Heavy Snow in Idaho, December 10, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
258 AM MST THU DEC 10 2015

.SHORT TERM...THU THROUGH SAT NIGHT. POSSIBLE LIGHT SNOW
DEVELOPING IN THE CENTRAL IDAHO MOUNTAINS ALREADY THIS MORNING.
THE UPPER LEVEL JET THAT COULD HAVE ENHANCED PRECIPITATION
PRODUCTION IN THE CENTRAL IDAHO MOUNTAINS HAS SLID MUCH FARTHER
SOUTH...AND SO HAVE DECIDED TO GO WITH A WINTER WEATHER ADVISORY
FOR THE 7000 TO 9000 FOOT ELEVATIONS IN THE WOOD RIVER REGION AND
IN THE SAWTOOTHS. PEAK PERIOD OF SNOW APPEARS TO BE DURING THE
AFTERNOON...WITH A STRONG TAPERING OFF AFTER 10/1700 MST...THOUGH
NOT TO ZERO. ABOVE 9000 FEET...ACCUMULATIONS SHOULD BE IN THE 10
TO 20 INCH RANGE. HAVE INCLUDED BLOWING SNOW WHEREVER WIND IS 18
MPH AND TEMPERATURE BELOW 30 DEG AND SNOW ACCUMULATION IS AT LEAST
1/2 INCH.

BY TONIGHT...TEMPERATURES WILL TURN COLDER THAN OVERNIGHT LOWS
HAVE BEEN RECENTLY. THIS SHOULD ALLOW SOME LIGHT SNOW TO DEVELOP
IN THE SNAKE RIVER PLAIN...BUT SHOULD BE HALF INCH OR LESS. SINCE
IT OCCURS AT NIGHT...DO NOT FORSEE A NEED FOR ANY SORT OF ADVISORY
FOR THE MAGIC VALLEY OR SNAKE RIVER PLAIN.

LIGHT SNOW MAY PERSIST IN THE MOUNTAINS ON FRI AND FRI
NIGHT...MAINLY DUE TO UPSLOPE CONDITIONS AND CONTINUED MOISTURE.
THE NEXT STORMS TIMING IS MORE UNCERTAIN...WITH THE GFS MOVING IT
IN QUICKER...AS EARLY AS FRI AFTERNOON. HAVE COMPROMISED FOR THIS
PERIOD...BIASING SLIGHTLY HIGHER THAN THE SLOWER NAM. BUT BELIEVE
THAT SAT AFTERNOON HAS THE BETTER CHANCE...CONTINUING INTO SAT
NIGHT. THIS STORM RETURNS SOUTHERLY FLOW AND MILD AIR AFTER A
COLDER FRI AND FRI NIGHT. STILL...TEMPERATURES ARE ABOVE NORMAL
DURING THE ENTIRE PERIOD.

WIND-WISE...LOCAL STUDY INDICATED POTENTIAL FOR A WIND ADVISORY
FOR A FEW HOURS DURING THE AFTERNOON...BUT AFTER ONLY ONE ZONE
VERIFYING YESTERDAY...IT MAY BE OVER PREDICTING ADVISORY LEVEL
WINDS WITH THIS STORM. THUS HAVE LEFT WINDY CONDITIONS IN THE
SNAKE RIVER PLAIN WITH NO NEED FOR AN ADVISORY.  MESSICK

.LONG TERM...SUNDAY THROUGH NEXT THURSDAY. GFS AND ECMWF
CONTINUE TO SHOW GOOD AGREEMENT HEADED INTO NEXT WEEK. MODELS SHOW
WIDESPREAD PRECIPITATION MOVING THROUGH THE REGION SUNDAY AND
SUNDAY NIGHT. PRECIPITATION MAY BEGIN AS SNOW ON THE VALLEY FLOORS
SUNDAY MORNING BUT SHOULD CHANGE OVER TO RAIN BY LATE MORNING OR
AFTERNOON. SNOW LEVELS WILL RISE TO ABOVE 5500 FEET. THE COLD
FRONT WILL MOVE THROUGH SUNDAY NIGHT WITH VERY COLD AIR SETTLING
OVER THE REGION ONCE AGAIN FOR NEXT WEEK. THIS SYSTEM LOOKS TO BE
A VERY HEAVY SNOW PRODUCER FOR THE MOUNTAINS AND HIGHLANDS. SNOW
AMOUNTS HIGHLY UNCERTAIN FOR THE VALLEY FLOORS MAINLY BECAUSE OF
TIMING OF THE INITIAL WARM AIR AND THEN THE QUESTION OF HOW MUCH
PRECIPITATION WILL REMAIN IN THE SNAKE PLAIN AFTER THE COLD FRONT.
THINK THAT SNOW WILL HANG AROUND INTO MONDAY BUT WILL MAINLY
AFFECT THE EASTERN HIGHLANDS BECAUSE OF UPSLOPE FLOW INTO THAT
AREA...ALTHOUGH SOME SNOW IS POSSIBLE ACROSS THE CENTRAL MOUNTAINS
AND MAYBE THE SNAKE PLAIN. SNOW CHANCES DECREASE THROUGH THE
WEEK...BUT NOT ENOUGH TO REMOVE THE THREAT FOR SNOW IN THE
FORECAST AT THIS TIME AS THE MODELS SHOW SEVERAL WEAK SYSTEMS
MOVING THROUGH THE AREA.

VALLE

&&

.AVIATION...ANOTHER STORM SYSTEM WILL BRING SOME PRECIPITATION TO THE
REGION ONCE AGAIN. EXPECT MAINLY VFR CEILINGS ONCE AGAIN
TODAY...HOWEVER SOME LOWER CEILINGS WERE NOTED AROUND THE KIDA AREA
BUT SHOULD LIFT THIS MORNING. LOWER VIS AND CEILINGS ARE MORE LIKELY
TODAY AROUND KSUN AS THE CENTRAL MOUNTAINS WILL HAVE THE BETTER
CHANCES FOR SNOW TODAY. EXPECT GUSTY CONDITIONS ACROSS THE REGION
ONCE AGAIN TODAY AS WELL.

VALLE

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO 6 AM MST
FRIDAY FOR IDZ018-031.

&&