Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 222055

Area Forecast Discussion
National Weather Service Billings MT
255 PM MDT SUN MAY 22 2016

.SHORT TERM...valid for Mon and Tue...

An area of thunderstorms has developed and was moving NE through
the eastern zones at 2030Z. A few other storms were located over
far SE MT and Sheridan County. These storms were in an area of
positive vorticity advection and approaching jet divergence.
Mesoanalysis showed strong bulk shear...up to 70 kt E of
KBIL...this afternoon. There was little cape, but lapse rates were
very steep. Thus cannot rule out a stronger storm over Sheridan
County and SE MT through early this evening and will mention
possible gusty winds/small hail in this area with thunderstorms.
The area of strong shear will move E with time ending the threat
of strong storms.

Otherwise, the upper low seen spinning over SE Alberta on water
vapor imagery this afternoon, will continue to affect the weather
through Tue. night. After the chance of early evening
thunderstorms, the loss of insolation will lessen lapse rates and
the rest of the night will be dry. Gusty afternoon winds will
diminish as well. The upper low will reach SW Saskatchewan by 00Z
Tuesday. Monday did not look that unstable with the exception of
steep lapse rates again, and good mixing. After a chance of
mountain showers in the morning...chances for convection will
increase again across the plains. The airmass will be relatively
dry over the SE half of the area so kept pops out of this area.
Temperatures will be similar to today`s readings and it will be
breezy in the afternoon. A cold front will slide SE through the
region Mon. night. Chances for convection will continue in the
evening then the area will be mainly dry overnight.

The upper low center remains stationary through Tue. night with SW
flow aloft over the area. Surface low pressure will move into WY
on Tue., allowing the low-level flow to turn E. Moisture will
increase over the area and the SREF showed possible 500 j/kg of
cape over the area with some increased shear in the SE. Kept
chances for showers and thunderstorms across the region through
Tue. night. Given increased instability and shear, some of the
storms could become strong. Again, do not expect much change in
high temperatures for Tuesday. Arthur

.LONG TERM...valid for Wed...Thu...Fri...Sat...Sun...

Not much change in the extended models from yesterday and thus few
adjustments to the going forecast. Upper low currently over
Alberta will persist over Alberta/Saskatchewan through late week,
cut off from both northern and southern streams. Weak pulses of
energy rotating around this system will keep a chance of showers
and afternoon/evening thunderstorms in the forecast Wed/Thu. Next
upper low moving into the Pacific NW will generate shortwave
ridging helping to hasten the filling and dissipation of the
Canadian cutoff low and allowing temperatures to work back into
the 70s for the weekend. Residual instability and weak flow aloft
will support continued diurnal precipitation chances Fri, and a
stronger shortwave late Sat may pose the next severe thunderstorm
threat for the area. By Sunday the Pacific NW system may slide
through the area or drop south into the Great Basin depending on
model choice. Canadian solution brings system into position for a
good precipitation event starting late Saturday so will have to
keep an eye on next weekend. Overall looks like a pretty quiet
and seasonal pattern through the work week. Chambers


Scattered showers and some isolated thunderstorms will persist
late this afternoon through mid evening before dissipating with
sunset. Thunderstorms will be mainly near terrain in the west and
east of a Miles City to Sheridan line in the east. Local
visibility restrictions to MVFR levels can be expected near
precipitation. Outside of convection expect VFR conditions.

Southwest winds will remain gusty along the western foothills
this evening with gusts in the KLVM vicinity of 30 to 40 kts at
times, winds will taper to gusts in the 15 to 30kt range
overnight. Elevated SW-W winds will also be possible along the
east slopes of the Bighorn mountains including KSHR, with gusts to
25kts at times. Chambers


    Mon     Tue     Wed     Thu     Fri     Sat     Sun
BIL 043/066 044/067 046/069 047/069 048/070 049/071 049/074
    22/T    23/T    33/T    32/T    34/T    43/T    22/T
LVM 039/059 038/061 040/065 040/065 041/065 041/067 042/069
    23/T    34/T    44/T    35/T    54/T    43/T    33/T
HDN 041/070 041/070 045/071 048/071 049/072 049/074 050/076
    22/T    22/T    33/T    33/T    33/T    33/T    22/T
MLS 046/071 046/072 050/072 050/073 050/072 051/075 053/077
    31/U    12/T    33/T    33/T    23/T    32/T    22/T
4BQ 043/072 041/072 046/070 046/070 048/070 048/073 051/074
    31/U    12/T    44/T    33/T    33/T    32/T    22/T
BHK 042/071 042/073 046/069 047/070 047/069 048/072 051/076
    31/U    12/T    45/T    33/T    33/T    32/T    22/T
SHR 038/067 039/067 042/065 042/066 044/066 045/069 047/071
    31/B    12/T    33/T    33/T    33/T    33/T    22/T




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