High Wind in Washington, August 28, 2005

AREA FORECAST DISCUSSION...UPDATED AVIATION DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
1030 AM PDT SUN AUG 28 2005

.SYNOPSIS...AN UPPER LEVEL RIDGE WILL REMAIN OVER WASHINGTON AND
IDAHO THROUGH THE WEEKEND KEEPING THE WEATHER DRY AND TEMPERATURES
WARM. THE RIDGE WILL BEGIN TO BREAK DOWN LATE TODAY AS A STRONG UPPER
LEVEL TROUGH AND COLD FRONT HEADS INTO THE PACIFIC NORTHWEST MONDAY.
THIS WILL BRING COOLER AND UNSETTLED WEATHER FOR THE FIRST PART OF
THE WEEK BEFORE A WARMING A DRYING TREND.

&&

.DISCUSSION...
TODAY...WARM AND DRY WILL CONTINUE TO BE THE FCST FOR ALL OF ERN WA/N
ID THE REST OF THE WEEKEND. STRENGTHENING WARM SWLY STEERING FLOW
ALOFT WILL PREVAIL OVER THE PAC NW...AHEAD OF THE UPPER TROF AND SFC
COLD-FRONT MOVG SE DOWN THE BC COAST THIS MORNING. THIS FRONT SHOULD
REACH THE CASCADES LATE IN THE AFTERNOON. ONLY ISSUE OF NOTE WILL BE
WINDS NEAR THE CASCADES. DEEPENING MARINE LYR AND ONSHORE FLOW AHEAD
OF THE AFOREMENTIONED FRONT WILL HELP TO PRODUCE A MARKED TEMP AND
PRESSURE GRADIENT ACROSS THE CASCADES...ESPECIALLY IN THE LATE
AFTERNOON AND EARLY EVENING. GUIDANCE SUGGESTS THAT MARINE AIR MASS
WILL BE SUFFICIENTLY DEEP THAT MIN RH FOR THESE LOCATIONS WILL REMAIN
ABOVE RFW CRITERIA.

TONIGHT THROUGH TUES...MAIN FOCUS WILL BE ON SHOWER AND THUNDER
POTENTIAL MON AND MON NT...WITH A SECONDARY FOCUS ON WINDS THIS
EVENING. TREND OF UPPER TROF HAS BEEN ONE OF SLOWER PROGRESSION EWD
AS VORT MAX DIGGING SWD ON THE BACK SIDE OF THE TROF STRETCHES AND
SHEARS THE UPPER TROF. HOWEVER...EVEN WITH FOLLOWING A SLOWER TREND,
THE TROF AND SFC COLD-FRONT SHOULD MOVE ACROSS THE CASCADES AND
INTO ERN WA TONIGHT NT AND MON. GUIDANCE IS SIMILAR IN SHOWING DEEP
LG-SCALE FORCING FOR ASCENT INCREASE STEADILY ACROSS ERN WA ALONG THE
MID-LEVEL FRONTAL BAND AS IT MOVES ACROSS THE CASCADES MON MORNING.
RELATIVELY DRY (LOW RH) AND STABLE TROPOSPHERE VCNTY THIS FRONTAL
BAND WILL MEAN THAT INITIALLY PCPN WILL NOT BE A BIG THREAT. HAVE
INCLUDED CHC POPS FOR THE MTNS ACROSS THE WRN AND NRN PART OF MY CWA
TO ACCOUNT FOR THIS. VERY SHALLOW LYR OF POTENTIAL INSTABILITY IN THE
MID LEVELS IS THE ONLY REASON WEVE PUT THE MENTION OF ISOLD SHOWERS
IN THE LOWER VALLEYS THRU MON MORNING. THE UPPER TROF SQUARELY OVER
THE PAC NW MON...WITH COOLER AND MORE UNSTABLE AIR MASS FAVORING
SHOWERS. DEEPEST INSTABILITY WITH UNCAPPED SBCAPE PER ETA IS LOCATED
OVER THE NE WA MTNS...BUT THIS WILL BE MORE OF A FUNCTION OF THE
TRACK OF THE UPPER VORT MAX AND COLDEST AIR ALOFT. THIS IS NOT
SOMETHING THAT WE CAN NAIL DOWN TO SPECIFICS ATTM...SO HAVE THEREFORE
KEPT THE MENTION OF ISOLD/SCT THUNDER FOR NEARLY ALL ZONES MON
AFTERNOON AND EVENING BEFORE LOSS OF PEAK HEATING ENDS THE THUNDER
THREAT BY 6Z TUES. FILLING UPPER TROF TO MOVE E INTO MT MON NT AND
TUES...WITH UNSTABLE W/NW FLOW KEEPING THE THREAT OF SHOWERS IN THE
FCST FOR ALL OF N ID THRU TUES. RISING HTS ALOFT AND STABILIZING AIR
MASS WILL END THE SHOWER THREAT BY TUES MORNING FOR THE BASIN AND
CASCADES ZONES. AS FAR AS WINDS...CAA THRU A SIGNIFICANT DEPTH OFF
THE SFC WILL ALLOW FOR BREEZY TO WINDY WEST WINDS FOR MOST ZONES
TONIGHT AND MON.  THIS WILL BE ESPECIALLY TRUE FOR TOWNS NEAR THE
CASCADES FOLLOWING FRONTAL PASSAGE TONIGHT AND MON MORNING. SFC DEW
PT TEMPS AND RH SHOULD REMAIN SUFFICIENTLY HI TO NOT REQUIRE AN RFW
AS THE MODIFIED MARINE AIR MASS CRESTS THE CASCADES. BZ

