strong to severe storms Friday afternoon and evening. SPC
currently has a marginal risk from Rosebud County east with a
slight risk for northeast areas.

A cold front associated with the aforementioned shortwave will
push through the area Friday night, ushering in gusty northwest
winds and increasing relative humidities. Cooler conditions and
building high pressure are expected for Saturday with gusty
northwest winds continuing through the day, gradually decreasing
during Saturday evening. High temperatures are expected to range
from the upper 90s to low 100s Friday with 80s expected on

As far as fire weather concerns, hot and dry conditions are
expected across the area on Friday along with showers and
thunderstorms. Minimum RH values are expected to be generally in
the teens. The merging areas of low pressure at the surface will
cause winds to be generally light and variable across the majority
of the area during the day on Friday. The exception is the far
east where southeasterly winds will be gusty Friday, however
increasing moisture should keep minimum RH values above 20
percent. Northwest winds gusting up to 35 mph and increasing RH
values will overspread the area Friday night, with gusty
northwest winds continuing into Saturday. Minimum RH values are
expected to be in the teens and twenties on Saturday. Have kept a
headline in the FWF for the dry and hot conditions ahead of the
cold frontal passage and for the continued gusty winds on
Saturday. STP

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

Ridging builds in on Sunday, giving a dry, mostly sunny day to
the region. High temps should increase to the 90s most places as
flow turns more southerly. Next chance of showers and
thunderstorms should arrive on Monday for southeastern MT as a
shortwave trough slides northeast out of Wyoming during the
afternoon. Expect temperatures to stay consistently in the low to
mid 90s in most places from Monday through Wednesday. Generally
zonal flow aloft with weak disturbances sliding through bringing
afternoon thunderstorm chances. Wed/Thurs becomes more interesting
as front slides south from Canada bringing more substantial
thunderstorm chances across most of the area. Will continue to
monitor this portion of the forecast to see if the global models
become more consistent with future runs to warrant a bump in the
PoPs. Walsh



VFR conditions will prevail at all sites with clear skies and
light winds 10 kts or less. Walsh



    Fri     Sat     Sun     Mon     Tue     Wed     Thu
BIL 064/099 062/086 058/090 061/094 062/093 062/092 062/087
    12/T    21/U    11/U    11/U    11/U    13/T    32/T
LVM 056/097 052/084 048/089 049/092 052/091 052/091 053/086
    11/N    11/U    11/U    12/T    21/U    13/T    33/T
HDN 062/100 059/087 055/092 057/095 059/094 060/094 059/088
    12/T    21/U    11/U    11/U    11/U    13/T    32/T
MLS 068/102 066/087 059/091 063/095 065/095 065/093 064/088
    23/T    31/U    11/U    12/T    22/T    22/T    22/T
4BQ 065/103 064/088 058/091 061/094 062/095 063/094 062/090
    13/T    31/U    11/U    22/T    22/T    23/T    32/T
BHK 064/098 063/085 055/087 059/092 060/091 060/089 060/086
    24/T    31/N    11/U    13/T    33/T    33/T    33/T
SHR 059/100 057/087 053/090 054/093 057/093 056/093 057/088
    12/T    21/U    11/U    22/T    22/T    23/T    33/T




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