000 FXUS66 KOTX 141148 AFDOTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPOKANE WA 445 AM PDT WED MAY 14 2008 .SYNOPSIS... A SURGE OF MOISTURE WILL CONTINUE TO POUR IN FROM THE NORTHWEST THROUGH MOST OF THE DAY...RESULTING IN CONSIDERABLE CLOUDS AND OCCASIONAL PRECIPITATION...ESPECIALLY OVER SOUTHEAST WASHINGTON AND CENTRAL IDAHO. THIS MOISTURE WILL SHIFT EAST OVERNIGHT... ALLOWING A STRONG UPPER LEVEL RIDGE TO MOVE OVER THE PACIFIC NORTHWEST. THIS RIDGE WILL GROW PROGRESSIVELY STRONGER THROUGH THE WEEK RESULTING IN THE MUCH ABOVE NORMAL TEMPERATURES THROUGH THE WEEKEND. && .DISCUSSION... UPDATED AVIATION TODAY AND TONIGHT...IR AND WATER VAPOR PICTURES THIS MORNING CONTINUE TO INDICATE AN EXTENSIVE PLUME OF MOISTURE STREAMING OUT OF THE NW AHEAD OF AMPLIFYING UPPER LEVEL RIDGE. PRECIPITABLE WATER CONTENT WITHIN THIS PLUME WAS RATHER IMPRESSIVE WITH THE LATEST GPS PRECIPITABLE WATER PLOTS INDICATING VALUES APPROACHING ONE INCH...WHICH IS OVER 200 PERCENT OF THE DAILY NORMALS FOR EASTERN WA. AS THE OFFSHORE RIDGE CONTINUES TO AMPLIFY TODAY...THE FLOW OVER THE CWA WILL BECOMING INCREASINGLY NW...WHICH TYPICALLY IS A RATHER UNIMPRESSIVE FLOW REGIME FOR PRECIPITATION. HOWEVER IN THIS CASE...GIVEN THE HIGH MOISTURE CONTENT...THE FORECAST WILL NOT BE DRY. THE 295 AND 300K ISENTROPIC SURFACES OFF BOTH THE NAM AND GFS ARE DEPICTING MODERATE ASCENT AND GOOD MOISTURE TRANSPORT THROUGH AT LEAST THE FIRST HALF OF THE DAY OVER THE SE HALF OF THE CWA INCLUDING THE PALOUSE...LEWISTON AREA...CAMAS PRAIRIE...AND CENTRAL IDAHO PANHANDLE. THIS WILL LIKELY EQUATE TO CONTINUED PRECIPITATION THROUGH AT LEAST THE MORNING. DESPITE SIMILAR ISENTROPIC SURFACES...THE GFS WAS THE DRIER SOLUTION COMPARED TO THE NAM...HOWEVER EACH SUCCESSIVE RUN OVER THE PAST 5 RUNS HAS GOTTEN WETTER AND THUS WE WILL TREND THE FORECAST IN THAT DIRECTION. SURPRISINGLY THE GFS MOS POPS DO NOT REFLECT THE RAW MODEL DATA AND IN THIS CASE WE WILL FAVOR THE MUCH WETTER ETA MOS. ACROSS THE NW HALF OF THE CWA...CONTINUED NW FLOW OVER THE CASCADE CREST AND ASSOCIATED DOWNSLOPE MOTION WILL KEEP THESE AREAS MAINLY DRY...EXCEPT ALONG THE IMMEDIATE CREST. BY LATE AFTERNOON AND INTO THE EVENING THE UPPER LEVEL RIDGE IS EXPECTED TO SLIDE INTO WESTERN WA WITH THE MOIST NW UPPER LEVEL JET PUSHING INTO WESTERN MONTANA. THIS WILL SLOWLY END THE THREAT OF PRECIPITATION BUT GIVEN THE AMPLE MOISTURE CONTAINED WITHIN THIS SYSTEM AND NW UPSLOPE FLOW INTO