Scientific Forecaster Discussion

Return to Local Conditions & Forecast
Area forecast discussion 
National Weather Service Boise Idaho
246 PM MDT Wednesday Apr 23 2014

Short term...tonight through Friday...a weak short wave trough
along with marginal instability was allowing for scattered light
valley rain and mountain snow showers to initiate this afternoon.
Most of the activity was located in the north...but radar imagery
was depicting showers south to the Idaho/Nevada border. The activity will
weaken after sunset as we lose daytime heating and the wave passes
by to the east. Next and more significant system will be the
upper trough which is still strengthening in the North
Pacific/Gulf of Alaska. Precipitation is already spreading into
the pacnw ahead of it this afternoon...and will gradually work
eastward into southeast Oregon and SW Idaho late tonight through Thursday
morning. Snow levels will start out at around 5000 feet then rise
to around 6000 feet later Thursday. Although the instability is
marginal in the afternoon...still looking for a slight chance of
thunderstorms in portions of southeast Oregon/SW Idaho. Upper trough
will continue to work toward the West Coast Thursday night and
Friday. Ahead of it...the moist southwest flow will keep showers
going across the region. Total liquid precipitation amounts of up
to a half inch in the valleys and a half to one inch in the
mountains are expected. Snow will accumulate in the
mountains...mainly above 6000 feet. Temperatures will remain below

Long term...Friday night through Wednesday...models remain in
good agreement with a cool unsettled pattern through the weekend
and into early next week. Precipitation will be on the decrease
over the area Saturday afternoon as a splitting upper level trough
moves to the east. Eastern Oregon and southwest Idaho south of the
Snake River may see a brief break in precipitation Saturday night
as the southern section of the trough continues to move east while
the slower northern section of the trough remains over northern
Idaho for chance probability of precipitation. Sunday a weaker through will move through
the flow that will help push the previous trough over northern
Idaho to the east and will spread another round of precipitation
over all forecast zones for Sunday. Sunday night precipitation
will move to the east as a ridge of high pressure builds along the
West Coast. Dry conditions over the region Monday through
Wednesday as the ridge continues to strengthen. Models begin to
diverge by Tuesday on how strong the upper level ridge will get so
there are differences on how warm temperatures will be by
Wednesday. For now will forecast high temperatures on Wednesday
around 6 degrees above normal...but if the European model (ecmwf) solution is
correct could see even warmer temperatures.


Aviation...widely scattered showers this evening with isolated
MVFR conditions and mountain obscuration. Warm front will be
moving north over the forecast area tonight with widespread
precipitation moving into the region after 06z. As precipitation
moves over the region mountains will become obscured with areas of
MVFR and local IFR conditions. Snow levels at or above 4500 feet mean sea level.
Surface winds tonight will be southeast to southwest 5-15 knots.
Winds aloft will be southwest to west around 30 knots up through
10k feet mean sea level.


Boi watches/warnings/advisories...




long term....ja/wh