Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 130341
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
841 PM MST FRI DEC 12 2014

.UPDATE...DEEP UPPER LOW CENTERED BETWEEN VEGAS AND RENO THIS
EVENING. ELONGATED TROUGH SLOWLY MOVING THROUGH WESTERN STATES.
DEEP SOUTHERLY FLOW STILL IN PLACE OVER EAST IDAHO WITH SFC COLD
FRONT MOVING INTO SOUTHWEST IDAHO AND TROUGH AXIS TO THE WEST AS
WELL. TIMING FOR SFC COLD FRONT STILL LOOKS TO BE BETWEEN 10PM-
12AM FOR BURLEY AND 3-5AM FOR POKY/IF. EXPECT PRECIP TO MARCH
ACROSS THE STATE WITH THE COLD FRONT AS WELL. SNOW LEVELS NOT
QUITE DROPPING TO VALLEY FLOORS AT LEAST IN SNAKE PLAIN BUT SHOULD
BE TO VALLEY FLOORS FOR ALL OF CENTRAL MTNS AND MOST OF EASTERN
HIGHLANDS NORTH OF SODA SPRINGS. HAVE MADE A FEW ADJUSTMENTS TO
POP/QPF OVENIGHT WHICH RESULTED IN SLIGHTLY LOWER SNOW TOTALS
TONIGHT THROUGH SATURDAY ESPECIALLY AT HIGHER ELEVATIONS. MAIN
CHARACTER OF FCST REMAINS THE SAME WITH 2-6 INCHES ACCUMULATION
ABOVE 7000 FT. WEB CAMS IN CENTRAL MTNS SHOW SNOW ALREADY FALLING
AT 7200 FT AND TEMPS SUPPORT RAIN OR RAIN/SNOW MIX AT STANLEY AT
6500 FT. NO OTHER UPDATES ANTICIPATED THIS EVENING. DMH


&&

.PREV DISCUSSION... /ISSUED 154 PM MST FRI DEC 12 2014/

SHORT TERM...SOUTHEAST IDAHO ENJOYING SOME RATHER WARM TEMPERATURES
FOR DECEMBER WITH SOUTHERLY AIR AHEAD OF THE APPROACHING TROUGH.
THE POCATELLO REGIONAL AIRPORT SO FAR HAS REACHED 59 DEGREES...THE
RECORD FOR THIS DATE IS JUST 53F. THERE ARE A COUPLE OF MOUNTAIN
SITE OBSERVATIONS REPORTING TEMPERATURES IN THE LOW 40S AT 8000 FEET
OF ELEVATION. MUCH OF THE PRECIPITATION IS STILL BACK IN CENTRAL
NEVADA AND EASTERN OREGON. IT COULD TAKE ANOTHER 3 TO 5 HOURS YET
FOR PRECIPITATION TO MOVE INTO THE CENTRAL MOUNTAINS...MAYBE CLOSER
TO MIDNIGHT FOR THE SNAKE PLAIN. SNOW LEVEL IN THE SNAKE PLAIN IS
STILL EXPECTED TO DROP TO THE VALLEY FLOOR AROUND 6-7 AM SATURDAY SO
A CHANGE OVER FROM RAIN TO SNOW IS IN ORDER. THIS LOW PRESSURE
DISTURBANCE HAS STRETCHED NORTH AND SOUTH QUITE A BIT AS IT MOVES
INLAND RESULTING IN A WEAKER OVER ALL DISTURBANCE. SNOW GETS REDUCED
WITH THE CHANGE FROM RAIN TO SNOW AND WET GROUND. SNOW AMOUNTS
THROUGH SATURDAY EVENING COULD BE 6 MAYBE 7 INCHES ON THE HIGHER
PEAKS BETWEEN SUN VALLEY AND STANLEY....THE LOWER SLOPES ONLY 1 TO
4. FOR THE SNAKE PLAIN HALF TO 1.5 INCH....MIGHT GET 2 INCHES ON
SOME BENCH AREAS TO THE EAST SIDE OF THE PLAIN. THE EASTERN
HIGHLANDS LOOK LIKE MOSTLY 1 TO 3 WITH 4-5 ON SOME HIGHER RIDGE
AREAS. SOME ADDITIONAL LIGHT SNOW WILL LINGER OVER THE EASTERN
HIGHLANDS THROUGH SUNDAY AFTERNOON AS THE TROUGH MOVES OFF TO THE
EAST. THE NAM12 MODEL PROVIDES EVIDENCE OF A SURFACE TROUGH OR WIND
CONVERGENCE AREA ON SUNDAY BETWEEN REXBURG AND BLACKFOOT THAT ALSO
RETREATS EASTWARD THROUGH THE DAY AND COULD SERVE TO KEEP SOME
SHOWERS GOING. SUNDAY NIGHT MOSTLY CLEAR AND COLDER WITH SOME SINGLE
DIGITS AROUND STANLEY...MAYBE ISLAND PARK AND WAYAN. MONDAY MOSTLY
DRY AND ABOUT 20 DEGREES COLDER THAN IT IS TODAY. RS