TUESDAY NIGHT THROUGH SATURDAY...MODELS IN FAIRLY GOOD AGREEMENT OF
DRY AND NEAR NORMAL TEMPERATURES TUESDAY NIGHT THROUGH THURSDAY
AS THE PACIFIC NORTHWEST REMAINS IN ZONAL WESTERLY FLOW. THURSDAY
NIGHT THERE IS A TRANSITION TO SOUTHWESTERLY FLOW AS AN UPPER LEVEL
TROUGH MOVES DOWN THE BRITISH COLUMBIA COAST. SHORTWAVES WILL ADVECT
INTO THE AREA...WITH THE COLD FRONT PASSAGE LATE SATURDAY NIGHT OR
EARLY SUNDAY MORNING.   /KOCH

&&

.AVIATION...COLD FRONT WILL MOVE ACROSS THE CASCADES LATE TONIGHT
AND MOVE INTO THE IDAHO PANHANDLE BY MONDAY MORNING. THERE COULD BE
SOME ISOLATED TO WIDELY SCATTERED CONVECTION BREAKING OUT AHEAD OF
THE FRONT EARLY MONDAY MORNING ACROSS EXTREME EASTERN WASHINGTON AND
NORTH IDAHO. THERE COULD BE SOME MVFR CONDITIONS WITH THE FRONT IN
THE SHOWERS FOR ALL LOCATIONS AS THE FRONT MOVES ACROSS THE FORECAST
AREA.

&&

.PRELIMINARY POINT TEMPS/POPS...
SPOKANE        88  58  74  46  72  48 /   0  20  40  30  10  10
COEUR DALENE  90  54  73  45  69  45 /   0  10  40  30  10  10
PULLMAN        89  55  72  43  71  44 /   0  10  30  20  10  10
LEWISTON       97  62  79  53  76  52 /   0   0  30  20  10   0
COLVILLE       93  54  77  45  76  46 /   0  20  40  30  10  10
SANDPOINT      88  48  72  45  68  44 /   0  10  40  30  20  10
KELLOGG        85  48  73  46  72  45 /   0  10  40  30  20  10
MOSES LAKE     91  59  79  50  79  49 /   0  10  20  10   0   0
WENATCHEE      89  61  77  55  78  57 /   0  20  20  10   0   0
OMAK           93  58  79  47  79  50 /   0  20  20  20   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&