AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 202 AM PST THU JAN 11 2001
.OVERVIEW...
AFTER A PERIOD OF PROGRESSIVE FLOW OVER THE PAC AND A SPLIT OVER WRN
NORTH AMERICA...THE PATTERN APPEARS TO BE TRANSITIONING TO SOMETHING
THAT LOOKS A LOT LIKE WHAT WAS EXPERIENCED DURING A GOOD CHUNK OF MID
OCT-MID DEC 2000...A STRONG JET AND ZONAL FLOW ALONG 40N IN THE WRN
AND CNTRL PAC...A REGION OF EXPLOSIVE CYCLOGENESIS 40N-45N/180-
150W...AND A PERSISTENT RIDGE IN THE PAC NW. AFTER ONLY VERY LIGHT IF
ANY PCPN AMOUNTS TODAY...AND AGAIN SAT/SAT NIGHT WITH THE NEXT
SPLITTING SYS...IT LOOKS BONE DRY OUT TO NEXT WED AND MAYBE BEYOND.
SEASONAL TO BELOW SEASONAL TEMPS IN THE INTR LOWLANDS DURING THE
MEDIUM RANGE FORECAST PERIOD WILL BE DUE TO STRONG SFC-BASED
INVERSIONS INSTEAD OF A COOL AIR MASS.
THE 00Z AVN AND 06Z MESOETA APPEAR TO BE WELL INITIALIZED PER
SATELLITE AND ACARS DATA AND LOOK REASONABLE IN HOW THEY DEPICT THE
VERTICALLY STACKED 988 MB LOW MOVING INTO N CNTRL CA AND ITS
INTERACTION WITH A SEWD MOVING NRN STREAM SHORT WAVE TROF NEAR THE
CHARLOTTES. ALL MODELS ARE CONSISTENT WITH THEIR HANDLING OF THE NEXT
SPLITTING SYS SAT/SAT NIGHT. AND ALL INCLUDING THE MRF ENSEMBLES WITH
LITTLE DEVIATION SHOW THE STRONG RIDGE FOR SUN-WED. OVERALL HIGH
CONFIDENCE IN TODAYS FORECAST.
.SHORT TERM...
A NWD MOVING DEFORMATION ZONE SPREADING OUT FROM THE CA LOW HAS
PRODUCED ABUNDANT MID LVL MSTR OVER WRN WA...KHQM WAS LUCKY TO GET
0.02 INCHES OF RA AS STRONG NELY GRADIENTS PRODUCES DOWNSLOPE OFF THE
MOUNTAINS AND A DRY AMS BELOW 8 KFT. GRADIENTS ARE RELAXING AND THE
AIR MASS IS MOISTENING SOMEWHAT...BUT DYNAMICS ARE ALSO WEAKENING.
HENCE WILL MAINTAIN LOW END CHANCE POPS FOR TODAY ACROSS THE AREA.
GRADIENTS WILL BE LIGHT TONIGHT...BUT ABUNDANT CLOUD COVER WILL KEEP
FOG TO A MINIMUM. FRI WILL SEE THE AMS DRYING IN RESPONSE TO NLY FLOW
ALOFT AS THE CA LOW WEAKENS AND MOVES E AND SHORT WAVE RIDGING
APPROACHES FROM THE W. WILL UP POPS A BIT TODAY BUT WILL MAINTAIN THE
GENERAL IDEA OF THE PREVIOUS FORECAST PACKAGES.
.EXTENDED...
AVN/MRF/CANADIAN/ECMWF MODELS ALL SHOW THE NEXT FRONT SPLITTING AS IT
MOVES ONSHORE. OFFSHORE GRADIENTS IN RESPONSE TO ABOVE NORMAL HEIGHTS
OVER BC WILL SHUNT THE ENERGY/MOISTURE WITH THIS FRONT MAINLY TO THE
S OF WA. BUT ALL SOLUTIONS DO BRING AT LEAST A FEW HUNDREDTHS OF PCPN
INTO THE AREA WITH THIS PASSING SYSTEM...SO WILL REINTRODUCE A CHANCE
OF RA...MAINLY COAST AND S...FOR SAT/SAT NIGHT. PERSISTENT RIDGING
AND STRENGTHENING INVERSIONS SUN-WED WILL PROVIDE THREAT OF
STAGNATION AND FOG IN THE INTERIOR. SOME MIXING ON THE COAST WILL
PROVIDE WARMER CONDITIONS THERE WHILE THE MOUNTAINS ARE HIGH/DRY/AND
WARM ABOVE THE INVERSION. HOPEFULLY THIS PATTERN CAN CHANGE QUICKLY
SO SOME WATER CAN BE STORED FOR THE SUMMER.
UIL 421 SEA 321 OLM 421 ALBRECHT
.KATX...VCP21/CSR31...OPERATIONAL
.SEW...SMALL CRAFT ADVISORY W ENTRANCE TO THE STRAIT.
.SMALL CRAFT ADVISORY COAST FOR HEAVY SWELL.
.MINOR TIDAL OVERFLOW POSSIBLE PUGET SOUND AND STRAIT OF JUAN
DE FUCA.
