Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Billings Montana
234 am MDT Tuesday Jul 22 2014
Short term...valid for today and Wednesday...
Weak shortwave energy continues to lift through a relatively moist
and unstable west-southwest flow aloft...and per latest rap 500 mb analysis our
heights have not yet begun to rise. At 2 am there exists a few
light showers in our County Warning Area but there is more upstream from south
central Montana to northern Nevada. Height rises will commence later today
but in the meantime areas of pv interacting with precipitable waters on the
order of an inch should be enough for isolated showers/thunderstorms across
much of the area today...and cannot discount some afternoon development
as middle level cap will be slow to develop. Feel that by late afternoon
or early evening the pv will have lifted north and most shower
activity will end. Temperatures today will be close to normal with highs
in the middle 80s to lower 90s.
Most important issue to address today exists in our east. Slower
onset of height rises will result in a slight risk of severe
storms from Miles City to Broadus east. Ascent will come in the
form of weak shortwave energy along a middle level warm front...and
a low level jet by evening...with 1000+ j/kg of cape and 0-6km
bulk shear on the order of 50 kts. Hail and to a lesser degree
wind will be the primary threats. Low level southeasterly flow
will keep the high precipitable water air in place...so heavy rain is also a
possibility. Will highlight the risk for severe weather for this
afternoon and early evening in our east in the hwo/graphic.
Ridge will strengthen tonight and Wednesday with heights expected
to climb into the 590s...corresponding with 700mb temperatures to near
+16c. This tongue of very warm middle level air and lack of
significant forcing will limit our convective potential
considerably. Instability and shear profiles will be impressive
close to the Dakotas border on Wednesday with strong southeasterly surface flow
developing...so if a storm is able to develop it will have a very
favorable environment to work with. Will keep with isolated thunderstorms
mentioned in our east. Our central and west parts will be much
drier with deeper mixing. Have removed mention of thunderstorms for most
of this area but kept isolated probability of precipitation in our northwest...closer to cooler middle
level temperatures and shortwave energy in western Montana. Could see some
ridge runner convection across northern Montana Wednesday night...but
feel this will stay north of our County Warning Area.
As for temperatures...Wednesday should be the warmest day yet of
2014 for most of our County Warning Area. Given the 700mb temperatures expected we should
see some areas reach the 100 degree mark...perhaps Billings. Have
raised temperatures a few degrees both Wednesday and Wednesday night.
The record high of 101f may be approached at Livingston...
especially if SW winds mix out. Records at Billings...Miles City
and Sheridan appear too high to be reached on Wednesday.
Of course...the hot weather will continue to work on our drying
fuels...setting the stage for a potentially critical fire weather
day by Thursday.
Long term...valid for Thursday...Fri...Sat...sun...Mon...
Thursday still shaping up for a possible critical fire weather day
as a deep trough and associated closed low aloft crash through the
high pressure ridge that will be over the area. Models consistency
remains very good with confidence continuing to increase with this
system. 850 mb temperatures are expected to range from +28c to 30c
across the forecast area. Strong compressional heating will take
place ahead of a cold front that will move through during the late
afternoon hours. GFS soundings continue to indicate mixing up to
near 500 mb. This will cause temperatures over the central and
eastern zones to climb to near 100 degrees at a few locations.
Gusty winds developing with the frontal passage and this combined
with humidities in the teens...will create dangerous fire weather
conditions. Zonal flow setting up Friday for dry and cooler
weather. Dry weather and near to slightly above seasonal
temperatures will continue through early next week as another
ridge of high pressure builds over the northern plains. Richmond
Isolated showers and thunderstorms will develop over the area
today. MVFR conditions can be expected in or near any storms.
There is a threat of severe thunderstorms east of a line from
Miles City to Broadus this afternoon and evening. Large hail
and strong winds will be the primary threat with these storms.
Preliminary point temp/pops...
Today Wednesday Thursday Friday Sat sun Monday
bil 090 063/098 066/098 057/085 057/085 058/087 059/090
2/T 11/u 11/north 11/u 11/u 11/u 11/u
lvm 090 055/099 056/091 049/083 049/083 049/088 051/090
2/T 21/b 11/north 10/u 01/u 11/u 11/u
hdn 092 059/100 062/101 057/086 056/086 057/088 058/091
2/T 11/u 11/g 11/u 11/u 11/u 11/u
mls 090 065/098 067/097 059/085 058/085 059/086 059/088
3/T 22/T 21/u 11/u 11/north 11/u 11/u
4bq 090 061/098 064/100 058/085 058/085 058/085 058/088
3/T 22/T 21/u 11/u 11/u 11/u 11/u
bhk 086 060/091 062/096 057/083 053/083 054/083 054/084
4/T 32/T 22/T 21/u 11/north 11/u 11/u
shr 090 057/098 059/098 053/084 053/084 053/085 054/087
2/T 11/u 11/u 11/u 11/u 11/u 11/u