Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 270258

Area Forecast Discussion...Updated
National Weather Service Billings MT
858 PM MDT Tue May 26 2020


Have had a few showers over the mountains, and even a lightning
strike or two over the park this evening. All of this weak
activity is associated this the shortwave moving into the area.
The isolated PoPs in the forecast are still in line with the
latest short-range guidance. No update needed. Reimer



Tonight through Wednesday night...

Satellite imagery shows zonal flow across the region with mainly
scattered clouds. There is a line of weak showers in Carter/Fallon
counties, along an axis of higher instability on trailing end of
PV moving into the Dakotas, but this activity will exit our cwa
soon. Otherwise, we are underneath the subsident portion of the
upper level jet today, thus only light diurnal convection exists
over the mountains.

Shortwave in southern BC/Alberta will drop to the southeast
tonight, providing some ascent for showers across mainly our west
and south tonight into Wednesday, with a focus shifting to our
south due to a fropa/wind shift to the N-NW late tonight. There
should be some diurnal development tomorrow afternoon and early
evening, aided by weak PV trailing the wave departing to our
northeast, and a shift in low level winds to easterly (i.e.
upslope). Could be an isolated thunderstorm over the mountains,
but overall instability will remain shallow and do not see much of
a lightning risk. Temps on Wednesday should be a little cooler
than today with highs in the upper 60s and lower 70s most
locations...pretty close to late May normals.


Thursday through Monday...

A trough will swing south over southern Canada Thursday that will
bring slightly cooler temps to the area before warming through
the weekend. The surface high will shift east Thursday night
allowing for the ridging to build through Sunday.

Recent ensemble runs have trended Saturdays temps slightly cooler
than previously forecasted but still above normal for this time of
year. The biggest challenge with this forecast is the possibility
of convection Friday, Saturday and Sunday afternoons and
evenings. PoPs have been increased for much of the area to include
a slight chance until we can narrow down the best area for
thunderstorms. There is moderate instability along with shear in
the atmosphere that would allow for strong to severe storms to
form mainly along the foothills and out towards Billings. The big
inhibitor in the atmosphere is the capping that will be in place.
If there is enough energy to break the cap, there is a potential
for strong storms. If the cap is not broken, then thunderstorms
will remain weaker. We will have to see how it plays out over the
next few days and will make sure to update the forecast
accordingly. High elevation snow melt will also cause rivers to
rise early to mid next week. Rivers will have faster flows and
increased bank erosion.

The forecast high temperatures on Sunday are near record levels.
The record high temperature for May 31 is 92F for the three
stations Billings (set in 1936 and 1940), Miles City (set in 1966
and 1986) and Sheridan (set in 1940). The high temperature
forecast for Livingston this Sunday is 86F, which is three
degrees lower than the record high of 89F set in 1972.

High temps will remain near normal Thursday before warming into
the 80s on Friday and Saturday. High temps will then warm again
into the upper 80s to mid 90s on Sunday. Monday will cool back
into the 80s.



VFR flight conditions will prevail tonight and Wednesday. Brief
reductions to MVFR are possible mainly along the foothills due to
isolated showers, and mountains will be occasionally obscured in
scattered rain/snow showers. JKL



    Wed     Thu     Fri     Sat     Sun     Mon     Tue
BIL 055/072 050/070 050/080 056/085 059/093 059/088 058/086
    22/W    10/B    01/B    22/T    12/T    20/B    12/T
LVM 050/074 046/071 048/083 054/083 056/086 054/084 054/082
    22/W    00/B    02/T    23/T    11/B    01/B    23/T
HDN 054/072 048/071 048/082 055/086 059/094 058/088 057/087
    22/W    10/B    01/U    21/B    11/B    20/B    12/T
MLS 052/072 049/069 047/077 053/080 059/091 061/089 060/088
    11/B    10/B    00/B    11/B    11/B    20/B    11/B
4BQ 052/070 047/068 047/078 052/080 057/092 059/090 060/088
    13/W    21/B    02/W    11/B    11/B    10/B    11/B
BHK 049/071 045/068 043/073 049/075 053/084 059/088 059/085
    02/W    10/B    01/B    10/N    11/B    20/B    11/B
SHR 050/068 046/070 048/081 053/084 058/091 057/088 057/086
    25/T    21/B    12/T    22/T    21/B    10/B    11/B




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