FXUS66 KOTX 111211
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
253 AM PST FRI DEC 11 2009
.SYNOPSIS...
THE AREA WILL SEE YET ANOTHER DRY DAY AS COOL NORTHWEST FLOW
CONTINUES TO SURGE OUT OF BRITISH COLUMBIA. CONDITIONS WILL BEGIN
TO CHANGE BY SATURDAY AS THE NORTHWEST FLOW IS GRADUALLY REPLACED
BY SLIGHTLY MILDER AND MORE MOISTURE LADEN AIR FROM THE SOUTHWEST.
THIS TRANSITION WILL ALLOW A WARM FRONT TO SURGE TOWARD THE
WASHINGTON- OREGON BORDER ON SATURDAY AND REMAIN OVER THE AREA
THROUGH THE WEEKEND. THIS FRONT WILL LIKELY RESULT IN MODERATE TO
LOCALLY HEAVY SNOW EXTENDING FROM THE BLUE MOUNTAINS TO THE
CENTRAL IDAHO PANHANDLE. A MUCH WETTER FRONT WILL THEN CROSS THE
AREA ON TUESDAY BRINGING WIDESPREAD SNOW TO THE REGION.
TEMPERATURES WILL THEN SURGE ABOVE FREEZING FOR MOST VALLEYS AND
REMAIN THERE THROUGH THE END OF NEXT WEEK.
&&
.DISCUSSION...
TODAY AND TONIGHT...THIS WILL BE THE LAST QUIET AND DRY WEATHER
DAY OF THE WEEK OVER THE INLAND NW. THE SYNOPTIC PATTERN TODAY
WILL BE VERY SIMILAR TO THE PATTERN WE HAVE SEEN FOR MOST OF THE
WEEK. A VERY STRONG RIDGE OF HIGH PRESSURE WILL RESIDE OVER THE
GULF OF ALASKA AND EXTEND THROUGH WESTERN ALASKA. THIS LEAVES DEEP
NW FLOW EXTENDING FROM NORTH OF THE ARCTIC CIRCLE TO THE NORTHERN
TIP OF IDAHO. MEANWHILE...THE MOIST WESTERLY JET...WHICH HAS
IMPACTED SOUTHERN AND CENTRAL CALIFORNIA THROUGH MUCH OF THE WEEK
WILL BEGIN TO CREEP NORTHWARD AS A COMPACT SHORTWAVE TROF OFF CAPE
MENDOCINO HEADS ENE DURING THE NEXT 24 HOURS. MEANWHILE...THE
NORTHWEST FLOW OVER WESTERN CANADA...WILL DROP A SHEARED SHORTWAVE
TROF...CURRENTLY OVER THE YUKON...TOWARD THE WA-BC BORDER LATE
TONIGHT. LOOKS LIKE BOTH THE SYSTEM FROM THE SOUTH AND THE ONE TO
THE NORTH WILL MISS THE CWA DURING THIS PERIOD...AND BECOME MORE
OF AN IMPACT BEGINNING SATURDAY. THE MAIN IMPACT FOR TONIGHT WILL
BE AN INCREASING CLOUD TREND AS THE SYSTEMS BEGIN TO SANDWICH THE
INLAND NW.
TEMPERATURES...WILL REMAIN BELOW SEASONAL NORMALS...BUT SHOULD
CONTINUE TO MODERATE A COUPLE DEGREES COMPARED TO YESTERDAY.
