FXUS66 KOTX 051851
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
1051 AM PST SAT DEC 5 2009
.SYNOPSIS...
LIGHT SNOW SHOWERS...BLUSTERY NORTH-NORTHEAST WINDS AND MUCH
COOLER TEMPERATURES CAN BE EXPECTED ACROSS THE INLAND NORTHWEST
THIS WEEKEND. THIS IS THE RESULT OF A PAIR OF COLD UPPER LEVEL
DISTURBANCES THAT WILL MOVE THROUGH THE REGION. THEN DRY AND
UNSEASONABLY COLD WEATHER WILL PERSIST THROUGH MUCH OF NEXT WEEK.
&&
.DISCUSSION...
TODAY AND TONIGHT...THE INLAND NORTHWEST IS UNDER THE INFLUENCE
OF A AN UPPER LEVEL TROUGH THAT WILL MOVE SOUTH THROUGH THE AREA
OVER THE NEXT 36-48 HOURS. THE COLD FRONT MOVED THROUGH THE REGION ON
FRIDAY AFTERNOON. HOWEVER A SECONDARY SHORT-WAVE WILL MOVE DOWN
THE WEST SIDE OF THE TROUGH TODAY AND TONIGHT RESULTING IN LITTLE
SOUTHWARD MOVEMENT. THIS WILL PUT THE FOCUS FOR THE BEST LIFT AND
FORCING NEAR THE CASCADES. IN ADDITION SEVERAL WEAK DISTURBANCES
WILL MOVE THROUGH THE INLAND NORTHWEST THROUGH THIS TIME PERIOD.
FOR TODAY...AMPLE LOW AND MID LEVEL MOISTURE IS IN PLACE AND THE
WEAK WAVES ARE TAPPING INTO ENOUGH MID LEVEL INSTABILITY TO ERODE
AWAY THE STRATUS THAT HAS BEEN OVER THE REGION. THIS IS ALSO
RESULTING IN AREAS OF VERY LIGHT SNOW FLURRIES. EACH OF THESE
WAVES IS ALSO BRINGING A REINFORCING SHOT OF COOL ER AIR INTO THE
AREA HELPING TO DESTABILIZE THE LOWER ATMOSPHERE. BEHIND THESE
WEAK WAVES STRATUS IS PRONE TO QUICKLY BUILD BACK IN PLACE. AS SUCH
FLURRIES WILL BE KEPT IN THE FORECAST ACROSS A LARGE PORTION OF
THE FORECAST AREA TODAY. NORTH-NORTHWEST FLOW HAS RESULTED IN
GOOD UP-SLOPING FLOW INTO THE CAMAS PRAIRIE. EXPECT THE SNOW TO
BE ON THE DECLINE AS THE FLOW TURNS A BIT MORE NORTHEASTERLY
AFTER 15Z THIS MORNING...MOISTURE AGAIN IS LIMITED BUT THE
PRECIPITATION IS FALLING THROUGH A LAYER THAT IS GOOD FOR SNOW
GROWTH AND EXPECT AREAS IN THE CAMAS PRAIRIE TO RECEIVE 1 TO 2
INCHES OF LIGHT SNOW BEFORE THE SNOW ENDS EARLY THIS MORNING.
NORTHEASTERLY FLOW WILL ALSO RESULT IN UP-SLOPING CONDITIONS FROM
THE WATERVILLE PLATEAU WEST INTO THE CASCADES TODAY. SATELLITE
LOOPS INDICATES PLENTY OF MOISTURE WILL MAKE IT TO THE CREST THIS
MORNING. MODELS PWATS RISE TO AROUND .30 OF AN INCH BY LATE THIS
AFTERNOON WHICH IS QUITE GOOD FOR THIS COOL OF AN AIRMASS AND
DECIDED TO BUMP UP POPS ACROSS THE THE EAST SLOPES OF THE CASCADES
FOR TODAY.
THE NORTH-NORTHEAST GRADIENT WILL KEEP BREEZY WINDS DOWN THE
OKANOGAN VALLEY AND OTHER NORTH-SOUTH VALLEYS WITH THE WINDS
SPILLING INTO THE BASIN AND SPOKANE AREA BY THIS AFTERNOON.