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 201 AM PST THU JAN 11 2001
.OVERVIEW...
AFTER A PERIOD OF PROGRESSIVE FLOW OVER THE PAC AND A SPLIT OVER WRN
NORTH AMERICA...THE PATTERN APPEARS TO BE TRANSITIONING TO SOMETHING
THAT LOOKS A LOT LIKE WHAT WAS EXPERIENCED DURING A GOOD CHUNK OF MID
OCT-MID DEC 2000...A STRONG JET AND ZONAL FLOW ALONG 40N IN THE WRN
AND CNTRL PAC...A REGION OF EXPLOSIVE CYCLOGENESIS 40N-45N/180-
150W...AND A PERSISTENT RIDGE IN THE PAC NW. AFTER ONLY VERY LIGHT IF
ANY PCPN AMOUNTS TODAY...AND AGAIN SAT/SAT NIGHT WITH THE NEXT
SPLITTING SYS...IT LOOKS BONE DRY OUT TO NEXT WED AND MAYBE BEYOND.
SEASONAL TO BELOW SEASONAL TEMPS IN THE INTR LOWLANDS DURING THE
MEDIUM RANGE FORECAST PERIOD WILL BE DUE TO STRONG SFC-BASED
INVERSIONS INSTEAD OF A COOL AIR MASS.
THE 00Z AVN AND 06Z MESOETA APPEAR TO BE WELL INITIALIZED PER
SATELLITE AND ACARS DATA AND LOOK REASONABLE IN HOW THEY DEPICT THE
VERTICALLY STACKED 988 MB LOW MOVING INTO N CNTRL CA AND ITS
INTERACTION WITH A SEWD MOVING NRN STREAM SHORT WAVE TROF NEAR THE
CHARLOTTES. ALL MODELS ARE CONSISTENT WITH THEIR HANDLING OF THE NEXT
SPLITTING SYS SAT/SAT NIGHT. AND ALL INCLUDING THE MRF ENSEMBLES WITH
LITTLE DEVIATION SHOW THE STRONG RIDGE FOR SUN-WED. OVERALL HIGH
CONFIDENCE IN TODAYS FORECAST.
.SHORT TERM...
A NWD MOVING DEFORMATION ZONE SPREADING OUT FROM THE CA LOW HAS
PRODUCED ABUNDANT MID LVL MSTR OVER WRN WA...KHQM WAS LUCKY TO GET
0.02 INCHES OF RA AS STRONG NELY GRADIENTS PRODUCES DOWNSLOPE OFF THE
MOUNTAINS AND A DRY AMS BELOW 8 KFT. GRADIENTS ARE RELAXING AND THE
AIR MASS IS MOISTENING SOMEWHAT...BUT DYNAMICS ARE ALSO WEAKENING.
HENCE WILL MAINTAIN LOW END CHANCE POPS FOR TODAY ACROSS THE AREA.
GRADIENTS WILL BE LIGHT TONIGHT...BUT ABUNDANT CLOUD COVER WILL KEEP
FOG TO A MINIMUM. FRI WILL SEE THE AMS DRYING IN RESPONSE TO NLY FLOW
ALOFT AS THE CA LOW WEAKENS AND MOVES E AND SHORT WAVE RIDGING
APPROACHES FROM THE W. WILL UP POPS A BIT TODAY BUT WILL MAINTAIN THE
GENERAL IDEA OF THE PREVIOUS FORECAST PACKAGES.
.EXTENDED...
AVN/MRF/CANADIAN/ECMWF MODELS ALL SHOW THE NEXT FRONT SPLITTING AS IT
MOVES ONSHORE. OFFSHORE GRADIENTS IN RESPONSE TO ABOVE NORMAL HEIGHTS
OVER BC WILL SHUNT THE ENERGY/MOISTURE WITH THIS FRONT MAINLY TO THE
S OF WA. BUT ALL SOLUTIONS DO BRING AT LEAST A FEW HUNDREDTHS OF PCPN
INTO THE AREA WITH THIS PASSING SYSTEM...SO WILL REINTRODUCE A CHANCE
OF RA...MAINLY COAST AND S...FOR SAT/SAT NIGHT. PERSISTENT RIDGING
AND STRENGTHENING INVERSIONS SUN-WED WILL PROVIDE THREAT OF
STAGNATION AND FOG IN THE INTERIOR. SOME MIXING ON THE COAST WILL
PROVIDE WARMER CONDITIONS THERE WHILE THE MOUNTAINS ARE HIGH/DRY/AND
WARM ABOVE THE INVERSION. HOPEFULLY THIS PATTERN CAN CHANGE QUICKLY
SO SOME WATER CAN BE STORED FOR THE SUMMER.
UIL 421 SEA 321 OLM 421 ALBRECHT
.KATX...VCP21/CSR31...OPERATIONAL
.SEW...SMALL CRAFT ADVISORY W ENTRANCE TO THE STRAIT.
.SMALL CRAFT ADVISORY COAST FOR HEAVY SWELL.
.MINOR TIDAL OVERFLOW POSSIBLE PUGET SOUND AND STRAIT OF JUAN
DE FUCA.