HAMweather.com Area Forecast Discussion for County Warning Area PQR

Thu, 16 Feb 2012 07:01:59 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
851 PM PST WED FEB 15 2012

.SYNOPSIS...AN UPPER LEVEL RIDGE WILL BE OVER SOUTHWEST WASHINGTON 
AND NORTHWEST OREGON MOST OF TONIGHT WITH A MIXTURE OF FOG AND LOW 
CLOUDS AROUND. THE NEXT FRONT OFFSHORE WILL APPROACH THE COAST LATE 
TONIGHT THEN WEAKEN AS IT MOVES THROUGH THE PACIFIC NORTHWEST 
THURSDAY WITH SOME LIGHT PRECIPITATION ESPECIALLY ALONG THE COAST 
AND ALONG AND NORTH OF THE COLUMBIA RIVER. THE LEFT OVER FRONTAL 
BOUNDARY WILL LIKELY STALL OVER THE AREA THURSDAY NIGHT WITH CLOUDS 
AND SOME SPOTTY LIGHT PRECIPITATION. THEN THE NEXT MUCH STRONGER LOW 
PRESSURE SYSTEM WILL PUSH A STRONG COLD FRONT THROUGH THE AREA 
DURING THE DAY FRIDAY AND EARLY FRIDAY NIGHT FOR LOCALLY BREEZY 
CONDITIONS AND A GOOD SHOT OF RAIN...THEN FOLLOWED BY THE ASSOCIATED 
COLD UPPER LOW LATER FRIDAY NIGHT AND SATURDAY FOR PLENTY OF SHOWERS 
AND QUITE LOW SNOW LEVELS DOWN INTO AT LEAST THE HIGHER HILLS AND 
FOOTHILLS.

.SHORT TERM...A DECK OF LOW CLOUDS HAS PERSISTED THIS EVENING ACROSS
SOUTHWEST WASHINGTON AND ITS CLEARING HAS BEEN SLOWED. TO THE SOUTH
SOME LOWER CLOUDS OR FOG WAS WORKING ITS WAY NORTH ALONG THE LANE
COUNTY CASCADE FOOTHILLS. IT IS POSSIBLE THESE TWO LOW CLOUD SOURCES
WILL MERGE OVERNIGHT...SO EXPECT A MIXTURE OF LOCAL FOG AND AREAS OF
LOW CLOUDS OVERNIGHT TONIGHT.

HIGHER CLOUDS AHEAD OF THE NEXT SYSTEM ARE ALREADY STARTING TO SPREAD
ONSHORE THIS EVENING. THIS SYSTEM WILL BE WEAKENING AS IT MOVES
THROUGH THE UPPER RIDGE OVER OUR AREA. 500 MB HEIGHTS ONLY FALL TO
AROUND 564 DM...AND THIS WILL LIMIT THE STRENGTH OF THIS FRONT AND
KEEP THE SNOW LEVELS FROM BEING VERY LOW. THE FRONT HAD A GOOD 
MOISTURE SOURCE SO WE SHOULD GET SOME RAIN OUT OF IT ESPECIALLY 
ALONG THE COAST AND IN OUR NORTHERN INTERIOR ZONES ON THURSDAY BUT 
AMOUNTS WILL BE RATHER LIGHT.

THE FRONTAL BOUNDARY FROM THIS SYSTEM WILL THEN STALL OVER OUR AREA
THURSDAY NIGHT AND EARLY FRIDAY. THE MODELS HAVE BEEN VACILLATING ON
WHETHER WE WILL SEE MUCH IF ANY PRECIPITATION THURSDAY NIGHT AND
EARLY FRIDAY. WE WILL BE MOSTLY BETWEEN SYSTEMS...BUT A FEW SPRINKLES
OR A LITTLE DRIZZLE ARE NOT OUT OF THE QUESTION AND HAVE KEPT LOW 
CHANCE POPS FOR THIS.

