Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 222032
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
232 PM MDT SUN MAY 22 2016

.SHORT TERM...This afternoon through Wednesday. Showers and
isolated thunderstorms have developed once again this afternoon
as forcing from another disturbance rotating around the parent
closed low now centered over southern Alberta interacts with
diurnally-driven instability. Most of the activity has been in the
mountains and highlands, and this trend will continue into the
evening, with coverage remaining much more limited in the Snake
Plain. Instability is a little stronger today, but shear weaker
than previous days as stronger flow aloft has shifted east of the
area, but a few storms may briefly pulse up enough to produce
some small hail and gusty winds. Activity will dissipate after
sunset, with attention then turning to low temperatures and frost
potential again tonight. Lows this morning fell into the lower to
mid 30s across much of the Snake Plain, leading to patchy frost
although dewpoints/ground moisture appear to have stayed up enough
to minimize the coverage and duration of any frost. Similar
conditions are expected tonight, although it looks like we`ll have
less cloud cover over the Snake Plain, and dewpoints/ground moisture
will likely be a little lower due to the absence of widespread
rainfall in the Snake Plain today. This suggests slightly better
frost potential, and thus will issue a Frost Advisory for the
Snake Plain and Eastern Magic Valley to highlight this concern
since we`re in the midst of the growing season.

Upper-level troughing will continue to dominate the weather scene
through mid-week. The closed upper low currently centered over
southern Alberta will only edge slightly eastward over the next
few days, eventually weakening. Meanwhile the next upper jet
streak will dig down the West Coast, forming a new closed low
along the CA coast, which will help keep a longwave trough carved
out from the northern Rockies southwest across the Great Basin
and CA. Embedded shortwaves rippling through the trough, along
with diurnal destabilization, will keep shower and embedded
thunderstorm chances going through the period. Greatest coverage
will be during the afternoon and evening hours each day as
instability is maximized, with mountains/highland locations seeing
more widespread activity than lower elevations. Temperatures will
gradually moderate through mid-week, but still fall short of
average values for this time of year.

KB

.LONG TERM...Wednesday night through Sunday.
Model differences beginning to show up by next weekend but for the
most part the trend of unsettled weather should continue.   Expect a
continuation of mainly afternoon showers and thunderstorms with an
upper level trof in place Thursday.   AS this moves east the models
differ by the weekend with the GFS dropping strong closed low into
northern Oregon by Saturday afternoon while the European model
drives through an open trof with not as wet conditions next weekend.
Kept in at least a slight chance of precipitation through next
weekend with temperatures expected to be slightly below normal.
GK

&&

.AVIATION...Showers and isolated thunderstorms have developed this
afternoon again and have vicinity showers or thunder at all sites
with the best chance at SUN and BYI but IDA and PIH could also see a
showers overhead as well.   Expect it to remain VFR except right
under a shower for a brief time.   15 knot winds at BYI...IDA and
PIH should drop to 10 or less after sunset.   Expect afternoon
shower and thunderstorm development again on Monday.
GK

&&

.PIH Watches/Warnings/Advisories...
Frost Advisory from midnight tonight to 9 AM MDT Monday for
IDZ017-020-021.

Lake Wind Advisory until 6 PM MDT this evening for IDZ021.

&&

$$


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