THE CAMAS PRAIRIE AND CENTRAL ID PANHANDLE...WE SUSPECT PRECIP MAY HANG AROUND A LITTLE LONGER THAN FORECAST AND THUS GAVE THE NOD TO THE WETTER NAM SOLUTION. BY LATE EVENING ...CONDITIONS WILL DRY OVER THE ENTIRE CWA WITH GRADUALLY CLEARING SKIES. IF PRECIP IS SIGNIFICANT ENOUGH TODAY...RADIATION FOG WILL BE A DISTINCT POSSIBILITY LATE TONIGHT OVER THE VALLEYS OF CENTRAL IDAHO AND POSSIBLY ONTO THE PALOUSE. GIVEN THE TREND TOWARD A WETTER AND CLOUDIER FORECAST...WE ARE GOING WITH THE COOLEST MODEL TEMPS...SIMILAR TO THE ETA MOS FOR THE SE HALF OF THE CWA. FOR THE NW ZONES...THE CROSS CASCADE GRADIENT WILL BECOME FAIRLY STRONG BY AFTERNOON...SUGGESTING GOOD MIXING POTENTIAL AND THUS MUCH MILDER TEMPS COMPARED TO THE REMAINDER OF THE CWA. FX THURSDAY TO SATURDAY...A DOMINATING RIDGE WILL MEAN DRY AND FAIR CONDITIONS. GUIDANCE IS SHOWING 500 MB HEIGHTS AROUND 585-590 DM THURSDAY INTO SATURDAY AND CLIMATOLOGICAL HEIGHTS FOR MID-MAY ARE ABOUT 565 DM...SO GUIDANCE IS FORECASTING THIS TO BE A STRONG RIDGE. EXCEPT FOR A FEW PASSING HIGH CLOUDS...SKIES ARE EXPECTED TO BE MOSTLY CLEAR. 850 TEMPS RISE FROM THE MID TEENS ON THURSDAY TO THE LOWER TO MID-20S ON FRIDAY AND SATURDAY. THIS SUPPORTS TEMPS SOME 10 DEGS ABOVE NORMAL ON THURSDAY...SURGING TO ABOUT 15-20 DEGS ABOVE NORMAL FRIDAY AND SATURDAY. SATURDAY NIGHT THROUGH TUESDAY...GUIDANCE INDICATES SHORT-WAVE SYSTEMS STARTING TO SULLYING THE RIDGE`S DOMINANCE. HOW EFFECTIVE THE INITIAL SHORT-WAVES WILL BE IN INFILTRATING THE RIDGE REMAINS IN QUESTION. MUCH OF THIS WILL DEPEND ON HOW STRONG THE RIDGE THEY ENCOUNTER IS AND HOW THE SHORT-WAVE FEATURES TRACK AROUND THE OFFSHORE TROUGH. THERE REMAINS A FAIR AMOUNT OF MODEL-TO-MODEL AND RUN-TO-RUN INCONSISTENCY AS TO THE INTENSITY OF THOSE SHORT-WAVES AND WHETHER THE BRUNT OF THEIR ENERGY WILL BE DEFLECTED NORTH OR COME MORE DIRECTLY THROUGH AND PUT THE AREA INTO A MORE ZONAL FLOW. THUS THE QUESTION OF HOW THESE SHORT-WAVES WILL TRACK IS STILL IMPRECISELY ANSWERED. ON THE OTHER POINT...MODELS HAVE BEEN REASONABLY CONSISTENT IN THE STRENGTH OF THE RIDGE THAT BUILDS UP PRIOR TO THIS PERIOD. KEYING ON THAT...THE FORECAST LEANS TOWARD THE EXPERIENCE THAT THESE INITIAL WAVES WILL NOT BE ALL THAT EFFECTIVE IN BREAKING THE RIDGE`S DOMINANCE. SO THE FORECAST WILL REMAIN DRY UNTIL ABOUT TUESDAY...WHEN A GUIDANCE SHOWS A MORE SUBSTANTIAL SHORT-WAVE TROUGH BEING PROPELLED IN THE REGION BY A 160KT JET. FAVORING THE