FOR TONIGHT...THE FLOW BECOMES MORE EASTERLY AS THE SECOND LOW
TRACKS SOUTH ALONG THE WASHINGTON COAST. THIS WILL RESULT IN
DRYING CONDITIONS ACROSS THE EASTERN ZONES...BUT INCREASE THE UP-
SLOPING FLOW INTO THE EAST SLOPES OF THE CASCADES. SNOW
ACCUMULATIONS OF AROUND AN INCH WILL BE POSSIBLE NEAR WENATCHEE
WITH UP TO 2 INCHES POSSIBLE ON THE WATERVILLE PLATEAU. MUCH
COOLER CONTINENTAL POLAR AIR IS EXPECTED TO FLOW INTO THE REGION
TO BEGIN TO BIG COOL DOWN. TEMPERATURES WILL DROP INTO THE TEENS
WITH A FEW SINGLE DIGITS. A TIGHTENING OF THE PRESSURE GRADIENT
WILL RESULT IN BREEZY AND GUSTY NORTHEAST SATURDAY NIGHT. /TOBIN
SUNDAY THROUGH WEDNESDAY...EXPECT VERY LITTLE CHANGE IN THE SYNOPTIC
PATTERN AS A HIGH AMPLITUDE RIDGE PERSISTS OVER THE EASTERN PACIFIC
WITH A COLD CORE TROUGH SITUATED DOWNSTREAM...ACROSS THE WESTERN
TWO-THIRDS OF THE CONUS. THE RESULT IS A STEADY STREAM OF ARCTIC
AIR INTO THE INLAND NORTHWEST RESULTING IN DRY CONDITIONS BUT VERY
COLD TEMPERATURES. EXPECT TEMPERATURES THROUGH THE PERIOD TO BE
SOME 20 DEGREES BELOW NORMAL. ADD BREEZY WINDS INTO THE MIX FOR
SUNDAY AND MONDAY AND WE CAN EXPECT WIND CHILLS BELOW ZERO
DEGREES. THESE COLD TEMPERATURES AND DANGEROUS WIND CHILLS WILL
BE THE MAIN FOCUS OF THE SHORT-TERM FORECAST. WINDS WILL BE
HOWLING OUT OF THE EAST/NORTHEAST BY EARLY SUNDAY AND PERSIST
THROUGH THE DAY INTO EARLY MONDAY...IN RESPONSE TO A 10-15MB
PRESSURE GRADIENT ACROSS THE REGION WHICH WILL REST IN BETWEEN
A SFC LOW OVER NORTHERN CA AND ARCTIC HIGH SLIDING DOWN THE
CONTINENTAL DIVIDE. THIS WILL BRING SUSTAINED WINDS OF 15-20 MPH
ACROSS A MAJORITY OF THE IDAHO PANHANDLE AND EASTERN WA BUT
INCREASING UP TO 20-30 MPH THROUGH MUCH OF THE COLUMBIA BASIN.
UNDER THE STRONG COLD ADVECTION REGIME...IT APPEARS ALMOST
CERTAIN WE WILL EXPERIENCE WINDS FROM ALOFT MIXING DOWN TO THE
SFC. CROSS-SECTIONS VIA THE THE NAM/GFS SHOW SPEEDS OF 30-40KTS
LESS THAN 5000FT OFF THE SFC WHICH WAS USED...AND LOOKS TO BE
A GOOD APPROX FOR THE GUST POTENTIAL THROUGH THE DAY SUNDAY.
LOCALIZED CHANNELING THROUGH THE PURCELL TRENCH AND OTHER EAST-
WEST ORIENTED VALLEYS COULD ALSO YIELD SLIGHTLY HIGHER WINDS AT
TIMES.
