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AREA FORECAST DISCUSSION
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FXUS66 KOTX 231149
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
350 AM PST MON NOV 23 2009
.SYNOPSIS...
WEAK HIGH PRESSURE OVER THE REGION WILL PROMOTE DRY BUT MOSTLY
CLOUDY CONDITIONS TODAY. A WEAK PACIFIC WARM FRONT WILL BRING A
POSSIBILITY OF VERY LIGHT PRECIPITATION TONIGHT...WITH GENERALLY
DRY BUT CLOUDY WEATHER RETURNING TUESDAY AND THROUGH THANKSGIVING.
ON FRIDAY A COLD FRONT WILL PASS THROUGH WITH ANOTHER REASONABLE
CHANCE OF MOUNTAIN SNOW AND VALLEY RAIN OR SNOW. CONDITIONS WILL
REMAIN CLOUDY AND UNSETTLED INTO NEXT WEEKEND.
&&
.DISCUSSION...
TODAY THROUGH TUESDAY...AFTER YESTERDAY`S TROUGH
PASSAGE...SATELLITE INDICATES A WEAK UPPER LEVEL RIDGE BUILDING
OVER THE FORECAST AREA TODAY AHEAD OF THE NEXT STORM SYSTEM WHICH
IS APPROACHING THE PACIFIC COAST. IT WILL TAKE MUCH OF THE DAY FOR
THIS NEXT WAVE TO REACH THE FORECAST AREA...THUS A MAINLY DRY BUT
VARIABLY CLOUDY DAY IS ON TAP FOR THE INLAND NORTHWEST. THE MOIST
LOW LEVEL AIR MASS FROM YESTERDAYS PRECIPITATION WILL PROMOTE
AREAS OF MORNING LOW CLOUDS AND PATCHY FOG ACROSS THE EASTERN
BASIN...WITH DENSE MID AND HIGH CLOUDS ELSEWHERE. HIGH
TEMPERATURES WILL CREST AT ABOUT SEASONAL NORMALS TODAY WITH
DECREASING WINDS.
MODEL AGREEMENT IS REASONABLE WITH THE EVOLUTION OF THE INCOMING
STORM SYSTEM. MOST OF THE DYNAMIC ENERGY ASSOCIATED WITH THE
PARENT TROUGH WILL SWING NORTH INTO BRITISH COLUMBIA...HOWEVER A
STRONG AND FAVORABLY DIRECTED FETCH OF PACIFIC MOISTURE WILL
ENHANCE ALONG A WEAK WARM FRONT TONIGHT AND LIKELY PRODUCE SOME
LIGHT PRECIPITATION ACROSS THE NORTHERN AND EASTERN ZONES.
PRECIPITATION TYPE WILL BE MOUNTAIN SNOW...BUT OVER THE VALLEYS
AND BASIN P-TYPE WILL BE MORE AMBIGUOUS. A NIGH TIME PASSAGE AND
WET BULB COOLING AS THE AIR MASS MOISTENS UP ARGUES FOR LIGHT
SNOW...HOWEVER THE MAGNITUDE OF THE PRECIPITABLE WATER FETCH
SUGGEST A LOW LEVEL AIR MASS TOO WARM FOR SNOW. EITHER THE MODEL
FETCH MAGNITUDE IS BEING OVER FORECAST...OR THE PRECIPITATION OVER
THE BASIN AND THE LOWER NORTHERN VALLEYS WILL BE EITHER RAIN OR A
NON-ACCUMULATING MIX OF RAIN AND A FEW SOPPING WET SNOW FLAKES
WHICH WILL MELT UPON CONTACT WITH THE GROUND. THE AMSU
PRECIPITABLE WATER SATELLITE SUGGEST THE MODELS ARE INITIALIZING
THE MAGNITUDE OF THIS FETCH WELL...THUS WILL BET ON THE LATTER
REASONING AND EXPECT MOUNTAIN SNOW AND VALLEY/BASIN RAIN OR NON-
ACCUMULATING MIX WITH THIS NEXT WAVE. IN ANY EVENT AMOUNTS WILL BE
LIGHT...AND PRETTY MUCH PASS OUT OF THE REGION BY TUESDAY MORNING.
