Area Forecast Discussion
Issued by NWS Pocatello, ID

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521
FXUS65 KPIH 111741
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
1041 AM MST THU FEB 11 2016

.UPDATE...MINOR UPDATES THIS MORNING TO REMOVE MENTION OF FOG IN
THE UPPER SNAKE PLAIN AND EASTERN MAGIC VALLEY. FOG CONTINUES INTO
EARLY THIS AFTERNOON ON INTERSTATE 15 THROUGH MALAD AND THE UTAH
STATE LINE. RS

&&

.PREV DISCUSSION... /ISSUED 337 AM MST THU FEB 11 2016/

SHORT TERM...TONIGHT THROUGH SATURDAY. UPPER RIDGE AXIS CONTINUES
OVER EAST IDAHO. SFC BASED INVERSIONS REMAIN BUT MOST FOG APPEARS
TO BE LIMITED TO SOUTHERN HIGHLAND AREAS SOUTH OF POCATELLO.
LATEST VIIRS IMAGERY SHOWS THIS REGION EXTREMELY WELL WITH ANOTHER
SMALL POCKET ALONG INTERSTATE 15 NORTH OF IDAHO FALLS. VERY WEAK
SHORTWAVE OVER SOUTHEAST OREGON TRIES TO SLIDE INTO THE RIDGE
EARLY TODAY AND MAY BE ENOUGH ASSOCIATED MIXING TO PREVENT FOG
FROM SPREADING TOO FAR FROM CURRENT LOCATIONS. STRONGER SHORTWAVE
AXIS STILL SHIFTING INTO THE CA/OR COAST THIS MORNING AND EXPECTED
TO TOP RIDGE ALONG DIVIDE LATE TODAY AND OVERNIGHT. LATEST GFS
SPREADS PRECIP JUST INTO NORTHERN ZONES THIS EVENING WHILE LATEST
NAM KEEPS MOISTURE NORTH. HAVE ALLOWED WEAK POPS TO DROP INTO THE
NORTHEAST CORNER OVERNIGHT WITH VERY WEAK QPF/SNOW. OTHERWISE
BELIEVE SFC INVERSIONS TO REMAIN IN PLACE ESPECIALLY SOUTHERN
PORTIONS OF THE FCST AREA AND WILL KEEP MENTION OF AT LEAST PATCHY
FOG OVERNIGHT PER PERSISTENCE. RIDGE AXIS CONTINUES TO WEAKEN
INTO FRIDAY WITH NEXT SYSTEM ARRIVING AS EARLY AS FRIDAY NIGHT.
GFS SLIGHTLY FASTER WITH SHORTWAVE AXIS DROPPING THROUGH WA/OR
FRIDAY NIGHT BUT BOTH GFS AND NAM SPREAD PRECIP INTO WESTERN EDGES
OF CENTRAL MTN REGION BY SATURDAY MORNING. SHORTWAVE AXIS DRIVES
THROUGH EAST IDAHO DURING THE DAY SATURDAY WITH PRECIP GENERALLY
SAGGING SOUTHEAST BUT REMAINING FOCUSED OVER HIGHER ELEVATIONS.
HAVE WEAKENED POPS SLIGHTLY IN THE SOUTH BASED ON 00Z RUNS BUT
EARLY LOOK AT 06Z RUNS HAVE NAM BRINGING INTRODUCING MORE QPF INTO
THE SOUTHERN HIGHLANDS THAN THE GFS. REGARDLESS...QUICK MOVING
SYSTEM WITH LIMITED MOISTURE DOES MEAN TOTAL SNOW AMOUNTS FOR
SYSTEM REMAIN ON THE LOW SIDE WITH LESS THAN 3IN TOTALS EVEN AT
HIGHER ELEVATIONS. SFC FRONT DRIVES ACROSS THE REGION EARLY IN THE
DAY WITH FAVORABLE SFC GRADIENT AND 30-40KT 700MB WINDS. HAVE KEPT
INCREASED WINDS DURING THE DAY BUT ESPECIALLY IN THE AFTERNOON
ACROSS THE SNAKE PLAIN AND HIGHER ELEVATIONS. DMH

LONG TERM...SUNDAY THROUGH THURSDAY...OVERALL DISTURBED WEATHER
PATTERN FOR SUNDAY EXPECTED TO LEAD TO WIDELY SCATTERED TO NUMEROUS
SNOW SHOWERS WITH RAIN IN THE EASTERN MAGIC VALLEY/LOWER SNAKE RIVER
PLAIN. WINDS IN EXCESS OF 15-25MPH REMAIN IN THE FORECAST WITH
LIKELY HIGHER SPEEDS. HIGH PRESSURE RIDGE TO BUILD IN EARLY WEEK
WHICH WILL BRING WARMER TEMPERATURES...PERHAPS THE WARMEST WE`VE
SEEN IN A WHILE. TIMING DIFFERENCES EXIST BETWEEN GFS...EUROPEAN AND
CANADIAN MODEL SOLUTIONS REGARDING WEDNESDAY/THURSDAY SYSTEM.
EUROPEAN SOLUTION NOT SHOWING ANY RAIN/SNOW UNTIL EARLY THURSDAY
(CANADIAN FOLLOWING SUITE). GFS MORE AGGRESSIVE AND BRINGING
WIDESPREAD PRECIP LATE WEDNESDAY. DID NOT WANT TO AMEND FORECAST AND
LEFT PREVIOUS WIDESPREAD ACTIVITY AS IS AT THIS TIME. NP/DMH

AVIATION...AREAS OF MIST AND LOW STRATUS EXPECTED THIS MORNING AT
VALLEY LOCATIONS...PATCHY FOG CANNOT BE RULED OUT OCCASIONALLY AS
WELL. FOG MAY ONCE MORE REDEVELOP AGAIN TONIGHT WITH NO CHANGE IN
ATMOSPHERIC CONDITIONS. CEILINGS SHOULD BE IMPROVING MID-MORNING TO
VFR CONDITIONS AND IF THEY ARE TO REDUCE TONIGHT WOULD BE AFTER 00Z.
BURLEY COULD REDUCE EARLIER THAN THIS IN THE MID-AFTERNOON HOURS TO
IFR STRATUS DECKS - VERY LOW CONFIDENCE IN THAT BUT IT IS POSSIBLE.
SUN VALLEY WILL PERSIST WILL LIGHT WINDS AND MID TO HIGH LEVEL
CLOUDS THE NEXT 24 HOURS WITH VFR CONDITIONS. NP/DMH

AIR STAGNATION...HIGH PRESSURE AND SURFACE INVERSIONS CONTINUE
THIS MORNING WITH FOG SETTLING IN LOWER ELEVATION AREAS MAINLY
SOUTH OF POCATELLO. POOR AIR QUALITY CONTINUES IN THE CACHE
VALLEY. DESPITE WEAK FEATURE TOPPING THE RIDGE TONIGHT...AND
GRADUAL WEAKENING OF RIDGE THROUGH FRIDAY...SURFACE BASED
INVERSIONS ARE EXPECTED TO CONTINUE THROUGH FRIDAY. DIMINISHED AIR
QUALITY AND AT LEAST PATCHY FOG SHOULD CONTINUE. A STRONGER SYSTEM
WILL FINALLY TOPPLE THE RIDGE SATURDAY BRINGING SOME PRECIPITATION
BUT MORE IMPORTANTLY INCREASED WINDS TO THE REGION. THEREFORE AIR
QUALITY IS EXPECTED TO IMPROVE OVER THE WEEKEND. DMH

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$



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