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Area forecast discussion 
National Weather Service Pocatello Idaho
223 PM MDT Wednesday Aug 20 2014

Discussion...upper trough settling into pacnw. WV shows shortwave
ejecting through Montana and second shortwave digging southeast
from British Columbia Canada into Washington state. Ample moisture in place over
east Idaho with precipitable water values ranging from roughly .7 to near an inch.
Convection already ongoing over higher elevation areas with snake
plain generally dry so far this afternoon. Models slowly move
pacnw shortwave through Idaho overnight then drop another
shortwave right behind it. Convection should remain ongoing
overnight mainly higher elevation areas but will maintain
scattered probability of precipitation over snake plain as well. Models becoming more
persistent with dropping deeper shortwave into pacnw late
Thursday. Still seeing moisture dragged north through Great Basin
ahead of this feature so will maintain high probability of precipitation especially
eastern half of region. Upper low drops to eastern Washington/or during
the day Friday. Both NAM and GFS maintain deep convection across
east Idaho into Friday with precipitable water values staying above .75 and
nearing an inch in places. There is still some question as to how
far the dry air will penetrate into the region on relative dry
slots associated with minor features working around the low. Have
kept the lowest probability of precipitation on the western edges of the forecast area and
into portions of the snake plain but otherwise have continued
trend of nudging probability of precipitation upward and cooling off highs through the
period. GFS/NAM/ECMWF all support trough axis shifting across east
Idaho during the daty Saturday but all also continue wrap around
moisture sneaking into the central mountains. Upper low ejects
northeast into Montana Sunday night. East Idaho remains under
influence of trough with second shortwave dropping through pacnw
Sunday into Monday. Have made only very minor adjustments through
the extended period...keeping east Idaho mildly unsettled and
reamining cool. Dmh


Aviation...showers and storms will remain across the area through
tomorrow. VFR weather will be the norm except for periods of heavier
rainfall...which may cause temporary reductions in visibility. Winds
with storms and outflow boundaries may exceed 30kts. Keyes


Fire weather...showers and isolated/widely scattered thunderstorms
will continue through at least Friday. We will see locally heavy
rain and wetting rains with stronger storms across the area. At the
risk of sounding like a broken record...the models are still not
anywhere close to showing a strong trend one way or another
especially for the weekend and early next week. The models are now
showing the main low right over Idaho on Saturday...with a bit of a
break Sunday before the next storm arrives later Monday. Right
now...we didn't really change the previous forecast but will need to
especially on Saturday if the low passes overhead. This would be dry
a big dry slot and gusty winds for the snake plain and south-Central
Highlands. It does look like though we will see drier weather by
midweek as the pattern is trying to transition to more a ridge over
the west. Keyes


Pih watches/warnings/advisories...


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