641
FXUS65 KPIH 172135
AFDPIH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
235 PM MST TUE DEC 17 2024
SHORT TERM...THIS AFTERNOON THROUGH WEDNESDAY NIGHT
A WEAK AREA OF HIGH PRESSURE IS BUILDING OVER THE REGION THIS
AFTERNOON IN THE WAKE OF A TROUGH THAT BROUGHT WIDESPREAD SNOW TO
THE AREA. AFTERNOON SATELLITE IMAGERY STILL SHOWS WIDESPREAD CLOUD
COVER ACROSS MUCH OF THE SNAKE PLAIN AND INTO THE EASTERN HIGHLANDS
AND THIS WILL LIKELY CONTINUE INTO THE EVENING AND MUCH OF THE
OVERNIGHT. WILL LIKELY SEE SOME ADDITIONAL VERY LIGHT SNOWFALL OUT
OF THIS ACROSS THE EASTERN HIGHLANDS BUT GENERALLY NOT EXPECTING
MUCH MORE THAN A FEW ADDITIONAL TENTHS OF ACCUMULATION OUT OF THIS
BEFORE THE PRECIP LOOKS TO SHUT OFF LATER THIS EVENING. AS THE
AFOREMENTIONED RIDGE CONTINUES TO BUILD OVER THE AREA, WE WILL HAVE
TO WATCH OUT FOR SOME OVERNIGHT STRATUS/FOG ACROSS THE UPPER SNAKE
PLAIN, UPPER SNAKE HIGHLANDS AND INTO THE ARCO DESERT AND HAVE ADDED
FREEZING FOG INTO THE FORECAST ACCORDINGLY. CONFIDENCE ISN'T THE
HIGHEST WITH THIS BUT GIVEN AMPLE LOW LEVEL MOISTURE IN PLACE AND
BUILDING HIGH PRESSURE, IT CERTAINLY SEEMS PLAUSIBLE.
AFTER DAYBREAK TOMORROW, SKIES LOOK TO SLOWLY CLEAR THROUGHOUT THE
DAY ACROSS THE SOUTHERN HALF OF THE REGION. ACROSS THE CENTRAL
MOUNTAINS AND AROUND THE MONTANA DIVIDE, CLOUDS WILL LIKELY LINGER
AS THE WEAK RIDGE ALREADY WILL BEGIN TO ERODE AS A WEAK SHORTWAVE
DIPS INTO THE CENTRAL AND NORTHERN PORTION OF THE GEM STATE. THIS
WILL BRING ADDITIONAL CLOUDS AND SOME LIGHT SNOW TO THOSE AREAS BUT
THE MAJORITY OF THE REGION SHOULD REMAIN DRY THROUGHOUT THE DAY.
SNOWFALL ACCUMULATION WHERE IT DOES FALL WILL REMAIN AROUND AN INCH,
MAYBE AS HIGH AS 2 NEAR ISLAND PARK. VALLEY TEMPERATURES SHOULD
CLIMB INTO THE LOWER TO MID 40S WITH MID TO UPPER 30S THE NORM
ACROSS THE HIGHER TERRAIN. AFTER THIS WEAK WEDNESDAY SYSTEM, LOOKS
LIKE WE'LL SEE A FEW DRY AND RELATIVELY MILD DAYS. MORE ON THAT
BELOW. MCKAUGHAN
LONG TERM...THURSDAY THROUGH NEXT TUESDAY
A RIDGE OF HIGH PRESSURE WILL BRING DRY, QUIET WEATHER WITH LIGHT
WINDS FOR THURSDAY, FRIDAY, AND SATURDAY, WITH HIGH TEMPERATURES
RUNNING ABOUT 10 DEGREES ABOVE CLIMATOLOGICAL NORMALS FOR MID-
DECEMBER. THE RIDGE WILL BREAK DOWN STARTING SATURDAY NIGHT AND
SURRENDER TO AN ACTIVE/PROGRESSIVE PATTERN AGAIN, WITH THE FIRST
SHORTWAVE TROUGH BRINGING ELEVATION-DEPENDENT RAIN AND SNOW SATURDAY
NIGHT AND SUNDAY, THE SECOND SUNDAY NIGHT AND MONDAY, AND A THIRD
TUESDAY NIGHT AND WEDNESDAY. GLANCING AT NBM 50TH-PERCENTILE
SNOWFALL TOTALS AND THE ECMWF EXTREME FORECAST INDEX (EFI), NONE OF
THESE SYSTEMS LOOK PARTICULARLY STRONG AS FAR AS WINDS OR PRECIP AT
THIS JUNCTURE (NOR ARE THEY PARTICULARLY LONG-DURATION), WITH THE
THIRD (TUESDAY NIGHT AND WEDNESDAY) SYSTEM PERHAPS WETTER AND
WINDIER THAN THE OTHER TWO. SO FAR TEMPERATURES LOOK TO HOLD FAIRLY
STEADY THROUGHOUT THIS PERIOD TOO WITH NO SIGNIFICANT COOLDOWNS,
WHICH SHOULD KEEP ANY SNOW ACCUMULATIONS IN PLACES LIKE THE EASTERN
MAGIC VALLEY, RAFT RIVER REGION, SHOSHONE AREA, SNAKE PLAIN, AND
SOUTHERN HIGHLAND VALLEYS QUITE LIGHT WITH RAIN DURING DAYTIME
PERIODS. THERE ARE HINTS THAT THIS MORE ACTIVE/PROGRESSIVE PATTERN
MAY CONTINUE THOUGH BEYOND NEXT WEEK, SO...MULTIPLE OPPORTUNITIES
WHERE WE WILL NEED TO WATCH FOR SLICK TRAVEL IN A FEW SPOTS LIKE
MOUNTAIN PASSES AS WELL AS POTENTIAL TO BUILD SOME MOUNTAIN
SNOWPACK.
AVIATION
ALTHOUGH PRECIPITATION HAS ENDED, ABUNDANT LOW-LEVEL MOISTURE
REMAINS IN PLACE AND WILL MAKE FOR A CONTINUED IMPACTFUL, SOMEWHAT
LOW-CONFIDENCE FORECAST FOR AVIATION. LOW STRATUS IS LINGERING TODAY
OUTSIDE OF KSUN AND KBYI, AND A COMBINATION OF FOG AND LOW STRATUS
IS EXPECTED TO CONTINUE (AND PERHAPS EXPAND A BIT) TONIGHT. KPIH MAY
RESIDE RIGHT ON THE SOUTHERN EDGE OF THIS ACTIVITY PER NBM AND HRRR
GUIDANCE, AND WHILE IMPACTS ARE NOT CURRENTLY INCLUDED IN THE TAF,
WE CAN'T GIVE AN "ALL-CLEAR" WITH ANY LEVEL OF CONFIDENCE. NBM,
HRRR, AND MOS GUIDANCE ALL SUPPORT IFR CONDITIONS AT KIDA AND AT
LEAST MVFR CONDITIONS AT KDIJ, WITH TIMING ADJUSTED SLIGHTLY IN THE
18Z TAF PACKAGE. ALL AFFECTED TERMINALS SHOULD TREND BACK INTO VFR
CONDITIONS BY WEDNESDAY AFTERNOON.
PIH WATCHES/WARNINGS/ADVISORIES
NONE.
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