FXUS66 KOTX 012328
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
330 PM PST TUE DEC 1 2009
.SYNOPSIS...
DRY...COOL AND QUIET WEATHER CONDITIONS WILL PREVAIL OVER THE
REGION FOR MOST OF THE WORK WEEK. ANOTHER POTENTIAL WEATHER
SYSTEM MOVES INTO THE REGION BY FRIDAY. A SHARP COOL DOWN IS
INCREASINGLY LIKELY BY THE WEEKEND INTO NEXT WEEK.
&&
.DISCUSSION...
TONIGHT AND WEDNESDAY...SATELLITE LOOP THIS AFTERNOON INDICATES
THE FORECAST AREA IS UNDER A DRY NORTHERLY FLOW UNDER THE EAST
FLANK OF A STRONG UPSTREAM RIDGE. SURFACE HIGH PRESSURE OVER
SOUTHERN BRITISH COLUMBIA IS PROMOTING NORTHERLY WINDS FEEDING DRY
CANADIAN CONTINENTAL AIR THROUGH NORTHERN MOUNTAIN GAPS AND INTO
THE COLUMBIA BASIN. THE BUILDING RIDGE IS CREATING A STRENGTHENING
SUBSIDENCE INVERSION ALOFT LEADING TO A DRY AND STABLE AIR MASS
OVER THE REGION. LATEST MODEL RUNS ARE IN GOOD AGREEMENT IN
MAINTAINING THIS GENERAL PATTERN THROUGH THE NEXT 24 TO 36 HOURS
AT LEAST. FOR SENSIBLE WEATHER THIS SUGGESTS DRY AND MAINLY CLEAR
SKIES THROUGH WEDNESDAY...WITH THE MAIN ISSUE BEING
TEMPERATURES...AND A MINOR SIDE ISSUE CONCERNING FOG POTENTIAL IN
PROTECTED VALLEYS AND RIVER BOTTOMS. CURRENT DEW POINTS ARE DOWN
INTO THE 20S AND TEENS THROUGHOUT THE REGION. AFTER SUNSET A LONG
DARK NIGHT AND LESS WIND THAN LAST NIGHT WILL ALLOW TEMPERATURES
TO RADIATE GENERALLY INTO THE 20S AND POSSIBLY THE TEENS IN WIND
SHELTERED LOCATIONS BY DAWN. FOG POTENTIAL IS MINOR AND PATCHY FOR
WEDNESDAY MORNING AND MAINLY LIMITED TO RIVER VALLEYS WHERE
RELATIVELY WARM RIVER TEMPERATURES MAY FEED SOME MOISTURE INTO THE
COLD AIR AT THE SURFACE INTERFACE LAYER PRODUCING SHALLOW MIST AND
FOG. HIGH TEMPERATURES ON WEDNESDAY WILL BE INFLUENCED BY COPIOUS
SUNSHINE BUT LIMITED BY COLD STARTING TEMPERATURES TO A FEW
DEGREES COOLER THAN CURRENT READINGS...CRESTING MORE OR LESS
AROUND CLIMATOLOGICAL NORMALS. /FUGAZZI
WEDNESDAY NIGHT TO FRIDAY...QUIET WEATHER IS EXPECTED WITH A RIDGE
BUILDING ONSHORE...UNTIL A SYSTEM ENTERS FRIDAY. LOOK FOR JUST A
FEW HIGH CLOUDS AND A RISK OF PATCHY NIGHT/EARLY AM FOG IN SHELTERED
NORTHERN AND CASCADE VALLEYS...L-C VALLEY AND MOSES LAKE AREA INTO
THURSDAY. THE SYSTEM NEARS THURSDAY NIGHT WITH INCREASING CLOUDS.
THE SYSTEM MOVES IN FRIDAY...WITH INCREASING SYNOPTIC LIFT. THERE
WILL BE AN INCREASE IN THE RISK FOR SNOW ACROSS THE MTN ZONES...
