Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 270227

Area Forecast Discussion...Updated
National Weather Service Billings MT
827 PM MDT THU MAY 26 2016

Pesky upper low over northeast Montana produced a few showers and
thundestorms across the area late this afternoon and early this
evening. Cyclonic flow was weakening as the low finally pulls
eastward and this, combined with decreasing sunshine, has caused a
weakening trend to the showers across the area. Have adjusted pops
downward a touch. Will keep the mention of isolated pops as still
some ascent and high resolution models were hinting at activity
holding together until around midnight. Some returns remained over
northern Montana, so this seemed reasonable. TWH


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

An upper low continues to be located over Northeast Montana this
afternoon and will slowly shift east/southeast into this evening
and during the overnight hours. Satellite showing the clear skies
earlier today have filled with clouds as a result of a cold pool
of air aloft. However, there will remain some breaks in the clouds
at times for the remainder of the afternoon across the forecast

Current radar is showing scattered showers and isolated
thunderstorms across the entire forecast area with movement
northwest to southeast. We will continue high chance of showers
through early evening then just a slight chance mid evening
through midnight. Expect the majority of clouds and showers to
quickly dissipate around sunset due to loss of daytime heating.
Given the low freezing levels, any shower or thunderstorm will
have the potential to produce some very small hail. Overnight
lows will be near seasonal values with readings in the 40s.

Friday & Saturday...An upper level disturbance over the Pacific
Northwest will move across the Canadian border Friday into
Saturday. Models show the strongest energy remaining to our west
and northwest across North Central Montana during the afternoon
Friday. A Pacific front will move across the forecast area Friday
afternoon. This front combined with the upper level disturbance
will bring increasing chances for showers and thunderstorms across
our central and western areas Friday afternoon and evening. We
have increased chances into the likely category from Park County
northeast through Wheatland and Musselshell Counties due to the
fact the best dynamics will be along and northwest of these areas.
Elsewhere, isolated to scattered showers and thundestorms will be
possible. We are not expecting any widespread severe weather but
an isolated strong to severe storm is not out of the question.

A fast zonal flow aloft will be over the forecast area Saturday.
Some weak upper level energy and vorticity will also move across
the area bringing continued chances for showers and isolated
thunderstorms. However...coverage should be less than the past few
days. Best CAPES will be across the eastern portions of the state
but overall shear is not well organized. As a result, we are not
expecting any severe weather but a stronger storm may be possible.
Afternoon temperatures Friday and Saturday will be around normal
with readings in the upper 60s to lower 70s. Hooley

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

Made a few adjustments to the forecast based on latest model
trends...however...there was a fair amount of uncertainty in the
pattern based on the ECMWF the forecast will
continue to be narrowed down with time.

W flow will be over the region on Sun., and the morning looked
dry, so have removed those PoPs. A weak pacific trough approaches
the area Sun. afternoon and moves into the area during Sun. night.
Kept low PoPs over the central and western zones Sun. afternoon
and kept them across the area Sun. night with chance pops after
06Z Monday. Instability was weak, so had just a slight chance of
thunder. Westerly flow will push temperatures into the 70s on
Sunday. Model differences continued on Mon., with the GFS bringing
an upper low into MT and the ECMWF keeping the low N of the
Canadian border. CAPE was not very impressive on the GFS with the
highest values around 1000 j/kg along the Dakotas border. The Bulk
Shear does increase from the W however. CAPES were a little higher
on the ECMWF with shear increasing from the W as well. So, there
is the potential for strong to severe storms...especially over
western sections. Will need to watch this scenario. Continued the
scattered PoPs on Monday. Temperatures will be a little lower than
Sunday`s readings.

By late Tue., the GFS has the low over E MT and the ECMWF has the
low over ND. Kept highest PoPs in the E closest to the system.
Severe parameters were much weaker than on Monday. Expect highs
in the 60s on Tuesday. Upper ridging will gradually dry out the
airmass through Thursday with decreasing PoPs. Arthur



An isolated shower or thunderstorms will occur over the area
through 04Z. MVFR/IFR conditions will accompany the precipitation.
The showers and thunderstorms will decrease through 06z. There
will be areas of mountain obscuration this evening. MVFR/IFR
ceilings/patchy fog are expected E of KBIL late tonight, otherwise
VFR will prevail after 06z with localized mountain obscurations
through Friday morning. Showers and thunderstorms with MVFR/IFR
conditions will increase over the area, mainly from KBIL and west,
again Friday afternoon. Mountain obscurations will become
widespread over the Crazys, Absarokas and Beartooths, with areas
of obscuration over the NE Bighorns. RMS/TWH



    Fri     Sat     Sun     Mon     Tue     Wed     Thu
BIL 047/070 048/068 048/074 049/070 046/064 044/068 047/074
    23/T    43/T    22/T    34/T    44/T    42/W    11/B
LVM 040/065 040/065 039/070 042/067 040/060 038/068 043/072
    26/T    63/T    22/T    34/T    44/T    31/B    11/B
HDN 043/073 047/070 045/076 048/075 047/066 042/068 045/076
    23/T    33/T    22/T    34/T    55/T    43/W    22/W
MLS 047/073 050/073 048/077 053/075 051/067 047/068 048/075
    22/T    24/T    21/U    44/T    55/T    54/W    22/W
4BQ 044/073 046/071 045/076 048/075 046/066 044/069 044/076
    22/T    14/T    21/B    44/T    55/T    43/W    22/W
BHK 043/070 048/071 046/075 048/072 046/067 043/065 043/072
    22/T    16/T    21/U    44/T    55/T    54/W    22/W
SHR 041/070 045/068 043/074 044/072 043/063 040/066 042/075
    23/T    33/T    22/T    34/T    44/T    43/W    22/W




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