OVERNIGHT LOWS WILL BE TROUBLESOME AGAIN AND MUCH WILL DEPEND ON
POTENTIAL CLOUD COVER. ITS QUITE LIKELY...THE NORTHERN ZONES WILL
CLOUD UP EARLY IN THE EVENING...WHEREAS THE SOUTHERN ZONES WILL
CLOUD UP LATE. MEANWHILE ITS CONCEIVABLE THAT THERE WILL BE A
REGION ACROSS THE CENTRAL PORTION OF THE CWA WHERE SKIES WILL
REMAIN PARTLY CLOUDY THROUGH MOST OF THE NIGHT. THIS IS WHERE WE
WOULD EXPECT TO SEE THE COLDEST MIN TEMPS. THE MODEL GUIDANCE IS
ALL OVER THE MAP WITH POTENTIAL TEMPERATURES FOR TONIGHT AND THE
BUST POTENTIAL IS QUITE HIGH. FX
...HEAVY SNOW POSSIBLE ACROSS PORTIONS OF SOUTHEASTERN WASHINGTON
AND THE CENTRAL IDAHO PANHANDLE OVER THE WEEKEND...
SATURDAY THROUGH MONDAY...WE WILL SEE A CHANGE IN THE WEATHER
PATTERN AS THE PERSISTENT NORTHERLY JET RESPONSIBLE FOR THE
BITTER COLD... RELAXES AND BRIEFLY ORIENTS MORE ZONALLY. THIS WILL
ALLOW SHORTWAVE ENERGY AND PACIFIC MOISTURE CURRENTLY CREEPING
TOWARD SOUTHWESTERN OREGON TO CONTINUE TO THE NORTHEAST BRINGING
THE THREAT FOR HEAVY SNOW TO SOUTHEASTERN AREAS OF THE CWA. IT IS
NOT A STRONG FRONT WITH QUICK BURSTS OF SNOW THAT WE ARE LOOKING
FOR TO ACHIEVE HEAVY SNOW AMTS ...BUT A DURATION TYPE EVENT THAT
WILL LINGER FROM SATURDAY MORNING THROUGH SUNDAY NIGHT...INTO
MONDAY MORNING. THE ONSET OF SNOW WILL BEGIN WITH THE ARRIVAL OF A
WARM FRONT SATURDAY MORNING MOVING FROM SOUTH TO NORTH ACROSS THE
BLUES AND CAMAS PRAIRIE INTO THE PALOUSE AND PANHANDLE MTNS. THE
FRONT WILL STALL ROUGHLY ALONG A LINE FROM MULLAN TOWARD THE
NORTHERN BLUE MTNS. WHERE THIS FRONT STALLS IS THE CHALLENGE OF
THE FORECAST AND WILL BE WHERE A LONG DURATION OF SNOW WILL FALL.
GFS...EC...NAM HAVE ALL PLACED THIS FRONT ALONG THE AFOREMENTIONED
LINE BUT HAVE SINCE WAVERED SLIGHTLY NORTH AND SOUTH FROM AS FAR
NORTH AS SPOKANE TO THE LEWISTON AREA. ONCE THE FRONT BECOMES
STATIONARY...WE CAN EXPECT SNOW TO CONTINUE TO FALL AS MOIST
ISENTROPIC ASCENT ALONG THE 280-290K SFC CONTINUES STRAIGHT
THROUGH SUNDAY MORNING. SUNDAY MORNING...ANOTHER ARCTIC WAVE
PIVOTS ACROSS BRITISH COLUMBIA SENDING ANOTHER SHOT OF COOLER AIR
INTO THE INLAND NW...AND THE FRONT WILL PUSH TO THE SOUTH AS A
STRONG SFC-400MB COLD FRONT FORCING MOISTURE UP ALONG THE FRONT
BRINGING CONTINUED THREAT FOR SNOW ALONG THE FRONTAL
BOUNDARY...BUT NOW AS NORTH TO SOUTH MOVING COLD FRONT. ADDITIONAL
POST-FRONTAL SNOW SHOWERS WILL BE POSSIBLE IN THE UNSTABLE
AIRMASS; ESPECIALLY IN THE BLUES AND CAMAS PRAIRIE AS WINDS TREND
W/NW. OVERALL...ITS A RATHER COMPLEX SITUATION WITH HEAVY SNOW
POTENTIAL FOCUSED ALONG A FRONTAL BOUNDARY...MOVING IN AS A WARM
FRONT...REMAINING IN PLACE AS A STATIONARY BOUNDARY...AND
DEPARTING AS A COLD FRONT. SNOW AMOUNTS LOOK TO RANGE FROM 4 TO 6
INCHES IN THE VALLEYS WITH 8 TO 12 INCHES IN MTNS. OROGRAPHIC FLOW
FROM THE W/SW PRIOR TO THE COLD FRONT PASSAGE WILL FURTHER ASSIST
THE LIFT FOR MUCH OF THE PALOUSE AND SOUTHERN PANHANDLE MTNS THUS
THIS IS WHERE THE HIGHEST SNOW AMTS ARE FORECAST RIGHT NOW.
