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Area forecast discussion 
National Weather Service Boise Idaho
849 PM MDT Wednesday Aug 20 2014

Discussion...an upper level short wave located over western
Washington as of 830 PM MDT will move toward the area tonight.
This is helping to keep convection going...and will continue to do
so for several more hours. The influence of this wave is being
felt more strongly to our north...and we believe it is still
possible to have increased convection over eastern Oregon and SW
Idaho in advance of its arrival. We updated back around 6 PM and
increased probability of precipitation because of this feature. No additional changes are
expected.

&&

Aviation...VFR..isolated showers and thunderstorms except showers
scattered east of a line from kmyl to kboi to klkn. After
08z...isolated thunderstorms and showers east of a line from kbke to
kboi to klkn. Surface winds northwest 5 to 10 kts...except in
vicinity of thunderstorms where gusts to 35 knots possible. Winds aloft
west 20 kts at 10k feet mean sea level.

&&

Previous discussion...
short term...tonight through Friday...thunderstorms near the Idaho-
Nevada border and across central Idaho are tapping very moist air
/up to 1 inch precipitable water south/ while isolated cells west to near Vale
are near the cold frontal lift and precipitable water near 0.75 inches. Lapse
rates 850-700 mb are quite unstable around 9.8c/km but bulk shear
is weak 20kts or less. So gusty downdraft winds and brief heavy
rain look to be the main threat for this evening. Upper level
cooling and partial clearing tonight will decrease precipitation chances
west to east. Thursday the surface low stalls around south central
Idaho and Friday lifts to central Idaho...so lingering precipitation
chances mainly across the east and southeast...and moderate west to northwest
winds over Oregon with lesser flow near the low are expected over
Idaho. Upper level trough over the NE Gulf of Alaska will carve out a
cool upper low center over the pacnw Thursday through Friday for a
round of below normal high temperatures.

Long term...Friday night through Wednesday...unseasonably cool
upper level trough will slowly move across the forecast area through
Sunday. The position of the low will favor precipitation mainly over
the central Idaho mountains with southeast Oregon and the rest of
southwest Idaho mostly dry. Temperatures will be up to 10 degrees
below normal through Monday. By Tuesday the trough will begin to
shift eastward putting the area under a dry northwesterly flow with
warming temperatures as a ridge begins to build off the Pacific
northwest coast.

&&

Boi watches/warnings/advisories...
Idaho...none.
Or...none.

&&

$$

Weather.Gov/Boise

Discussion...snow pellets
aviation.....Rd
previous short term...vm
previous long term....ka/ab

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