Heavy Snow in Idaho, December 24 to 25, 2006

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
1009 PM PST SUN DEC 24 2006

.SYNOPSIS...A VIGOROUS FRONTAL SYSTEM WILL BRING ANOTHER ROUND OF
WINTRY PRECIPITATION TO THE INLAND NORTHWEST TONIGHT THROUGH
CHRISTMAS DAY. RELATIVELY WARM AIR SURGING NORTHWARD AHEAD OF THE
SYSTEM WILL FORCE SNOW LEVELS TO RISE LATE TONIGHT INTO EARLY
CHRISTMAS MORNING...KEEPING THE GREATEST SNOW ACCUMULATIONS LIMITED
TO THE MOUNTAINS. VALLEY LOCATIONS ACROSS NORTH CENTRAL AND
NORTHEAST WASHINGTON AS WELL AS NORTH IDAHO MAY EXPERIENCE A
WINTRY MIXTURE OF SNOW...FREEZING RAIN OR SLEET BEFORE CHANGING TO
RAIN IN THE AFTERNOON.

&&

.DISCUSSION...
REST OF TONIGHT AND MONDAY...VERY DEEP LOW...CENTERED NEAR 53/140
CONTINUES TO PUSH A WELL DEFINED OCCLUDED FRONT INTO THE PACNW
THIS EVENING. AS OF 00Z...THE PRESENCE OF THE DEEP LOW RESULTED IN
A WENATCHEE TO SEATTLE PRESSURE GRADIENT OF -15MBS...OR NEARLY 5
TIMES AS DEEP AS THE GFS HAD FORECAST AND 1.5 TIMES STRONGER THAN THE
NAM FORECAST. THE STRONG OFFSHORE GRADIENT NO DOUBT CONTRIBUTED
TO A STRONGER THAN EXPECTED OFFSHORE WIND AND DEEPER THAN EXPECTED
COLD AIR DAMMING. THE KELWONA SOUNDING SHOWED EVIDENCE OF THIS
WITH A WET BULB PROFILE WELL BELOW ZERO. THE SPOKANE SOUNDING
ALSO SHOWED A SIMILAR WET BULB PROFILE...ALL BELOW ZERO. GIVEN THE
DEEPER THAN EXPECTED COLD POOL AND STRONGER OFFSHORE FLOW...ITS
NOT SURPRISING THAT FREEZING RAIN REPORTS HAVE PROVED
SCANT...WHILE MOST OF THE NW ZONES FROM WENATCHEE TO REPUBLIC HAVE
REPORTED STEADY SNOW SINCE LATE THIS AFTERNOON WITH MOST REPORTS
RANGING FROM 1 TO 3 INCHES. COLD AIR DAMMING WILL CONTINUE IN
THESE AREAS UNTIL THE COLD FRONT PUSHES THROUGH THE CASCADES
BETWEEN 08-11Z. SATURATED SOUNDINGS AND STRONG OMEGA VALUES
THROUGH THE DENDRITIC LAYER SUPPORT ANOTHER 1 TO 2 INCHES OF SNOW
IN THESE AREAS BEFORE IT TAPERS OFF. THUS WE HAVE UPGRADED THE
WINTER WEATHER ADVISORIES TO HEAVY SNOW WARNINGS FOR THE
WENATCHEE/OMAK AREAS AS WELL AS THE WATERVILLE PLATEAU.