SCATTERED LIGHT SNOW SHOWERS WILL BE POSSIBLE MONDAY ALONG
AN UPPER-LEVEL WAVE SWINGING ACROSS SOUTHERN
BC...OTHERWISE...THIS WILL BE ONE OF THE FEW DRIER PERIODS BECAUSE
THE WEATHER WILL TURN QUITE UNSETTLED BY MONDAY NT THROUGH MUCH OF
THE WEEK AS A SERIES OF PACIFIC STORM SYSTEMS BARREL INTO THE
COAST. AFTER THE FIRST WAVE BRINGS WIDESPREAD SNOW TO THE
REGION...EXPECT THE COOLER AIR TO SCOUR OUT AND THE NEXT FEW
SYSTEMS BEGIN TO RISE SNOW LEVELS INTO THE 2-3K FT RANGE.
&&
.AVIATION...
DRY NORTHWEST FLOW WILL CONTINUE THROUGH 12Z SAT RESULTING IN VFR
CONDITIONS FOR ALL TAF SITES. A MOIST WEATHER SYSTEM...CURRENTLY OFF
THE NORCAL COAST...WILL DRIFT NE OVERNIGHT AND WILL BRING INCREASING
CLOUDS TO KLWS AND KPUW AFT 06Z SAT. LOOKS LIKE ANY CHANCE FOR MVFR
CIGS WOULD IMPACT KLWS...BUT BEST CHCS WILL HOLD OFF UNTIL AFT 12Z
SAT. ANOTHER FRONT WILL NEAR THE BC/WA BORDER TONIGHT...BUT CIGS
WILL GENERALLY REMAIN ABOVE VFR LVLS WITH A CHC OF LIGHT SNOW. FX
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 22 12 22 17 25 15 / 0 0 20 50 50 50
COEUR D'ALENE 25 13 23 20 26 18 / 0 0 30 50 60 60
PULLMAN 25 16 27 26 29 22 / 0 0 80 90 80 70
LEWISTON 26 17 31 29 34 27 / 0 0 80 70 60 60
COLVILLE 21 14 23 20 26 13 / 0 10 20 20 50 40
SANDPOINT 23 13 22 18 21 15 / 0 10 50 40 60 70
KELLOGG 23 13 26 25 28 20 / 0 0 60 80 90 80
MOSES LAKE 22 7 24 13 29 15 / 0 0 20 20 10 20
WENATCHEE 21 10 22 17 28 19 / 0 0 10 10 10 20
OMAK 22 10 23 12 27 9 / 0 0 10 10 20 30
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...WINTER STORM WATCH FROM SATURDAY MORNING THROUGH SUNDAY EVENING
FOR CENTRAL PANHANDLE MOUNTAINS...IDAHO PALOUSE...LEWIS AND
SOUTHERN NEZ PERCE COUNTIES...LEWISTON AREA.
WA...WINTER STORM WATCH FROM SATURDAY MORNING THROUGH SUNDAY EVENING
FOR LOWER GARFIELD AND ASOTIN COUNTIES...NORTHEAST BLUE
MOUNTAINS...WASHINGTON PALOUSE.
&&
$$