AS FOR TEMPERATURES...THE COLDEST AIRMASS...IN REGARDS TO 850MB
TEMPERATURES WILL BE ARRIVING SUNDAY AND LINGERING THROUGH TUESDAY
WITH 850MB TEMPERATURES COOLING FROM -15 TO -20 CELSIUS. FURTHER
INVESTIGATION INTO THE MODEL CONSENSUS 925MB TEMPERATURES...SUGGEST
THE PREVIOUS FORECAST WAS IN THE BALLPARK AND TEMPERATURES WERE
ONLY TWEAKED SLIGHTLY. THE MAIN CHANGES WERE TO FURTHER COOL THE
METHOW VALLEY...CAMAS PRAIRIE WHERE LIGHT SNOW DEPTHS ARE/WILL BE
PRESENT AND THESE LOCATIONS EVEN WITHOUT SNOW TEND TO BE COLD
SPOTS UNDER THESE ARCTIC REGIMES. OTHERWISE...EXPECT HIGH
TEMPERATURES NEARLY 15-25 DEGREES BELOW SEASONAL NORMALS WITH
WIDESPREAD TEENS AND UPPER SINGLE DIGITS FOR HIGHS AND SINGLE
DIGIT/BELOW ZERO OVERNIGHT LOWS.
THE COMBINATION THE FRIGID AIR AND BREEZY WINDS SUNDAY NT INTO
MONDAY MORNING HAS PROMPTED THE ISSUANCE OF A WIND CHILL WATCH
FOR AREAS OF THE NORTHERN IDAHO PANHANDLE WHERE WIDESPREAD WIND
CHILL VALUES WILL BE APPROACHING CRITICAL READINGS OF -20F OR
COLDER. THIS DOESN'T MEAN THE REMAINDER OF THE REGION IS IN THE
CLEAR...JUST WIND CHILLS WILL BE GENERALLY IN THE 0 TO -15 F RANGE.
SOME OF THE HIGHER ELEVATIONS FROM THE EAST SLOPES INTO THE
NORTHEAST MTNS WILL FLIRT NEAR -20 F AND THIS WILL BE COVERED IN
THE HWO.
WEDNESDAY INTO NEXT WEEK...EXPECT A SLOW MODIFICATION OF THE AIRMASS
BUT REMAINING GENERALLY COOL WITH TEMPERATURES STILL BELOW NORMAL.
THERE ARE STILL LARGE SPREAD AMONGST THE GUIDANCE IN REGARDS TO
WHEN THE NEXT THREAT FOR PRECIPITATION WILL BE AND TO WHAT EXTENT
THE AIRMASS WILL MODIFY. /SB
&&
.AVIATION...
REMNANTS OF OUR PAST 48HR BASIN/PALOUSE STRATUS ARE STILL HANGING
TOUGH AT KPUW. EXPECT KPUW TO GO FROM LIFR TO VFR BETWEEN 19-21Z AS
THE LOW LEVEL FLOW BECOMES MORE NORTHEASTERLY. THE FOCUS WILL
SWITCH TO KEAT THIS EVENING WHERE UPSLOPE EAST-NORTHEAST FLOW WILL
PRODUCE SOME LIGHT SNOW SHOWERS MOST LIKELY BETWEEN 00-06Z THIS
EVENING...WITH BRIEF LIFR/IFR CONDITIONS POSSIBLE.
OTHERWISE...EXPECT 15-25KT EAST TO NORTHEAST WINDS TO DEVELOP
TONIGHT REGION WIDE.
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 28 15 18 5 11 1 / 10 10 0 0 0 0
COEUR D'ALENE 29 13 17 3 10 0 / 20 10 0 0 0 0
PULLMAN 27 15 20 7 13 4 / 30 10 0 0 0 0
LEWISTON 30 19 26 11 18 7 / 30 10 0 0 0 0
COLVILLE 31 16 21 4 13 3 / 20 40 0 0 0 0
SANDPOINT 29 12 13 0 8 -3 / 20 20 0 0 0 0
KELLOGG 27 11 14 -1 7 -1 / 40 10 10 10 0 0
MOSES LAKE 33 16 24 9 16 1 / 10 30 0 0 0 0
WENATCHEE 33 17 23 7 16 5 / 30 70 10 0 0 0
OMAK 32 16 23 5 15 4 / 20 70 0 0 0 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...WIND CHILL WATCH FROM SUNDAY EVENING THROUGH MONDAY MORNING FOR
CENTRAL PANHANDLE MOUNTAINS...NORTHERN PANHANDLE.
WA...NONE.
&&
$$
