Weather Service Report

FXUS65 KBYZ 160251

Area Forecast Discussion...Updated
National Weather Service Billings MT 
851 PM MDT Sun Jul 15 2018


Main update was to shrink pops a bit towards the southern
mountains and foothills this evening and overnight. Shortwave
energy was tracking a bit farther south with isolated showers and
thunderstorms farther south as a result. Have also adjusted sky
cover and temperatures to current trends. The rest of the forecast
remains on track and the previous forecast discussion and an
updated aviation discussion are below. STP


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

Surface high pressure currently sitting over eastern Montana 
providing a cooler day today compared to the last couple. Low 
level flow was easterly and this providing a bit of upslope, and 
thus seeing some cumulus develop along the foothills and over the 
mountains. Weak shortwave energy progged across southern Montana 
and northern Wyoming this evening, and this should be enough to 
generate a few showers and thunderstorms. Both global and high 
resolution models were consistent in confining the activity over 
the mountains and foothills, with a hint at some spreading out 
into far southeast Montana.

Monday will be a little warmer. The surface high slides southeast
and brings the low level flow back to the southeast, allowing for
return moisture. Precipitable waters climb above an inch in the 
southeast, with nearly an inch everywhere else. A shortwave trough
kicks out of Oregon and slowly enters western Montana, with the 
leading edge nosing into western and southern zones. This will 
initiate a good chance of showers and thunderstorms as this 
system moves across. Highest PoPs on Monday will be over western 
and southern zones, with PoPs spreading east Monday night.

The system kicks into central Montana Tuesday, and this will 
spread the most likely locations for convection into southeast 
Montana. The ECMWF was a little slower and this would pull the 
good chance of convection into the central zones. PWATs will rise 
to around an inch and a third over southeast Montana, with weak 
shear. Capes should be able to reach around 1000 j/kg Tuesday 
afternoon and evening. Am expected much better coverage of 
convection across central and eastern zones, with pulsing storms. 
Shear is projected to be weak, so should not see organized strong 
storms. Will however, have the ability to see some pulsing hail. 
Storms will be slowing moving, and with high PWATs, the risk of 
heavy rain is real. Will continue to advertise that in a HWO and 
weather story. TWH

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

Extended forecast period appears warm and dry throughout, with
exception of occasional isolated showers/thunder in high terrain.
Upper level ridging will prevail through the bulk of the period. 
Temps will be a few degrees above normal, with highs in the low 
90s through the period.

The only chance for weather at this time appears to be tied to
exiting upper level trof, with lingering showers and general 
thunderstorms over eastern MT. Meanwhile, the rest of the region 
will see a drying trend as the upper ridge builds in.

There is some indication of the ridge breaking down at the end of
the period, with a cold front crossing the region on Sunday. This
FROPA appears mainly dry, and has been pushed further down the 
line in last few model runs. Therefore have continued with
inherited mainly dry forecast. AAG



VFR will dominate overnight into Monday morning. An isolated
shower or thunderstorm possible along the WY/MT border. borsum 



    Mon     Tue     Wed     Thu     Fri     Sat     Sun     
BIL 060/087 063/084 061/092 062/091 061/092 063/092 062/092
    12/T    34/T    51/U    10/U    11/U    10/U    10/U
LVM 055/083 056/082 054/088 052/088 051/090 054/090 053/090
    13/T    45/T    20/U    10/U    11/U    10/U    10/U
HDN 059/089 062/086 059/092 060/091 060/093 062/092 063/092
    12/T    35/T    51/U    10/U    11/U    10/U    00/U
MLS 059/088 063/087 063/088 062/090 062/090 065/092 065/092
    00/U    13/T    61/B    10/U    01/U    10/U    00/U
4BQ 062/088 063/086 061/087 061/090 060/091 064/093 064/093
    21/U    25/T    61/B    10/U    01/U    10/U    10/U
BHK 057/084 057/084 061/082 059/087 058/086 061/089 061/089
    01/U    01/B    52/W    10/U    01/U    11/U    10/U
SHR 057/086 057/084 056/090 057/090 054/092 058/093 058/093
    23/T    45/T    41/U    10/U    11/U    10/U    10/U





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