Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Billings Montana
909 am MDT Friday may 29 2015
most of the precipitation has ended across the Big Horn foothills
this morning. There are a few showers or mist occurring just west
of Billings. So overall...I reduced probability of precipitation quite a bit over the big
horns vicinity...but added a slight chance to Billings for those
few showers drifting in from the west. Reduced sky cover over
north central zones per satellite imagery and refined areas of
morning fog per surface observation. Bt
Short term...valid for today and Sat...
A relatively quiet and dry day is expected today before a chance
of storms returns along with much warmer weather on Saturday.
Today...some showers will linger near the foothills /especially in
the Sheridan area/ early this morning per recent radar trends and
rap simulations. Otherwise...by this afternoon we have only a low
chance of a shower or storm near the higher terrain as weak 500-mb
ridging occurs aloft and low-level drying stabilizes the air mass
across the plains. Highs today should be in the 60s f...but we did
weight the forecast slightly toward the cooler side of the multi-
model consensus given wet ground conditions and early-day cloud
cover. Extensive stratus formed over the area during the night and
observational trends as of 09 UTC and recent rap and hrrr model
simulations suggest the clouds will linger well into the morning
in many areas. Patchy fog is also in the forecast early this
morning given the moist near-surface layer.
Tonight...we have some low probability of precipitation in place near the higher terrain
this evening...and over western parts of south central Montana through
the night as flow aloft flattens a bit. The air mass will be drier
than it has recently and so temperatures should be a bit cooler as
well. In fact...forecast lows at Baker are in the upper 30s f.
Saturday into Saturday night...the air mass will warm considerably
and highs on Saturday will jump well into the 70s f in most places
per the 00 UTC multi-model consensus. The 00 UTC model suite is in
rather good agreement in calling for a shortwave trough to cross
the region from west to east...and southeast low-level flow looks
sufficient to push afternoon dewpoints into the upper 40s and even
near 50 f in many areas beneath middle-level lapse rates near 7 c/km.
This scenario will likely be sufficient for scattered showers and
thunderstorms...especially over south central Montana. Middle-level winds
will be stronger than they were this past week...with 0-6-km bulk
wind shear of 40-45 knots supportive of organized storms. However...
we are downplaying the risk of strong storms at this point due to
a lack of stronger instability. The 00 UTC NAM and GFS as well as
the last four runs of the sref suggest MLCAPE will only peak from
200 to 400 j/kg in most areas...which may not be enough to support
long-lived strong updrafts. Thus...while we do believe there will
be some showers and storms...the risk of severe storms currently
appears too low for US to do any special messaging like issuance
of a hazardous weather outlook. Schultz
Long term...valid for sun...Mon...Tue...Wed...Thu...
Still looking at an unsettled pattern for the extended...but
there was growing uncertainty in timing for any strong to severe
storms. Models and ensembles continued to be in good agreement
overall. The naefs showed high precipitable waters continuing over
the area through Monday.
Sun will feature zonal flow aloft with weak shortwaves in the
flow. Convection will form over the high terrain and move across
the plains. Cannot rule out the possibility of some strong to
severe storms based on the cape/shear on the sref and WRF.
However...the GFS did not have very strong cape and shear values.
Sun will be a warm day with temperatures reaching the 80s.
Shortwave ridging moves across the area on Monday followed by SW flow
ahead of the next Pacific low. Models spread convection over much
of the area. GFS showed increasing convective available potential energy and shear on Monday so will
have to watch for strong storms. Temperatures in the 80s will
continue over the area.
SW flow and shortwaves will be over the area Tuesday through Thursday ahead
of the Pacific low. However...noted the European model (ecmwf) has less energy over
the area than the GFS on Thursday. Continued convective chances through
this period along with a cooling trend. Unlike last night/S
runs...models did not look as certain for strong/severe storms for
Tuesday and Wednesday. Will need to keep an eye on this possibility with
future model runs. Unsettled weather will continue on Friday as
models try to close off the Pacific system in the vicinity of the
forecast area. Arthur
MVFR to LIFR ceilings and patchy fog continue across the region this
morning...but are improving from north to south. This trend should
continue through the rest of the day. A slight chances for showers
and afternoon thunderstorms remains for areas west and south of
kbil. Chances for showers and thunderstorms will continue into
this evening over area mountains...with obscurations through much
of the day. MVFR or lower conditions are possible with any showers
or storms. Otherwise...VFR will return to the area for the
afternoon and evening. Aag
Preliminary point temp/pops...
Today Sat sun Monday Tuesday Wednesday Thursday
bil 063 047/078 053/083 056/082 054/078 051/072 050/072
2/west 02/T 32/T 23/T 43/T 33/T 33/T
lvm 065 045/073 051/079 053/077 048/071 046/067 043/070
2/T 24/T 43/T 25/T 45/T 44/T 33/T
hdn 066 046/080 052/084 055/086 054/079 052/074 050/076
1/b 02/T 32/T 25/T 42/T 33/T 33/T
mls 063 045/077 053/081 058/085 057/078 054/073 052/074
0/u 02/T 42/T 23/T 43/T 43/T 23/T
4bq 062 044/076 054/081 057/084 057/078 054/073 051/074
0/b 01/b 22/T 22/T 32/T 44/T 33/T
bhk 060 039/068 046/077 053/082 054/076 051/073 049/073
0/b 01/north 42/T 22/T 32/T 44/T 33/T
shr 061 042/076 049/079 053/080 052/075 048/070 046/071
2/west 12/T 22/T 23/T 33/T 44/T 43/T