FXUS66 KOTX 081224
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
429 AM PST TUE DEC 8 2009
.SYNOPSIS...
A FRIGID ARCTIC AIRMASS WILL RESIDE OVER THE INLAND NORTHWEST AT
LEAST THROUGH THE END OF THE WEEK. TEMPERATURES TODAY WILL BE ABOUT
20 TO 25 DEGREES BELOW NORMAL...BUT WILL SLOWLY MODERATE THROUGH THE
WEEK AS THE NORTHERLY FLOW WEAKENS. THE WEATHER WILL GENERALLY BE
DRY...HOWEVER A WEAK DISTURBANCE COULD PRODUCE SOME LIGHT SNOW OVER
EXTREME NORTHEAST WASHINGTON AND THE IDAHO PANHANDLE LATE TONIGHT
AND WEDNESDAY. THE NORTHERLY FLOW WILL TURN INCREASINGLY ONSHORE BY
THE WEEKEND RESULTING A CHANCE OF SNOW FOR MOST LOCATIONS.
&&
.DISCUSSION...
TODAY AND TONIGHT...THE FOCUS FOR TODAY WILL BE COLD TEMPERATURES
AS NORTHERLY FLOW CONTINUES OVER THE REGION. ONCE AGAIN THE
DOMINANT PATTERN OVER THE REGION WILL BE THE DEEP NORTHERLY FLOW
EXTENDING FROM THE NORTHWEST TERRITORIES TO THE PACIFIC NORTHWEST.
THE MOISTURE CONTENT IN THIS AIRMASS IS EXTREMELY DRY WITH
PRECIPITABLE WATER VALUES EXPECTED TO DROP TO .05 INCHES BY THIS
AFTERNOON...OR ROUGHLY 15 PERCENT OF NORMAL. NEEDLESS TO SAY...THE
CHANCES FOR PRECIPITATION WITH SUCH A DRY AIRMASS SHOULD BE NEXT
TO NOTHING WITH PLENTY OF SUN EXPECTED. DESPITE THE
SUNSHINE...TEMPERATURES WILL STRUGGLE TO CLIMB SIGNIFICANTLY TODAY
AS THE WINDS THROUGH THE MIXED LAYER WILL BE VERY LIGHT.
NONETHELESS...SINCE MOST OF THE GROUND IS BARE...THE SOLAR HEATING
WILL PRODUCE LARGER DIURNAL SWINGS THAN IF THE GROUND WERE COVERED
WITH SNOW. WHERE THERE WAS A LITTLE BIT OF SNOW...INCLUDING THE
WATERVILLE PLATEAU...SOUTHERN OKANOGAN VALLEY...AND CASCADE
VALLEYS...THE MODELS REALLY OVERDID THE EXPECTED COOLING ASSOCIATED
WITH THE REFLECTIVE SNOW COVER. RAW MODEL GUIDANCE FROM THE GFS AND
NAM WAS GENERALLY MUCH TOO COLD OVER THESE AREAS...AND REMAINED SO
AS WELL THIS MORNING. ACCORDINGLY WE WILL HEDGE A LITTLE CLOSER TO
THE MOS GUIDANCE TEMPERATURES FOR THOSE AREAS. ASIDE FROM THE MODEL
DIFFERENCES IN TEMPS...WE WOULD EXPECT READINGS TO BE FAIRLY SIMILAR
TO YESTERDAY WITH 850 AND 925 MB TEMPS VARYING JUST A TAD TODAY.
MOST OF THE CHANGES WILL SHOW SUBTLE WARMING...HOWEVER THAT WARMING
WILL BE OFFSET BY WEAKER WINDS IN THE MIXED LAYER.
FOR TONIGHT...THE SHORT RANGE MODELS CONTINUE TO SUGGEST A WEAK
WEATHER SYSTEM WILL APPROACH FROM THE NORTH AFTER 06Z. THIS SYSTEM
IS CURRENTLY OVER NORTHWEST ALBERTA AND DID NOT LOOK IMPRESSIVE ON
THE LAST SATELLITE PIX. SURFACE REPORTS IN THAT REGION WERE ONLY
DEPICTING A FEW FLURRIES WHICH MAKES SENSE GIVEN LESS THAN OPTIMAL
SATURATION THROUGH THE DENDRITIC LAYER. THIS WILL LIKELY BE THE
CASE LATE TONIGHT AS THE MOISTURE MOVES INTO EXTREME NE WA AND N
IDAHO LATE. ALTHOUGH SNOW WILL BE POSSIBLE...MAINLY DUE TO WEAK
ELEVATED WARM AIR ADVECTION...AMOUNTS WILL BE VERY LIGHT.
MEASURABLE PRECIPITATION WILL LIKELY HOLD OFF UNTIL AFTER 12Z. LOW
TEMPS WILL BE TRICKY AND MUCH WILL DEPEND ON CLOUD COVER. ITS VERY
LIKELY LOW TEMPS WILL OCCUR BEFORE MIDNIGHT OVER THE NE QUARTER OF
THE CWA AS THE INCOMING CLOUDS WILL BRING SLOWLY WARMING TEMPS.