ON TUESDAY THE RIDGE BUILDS BACK WITH SURFACE HIGH PRESSURE
BECOMING ESTABLISHED OVER THE REGION ONCE AGAIN FOR ANOTHER DRY
BUT MOSTLY CLOUDY AND SEASONABLY COOL DAY. /FUGAZZI
TUESDAY NIGHT THROUGH THURSDAY...THE INLAND NW BRIEFLY TRANSITIONS
TO A DRIER PATTERN AS A WARM FRONT LIFTS THROUGH AND A SHORT-WAVE
RIDGE BUILDS IN. WEAK BUT MOIST ISENTROPIC ASCENT WILL PROVIDE
MID/HIGHER CLOUDS FOR MUCH OF THE REGION AND RISK FOR PRECIP OVER
THE CASCADES AND NORTHERN MTN ZONES THROUGH WEDNESDAY. A NEAR
ISOTHERMAL PROFILE IN THE SFC-800 MB LAYER SUPPORTS EITHER RAIN OR
WET SNOW OR A MIX. EITHER WAY PRECIP AMOUNTS LOOK LIGHT. THE MID
AND HIGHER CLOUDS AND PRECIP RISK RETREAT TO THE CANADIAN BORDER
AND CASCADES BY WEDNESDAY NIGHT...AS THE SHORT-WAVE RIDGE
CONTINUES TO BUILD. AT MOST OTHER TIMES OF THE YEAR THE BUILDING
RIDGE WOULD SUPPORT WARMING TEMPERATURES. YET THE RIDGING WILL
FAVOR STRATUS/FOG IN THE VALLEYS...INHIBITING TEMPERATURES FROM
WARMING. THUS CONFIDENCE IN PRECISE NUMBERS IS LOW. ATTM VALUES
LAY SLIGHTLY ABOVE NORMAL. HOWEVER STRATUS/FOG IS MORE PERSISTENT
...VALUES COULD BE LOWER. IN FACT IT IS POSSIBLE MOUNTAINS WILL
SEE WARMER TEMPERATURES THAN THE VALLEYS...ESPECIALLY AWAY FROM
THE SOUTHEAST CWA. THE SOUTHEAST CWA WILL BE MOST APT TO MIX OUT
WITH A SOUTHEAST WIND...AND SO SEE BETTER WARMING.
THURSDAY NIGHT INTO FRIDAY...THE PRECIPITATION RISK INCREASES AND
EXPANDS EAST FROM THE CASCADES INTO IDAHO AS THE NEXT COLD FRONT
PASSES. RIGHT NOW IT DOES NOT LOOK LIKE A SIGNIFICANT SNOW
PRODUCER...BUT RATHER A RAIN OR A RAIN/SNOW MIX THREAT WITH
PRECIPITATION TIED MORE TO THE FRONT. THE SYSTEM BEGINS TO MOVE
EAST FRIDAY NIGHT INTO SATURDAY. THE NW FLOW BEHIND IT PUSHES THE
PRIMARY PRECIPITATION CHANCES TO THE ID PANHANDLE AND FAR SE
ZONES. THEREAFTER MODEL CONSISTENCY FALTERS. CURRENT RUNS SUGGEST
A WARM FRONT SKIMS BY AND A SHORT-WAVE RIDGE BUILDS IN SATURDAY
NIGHT INTO SUNDAY...SUPPORTING SOME LOW PRECIP RISK OVER THE FAR
NRN AND ERN MOUNTAINS. YET PREVIOUS RUNS WERE A BIT WETTER. UNTIL
BETTER AGREEMENT IS ESTABLISHED SOME LOW-GRADE POPS ARE WARRANTED
...THOUGH AT THIS POINT THEY REMAIN BELOW CLIMO. /JCOTE
&&
.AVIATION...
A SHORTWAVE RIDGE WILL MOVE OVERHEAD TODAY RESULTING IN WEAKENING
WINDS AND LARGELY VFR CONDITIONS AREA WIDE. MAIN FORECAST CHALLENGE
IN THE SHORT TERM WILL BE WHETHER OR NOT LOW STRATUS WILL DEVELOP
ALONG THE KGEG-KCOE CORRIDOR. BETWEEN THE 12Z KOTX SOUNDING
DISPLAYING A SHALLOW MOIST LAYER APPROX 800FT AGL...WINDS BACKING TO
A MORE FAVORABLE SW UPSLOPE FLOW...AND THE 06Z NAM MODEL SUGGESTING
A SLIGHT INCREASE IN THE 925-850MB RH THIS MORNING...BELIEVE THERE
IS A 50:50 CHANCE OF STRATUS DEVELOPING BRIEFLY AT KGEG-KCOE. OTHER
THAN THAT...A WEAK WARM FRONT WILL MOVE INTO NORTHERN WA AND THE ID
PANHANDLE TONIGHT RESULTING IN RAIN AND SNOW SHOWERS. HOWEVER...SOME
UNCERTAINTY EXISTS ON WHETHER OR NOT PRECIP...AND SUBSEQUENT MVFR
CIGS...WILL REACH THE KGEG-KCOE CORRIDOR LATE TONIGHT. /NEUMAN
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 38 33 39 31 41 31 / 10 50 10 10 0 0
COEUR D`ALENE 38 33 39 31 41 31 / 10 50 10 10 0 0
PULLMAN 39 34 41 29 43 32 / 10 50 30 0 0 0
LEWISTON 45 34 45 34 45 34 / 10 30 20 0 0 0
COLVILLE 39 34 40 29 40 27 / 30 70 10 20 20 10
SANDPOINT 37 30 35 27 36 26 / 20 60 10 20 20 10
KELLOGG 34 28 37 28 40 29 / 20 60 30 10 10 0
MOSES LAKE 43 28 44 31 44 30 / 10 10 10 0 0 0
WENATCHEE 42 31 43 32 43 32 / 10 20 10 10 10 0
OMAK 40 27 43 29 43 29 / 50 60 10 20 10 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
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