Area Forecast Discussion
Issued by NWS Pocatello, ID

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915
FXUS65 KPIH 312059
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
200 PM MST SUN JAN 31 2016

.SHORT TERM...TONIGHT THROUGH WEDNESDAY. EARLY AFTERNOON SATELLITE
IMAGERY WAS SHOWING A LOW PRESSURE TROUGH DIGGING SSE THROUGH
OREGON/NRN CALIFORNIA WITH MID AND UPPER CLOUDS LIFTING INTO SRN
IDAHO IN ADVANCE OF THE TROUGH. IN ADDITION TO THE INFLUX OF MID-
LEVEL MOISTURE...LOW LEVEL MOISTURE REMAINS TRAPPED ACROSS THE SE
SNAKE RIVER PLAIN AND HIGHLANDS WHICH WAS SUPPORTIVE OF SNOW BANDS
EARLIER THIS MORNING. SATELLITE DERIVED LAPSE RATES WERE SHOWING
SOME DESTABILIZATION ACROSS THE NRN MOUNTAINS/SNAKE PLAIN WHERE
AFTERNOON SUNSHINE AND WEAK CYCLONIC FLOW MAY COMBINE TO SUPPORT
WEAK CONVECTIVE SHOWERS THIS AFTERNOON. AT PRESENT WE SEE VERY
LITTLE EVIDENCE OF THAT TYPE OF ACTIVITY ON LOCAL RADAR. THE MODELS
DRIVE THE NRN CALIFORNIA TROUGH SSE ALONG THE SIERRA TONIGHT AND
THEN EAST THROUGH THE 4-CORNERS REGION MONDAY WITH ATTENDING SHOWER
ACTIVITY REMAINING LARGELY SOUTH OF THE REGION. HAVE GENERALLY
MAINTAINED A SLIGHT CHANCE MENTION OF SNOW SHOWERS OVER THE FORECAST
AREA THROUGH MONDAY GIVEN THE PASSAGE OF THE UPPER TROUGH. AS THE
LOW EJECTS EAST THROUGH THE 4-CORNERS MONDAY...BRISK NORTH WINDS
WILL DEVELOP ACROSS THE AREA STARTING LATE TONIGHT AND CONTINUING
THROUGH THE DAY MONDAY. WIND CHILL READINGS ARE EXPECTED TO BE
FAIRLY COLD MONDAY MORNING BUT NOT AT LEVELS TO REQUIRE ANY WARNING
PRODUCTS...BUT STILL A COLD MORNING AT THE OLD BUS STOP. NW FLOW
TAKES CHARGE TUESDAY AND THE GFS WAS SHOWING SCATTERED SHOWER
ACTIVITY DEVELOPING ACROSS THE SE HIGHLANDS IN A WEAKLY
UNSTABLE/UPSLOPE FLOW THAT WANES TUESDAY NIGHT INTO WEDNESDAY AS A
TRANSIENT SHORT-WAVE RIDGE BUILDS EAST ACROSS OREGON/WASHINGTON
AHEAD OF THE NEXT PAC TROUGH MIGRATING INTO THE NW COAST. DAYTIME
TEMPERATURES REMAIN BELOW CLIMATOLOGICAL NORMS THROUGH THE PERIOD.
HUSTON

.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY. THE NEXT STORM MOVES
INTO EASTERN IDAHO WEDNESDAY NIGHT AND THURSDAY. THE GFS IS SEVERAL
HOURS QUICKER IN TERMS OF WHEN THINGS START...BUT BOTH THE GFS AND
ECMWF AGREE ON KEEPING THE SNOW AROUND WELL INTO THURSDAY. THERE
WILL BE SOME WIND...SO BLOWING AND DRIFTING MAY BECOME AN ISSUE IN
THE MOUNTAINS. IT LOOKS WARM ENOUGH IN THE SNAKE PLAIN AND OTHER
LOWER VALLEYS THAT ANY THREAT WOULD BE MINIMAL OR AT LEAST MORE
LOCALIZED. HEADING INTO THE WEEKEND...THIS IS WHERE THE MODELS HAVE
BEEN SHOWING SOME DISAGREEMENT. THEY ARE TRENDING DRIER HEADING INTO
FRIDAY...BUT THE HAS BEEN SOME WAFFLING BACK AND FORTH ON HOW MUCH.
THE PAST COUPLE OF RUNS HAVE GONE MUCH DRIER. FOR THE MOMENT...WE
DID LEAVE SOME MENTION OF PRECIPITATION IN THE FORECAST BUT WE WILL
LIKELY CHANGE THAT PRETTY QUICKLY IF THE TREND INDEED CONTINUES. THE
OVERALL PATTERN IS SETTING WITH ANOTHER HUGE LOW OVER THE CENTRAL
U.S. AND RIDGE OVER THE WEST HEADING INTO NEXT WEEK. THE STORM
RESPONSIBLE FOR THAT MOVES INTO THE STATE LATER SATURDAY...MOVING
EAST ON SUNDAY. THE RUB LIES WITH HOW THIS PATTERN SETS UP. FOR
INSTANCE...THE GFS HAS THE BUILDING RIDGE ALONG THE COAST WHILE THE
EC HAS IT OFFSHORE. FOR NOW...WE DID LEAVE A SLIGHT CHANCE OF
SHOWERS IN MAINLY FOR THE HIGHER ELEVATIONS WHICH FOLLOWS A SLOWER
PROGRESSION.  KEYES
&&

.AVIATION...WE CONTINUE WITH QUITE A BIT OF LOW LEVEL MOISTURE
ACROSS EASTERN IDAHO. THAT HAS LED TO AREAS OF STRATUS ACROSS THE
AREA INCLUDING MUCH OF THE SNAKE PLAIN. THERE IS ALSO SOME LIGHT
SNOW LINGERING NEAR AND EAST OF KPIH AND KIDA. MEANWHILE...WE`VE
STARTED SEEING THE NORTHERLY WIND PATTERN DEVELOP WITH THE LOW TO
OUR SOUTH AND WEST. GETTING KSUN OUT OF THE WAY...IT`S POSSIBLE THAT
SOME SCATTERED LOW CLOUDS WORKS IN THERE AS THE WIND DROPS OFF AND
TRIES TO TURN UPVALLEY. HOWEVER...THAT IS NOT TOO LIKELY BASED ON
WHERE THE STRATUS IS RIGHT NOW. THEY SHOULD REMAIN VFR THROUGH
TOMORROW...WITH RATHER STRONG NORTHWEST WINDS TONIGHT/MONDAY MORNING
ON THE ORDER OF 12-15 KTS AT TIMES. THE CONCERN IS HOW CONFIDENT ARE
WE ON LOW CLOUDS OR FOG AT KBYI...KPIH AND KBYI. WE ARE SEEING SOME
THINNING AROUND THE PLAIN. HOWEVER...WITH THE WINDS TODAY IT HAS
BEEN SLOW TO CLEAR ON IN SOME CASES MOVE IN AND OUT THE AIRPORT
SITES. WINDS SHOULD ACTUALLY PICK UP WHICH MEANS ANY WIDESPREAD OR
DENSE FOG IS NOT EXPECTED. WE DID INCLUDE SOME LIGHT FOG AT KBYI AND
KPIH SINCE THAT IS UPSLOPE FLOW. THERE SHOULD STILL BE SOME STRATUS
AROUND AT ALL 3 SITES...ENOUGH FOR AT LEAST MVFR IF NOT IFR WEATHER.
CONDITIONS WILL EVENTUALLY IMPROVE MONDAY.  KEYES
&&

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

$$



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