FARTHER SOUTH...WE WOULD EXPECT ANOTHER VERY CHILLY NIGHT...WITH
READINGS IN THE SINGLE DIGITS BELOW ZERO TO A FEW DEGREES ABOVE. FX
WEDNESDAY THROUGH THURSDAY NIGHT...COLD AND MOSTLY DRY CONDITIONS
WILL CONTINUE ACROSS THE FORECAST AREA AS THE REGION REMAINS UNDER
NORTHWEST FLOW ALOFT. A STRONG UPPER LEVEL LOW OVER NORTH CENTRAL
CANADA WILL MOVE SOUTH TO THE CANADIAN PRAIRIES...ALLOWING SEVERAL
WEAK IMPULSES TO SWEEP THROUGH THE NORTHEAST PORTION OF THE FORECAST
AREA. MOISTURE WILL BE AT A PREMIUM SO MEASURABLE PRECIPITATION WILL
BE LIMITED TO THE NORTHEAST MOUNTAINS WITH PERHAPS SOME SCATTERED
FLURRIES STRETCHING FROM REPUBLIC SOUTHEAST TO SPOKANE COUNTY ON
WEDNESDAY...THEN SHIFTING EAST OVERNIGHT. TEMPERATURES WILL START
OUT AROUND 20 DEGREES BELOW SEASONAL NORMALS THEN BEGIN A GRADUAL
WARMING TREND AS THE FLOW TAKES ON MORE OF A MARINE INFLUENCE.
FRIDAY THROUGH MONDAY...AFTER A DRY AND COLD DAY ON FRIDAY THE
WEATHER PATTERN WILL BECOME MORE ACTIVE WITH A SUCCESSION OF
SHORTWAVE DISTURBANCES MOVING THROUGH THE REGION. WARM FRONTAL
PRECIPITATION WILL SPREAD ACROSS THE AREA ON SATURDAY INTO SUNDAY.
THERE IS THE POTENTIAL FOR BANDS OF MODERATE TO HEAVY SNOWFALL
WITH THIS SYSTEM BUT MODELS HAVE BEEN INCONSISTENT IN THE
PLACEMENT OF THE SWATH OF HEAVY QPF AND THE LATEST RUN OF BOTH THE
GFS AND ECMWF HAVE BACKED OFF CONSIDERABLY WITH QPF AMOUNTS. THE
00Z RUN OF THE GFS IS NOW TRENDING TOWARD THE 12Z ECMWF IN PLACING
THE BAND OF HEAVIER QPF ACROSS THE SOUTHERN THIRD OF THE FORECAST
AREA...SOUTH OF THE SPOKANE-COEUR D'ALENE AREA. THE TOTAL QPF FROM
THE GFS IS NOW A MODEST QUARTER INCH WHICH WOULD BE ABOUT 3 TO 4
INCHES OF SNOWFALL. THE 00Z EC NOW DEPICTS THE AREA OF HEAVIER
QPF IN THE CENTRAL PANHANDLE WITH ONLY LIGHT AMOUNTS FOR THE
SPOKANE AREA. AS CONFIDENCE IN THE DETAILS IS LOW...ONLY MINOR
CHANGES WERE MADE TO THE POP AND WEATHER GRIDS FOR THIS
PERIOD...MAINLY TO REMOVE THE MODERATE SNOW. TEMPERATURES WILL
CREEP UP TOWARD NORMAL VALUES BUT SHOULD REMAIN COLD ENOUGH FOR
MAINLY SNOW AS PRECIP TYPE THROUGH SUNDAY. ANOTHER VERY MOIST
SYSTEM COULD AFFECT THE REGION ON MONDAY WITH VALLEY RAIN AND
MOUNTAIN SNOW. /KELCH
&&
.AVIATION...
ARCTIC HIGH PRESSURE WILL BRING VFR CONDITIONS REGION WIDE THROUGH
12Z WEDNESDAY. EXPECT LIGHT WINDS WITH ONLY A PASSING HIGH CIRRUS.
AFTER 06Z WED...A WEAK DISTURBANCE WILL APPROACH THE NE CORNER OF WA
AND THE NRN TIP OF ID RESULTING IN INCRSG CLDS AND A SML CHC OF
-SHSN NORTH AND EAST OF ALL TAF SITES. FX
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 12 2 15 7 19 11 / 0 0 0 0 0 0
COEUR D'ALENE 12 3 14 7 20 11 / 0 0 10 0 0 0
PULLMAN 14 2 16 9 19 14 / 0 0 0 0 0 0
LEWISTON 15 5 22 11 24 15 / 0 0 0 0 0 0
COLVILLE 15 7 17 10 21 12 / 0 10 10 0 0 0
SANDPOINT 12 5 13 6 17 9 / 0 10 20 10 0 0
KELLOGG 11 -1 11 4 18 8 / 0 10 20 20 10 10
MOSES LAKE 17 3 20 8 22 12 / 0 0 0 0 0 0
WENATCHEE 17 4 22 9 22 13 / 0 0 0 0 0 0
OMAK 15 4 21 5 21 8 / 0 0 0 0 0 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
