FXUS66 KOTX 021014 AFDGEG AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPOKANE WASHINGTON 230 AM PST FRI APR 2 2004 .SYNOPSIS...HIGH PRESSURE WILL BRING MOSTLY CLEAR AND MILD CONDITIONS TO THE REGION THROUGH SATURDAY MORNING. LATE SATURDAY AND SUNDAY A PACIFIC WEATHER SYSTEM WILL INCREASE THE THREAT FOR SHOWERS AND A FEW THUNDERSTORMS OVER THE AREA. && .DISCUSSION... TODAY THROUGH TONIGHT...MAIN SYNOPTIC FEATURES ON SATELLITE WHICH WILL IMPACT REGIONAL WEATHER IN THE SHORT TERM INCLUDE THE UPPER LEVEL CUT-OFF LOW SPINNING OVER CALIFORNIA AND NEVADA THIS MORNING. WHILE THIS LOW IN ITSELF IS NOT A THREAT...THE SOUTHERLY FLOW AROUND THE EASTERN FLANK OF THIS FEATURE IS FORCING A WELL DEFINED TONGUE OF SUB-TROPICAL MOISTURE REMINISCENT OF A SUMMER MONSOONAL PUSH TOWARD THE FORECAST AREA. THE OTHER FEATURES OF INTEREST ARE A STRONG UPPER LEVEL RIDGE AXIS ALONG 130N...AND THE DEEP UPSTREAM PACIFIC TROUGH NEAR 150W. LATEST MODEL RUNS ARE QUITE SIMILAR FOR THE NEXT 24 TO 36 HOURS AND SATELLITE EXTRAPOLATION SUPPORTS MODEL FORECASTS. FOR TODAY FORECAST AREA WILL BE DOMINATED BY THE UPPER LEVEL RIDGE HOOKING INTO THE NORTHWEST FROM THE PACIFIC. EXPECT NO SIGNIFICANT WEATHER WITH MOSTLY CLEAR SKIES AND TEMPERATURES REACHING WELL ABOVE NORMAL THROUGHOUT THE FORECAST AREA. TONIGHT MOSTLY CLEAR SKIES WILL PROMOTE RADIATIONAL COOLING BUT BY THEN AN INCREASING NORTHEASTERLY GRADIENT WILL KEEP VALLEY WINDS UP ENOUGH TO PROMOTE TURBULENT MIXING NEAR THE SURFACE AND PREVENT LOW TEMPERATURES FROM REACHING THE FREEZING MARK AT MOST STATIONS. SATURDAY THROUGH SUNDAY...WEATHER MAY LIVEN UP THIS WEEKEND OVER THE NORTHWEST AS TWO SYNOPTIC FEATURES BEGIN TO INTERACT. BY LATE SATURDAY THE DEEP MOISTURE FETCH WORKING IT'S WAY UP FROM THE SOUTH WILL REACH EASTERN WASHINGTON AND NORTH IDAHO RAISING PRECIPITABLE WATER VALUES INTO THE .5 TO .8 INCH RANGE. MEANWHILE THE NEXT PACIFIC TROUGH WILL CLOSE WITH THE COAST AND HURL A SHORT WAVE INTO THE REGION. ETA AND GFS DIFFER IN THE SPEED AND STRENGTH OF THIS NEXT SYSTEM. GFS IS SIMILAR TO YESTERDAY'S 00Z RUN WITH THE STRENGTH OF THE INCOMING WAVE AND ASSOCIATED MID LEVEL COLD FRONT...AND MORE CONSISTENT WITH PREVIOUS RUNS THAN THE ETA. GFS ALSO INITIALIZES VORT FEATURES OUT OVER THE PACIFIC WELL AT THIS TIME AND HAS A GOOD GRIP ON THE UPPER LEVEL MOISTURE PLUME APPROACHING FROM THE SOUTH. THUS WILL USE GFS