Flash Flood Warning 4, NWS Spokane, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WASHINGTON
230 PM PDT TUE AUG 17 2004

.SYNOPSIS...A WEAK RIDGE WILL LIE OVER THE INLAND NORTHWEST THROUGH
THE WEEK. THIS WILL KEEP TEMPERATURES WARM...BUT WITH THE POSSIBILITY
OF SHOWERS AND THUNDERSTORMS DEVELOPING ACROSS THE AREA EACH DAY
THROUGH FRIDAY.

&&

.DISCUSSION...
TONIGHT THROUGH FRIDAY...A STRONG LOW PRESSURE SYSTEM LIES OVER THE
GULF OF ALASKA AND ANOTHER STRONG LOW LIES OVER THE CENTRAL U.S.
THIS LEAVES THE INLAND NORTHWEST IN A WEAK RIDGE PATTERN SANDWICHED
IN BETWEEN. THE MOIST AND UNSTABLE AIRMASS IN PLACE OVER EASTERN
WASHINGTON AND NORTH IDAHO HAS ALLOWED A FEW SHOWERS AND
THUNDERSTORMS TO DEVELOP THIS AFTERNOON. EXPECT ADDITIONAL SHOWERS
AND THUNDERSTORMS TO FORM LATE THIS AFTERNOON AND EVENING ACROSS MUCH
OF THE FORECAST AREA. THROUGH THE NEXT FEW DAYS THE RIDGE WILL
REMAIN IN PLACE BUT FLATTEN WITH TIME. THE ATMOSPHERE WILL REMAIN
UNSTABLE...BUT IN THE ABSENCE OF A STRONG SHORTWAVE EXPECT MAINLY
DIURNAL MOUNTAIN SHOWERS/THUNDERSTORMS THE NEXT FEW DAYS. CC

FRIDAY NIGHT THROUGH TUESDAY...MODELS GRAPPLING WITH WHAT APPEARS
TO BE A SIGNIFICANT PATTERN CHANGE. MODELS ARE IN REASONABLE
AGREEMENT INTO SATURDAY WITH THE NORTHERN EXTENSION OF THE RIDGE
BREAKING OFF AND BEGINNING TO FORM A BLOCKING PATTERN OVER ALASKA...
WHICH IN-TURN INITIALLY MEANS FLATTER MORE PROGRESSIVE FLOW OVER THE
NORTHWEST. BEYOND THIS MODELS HAVE BEEN DIVERGENT BETWEEN KEEPING
FLOW RELATIVELY FLAT AND PROGRESSIVE ACROSS THE REGION OR CREATING
MORE MERIDIONAL FLOW WITH WEATHER PRODUCING WAVES PROPAGATING THROUGH
THE REGION. LATEST GFS SEEMS TO BE TRANSITIONING TOWARD THE UKMET AND
ECMWF...BOTH OF WHICH FAVOR THE LATTER SOLUTION. DEVELOPING BLOCK
PATTERN OVER THE ALASKA REGION TYPICALLY TENDS TO PRODUCE MORE
CYCLONIC FLOW OVER THE NORTHWEST. IN LIGHT OF THIS...HAVE TRENDED
FORECAST TOWARD A MORE SHOWERY WEATHER PATTERN BY SUNDAY WITH
TEMPERATURES TRENDING MORE TOWARD SEASONAL NORMS. IF CURRENT MODEL
PROGNOSTICATIONS HOLD TRUE...FOLLOWING FORECASTS WILL LIKELY HAVE TO
ADJUST POPS UP AND TEMPERATURES DOWN. /JVW

&&

.PRELIMINARY POINT TEMPS/POPS...

SPOKANE        064 089 062 091 060 091/ 20 10 10 00 05 10
COEUR DALENE  062 089 060 091 058 091/ 20 10 10 00 00 00
PULLMAN        061 088 059 090 057 090/ 20 10 10 00 00 00
LEWISTON       069 093 067 095 065 095/ 20 10 10 05 05 05
COLVILLE       061 091 059 093 057 093/ 20 10 10 10 10 10
SANDPOINT      063 089 061 091 059 091/ 20 10 10 10 10 10
WALLACE        061 083 059 085 057 085/ 20 10 10 10 10 10
MOSES LAKE     066 092 064 094 062 093/ 20 00 00 00 00 00
WENATCHEE      070 091 068 093 066 091/ 20 00 00 00 00 00
OMAK           068 094 066 096 064 094/ 20 10 10 00 05 05
&&

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