Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 131956

Area Forecast Discussion
National Weather Service Pocatello ID
156 PM MDT Fri Oct 13 2017

.SHORT TERM...Quick moving storm system has entered our area today
with brief periods of snow in the central Idaho mountains. Expect
this to become more widespread after 8 pm as a strong cold front
will rapidly pushed by (6 pm to 10 pm). Snowfall amounts in the
mountains could reach up to 4 inches while in the lower valley
locations through 6 am on Saturday could see a dusting to 3
inches. Prior to the cold front strong gradient winds in the upper
Snake Valley have prompted a dust advisory and expect to see
these conditions persist through sunset. Impacts along I15 north
of Idaho Falls and I84 Burley Interchange to the Idaho/Utah border
are possible. The storm will be short lived and be moving out of
Idaho between 6 am and noon on Saturday with breezing conditions
and clearing skies. Cold temperatures overnight expected into
Sunday. VP

.LONG TERM...Sunday night through next Friday. The first half of the
week will feature a building ridge of High Pressure across the Great
Basin. This is expected to bring increasingly warming temperatures
each day through Wednesday across SE Idaho. In fact, temperatures
may warm to near to above climatological averages by mid-week across
the region (and it`s been a while since we`ve been able to say that)
-- with high temperatures well into the 60s across the Snake Plain
 by Wednesday. This may even be conservative based on recent
 trends, which indicate a slower progression of an approaching
 Pacific trough for the second half of the week, which allows more
 time for a warming trend to develop. Current indications suggest
 precipitation associated with the next trough may not begin until
 late Thursday across the Central Mountains and will not
 overspread all of SE Idaho until Friday, and this trend is
 reflected in the latest forecast. There is still some
 disagreement in the timing of this trough, and there will
 probably remain some differences over upcoming forecast cycles,
 but model agreement is decent enough to nudge the forecast
 towards this slower arrival. Expect breezy to occasionally windy
 conditions to develop by Thursday as the trough draws nearer. AD


.AVIATION...Two major changes were made to the TAFs late this AM.
The first was to increase overnight winds into the 12G22+
category, especially between 03z-10z, at the Snake Plain
terminals. This is well- reflected in the GFS MOS and LAMP
guidance, and to a lesser degree, NAM guidance as well. These
enhanced/gusty winds are likely tied to the cold frontal
approach/passage, and may only last a few hours per terminal. The
second change was to delay heaviest precip and lowest cigs at
KDIJ, now really starting after 05Z. However, the ongoing TEMPO
group remains intact from 08Z-12Z, which still appears to be the
period of greatest concern for occasional IFR conditions.

Otherwise, only minor adjustments were made to best pin down
start/end times of precip and lowest ceilings tonight, and to nudge
wind expectations toward the latest guidance. Rain/snow showers
affecting the Central Mntns are expected to increase and spread E
and S this eve, then clear from NW to SE behind the cold front Sat
AM. MVFR cigs remain possible for a period early tonight at
KPIH/KIDA/KBYI, and late tonight into Sat AM at KDIJ. Vsbys at KDIJ
may drop to 4SM or lower if snow can set up over the airport,
especially in the TEMPO period. Forecast confidence for this system
is moderate, and as always, trends will be monitored this eve for
any needed amendments. Skies should begin to clear progressively
behind the front Sat AM across the region, but this should occur
close to the end of the current TAF period. - KSmith


.FIRE WEATHER...A low pressure trough with attending snow and lower
valley rain showers will advance through the region today exiting
east across the Wyoming border late Saturday morning. Accumulating
snowfall is expected within the mountains before drier conditions
work into the region under NW flow Saturday afternoon. Dry and
gradually warmer daytime temps are expected early next week before
the next Pacific storm system moves onshore Wednesday night and
Thursday for a wet and windy latter half of the week. Huston


Blowing Dust Advisory until 9 PM MDT this evening for IDZ020.


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