Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Billings Montana
929 PM MST Wednesday Jan 28 2015
weak shortwave continues to produce a few echoes in our central
parts...and will sustain flurries/sprinkles through midnight...
with descent spreading in thereafter ending any precipitation chances.
There was a brief period of upslope enhancement along the southeast edge
of the beartooth foothills earlier this evening...and in fact we
received a spotter report of about an inch of snow in Red Lodge.
Precipitation is much lighter now. Area of stratus continues to clip our
far east near Baker and Ekalaka. Soundings may be a bit overdone
with the low level moisture based on local metars...but given the
boundary layer moisture and instability with temperatures no colder than
-8c...feel some light freezing drizzle is still a possibility
mainly over the hills of Fallon and northern Carter counties where
the terrain will be closer to the cloud bases. Only other issue is
fog potential. Dew pt depressions at jdn and mls already down to
2-3f...with clear skies and decreasing winds expected through the
night. Hrrr is pinging northern Rosebud with fog tonight...and
this area just west of the currently observed west-northwest winds makes
sense. Could see some valley fog develop near or maybe just east
of Billings too... with stronger drainage expected to hold off until
around 15z tomorrow. Have expanded coverage of patchy fog westward
to include these areas. Jkl
Short term...valid for Thursday and Friday...
Short wave that brought some snow to the high country last night
has excited the region...but cold air is being pulled down from
the north behind it. Associated stratus on visible satellite
imagery was moving into our northern zones at midday and is
expected to spread across much of our central/eastern zones by
evening. Cross sections indicate the stratus will linger through
the night before gradually dissipating early Thursday from west to
east. There will be a typical trade-off between cold air advection and lingering
stratus tonight to make overnight lows tricky in our east...but
feel cold air advection will generally win out and have stuck close to inherited
forecasts/guidance. There will certainly be a cooler air mass in
place over US tomorrow...but nothing drastic and we should briefly
see some sunshine around midday keeping US on the mild side
compared to seasonal averages.
The overall flow pattern is still anticyclonic Thursday with some
weak quasi low pressure lingering over the Great Basin.
However...we begin to transition to a brisk northwest flow aloft with
short wave energy out of Canada tracking through NE Montana by
late Friday night. This may open the door to unsettled and much
cooler weather for the weekend. Please see the long term
discussion below for more details. Bt
Long term...valid for Sat...sun...Mon...Tue...Wed...
A change in the pattern to colder weather with periods of snow
appears likely for the extended period beginning on Sat. While
models agreed with this overall scenario...the pattern details
differed between them.
Jet energy will dive southeast into the area on Sat accompanied by a
shortwave and backdoor cold front. GFS was the most aggressive
model in bringing quantitative precipitation forecast SW into the area compared to the other
models. The Canadian and European model (ecmwf) bring the quantitative precipitation forecast in on Sat night.
Based on the timing uncertainty...slowed down arrival of higher
probability of precipitation in the SW part of the area on Sat...and went with mainly
chance probability of precipitation Sat night.
Flow then transitions into a flat northwest flow on the models for sun
into Tuesday. Models had Pacific moisture overrunning the surface
boundary on sun but differed in their quantitative precipitation forecast depictions. Weak
shortwave energy reinforces the cold air over the region on Monday
and Tuesday while Pacific moisture continues to overrun the boundary.
Blended probability of precipitation for this time frame with the superblend guidance as
the models differed in precipitation details. Inherited Tuesday probability of precipitation
Energy then wraps around the Hudson Bay low for the end
of the period. This energy will reinforce the cold airmass over
the area. Will continue to use a model blend for probability of precipitation.
Temperature profiles also differed between the models for much of
the period so went with superblend. Result was periods of
seasonal and below normal temperatures. Arthur
Low clouds and patchy fog will result in MVFR/IFR conditions east
of kbil through early Thursday morning. Some freezing drizzle is
also possible around kbhk. Area mountains will be obscured at
times. Elsewhere...VFR conditions will prevail under partly cloudy
Preliminary point temp/pops...
Thursday Friday Sat sun Monday Tuesday Wednesday
bil 028/048 030/050 028/038 019/030 022/041 027/039 019/032
10/u 00/u 03/west 33/j 33/west 32/west 23/j
lvm 028/048 027/048 024/040 020/036 025/045 029/043 024/038
00/u 00/u 03/west 23/j 43/west 32/west 23/west
hdn 022/046 025/048 023/035 015/029 017/038 021/035 015/030
10/u 00/u 03/west 32/j 33/j 33/j 23/j
mls 025/044 027/044 024/032 011/023 014/032 017/028 011/025
10/u 00/u 04/j 22/j 22/j 23/j 22/j
4bq 025/048 027/049 025/037 015/029 018/039 021/035 016/030
00/u 00/u 03/west 32/j 22/west 23/j 22/j
bhk 025/040 024/043 021/028 007/020 009/029 015/027 009/023
10/b 00/u 04/j 32/j 22/j 23/j 22/j
shr 022/044 020/045 020/037 015/029 016/040 020/038 017/032
10/u 00/u 03/west 32/j 22/west 32/j 23/j