Area Forecast Discussion
Issued by NWS Pocatello, ID

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256
FXUS65 KPIH 190856
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
256 AM MDT THU MAY 19 2016

.SHORT TERM...Today through Saturday night. A strong area of upper
level low pressure will wobble southward into Washington State by
this afternoon...with an associated cold front slated to slide
south-eastward across SE Idaho this afternoon. Showers and
thunderstorms, some strong to possibly severe, are expected to
develop along and ahead of the cold front, with activity first
developing across the Central Mountains shortly after sunrise. By
Noon, shower and thunderstorm initiation should be underway across
the Arco Desert south to the Utah border. By mid-afternoon...continued
south and east cold frontal progression will force showers and
thunderstorms across all but far SE Idaho. By this evening...the
majority of the activity will be confined to the Eastern
Highlands. Stout wind shear combined with favorable frontal and
jet dynamics will combine with a surge of enhanced atmospheric
moisture to support the shower and thunderstorm activity this
afternoon and eve from the Snake Plain south and east to the
Wyoming and Utah borders. Thunderstorms will have the potential to
produce strong wind gusts, hail, heavy rain and frequent
lightning. The overall thunderstorm coverage will be driven by the
amount of instability generation...which will be modulated by the
amount of sunshine in the pre-frontal environment. At this
time...it appears the most sunshine will occur from roughly the
Interstate 15 corridor east...thus the severe weather threat
increases as one heads eastward. This potential severe weather
threat will be somewhat different from the typical high desert SE
Idaho event which is typically dominated by mainly dry outflow
winds. Due to the presence of enhanced atmospheric moisture,
locally heavy rainfall potential is higher than during our typical
thunderstorm event. Thunderstorms will gradually end from west to
east during the post-sunset hours as the cold front marches into
Wyoming. Outside of thunderstorms, gusty south-southwest winds
will cause chop on area waterways...thus the Lake Wind Advisory
for American Falls Reservoir continues. Strong winds will also be
encountered across the south and east highlands
today...potentially creating some difficult travel.

The above-referenced upper low will meander into the Great Basin
Friday and Saturday...continuing the theme of unsettled weather. A
band of heavier showers with embedded thunder is becoming
increasingly likely on Friday from the Interstate 15 corridor
westward, so have increased precipitation totals in these areas.
Locally heavy rainfall will be possible with this activity.
Showers are expected to continue through Saturday night...most
numerous across the Central Mountains. Snow levels drop to around
7000 feet, with several inches of snow possible at mid and upper
slopes, including pass level. At this time, the best potential for
snowfall is Friday night into Saturday. AD/Hedges


.LONG TERM...Sunday through Thursday. A large upper trof will
dominate the Pac NW thru Tue...resulting in scattered showers and
isolated aftn tstms along with cool temps. The only real improvement
comes on Thu when upper ridging builds into the west. Still a threat
for widely scattered showers Thu aftn...but mainly in the mtns.
Temps also begin to moderate on Thu. Hedges


&&

.AVIATION...Showers and a few tstms will move into the region this
aftn with a cold front. Some tstms may produce gusty winds and hail
this aftn and early eve. Sct showers expected to continue thru
tonight. Low VFR cigs expected to prevail this aftn and eve with
ocnl MVFR cigs at KSUN this aftn. Hedges



&&

.PIH Watches/Warnings/Advisories...
Lake Wind Advisory from noon today to 7 PM MDT this evening for
IDZ021.

&&

$$



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