Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Boise Idaho
1002 am MDT Friday Oct 31 2014
Discussion...upper level trough moving onto the West Coast this
morning with a piece of energy splitting off towards California.
Expect increasing clouds today and another warm day especially in
southwest Idaho and areas east. Precipitation on track to reach
southeast Oregon zones later this afternoon and southwest Idaho
overnight. Trough will bring lower snow levels...cooler
temperatures...and widespread rain and mountain snow showers. No
updates to the forecast planned.
Aviation...VFR today across southeast Oregon and SW Idaho with increasing
and lowering ceilings from west to east. MVFR ceilings and
precipitation will develop over southeast Oregon after 00z this evening...
obscuring higher mountains lower ceilings and precipitation will develop
over SW Idaho Saturday afternoon. Gusty easterly surface winds today
will shift to the northwest in Oregon Saturday morning and during
the afternoon on Saturday.
Saturday night and Sunday...MVFR to IFR conditions in southeast Oregon and
the mountains of SW Idaho will obscure mountains Saturday night. Conditions
improve over southeast Oregon early Sunday and by Sunday afternoon in SW
Idaho. Gusty northwest winds 15 to 30 kts through Sunday.
short term...today through Saturday...big changes in store the
next couple of days...from mild and dry weather conditions
today...to showery...cool...and breezy conditions on Saturday. An
upper trough continues to dig just off the West Coast while a
high-amplitude upper ridge exists over the central U.S.
Our area is situated between these two features...with a
southwest flow aloft encompassing southeast Oregon and SW Idaho this
morning. A frontal band of precipitation resides to our
west...extending S-north across the western half of Oregon. This
frontal band will gradually shift eastward with showers spreading
into southeast Oregon this afternoon and evening. SW Idaho looks to
remain in the dry SW flow through this evening. Temperatures will
be mild once again today...although not quite as warm as
yesterday. A stacked low pressure system /surface-aloft/ will
develop and track across northern Nevada and southern Idaho Friday
night and Saturday. Showers will develop in SW Idaho while
continuing in southeast Oregon on Saturday as the low tracks
northeastward. A surface low will form in northern Nevada...and
strengthen as it moves into S-central Idaho Saturday afternoon.
This will induce a tight northwest-southeast across southeast Oregon where it will
become breezy to locally windy by the afternoon. Highest quantitative precipitation forecast
totals through Saturday will be in the Steens Mountain of southeast
Oregon where the amounts exceed an inch. Snow levels will remain
high enough to limit snow accumulations of 1-3 inches /except 6
inches or more in the Steens/ above 5000 feet...with the bulk of
the snow occurring on the western and colder side of the low.
Long term...Saturday night through Thursday...the upper level
trough exits to the east on Sunday with precipitation ending for
most of our County Warning Area by Sunday evening. Westerly flow aloft transports
more moisture inland starting Monday...bringing isolated to
scattered showers to our northern zones through Thursday. Forecast
confidence decreases after Wednesday as models fall out of
phase... but southeast Oregon and southwest Idaho are expected to
remain mostly dry. Sunday night will see the coldest temperatures
with readings falling below freezing at most locations. A warming
trend will return temperatures to near normal Tuesday and a few
degrees above normal Wednesday and Thursday.
previous short term...bw
previous long term....jt