GFS/GEFS SOLUTION...THE INITIAL SHORT-WAVES ARE NOT EXPECTED TO BREAK THE RIDGE. BUT THEY ARE EXPECTED TO DAMPEN IT AT LEAST A BIT. WITH THIS DAMPENING ALL MODELS DO INDICATE SOME DOWNWARD TREND IN 850 TEMPS ON SUNDAY (AS COMPARED WITH SATURDAY). THEY DIFFER GREATLY HOWEVER ON HOW MUCH OF A DROP OCCURS. THE GFS/GEFS/DGEX SHOW 850 TEMPS DROP 1 OR 2 DEGS...THE ECMWF DROPS 850 TEMPS 5 TO 7 DEGS. THE FORECAST LEANS TOWARD THE MILDER SOLUTION OF THE GFS/GEFS. EITHER SOLUTION KEEPS FORECAST TEMPERATURES ABOVE AVERAGE. GREATER DIVERGENCE IN 850 TEMP CONTINUES ON MONDAY. THE GFS/GEFS/DGEX RE-AMPLIFY THE RIDGE AHEAD OF THE APPROACHING TROUGH...AND 850 TEMPS REMAIN AROUND 20 DEG C. THE ECMWF CONTINUES TO DROP 850 TEMPS TO BETWEEN 8-11 DEG C. WHILE THE MILDER SOLUTION REMAINS FAVORED...THERE IS NOT ENOUGH RUN-TO- RUN CONSISTENCY IN EITHER SOLUTION TO DISCOUNT THE ECMWF COMPLETELY. SO FORECAST TEMPERATURES FOR MONDAY CONTINUE TO INDICATE A SLIGHT COOLING TREND...BUT ONCE AGAIN TEMPERATURES ARE EXPECTED TO REMAIN ABOVE AVERAGE. BY TUESDAY GFS/GEFS/ECMWF/DGEX ARE ALL INDICATING 850 TEMPS COOLING TOWARD THE UPPER SINGLE DIGITS TO LOWER TEENS...WHICH SUPPORTS PUSHING TEMPERATURES BACK CLOSER TO AVERAGE FOR THIS TIME OF YEAR. /JCOTE && .AVIATION... LOW AND MID LEVEL FLOW WILL TREND WEST/NORTHWEST ACROSS EASTERN WA AND NORTHERN ID THROUGH 14-15Z BRINGING AN END TO AREAS OF MVFR/IFR CIGS ACROSS KCOE-KSFF-KGEG. AS CONDITIONS IMPROVE TO THE NORTH... KPUW-KLWS WILL EXPERIENCE CONTINUED LIGHT RAIN WITH BRIEF MVFR CIGS. HOWEVER THE DRIER AIRMASS WILL SLOWLY SETTLE SOUTHWARD UNDER THE PREVAILING MID-LEVEL FLOW WITH CIGS RAISING TO 5-6K FT BEFORE SKIES CLEARING AFT 04Z. VFR CONDITIONS WILL DOMINATE ALL SITES IN THE CENTRAL AND WEST BASIN INCLUDING KMWH-KEAT. SKIES BECOMING MOSTLY CLEAR OVERNIGHT ACROSS ALL TAFS AND POSSIBLE ADDITION OF SHALLOW FOG AFT 11Z THURSDAY NOT OUT OF THE QUESTION. /BODNAR && .PRELIMINARY POINT TEMPS/POPS... SPOKANE 62 45 78 49 85 54 / 30 0 0 0 0 0 COEUR D`ALENE 60 44 79 47 85 51 / 40 0 0 0 0 0 PULLMAN 60 44 76 49 83 51 / 60 0 0 0 0 0 LEWISTON 67 52 82 54 90 58 / 50 10 0 0 0 0 COLVILLE 66 44 85 46 86 49 / 40 0 0 0 0 0 SANDPOINT 60 41 79 44 83 50 / 30 0 0 0 0 0 KELLOGG 57 42 76 42 81 45 / 70 10 0 0 0 0 MOSES LAKE 73 49 86 53 91 59 / 10 0 0 0 0 0 WENATCHEE 73 54 87 57 91 61 / 10 0 0 0 0 0 OMAK 72 46 86 50 90 53 / 10 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...NONE. WA...NONE. && $$