MAINLY LATE IN THE DAY. A BLEND OF THE ECMWF AND GFS WAS USED FOR
TIMING. MODELS DO NOT SHOW A SIGNIFICANT MOISTURE TAP...SO IF
ANYTHING FALLS IT IS EXPECTED TO BE LIGHT. A FEW FLURRIES ARE NOT
OUT OF THE QUESTION IN THE SPOKANE/C'DA AREA TO PALOUSE LATE FRIDAY
...YET THE RISK IS TOO REMOTE ATTM FOR THAT DETAIL. SLIGHTLY BELOW
NORMAL TEMPERATURES ARE EXPECTED. /JCOTE
...VERY COLD TEMPERATURES AND BREEZY WINDS EXPECTED ACROSS THE
REGION OVER THE WEEKEND INTO THE BEGINNING OF NEXT WEEK....
FRIDAY NT THROUGH TUESDAY...A DEEP COLD CORE 530 DAM UPPER LOW
WILL DIG INTO THE BASE OF A HIGH AMPLITUDE RIDGE ANCHORED OVER
THE EASTERN PACIFIC DRAGGING THE COLDEST AIR INTO THE REGION WE
WILL HAVE EXPERIENCED YET THIS SEASON. THERE IS GENERALLY STRONG
AGREEMENT AMONGST THE GFS...EC...GEM...AND ENSEMBLE MEANS WITH THE
OVERALL PATTERN SHIFT BUT STILL SOME UNCERTAINTY ON THE DEPTH AND
SOUTHWESTWARD RETROGRESSION OF THE UPPER-LOW INTO BASE OF THE
RIDGE WHICH WILL HAVE MODERATE IMPLICATIONS ON THE DEGREE OF
COOLING. GOING WITH A MIDDLE OF THE ROAD APPROACH...GEFS
MEAN...850MB TEMPERATURES WILL BE CRASHING INTO THE NEGATIVE
SINGLE DIGITS SATURDAY AND CONTINUING TO COOL INTO THE NEGATIVE
MIDDLE TO UPPER TEENS SUNDAY INTO THE START OF THE WEEK. THE ECMWF
WHICH WAS ON THE WARMER SIDE OF THE SPECTRUM HAS ALSO TRENDED
COOLER ON THE 12Z PACKAGE FURTHER SUPPORTING THE GEFS MEAN
SOLUTION AND THE FORECAST WILL LEAN TOWARD A GEFS MEAN/12Z ECMWF
BLEND.
THE UPPER-LOW SAGS SOUTHWARD THROUGH THE INLAND NW FRIDAY NT
INTO EARLY SATURDAY WITH THE INITIAL PUSH OF ARCTIC AIR AND SMALL
WINDOW FOR SCATTERED LIGHT SNOW SHOWERS. THERE ISN'T MUCH CONCERN
REGARDING SNOW POTENTIAL AT THIS TIME WITH AMTS GENERALLY LIGHT TO
NONE. IT WILL BE THE STRONG COLD ADVECTION AND WINDS DEVELOPING
THAT WILL BE THE FOCUS...ESPECIALLY DOWN THE OKANOGAN HIGHLANDS
AND INTO THE WATERVILLE PLATEAU AS A 1050MB ARCTIC HIGH SLIDES
DOWN NORTHERN BRITISH COLUMBIA SETTING UP A 7-12MB SFC PRESSURE
GRADIENTS ACROSS THE CWA WHICH WILL INCR WINDS NEAR 10-25 MPH WITH
GUSTS INTO THE 30-45 MPH RANGE. SATURDAY NIGHT THROUGH MONDAY THE
ARCTIC HIGH CONTINUES TO SLIDE DOWN THE DIVIDE AND GRADIENTS SHIFT
TO A MORE NORTHEASTERLY ASPECT SHIFTING THE STRONGEST WINDS INTO
THE ID PANHANDLE AND COLUMBIA BASIN...WITH SPECIAL EMPHASIS DOWN
THE PURCELL TRENCH AND SOUTHEASTERN WASHINGTON (MAINLY ALONG AND
SOUTH OF A LINE FROM SPOKANE-PULLMAN TO MOSES LAKE. BY MONDAY
NIGHT....THE GRADIENTS WEAKEN AND WINDS WILL CALM.
