Severe Thunderstorm Warning 17, NWS Spokane, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WASHINGTON
230 PM PDT WED AUG 4 2004

.SYNOPSIS...A PACIFIC WEATHER SYSTEM WILL MOVE INTO THE AREA FROM
THE SOUTH CAUSING SHOWERS AND THUNDERSTORMS TONIGHT AND THURSDAY
OVER MOST OF THE AREA.  A STRONGER PACIFIC STORM WILL MOVE ACROSS
THE AREA ON FRIDAY FOR MORE SHOWERS...CLOUDS AND WIND.  A WARMING
AND DRYING TREND IS EXPECTED BY SUNDAY INTO NEXT WEEK.

&&

.DISCUSSION...VERY ACTIVE PATTERN TO DEAL WITH.  NEGATIVE TILT
SHORT WAVE OVER SOUTHWEST OREGON WILL EJECT OVER OUR AREA TONIGHT
AND THURSDAY.  AFTER A BRIEF BREAK ON THURSDAY NIGHT...THE MAIN
PACIFIC TROUGH GETS KICKED ONSHORE FRIDAY.

TONIGHT...CONVECTION IS FIRING OVER ALL OF THE MOUNTAIN RANGES THIS
AFTERNOON BUT IT IS UNABLE TO MOVE ONTO THE LOWER TERRAIN.  THE
AREA TO WATCH IS IN CENTRAL OREGON NEAR REDMOND.  THIS IS WHERE THE
BEST INSTABILITY WILL MEET UP WITH THE DYNAMICS FROM THE
APPROACHING SHORT WAVE.  CONVECTION THERE SHOULD BECOME ORGANIZED
LATE THIS AFTERNOON...AND WITH THE HELP OF THE DYNAMICS ALOFT...
MOVE ONTO THE LOWER TERRAIN OF THE COLUMBIA BASIN THIS EVENING. SOME
OF THESE STORMS COULD BE SEVERE IN THE COLUMBIA BASIN.  AS THE SUN
SETS THE DYNAMICS WILL CONTINUE TO FORCE CONVECTION OVERNIGHT.
EXPECT SOMEWHAT OF A COMMA-LIKE SYSTEM TO DEVELOP WITH SOME
DEFORMATION PRECIP POSSIBLE ALONG THE CASCADES AND OKANOGAN VALLEY
SO HAVE GONE WITH THE HIGHEST POPS THERE INITIALLY.

THURSDAY...CONVECTION WILL MOVE FROM THE BASIN INTO THE
NORTHERN/EASTERN MOUNTAINS BY MID-DAY.  THUS THE BEST POPS WILL BE
THERE WITH DRYING IN THE BASIN AND EAST SLOPES.  TEMPERATURES WILL
BE DOWN CONSIDERABLY DUE TO THE CLOUD COVER OVER THE
NORTHERN/EASTERN MOUNTAINS.  ISOLATED SEVERE STORMS WILL BE POSSIBLE
IN THE AFTERNOON...BUT MOST OF THIS KIND OF ACTIVITY SHOULD BE IN
WESTERN MONTANA.

THURSDAY NIGHT...LINGERING SHOWERS IN THE EVENING.  MEANWHILE A
STRONG SYSTEM BY THE ALEUTIANS WILL KICK OUR PACIFIC TROUGH
ONSHORE WITH A VENGEANCE.  DYNAMICS WITH THIS SYSTEM ARE VERY
SIGNIFICANT FOR ANY TIME OF YEAR.  THE GFS HAS SHOWN SOME GOOD
CONSISTENCY OVER THE LAST FEW RUNS WITH THIS SYSTEM.  OF COURSE
THERES STILL SOME UNCERTAINTY WITH THIS SYSTEM BUT ITS WELL WORTH
WATCHING.

FRIDAY...STRONG SYSTEM MOVES ACROSS THE AREA WITH A NEGATIVE TILT.
GFS SUGGESTS CONVECTION WILL FIRE AHEAD OF THIS TROUGH DURING THE
AFTERNOON.  TEMPERATURES WILL BE COOL BUT WITH ALL THOSE DYNAMICS
IM NOT WORRIED ABOUT HAVING ENOUGH LIFT FOR THUNDERSTORMS.  BEST
CHANCES WOULD STILL BE OVER THE MOUNTAINS BUT EVEN THE BASIN COULD
SEE SOME ACTIVITY.  ALSO EXPECT SOME STRONG SOUTHWESTERLY WINDS.

FRIDAY NIGHT...MAIN DYNAMICS MOVE EAST BUT THE TROUGH AXIS WILL BE
OVER US FOR CONTINUED THREAT OF SHOWERS.  STRONG WESTERLY FLOW WILL
SHUT OFF THE BASIN AND EAST SLOPES BUT WILL KEEP THE PANHANDLE
MOUNTAINS IN A WET REGIME.   RJ

SATURDAY THROUGH WEDNESDAY...MODELS REMAIN IN FAIRLY GOOD AGREEMENT
IN BUILDING A STRONG RIDGE OVER THE INLAND NORTHWEST FOLLOWING THE
EXITING WAVE SATURDAY MORNING. SATURDAY SHOULD BE THE COOLEST DAY
DURING THE EXTENDED PERIOD WITH DAYTIME HIGHS RANGING FROM THE MID
70S TO MID 80S. BY SUNDAY...THE UPPER LEVEL RIDGE UMBRELLAS THE
REGION KEEPING THE ATMOSPHERE WARM AND DRY...DAYTIME HIGHS WILL
CLIMB INTO THE MID 80S AND LOW 90S. BY MONDAY DAYTIME TEMPERATURES
WILL WARM INTO THE UPPER 80S TO MID 90S. THE GFS TENDS TO
START BREAKING THE RIDGE DOWN BY TUESDAY...WHILE THE ECMWF KEEPS IT
STRONG. WILL FAVOR THE ECMWF IN THIS SCENARIO AS THE RIDGE ALMOST
ALWAYS PROVES STRONGER THAN THE GFS PROJECTS. WILL CONTINUE A DRY...
WARM FORECAST THROUGH WEDNESDAY.  /JVW

&&

.PRELIMINARY POINT TEMPS/POPS...

SPOKANE        058 079 055 074 049 079/ 50 60 10 20 40 05
COEUR DALENE  057 079 051 072 048 078/ 20 50 10 20 50 10
PULLMAN        053 078 052 073 048 077/ 30 40 10 20 40 00
LEWISTON       064 084 060 080 056 085/ 20 30 05 20 30 05
COLVILLE       055 078 050 079 047 082/ 30 60 10 30 60 10
SANDPOINT      058 075 049 073 046 077/ 20 60 20 30 60 10
WALLACE        060 075 050 072 046 074/ 20 50 20 30 50 20
MOSES LAKE     063 083 056 082 053 082/ 40 40 10 30 30 00
WENATCHEE      064 083 059 074 054 083/ 60 30 05 30 40 00
OMAK           061 080 056 080 049 083/ 60 60 10 40 50 05
&&

.OTX...
ID...NONE.
WA...NONE.