Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Boise Idaho
836 PM MDT Tuesday may 5 2015
Discussion...very dry air circulating around upper low in northwestern
Washington this evening. The dry air is coming inland across Oregon and
into western Idaho. Dew points in eastern Oregon have dipped below 10f
this evening and were still dropping in western Idaho. The upper
low will go straight south along 120w Wednesday...I.E. Along the
east slopes of the Cascades...and continue south through calif
to near l.A. Thursday...then turn eastward across southern Nevada and Arizona.
Circulation around the low will bring moisture into our southern zones
Wednesday night through Friday and our forecast has Middle-Range probability of precipitation
for it. Wednesday looks as windy as today but will also be several
degrees cooler. A little warmer and less windy Thursday and Friday.
All this is already in the current forecast.
Aviation...VFR. Surface winds generally northwesterly 10-20kt
decreasing to 5-15kt after sunset then increasing to northwesterly-
northerly 15-25kt Wednesday afternoon. Winds aloft at 10k feet mean sea level...
variable 5-15kt becoming northerly 10-20kt Wednesday afternoon.
short term...tonight through Thursday...upper trough moving into
the Pacific northwest will split as energy drops along the Cascades into
California. The accompanying instability and dynamics will drive
another round of afternoon shower and thunderstorm development on
Wednesday over higher terrain of southeast Oregon and mountains of SW Idaho.
The low drops into central California by Thursday. This will shift focus
of precipitation to far southeast Oregon and higher terrain of SW Idaho
..south of the central mountains with little dynamical support much
of the snake plain remains dry through Thursday morning. There is
model agreement that energy circulating around the low will track
through far SW Idaho on Thursday increasing chances of precipitation at
all elevations. Southern zones will be better positioned for
thunderstorm development on Thursday with showers to the north.
Temperatures are at or slightly below normal both days.
Long term...Thursday night through Tuesday...we will begin the
period with the closed low southwest of the region...over California. It
will remain south of US as it slowly churns east...continuing to
bring showers and afternoon/evening thunderstorms mainly to
southwest Idaho...until a short wave ridge builds over the region
on Sunday...giving the region a brief dry period before the next
low moves into the Pacific northwest early next week. Temperatures
will be at or just above normal through the extended.
previous short term...dg
previous long term....ab