FARTHER EAST...THE PRECIPITATION HAS YET TO BEGIN...HOWEVER THE
LATEST RADAR PIX SUGGEST IT WILL BEGIN IN THE SPOKANE AREA AND NE
WA BEFORE 1030PM AND CONTINUE THROUGH MID-MORNING. THE 285-295K ISENTROPIC
SURFACES INDICATE STRONG LIFT MOVING INTO THESE AREAS AND
PERSISTING THROUGH MUCH OF THE NIGHT WHILE STEADILY MOVING INTO
NORTH IDAHO. THUS PRECIPITATION IS NOT THE QUESTION...RATHER
PRECIP TYPE WILL PROVE THE MOST TROUBLING. NORTH OF SPOKANE AND
COEUR DALENE...THE LOW LEVEL THERMAL PROFILES ARE FAIRLY QUASI-
STATIONARY WITH TEMPS REMAINING BELOW FREEZING ALL NIGHT AND INTO
THE FIRST HALF OF MONDAY. MEANWHILE QPF FORECASTS FROM THE NAM
SUGGEST THE POSSIBILITY OF HEAVY SNOW WARNING AMOUNTS FOR THE
VALLEYS...ESPECIALLY NEAR THE CANADIAN BORDER WHERE THERE IS VERY
LITTLE CHANCE OF THE PRECIP TURNING TO RAIN. THE PRECIP IN SPOKANE
IN COEUR DALENE WILL PROVE MORE TROUBLING. THE LATEST BUFR DATA
FROM THE WRF STILL INSISTS ON ALL RAIN FOR THE AREA...HOWEVER WET
BULB COOLING SHOULD TEMPORARILY ELIMINATE ANY ABOVE FREEZING
PARCELS. SUSPECT THAT THE FREEZING LINE WILL SLOWLY MIGRATE
NORTHWARD OVERNIGHT BUT IT WONT STRAY TOO FAR NORTH OF THE
AREA...RESULTING IN A GRADUAL CHANGEOVER TO RAIN...BUT NOT BEFORE
1-2 INCHES OF SNOW PILES UP ABOVE 2K FEET. THE SAME SCENARIO IS
ALSO EXPECTED NORTH OF I 90 ACROSS THE COLUMBIA BASIN. THE
PRECIPITATION IN THESE AREAS IS EXPECTED TO TAPER OFF BEFORE MID-
MORNING. AS THE FRONT STALLS OUT OVER CENTRAL IDAHO...THE PRECIP
WILL BE SLOW TO DIMINISH. THE SILVER VALLEY WILL NEED TO BE
WATCHED CAREFULLY...AS LOCALLY HEAVY SNOWS COULD OCCUR...DESPITE
THE MODELS SHOWING SNOW LEVELS RISING WELL ABOVE THE VALLEY
FLOORS.

FARTHER SOUTH AND EAST...PERSISTENT OFFSHORE FLOW AND ASSOCIATED
WARMING OFF THE IDAHO MOUNTAINS INTO THE PALOUSE WILL ELIMINATE
ANY CHANCE FOR SIGNIFICANT SNOWFALL. FX

&&

.AVIATION...INCOMING WEATHER SYSTEM WILL RESULT IN WIDESPREAD
MVFR/IFR CONDITIONS NORTH OF A LINE FROM KCOE-KGEG-KEAT DUE TO
SNOW AND LOW CIGS. POCKETS OF FREEZING RAIN WILL ALSO BE POSSIBLE
NEAR THE CASCADES...HOWEVER IT SHOULD NOT IMPACT ANY TAF SITES.
FARTHER SOUTH MVFR CIGS WILL BE POSSIBLE ARE RAIN DEVELOPS FROM W
TO E. THE PRECIPITATION WILL END NEAR THE CASCADES AFT 08Z AND
SHOULD TAPER OFF NEAR SPOKANE AROUND 14Z. BY 19Z...PRECIP SHOULD
BE LOCALIZED TO THE CENTRAL ID PANHANDLE AND NEAR THE CASCADE
CREST...WITH MOST CIGS IMPVG TO VFR LEVELS. FX

&&

.PRELIMINARY POINT TEMPS/POPS...
SPOKANE        29  35  26  34  27  35 / 100  60  10  10  40  50
COEUR DALENE  29  36  27  33  28  34 / 100  70  20  10  40  50
PULLMAN        32  38  28  35  29  36 /  90  70  20  10  40  50
LEWISTON       35  44  31  40  32  41 /  60  70  30  10  40  40
COLVILLE       26  33  25  33  26  34 / 100  60  20  10  50  50
SANDPOINT      26  33  25  32  26  33 / 100  80  20  10  40  50
KELLOGG        28  33  26  35  27  36 / 100  80  40  10  40  50
MOSES LAKE     26  35  25  34  26  35 /  90  40  10  10  50  40
WENATCHEE      25  34  26  34  27  35 /  90  30  10  10  50  50
OMAK           24  32  24  33  25  34 / 100  30  10  10  40  50

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...HEAVY SNOW WARNING UNTIL 1 PM PST MONDAY FOR NORTHERN PANHANDLE.

     SNOW ADVISORY UNTIL 4 PM PST MONDAY FOR CENTRAL PANHANDLE
     MOUNTAINS.

WA...HEAVY SNOW WARNING UNTIL 1 PM PST MONDAY FOR NORTHEAST
     MOUNTAINS...OKANOGAN HIGHLANDS.

     HEAVY SNOW WARNING UNTIL 4 AM PST MONDAY FOR OKANOGAN VALLEY...
     WATERVILLE PLATEAU...WENATCHEE AREA.

