Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 110910

Area Forecast Discussion
National Weather Service Pocatello ID
210 AM MST Mon Dec 11 2017

.SHORT TERM...Today through Thursday. Inversion is still present
across the area courtesy of a strong, persistent upper ridge. Hard
to justify removing mention of patchy freezing fog, so made no
changes to weather today through Tuesday. We will see the ridge
influence weakening somewhat on Wednesday as it repositions itself
further west. This will allow some moisture to come through
eastern Idaho, which may give us a brief break from the fog. The
short-term forecast still remains dry. Guidance continues to
ignore the low-level inversion with high temperatures, so keeping
highs well below MOS. Hinsberger

.LONG TERM...Thursday night through next Sunday night. Models are
showing more consistency now with the blocking high pressure ridge
transitioning into a west-northwest flow pattern by Friday that will
continue through the weekend. This could add up to several inches of
snow in the central mountains and the eastern highlands.
Accumulation of snow in the Snake Plain and Eastern Magic Valley at
this time look fairly limited, but could not rule out a couple
inches on the bench areas to the east side of the Snake Plain.
Saturday and Sunday also look on the windy side. RS

.AVIATION...Dense fog developing near midnight between KBYI and KTWF
in proximity to the Snake River. Neither the 00Z NAM/MAV MOS for
KBYI show restrictions to ceilings/visibility, but some LIFR stratus
already reported, VCFG likely at sunrise. Persistent north winds at
KIDA could well prevent the field from fogging up. KPIH has bigger T-
Td spread, very light winds, local industry or American Falls
Reservoir could be a factor. Upper ridge moves more overhead Tuesday
morning with strengthening inversions, fog becomes more likely for
KIDA, KPIH, and KBYI as they are close to the river. RS

.AIR QUALITY...Inversions continue to hold and reduce air quality,
particularly for Franklin County where an Air Stagnation Advisory
remains in effect. The upper level ridge of high pressure will move
more directly overhead of southern Idaho Tuesday morning. This will
increase the strength of the near surface inversion conditions. RS



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