TEMPERATURES THROUGH THE PERIOD WILL OF THE COLDEST THIS SEASON.
ALTHOUGH THERE IS STILL SOME UNCERTAINTY ON THE DEGREE OF COOLING
ALOFT...A BLEND OF THE GEFS/EC SEEM A GOOD BET FOR NOW WHICH
SUGGEST 850MB TEMPERATURES COOLING INTO THE NEGATIVE SINGLE DIGITS
FRIDAY NT AND SATURDAY WITH FURTHER COOLING INTO THE NEGATIVE
TEENS CELSIUS SUNDAY THROUGH TUESDAY. THIS GENERALLY SUPPORTS
TEMPERATURES 10 TO 15 DEGREES BELOW NORMAL BY THE END OF THE
WEEKEND INTO NEXT WEEK. A COMBINATION OF STEADY WINDS AND LITTLE
TO NO VALLEY SNOW COVER SHOULD KEEP THE BL WELL MIXED AND PREVENT
OVERNIGHT LOWS FROM BOTTOMING OUT SATURDAY THROUGH
MONDAY...HOWEVER AS WINDS CALM MONDAY NIGHT...RADIATIONAL COOLING
WILL MAXIMIZE...AND MORNING LOWS TUESDAY WILL DIP INTO THE SINGLE
DIGITS TO LOW TEENS WITH POCKETS OF BELOW ZERO READINGS. THE ONLY
FLY IN THE OINTMENT WILL BE THE POSITION OF THE UPPER-LOW TO OUR
SOUTH AND WHETHER OR NOT A MID LEVEL CLOUD SHIELD WRAPS UP INTO
SOUTHERN WASHINGTON...THUS REDUCING RADIATIONAL COOLING.
THE COMBINATION OF BREEZY WINDS AND COLD TEMPERATURES WILL RESULT
IN DANGEROUS WIND CHILLS. ALL IT TAKES IS A WIND SPEED OF 15 MPH
WITH AMBIENT AIR TEMPERATURES OF 20F TO PRODUCE WIND CHILLS NEAR
6F. PLEASE REFER TO WIND CHILL CHART LOCATED AT:
WWW.WRH.NOAA.GOV/OTX/SAFETY/WINTER.PHP
FOR ADDITIONAL INFORMATION REGARDING THE UPCOMING COLD...REFER
TO WEATHER STORIES 2 AND 3. /SB
&&
.AVIATION...
A DRY...STABLE CANADIAN AIRMASS WILL PROMOTE VFR CONDITIONS
UNDER MOSTLY CLEAR SKIES THROUGH 00Z THURSDAY. THE ONE
EXCEPTION WILL BE VCNTY OF KSFF WHERE PATCHY RIVER WILL BE
POSSIBLE. /SB
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 22 34 18 33 19 32 / 0 0 0 0 0 10
COEUR D'ALENE 23 37 19 34 21 34 / 0 0 0 0 0 10
PULLMAN 25 32 21 33 23 33 / 0 0 0 0 0 10
LEWISTON 25 43 22 39 25 40 / 0 0 0 0 0 10
COLVILLE 22 36 20 35 25 36 / 0 0 0 0 0 10
SANDPOINT 21 31 16 29 21 29 / 0 0 0 0 10 20
KELLOGG 21 32 17 31 22 30 / 0 0 0 0 10 20
MOSES LAKE 22 38 19 35 20 36 / 0 0 0 0 0 10
WENATCHEE 24 37 24 37 25 39 / 0 0 0 0 0 10
OMAK 22 37 22 36 23 37 / 0 0 0 0 0 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