LONG TERM...MONDAY NIGHT THROUGH FRIDAY NIGHT. MODELS STILL SHOW
THE NEXT STORM MOVING INTO OUR AREA FOR MIDWEEK...AND SPLITTING. THE
MAIN ISSUE CONTINUES TO BE HOW MUCH SPLITTING WILL OCCUR. THE GFS
NOW HAS US BASICALLY DRY AS IT TAKES MOST OF THIS SYSTEM WELL SOUTH
OF US. ON THE OTHER HAND...THE ECMWF IS MUCH WETTER DUE TO A LITTLE
MORE ENERGY FARTHER NORTH AND MORE MOISTURE EMBEDDED IN THE SPLIT.
THE ENSEMBLES ACTUALLY SHOW LESS SPLITTING...SO THE ECMWF FITS A
LITTLE CLOSER TO THAT IDEA IN A SENSE. WE KEPT WITH THE PREVIOUS
IDEA OF SOME RAIN AND SNOW FOR THE MIDDLE OF NEXT WEEK ACROSS
EASTERN IDAHO...BUT DRIER THAN WHAT THE ECMWF WANTS TO PRODUCE. WE
SHOULD SEE HIGH PRESSURE AND A DEFINITIVE DRYING TREND A WEEK FROM
NOW. IT MAY BE SHORT LIVED THOUGH AS WE MAY SEE THE NEXT STORM
ALREADY MOVING IN BY NEXT SATURDAY. IT DOES APPEAR THOUGH WE WILL BE
COOLER THAN RECENT DAYS AND ACTUALLY BE WHERE WE SHOULD BE FOR THIS
TIME OF YEAR. KEYES

AVIATION...THE STRONGEST OF THE SOUTHERLY WINDS HAS LIKELY
PASSED...BUT UNTIL THE SYSTEM ARRIVES THIS EVENING WE WILL ACTUALLY
SEE AN OVERALL INCREASE IN SOUTH WINDS IN OTHER AREAS. AS THE
MOISTURE MOVES IN STARTING THIS EVENING...WE WILL SEE CEILINGS
AND/OR VISIBILITY DROPPING TO MVFR/IFR WEATHER. IT LOOKS LIKE THIS
WILL HAPPEN AROUND 1Z FOR KSUN...6Z FOR KBYI AND KPIH/KIDA AROUND
8Z. WE SHOULD SEE RAIN INITIALLY...BUT BECOMING A MIX OR ALL SNOW
AROUND SUNRISE FOR THE TAF SITES. KSUN AND KBYI SHOULD START
IMPROVING AROUND 18Z SATURDAY...WITH KPIH AND KIDA NOT REALLY
IMPROVING UNTIL SATURDAY NIGHT. AT THIS TIME...WE ARE NOT EXPECTING
CONDITIONS TO BE BAD ENOUGH TO CLOSE KSUN BUT THEY WILL BE CLOSE TO
MINIMUMS. KEYES

&&

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

$$







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