Area Forecast Discussion
Issued by NWS Pocatello, ID
FXUS65 KPIH 312018
Area Forecast Discussion
National Weather Service Pocatello ID
218 PM MDT WED AUG 31 2016
.Discussion...Low pressure trough will be moving inland tonight
through Friday. Several surface waves will develop on the leading
edge of the trough providing breeze afternoon winds Thursday and the
strongest winds on Friday. A Lake wind Advisory may be issued for
American Falls on Friday. The 12z model runs have backed off a
little on winds for Friday, just enough to make it uncertain if a
wind advisory will be needed. Satellite imagery this afternoon
indicates some destabilization in NE Nevada up through about Carey.
Expect some convection to develop the next couple of hours and
gradually move east tonight. Thursday morning a new surface low
generates and propagates northeast through the Snake Plain during
the the day. Isolated thunderstorms expected in the Snake Plain and
Eastern Highlands with this wave. Rather dry on Friday, but with
cooler temperatures. Winds should be the biggest problem. The
extended model continue to keep us under a broad low pressure trough
for the next several days. Multiple embedded disturbance, one Sunday
night/Monday, another Tuesday, followed by one Thursday. Each of
these seem to track across the pan handle more than southern Idaho
making it difficult to put high pops and rains in the forecast on
any one day. At least temperatures will be closer to normal, if not
a little below normal. RS
.AVIATION...Increasing winds this afternoon from the southwest to
south-southwest will near 12 to 15 kts with gusts to 22 kts.
Improving winds are expected between 03z and 06z below 10 kts. Today
will generally be shower activity at KSUN and KBYI with only
marginal instability across the region. Beginning late tomorrow
morning however, increased chances for isolated thunderstorms are
expected at all airport locations, a trend which will persist during
the day. Primary threats will include gustier winds and briefly
reduced visibility with thunderstorms passing through on station.
.FIRE WEATHER...Red Flag Warnings remain in effect through Thursday
evening for zones 422, 475, 476 for gusty winds and low relative
humidities. At 3 p.m., Red Flag Warnings will go into effect for
zone 413 and 427 for gusty winds and low relative humidities until
10 p.m. Scattered rain showers with a stray thunderstorm is also
possible during this time with showers likely to persist during the
overnight hours into Thursday morning. By 3 p.m. Thursday, a Fire
Weather Watch will go into effect for these same zones (413 and 427)
until 10 p.m. for outflow winds and scattered thunderstorms. Winds
may gust in excess of 40 mph during this time frame. Additionally,
zone 411 is under a Fire Weather Watch for outflow winds and
scattered thunderstorms from 3 p.m. to 10 p.m. Thursday.
The driving force behind these watches and warnings is a deep trough
of low pressure to our west. Waves of energy are pushing eastward
out ahead of the main wave, forecast to push southeastward in the
form of a cold front on Friday. These smaller, weaker waves are
providing increased cloud cover today and isolated showers.
Increased winds this afternoon associated with said has brought 20
mph wind gusts so far this morning across portions of the Upper
Snake Plain and Southern Highlands, a trend that will increase
upwards to 25 mph or so. Tomorrow afternoon shall be similar with
wind gusts to 30 to 35 mph in the Southern Highlands areas,
primarily across zone 413. Otherwise, gusts near 25 to 30 mph are
likely at their peak. Showers and thunderstorms are expected for
tomorrow as well, primarily for the Eastern and Southern Highlands
areas and in portions of the Snake Plain. CWR is between 5 and 15
percent and near 20 percent at ridge tops in these areas.
Friday`s cold front is on track to bring the strongest winds thus
far with gusts exceeding 40 mph expected in the Central Mountains
and Upper Snake Plain, and exceeding 30 mph across the Snake Plain
and areas southwards. Expect winds to start increasing early
morning, just after or near sunrise, and peak mid-afternoon. Little
to no precipitation will fall with this front. Red Flag Warnings are
likely to be issued on Friday for most Fire Weather Zones on Friday
in the coming day.
The weekend may bring some afternoon breezes to the Snake Plain
zones with isolated showers across the Highland locations
otherwise little concerns at this time. NP/Survick
Red Flag Warning until 10 PM MDT this evening for IDZ413-427.
Fire Weather Watch from Thursday afternoon through Thursday
evening for IDZ411-413-427.
Red Flag Warning until 10 PM MDT Thursday for IDZ422-475-476.