FOR THIS SYSTEM. BY SATURDAY AFTERNOON AIR MASS IS MOISTENED UP WITH THE SOUTHERLY PWAT FETCH. THE PACIFIC SHORT WAVE WILL INTERACT WITH THIS MOISTURE WITH A WEAK BUT IDENTIFIABLE JET FEATURE AND ASSOCIATED DIFFERENTIAL PVA CROSSING EASTERN WASHINGTON AND NORTH IDAHO LATE IN THE DAY AND INTO THE EVENING. WILL ASSUME MOISTURE AND UPPER LEVEL SUPPORT AVAILABLE FROM THIS INTERACTION. THE ASSOCIATED MID LEVEL COLD FRONT MOVING THROUGH THE BASIN WILL PROVIDE A FOCUSING BOUNDARY...ALTHOUGH EXACT TIMING IS STILL UNCERTAIN. INSTABILITY IS THE MAIN UNCERTAINTY AT THIS TIME...BUT BOTH MODELS INDICATE AN 850-700MB THERMAL RIDGE OVER THE IDAHO PANHANDLE DURING THE DAY THUS THE POTENTIAL FOR TEMPERATURES TO APPROACH 70 DEGREES AT MANY LOWER ELEVATION LOCATIONS. A RELATIVE MINIMUM dTHETAE/dz AXIS HAS BEEN DEPICTED IN THE GFS FOR THE LAST FEW RUNS PASSING OVER EASTERN WASHINGTON AND NORTH IDAHO DURING THE NIGHT. THUS POTENTIAL EXISTS FOR THUNDERSTORMS OVER THE EASTERN ZONES LATE SATURDAY AND SATURDAY NIGHT WHERE ALL THESE INGREDIENTS MERGE. ON SUNDAY POST FRONTAL AIR MASS WITH WESTERLY MID LEVEL FLOW WILL RETURN WEATHER TO MORE OF AN OROGRAPHIC SHOWER REGIME. SATURDAY NIGHT'S SURFACE COLD FRONT WILL BE QUITE WEAK AND WILL NOT HAVE MUCH OF A COOLING EFFECT ON SUNDAY'S HIGH TEMPERATURES. /FUGAZZI SUNDAY NIGHT THROUGH THURSDAY...NEW GFS RUN THIS MORNING IN LINE BETTER WITH THE EURO COMPARED TO LAST NIGHT'S SOLUTION. ALL MODELS NOW HAVE A GOOD AGREEMENT WITH KEEPING A MEAN RIDGE ACROSS THE REGION SUNDAY NIGHT INTO THURSDAY. THE GFS HAS A FEW VERY SMALL WAVES MOVING THROUGH THE RIDGE BOTH MONDAY AND THURSDAY...BUT WILL LEAVE OUT ANY MENTION OF PRECIPITATION FOR NOW BECAUSE OF UNCERTAINTY. IT WILL BE MOST LIKELY A BIT ABOVE NORMAL FOR TEMPERATURES DURING THE EXTENDED PERIOD UNDER THE RIDGE WITH CONTINUED BELOW NORMAL PRECIPITATION. /TC && .PRELIMINARY POINT TEMPS/POPS... SPOKANE 061 035 067 037 067/ 00 00 20 20 10 COEUR D'ALENE 060 036 068 038 068/ 00 00 20 20 20 PULLMAN 059 035 066 038 066/ 00 00 20 20 20 LEWISTON 064 038 073 042 073/ 00 00 05 20 20 COLVILLE 060 033 067 038 065/ 00 00 20 20 20 SANDPOINT 057 031 068 035 067/ 00 00 20 20 20 WALLACE 051 032 063 036 063/ 00 00 20 20 20 MOSES LAKE 066 035 070 038 068/ 00 00 05 05 05 WENATCHEE 067 036 069 040 067/ 00 00 05 05 10 OMAK 063 033 073 036 071/ 00 00 05 05 10 && .OTX... ID...NONE. WA...NONE. $$