Area forecast discussion
National Weather Service Billings Montana
309 PM MDT Wednesday Jun 19 2013
Short term...valid for Thursday and Friday...
Potential for severe thunderstorms this afternoon and evening
will be more widespread than previously thought as dewpoints were
in the 50s over much of the area. Shear will increase from west to east
across the area this afternoon and evening. Dewpoints in the 50s
were helping to feed high convective available potential energy...especially in the east. Surface
convective available potential energy ranged from 500 to 2000 j/kg from west to east across the area at
19z. Will have plenty of lift from difluent flow aloft...cold
front moving through west Montana...and strong shortwave seen in water
vapor imagery...rotating around the base of the negatively tilted
trough over the Pacific northwest. A severe threat will progress from west
to east across the region through the evening as dynamics move east.
Only hindrance to severe weather will be where the S to SW flow
will advect drier air into the region. Gusty winds will be
possible in these areas...currently expected from kbil S and
east...but will need to watch this evolving situation carefully this
afternoon. Expect severe weather to exit the area after 06z as
cold front moves east. BUFKIT soundings had a strong wind shift
behind the front with wind speeds well into the 30s.
Upper low will rotate slowly into the region Thursday through Friday
night. Downslope flow will compete with upper dynamics for
precipitation chances on Thursday. Continued the low chances over and
near the mountains with just a slight mention of thunder as
airmass will be much more stable than today/S airmass. A secondary
cold front will pass through the area Thursday night which will bring
scattered showers to the area. Models differed on placement of
precipitation Friday through Friday night. Dynamics aloft and inverted
surface trough over the east will bring a chance of showers and
thunderstorms to the area. Leaned on the sref for pop forecast.
Temperatures will be around seasonable values Thursday and Friday. Arthur
long term...valid for Sat...sun...Mon...Tue...Wed...
Extended models in fairly good agreement so did not make any
significant changes with this forecast issuance. Large upper low
currently over the Pacific northwest will slowly shift east across
the Canadian border Saturday and Saturday night and be situated
just north of North Dakota during the day Sunday. At the same
time...a few disturbances will get pulled northeast with a
southwest flow aloft bringing very good chances for showers and
thunderstorms to the entire forecast area Saturday and Saturday
night. Best chances will be near the Dakota borders where chances
have been increased to likely Saturday into Saturday night. The
upper low shifts further east Sunday leaving our forecast area in
a broad southwest flow aloft. At this time...no big disturbances
look to influence our area resulting in mainly dry conditions with
possibly an isolated shower/thunderstorm through the period.
Temperatures will be at or slightly below normal for the weekend
before warming to above normal readings by early to middle next week.
Hooley
&&
Aviation...
Scattered thunderstorms will develop along and west of a kshr-
kbil line this afternoon continuing into the evening hours. Some
thunderstorms may be severe with large hail and wind gusts around
55kts. Elsewhere...skies will remain mostly clear. VFR conditions
will prevail but expect IFR to LIFR conditions in and near
thunderstorm activity. A cold front will move across the forecast
area this evening into the overnight hours bringing gusty westerly
winds. Hooley
&&
Preliminary point temp/pops...
Thursday Friday Sat sun Monday Tuesday Wednesday
-----------------------------------------------------------
bil 051/077 052/073 052/069 051/078 054/082 058/082 059/082
31/u 33/T 34/T 41/b 11/b 22/T 21/u
lvm 042/070 041/072 042/067 046/079 046/082 051/081 054/085
33/T 34/T 35/T 40/b 22/T 22/T 21/u
hdn 051/078 052/074 050/072 050/078 052/082 054/083 058/083
20/u 33/T 24/T 41/b 11/b 22/T 21/u
mls 058/078 055/077 056/076 055/080 056/083 059/083 061/085
20/u 34/T 34/T 42/T 11/b 22/T 21/b
4bq 055/080 055/076 054/075 053/079 054/084 057/084 059/086
20/u 34/T 46/T 42/T 11/b 22/T 21/u
bhk 059/077 054/078 055/074 054/076 054/084 059/082 062/085
30/u 25/T 56/T 42/T 22/T 22/T 21/u
shr 048/078 048/075 048/073 047/076 049/081 052/082 053/084
21/u 24/T 34/T 41/b 11/b 22/T 21/u
&&
Byz watches/warnings/advisories...
Montana...none.
Wyoming...none.
&&
$$
Weather.Gov/Billings
