Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Boise Idaho
828 PM MDT sun Oct 4 2015
Discussion...wind gusts across Oregon blm lands and southern Idaho
Highlands which were in the 15-25 miles per hour range have dropped of into
the teens and will continue to weaken. Metar Airport locations
winds were 10 miles per hour or less...as of 8 PM and will be light diurnal
tonight and Monday. Gusty winds were due to the upper low to our
S which will continue to pull away so less wind expected Monday.
Highs in the middle 60s to lower 70s today will warm through Tuesday
but well shy of records /which range from around 80 at McCall to
the lower 90s at Mountain Home and Vale. 00z NAM moisture across S
central Idaho is above 10k feet mean sea level...there is weak lift late Monday
afternoon and precipitable water is slightly above normal. So a stray shower
may make it north of the Nevada border or develop over the highest terrain
of the Boise Mountains. Otherwise dry and clear or mostly clear
tonight through Monday.
Aviation...VFR. Clear skies except for isolated showers and
thunderstorms Monday afternoon and evening south of the Snake River
Valley and along the Oregon-Nevada border. Surface winds... variable
less than 10 kts. Winds aloft...variable 10 kts or less up through
10k feet mean sea level.
short term...tonight through Tuesday...one large upper level low
is well to our south over Southern California...while a weaker upper level
trough is located over Montana. We are in the longwave trough
axis...but in a dry and inactive portion. Therefore...we will
remain in a generally dry pattern with mostly clear skies in the
short term. The large upper low to the south will move slowly east
to near Las Vegas by the end of Tuesday as a ridge slowly builds into
the Pacific northwest. About the only chance we have for showers/storms will
be along the Nevada border Monday afternoon/evening and again Tuesday
afternoon...although we cannot rule out a shower over the higher
terrain of the Boise Mountains during the same times. Winds will be
light as the surface gradient remains weak. Temperatures will warm to
above normal tomorrow...and add a few more degrees on for Tuesday.
Long term...Tuesday night through Friday...Ridge of high
pressure will be over the intermountain west through the end of
the week. Wednesday the ridge will start out flat over the Pacific
northwest as a weak disturbance moves east across southern Canada.
Thursday and Friday the ridge will reamplify over the area but
models continue to have problems in placement of precipitation.
Models hinting at weak systems moving through the flow that could
bring precipitation to the northern zones. With uncertainty in the
models will keep the forecast mostly dry but will keep the slight
chance probability of precipitation over northern zones for Wednesday night and Thursday.
Temperatures through the end of the week will average 7-10 degrees
Friday night through Sunday....both the GFS and European model (ecmwf) continue to
show the progression of the next upper level system into our County Warning Area
during this period. Friday night ridging starts to break down. GFS
holds this ridge over top of US a little longer than the
European model (ecmwf)...however both models do indicate this next system making its
presence known by Sunday morning in northern Harney and Baker
counties. Probability of precipitation are looking to increase Sunday afternoon. By Sunday
evening model confidence is too low so kept probability of precipitation a little closer to
climatology. Temperatures will remain above normal both Saturday and
Sunday with Saturday being the warmest of the two.
previous short term...snow pellets
previous long term....ja/jc