     SNOW ADVISORY UNTIL 6 AM PST MONDAY FOR EAST SLOPES NORTHERN
     CASCADES.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SPOKANE WA
1050 PM PST SUN DEC 24 2006

IDZ001-004-WAZ037-038-041>044-260700-
NORTHERN PANHANDLE-CENTRAL PANHANDLE MOUNTAINS-
NORTHEAST MOUNTAINS-OKANOGAN HIGHLANDS-WENATCHEE AREA-
EAST SLOPES NORTHERN CASCADES-OKANOGAN VALLEY-WATERVILLE PLATEAU-
INCLUDING THE CITIES OF...SANDPOINT...RATHDRUM...BONNERS FERRY...
PRIEST RIVER...ST. MARIES...KELLOGG...PINEHURST...OSBURN...
WALLACE...MULLAN...COLVILLE...DEER PARK...CHEWELAH...NEWPORT...
KETTLE FALLS...REPUBLIC...INCHELIUM...WENATCHEE...LEAVENWORTH...
MAZAMA...TWISP...WINTHROP...OMAK...OKANOGAN...BREWSTER...
BRIDGEPORT...OROVILLE...WATERVILLE...MANSFIELD
1050 PM PST SUN DEC 24 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH
IDAHO...CENTRAL WASHINGTON...NORTH CENTRAL WASHINGTON AND
NORTHEAST WASHINGTON.

THE FOLLOWING WATCHES WARNINGS OR ADVISORIES ARE CURRENTLY IN EFFECT
   HEAVY SNOW WARNING IN EFFECT UNTIL 1 PM PST MONDAY FOR NORTH
     IDAHO PANHANDLE...NORTHEAST MOUNTAINS...OKANOGAN HIGHLANDS
   HEAVY SNOW WARNING IN EFFECT UNTIL 4 AM PST MONDAY FOR
     WENATCHEE AREA...OKANOGAN VALLEY...WATERVILLE PLATEAU
   SNOW ADVISORY IN EFFECT UNTIL 6 AM PST MONDAY FOR EAST SLOPES
     NORTH CASCADES
   SNOW ADVISORY IN EFFECT UNTIL 4 PM PST MONDAY FOR CENTRAL
     PANHANDLE MOUNTAINS

PLEASE SEE THE FOLLOWING PRODUCTS FOR MORE INFORMATION.
   SEAWSWOTX  /WWUS46 KOTX/

.DAY ONE...TONIGHT

A MOIST WINTER STORM MOVING IN FROM THE PACIFIC WILL SPREAD
WIDESPREAD SNOWS AND POCKETS OF FREEZING RAIN OVER EASTERN
WASHINGTON AND NORTH IDAHO TONIGHT.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THE MOIST PACIFIC STORM WILL EXIT EAST WASHINGTON AND NORTH IDAHO
DURING THE DAY ON MONDAY. ANOTHER STORM COULD POTENTIALLY BRING
MORE WINTER WEATHER TO THE AREA TUESDAY NIGHT AND WEDNESDAY.

IDZ002-003-026-027-WAZ031>036-260700-
COEUR DALENE AREA-IDAHO PALOUSE-LEWISTON AREA-
LEWIS AND SOUTHERN NEZ PERCE COUNTIES-NORTHEAST BLUE MOUNTAINS-
LOWER GARFIELD AND ASOTIN COUNTIES-WASHINGTON PALOUSE-
MOSES LAKE AREA-UPPER COLUMBIA BASIN-SPOKANE AREA-
INCLUDING THE CITIES OF...COEUR DALENE...POST FALLS...HAYDEN...
MOSCOW...LEWISTON...KAMIAH...CRAIGMONT...NEZPERCE...WINCHESTER...
ANATONE...PEOLA...CLARKSTON...PULLMAN...MOSES LAKE...EPHRATA...
OTHELLO...QUINCY...RITZVILLE...COULEE DAM...ODESSA...
ELECTRIC CITY...WILBUR...GRAND COULEE...COULEE CITY...SPOKANE
1050 PM PST SUN DEC 24 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH
IDAHO...NORTH CENTRAL IDAHO...EAST CENTRAL
WASHINGTON...NORTHEAST WASHINGTON AND SOUTHEAST WASHINGTON.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY
A MOIST PACIFIC STORM WILL EXIT EAST WASHINGTON AND NORTH IDAHO
DURING THE DAY ON MONDAY. ANOTHER STORM COULD POTENTIALLY BRING
WINTER WEATHER TO THE AREA TUESDAY NIGHT AND WEDNESDAY.