OF MORE SIGNIFICANCE IS THE MUCH STRONGER SYSTEM WE WILL SEE FRIDAY
AND SATURDAY. THE FRONT WILL MOVE ONSHORE FRIDAY AND EAST OF THE
CASCADES FRIDAY EVENING WITH A GOOD SHOT OF RAIN. SNOW LEVELS WILL 
INITIALLY BE ABOVE THE CASCADE PASSES. THERE WILL BE A SHOT OF WIND 
WITH THE FRONT AT THE COAST BUT PROBABLY NOT HIGH WIND...AND BREEZY 
CONDITIONS INLAND. THEN STRONG COLD ADVECTION BEHIND THE FRONT WILL 
DROP SNOW LEVELS TO AROUND 1000 OR 1500 FEET LATER FRIDAY NIGHT AND 
SATURDAY...POSSIBLY A LITTLE LOWER IN HEAVIER SHOWERS. ONSHORE FLOW 
IS LOOKING PRETTY GOOD...SO WE COULD SEE SNOW ADVISORY SNOW TOTALS 
IN THE CASCADES...FOOTHILLS...AND COAST RANGE. THE AIR MASS WILL 
LIKELY BE ON THE UNSTABLE SIDE SATURDAY SO SMALL HAIL AND EVEN SOME 
THUNDER IS POSSIBLE SATURDAY. THIS IS WELL COVERED IN THE CURRENT 
FORECASTS SO ONLY MINOR CHANGES MADE IN THE EVENING UPDATE. TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...SNOW LEVELS
DROP SIGNIFICANTLY AS THE UPPER LEVEL TROUGH PASSES TO THE SOUTH AND
EAST LATE SAT INTO SUNDAY. SHOWERS WILL CONTINUE INTO SUNDAY...
LENDING TO CONTINUED SNOW ACCUMULATIONS IN THE CASCADES AND POSSIBLY
THE FOOTHILLS AND COAST RANGE THROUGH AT LEAST EARLY SUN. A BROAD
UPPER LEVEL RIDGE BEGINS TO BUILD OUT OVER THE EASTERN PACIFIC LATE
SUN AND CONTINUING THROUGH MID WEEK. HOWEVER...THIS WILL NOT HINDER A
SERIES OF FRONTAL SYSTEMS AS THEY RIDE OVER THE RIDGE AND MOVE IN
OVER THE PAC NW. AT THIS TIME...INDIVIDUAL SYSTEM TIMING AND STRENGTH
IS NOT WELL AGREED UPON BY THE EXTENDED MODELS. HAVE KEPT THE
FORECAST GENERALLY PROGRESSIVE. BROWN

.AVIATION...EXPECT INCREASING HIGH CLOUDS TONIGHT WHICH WILL LIMIT
FOG FORMATION OVERNIGHT. STILL EXPECT LOCAL IFR IN THE WILLAMETTE
VALLEY AFTER 06Z THU...MAINLY SOUTH OF KSLE. LIGHT OFFSHORE FLOW
DEVELOPS LATE TONIGHT IN THE COLUMBIA RIVER GORGE. CIGS LOWER ALONG
THE COAST LATE TONIGHT AS THE NEXT FRONTAL SYSTEM APPROACHES. MVFR
EXPECTED AT KAST AROUND 15Z THU.

KPDX AND APPROACHES...VFR CONDITIONS CONTINUE AS HIGH CLOUDS
INCREASE. WRN APPROACHES MORE PRONE TO FOG MAY DROP INTO IFR VIS
AFTER 08Z. ENOUGH LOW-LEVEL OFFSHORE FLOW BY 12Z THU...ALBEIT
WEAK...SHOULD PRECLUDE FOG FORMATION OVER ERN APPROACHES. RAIN
REACHES THE TERMINAL AND APPROACHES AROUND 16Z THU...BUT PREDOMINANT
VFR FLIGHT CONDITIONS TO PREVAIL.WEISHAAR/27

.MARINE...HIGH PRES SHIFTS INLAND TONIGHT AS THE NEXT FRONTAL SYSTEM
APPROACHES THE WATERS. EXPECT WIND SPEEDS TO GRADUALLY PICK UP LATER
TONIGHT...WITH GUSTS NEAR 25 KT LIKELY OVER THE FAR NWRN WATERS BY
12Z THU...THEN SPREADING INTO THE MAJORITY OF THE NRN WATERS LATER
THU MORNING. SEAS WILL REMAIN ABOVE 10 FT THROUGH TONIGHT... THEN
FALL BELOW 10 FT BY 12Z THU. A STRONGER SYSTEM THAT COULD BRING
POTENTIAL GALES MOVES INTO THE REGION LATE FRI NIGHT OR SAT MORNING.
CONSIDERABLE MODEL DISCREPANCY WITH THIS SYSTEM. THE 12Z RUN OF THE
ENP CONTINUES THE TREND OF THE 06Z VERSION BY BLOWING UP SEAS WITH
THIS SYSTEM...INDICATING 25 TO 30 FT SAT. THIS LOOKS TO BE A DYNAMIC
FETCH SITUATION SO STILL NOT CONFIDENT THE MODELS WILL BE ABLE TO
DIAGNOSE THE EVENT VERY WELL. WILL MAINTAIN 20-FOOT SEAS THROUGH
SATURDAY. THIS LEAVES PLENTY OF ROOM TO BUMP UP WHEN MODEL CONFIDENCE
INCREASES. WEISHAAR/27

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY 
     FOR COASTAL WATERS FROM CAPE SHOALWATER TO CASCADE HEAD OUT 
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM PST THIS 
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER TO FLORENCE 
     OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 3 AM
     PST THURSDAY.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 10 AM 
     TO 2 PM PST THURSDAY.