Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Glasgow Montana
826 PM MDT Tuesday Jul 29 2014
Short term...for northeast Montana...tonight through Thursday...
adjusted winds using the latest high-resolution model guidance and
nudged upward in a few places where readings have been a bit
higher than expected. Otherwise forecast on track depicting a
quiet night under mainly clear skies and generally light easterly
Previous short term discussion...
mainly dry and warm conditions are expected to continue during
An upper ridge centered over the northern rockies will remain nearly
stationary through the period. Water vapor is showing a dry swath
running through northeast Montana but sandwiched between Pacific moisture
to our north and monsoonal moisture to our south. A large
circulation...centered in Utah this morning...is moving east. This
should not allow a repeat performance of showers/thunderstorms that we had
last night to occur tonight.
Models are pointing toward increasing instability in our NE zones
for tomorrow evening. The European model (ecmwf) model showed this best with some
light quantitative precipitation forecast. Will go with slight chance probability of precipitation for now.
Otherwise...hot conditions continue as 850 mb temperatures warm into the
20s*c by Thursday. Jamba
Long term...Thursday night through Tuesday...
As the long term forecast period represents the nearest chance of
any precipitation at all...felt it was best to update this portion
of the forecast with the latest model consensus data.
Although...some model consensus for some periods were difficult to
come by. Through Monday...adjusted the forecast grids to add a bit
more detail regarding the expected probability of precipitation.
Generally...synoptically speaking...the western states ridge of
high pressure will be undercut by a number of subtle short-wave
disturbances. The first of which will sneak into the ridge through
the Sierra Nevada and inter-mountain west region on Friday but is
only expected to bring accumulating precipitation for the periphery of
our County Warning Area. Other short-wave disturbances will approach from the
Pacific northwest...in effect flattening the high pressure ridge
from the north through the weekend. This period may bring better
chances for precipitation...but models disagree too much to allow anything
more than a slight chance confidence at this time. Bmickelson
Previous long term discussion...the long wave upper level pattern
of ridging over the west and a trough over the east continues
through the extended period. However there will be a generally
change as the trough weakens and moves farther east and the ridge
expands to the east. Monsoonal moisture riding the ridge will
bring an increasing chance for showers and thunderstorms beginning
Saturday that will last into next week.
Several embedded disturbances will ride through the ridge. Most
will split moisture north or south of northeast Montana but a
front slipping south into the area late Saturday could produce
showers and thunder. Convective parameters are not particularly
strong so the chance for severe will not be pronounced. Went ahead
and continued the chance for probability of precipitation through most of the period.
However there does not appear to be any large sweeping waves.
Moisture will be intermittent and temperatures will continue to be
seasonal. Models agree generally but not in detail. So will leave
that aspect on the vague side. Scattered
under a ridge of high pressure...VFR conditions will prevail for
all taf sites throughout the entire taf cycle. Skies are expected
to remain clear. Winds will be generally light out of the east or
northeast through the overnight hours but may pick up to near 10
kts at times. Bmickelson/maliawco