NORTHERN ARIZONA FORECAST DISCUSSION
NWS FLAGSTAFF AZ
AFDFLG 300 PM MST SAT FEB 10 2001
SYNOPSIS...A WEAK PACIFIC STORM SYSTEM WILL MOVE ACROSS NORTHERN
ARIZONA TONIGHT BRINGING A CHANCE OF PRECIPITATION...MAINLY TO THE
UTAH BORDER REGION. FAIR WEATHER IS EXPECTED TO RETURN ON SUNDAY AND
CONTINUE INTO MONDAY. ANOTHER...STRONGER STORM WILL AFFECT THE STATE
BEGINNING TUESDAY AND WILL BRING MOUNTAIN SNOW AND VALLEY RAIN TO
NORTHERN ARIZONA FOR MUCH OF THE WEEK.
DISCUSSION...CLOSED LOW HAS BEGUN TO MOVE ONSHORE OVER NRN CA THIS
MORNING. THIS SYSTEM IS BEGINNING TO OPEN UP AND WEAKEN AS A
STRONGER SYSTEM AMPLIFIES OVER THE PAC NW. EVEN THOUGH THERE IS SOME
WEAKENING...THERE IS STILL A MODERATE BAROCLINIC ZONE LOCATED AHEAD
OF IT OVER SRN CA/SRN NV AND UT. EXPECT THIS BAROCLINIC ZONE TO
SLOWLY SAG SWD OVERNIGHT AND LINGER OVER THE NORTHERN ZONES THRU
TOMORROW BEFORE WEAKENING. THIS BAROCLINIC ZONE WILL BE SUFFICIENT
TO PRODUCE SOME RAIN AND SNOW SHOWERS OVER THE NORTHERN ZONES AND
POPS REFLECT THIS. FARTHER SOUTH POPS NIL OR CLOSE TO IT. JET
ASSOCIATED WITH NEXT SYSTEM APPEARS TO BE UNDERDONE WHEN COMPARING
INITIAL ANALYSES WITH ACARS WINDS. SUSPECT THAT THIS SYSTEM WILL
MOVE SLOWER THAN MODELS SUGGEST AND WILL HAVE NO IMPACT UNTIL THE
EXTENDED PERIODS.
EXTENDED...SIGNIFICANT DIFFERENCES BETWEEN THE ECMWF AND MRF. MRF
DEVELOPS A MODERATE AMPLITUDE, LARGE WAVELENGTH TROUGH OVER MUCH OF
THE CONUS. ECMWF DEVELOPS MORE ZONAL FLOW WITH HIGHER HEIGHTS. BOTH
SOLUTIONS WILL RESULT IN TROUGHING OVER THE WEST BUT WITH LARGE
DIFFERENCES IN TEMPS AND TRAJECTORIES. ENOUGH DISPERSION IN MRF
ENSEMBLE MEMBERS TO CAST SOME DOUBT. ALSO...RECENT H5 OBS-FCST
BIASES BETWEEN VARIOUS MODELS AS WELL AS MODEL CORRELATIONS SUGGEST
THAT THE ECMWF HAS THE BETTER TRACK RECORD IN RECENT DAYS. GIVEN
THE UNCERTAINTY...WILL LEAN MORE TOWARD THE ECMWF SOLUTION BUT TEND
TO BROADBRUSH THE EXTENDED UNTIL SOME CONSENSUS EMERGES. DB
.FGZ...NONE
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 830 PM PST SAT FEB 10 2001
.OVERVIEW...
GLOBAL MODELS AND COMPOSITE IMAGERY SHOW A HIGH AMPLITUDE RIDGE ALONG
145W WITH A MEAN TROUGH NEAR 115W. NEARBY...A 524 DAM 500 MB LOW NEAR
BUOY 46005...AND ASSOCIATED 999 MB LOWS NEAR BUOY 46005 AND
KAST...ARE DRIVING SWD IN RESPONSE TO THE UPSTREAM RIDGING AND
INTERACTION WITH THE REMNANTS OF THE CIRCULATION OF THE OLD UPPER LOW
THAT PASSED WRN WA THU. AN OCCLUSION ASSOCIATED WITH THE LOW OFF NW
OREGON IS NEARLY STATIONARY AND APPEARS TO BE MAKING A TRANSITION TO
A DEFORMATION ZONE. OTHER THAN BEING A LITTLE WEAK AND TOO FAR E WITH
THE JET ON THE BACK SIDE OF THE OFFSHORE DIGGING LOW...THE 00Z MODELS
APPEAR RATHER WELL INITIALIZED AND ARE CONSISTENT WITH PREVIOUS
SOLUTIONS IN SHOWING DRYING WITH TIME.
.SHORT TERM...
THE OCCLUSION ON THE COAST IS HAVING DIFFICULTY MAKING EWD PROGRESS
AS INCREASING OFFSHORE GRADIENTS PROVIDE DRYING OVER THE INTERIOR.
PORTLAND RADAR DOES SHOW PCPN KTDO SWD MAKING SOME NWD PROGRESS...BUT
OBSERVATIONS ARE SHOWING LITTLE IF ANY ACCUMULATION AND THE -SN
REPORT AT SCAPPOSE OREGON INDICATES MAYBE SOME BRIGHT BANDING ON THE
RADAR. PER KUIL SOUNDING AND ACARS REPORTS FREEZING LEVELS RANGE FROM
1000-1500 FT ON THE COAST AND NEAR THE OREGON BORDER...TO 2000-3000
FEET KSEA-CYVR. WILL MAINTAIN LIKELY POPS ON THE COAST AND IN THE S
INTERIOR...CHANCE POPS NEAR KSEA...AND KEEP THINGS DRY KPAE-KCLM NWD.
PCPN WILL RAPIDLY END FROM THE N BY MORNING AS THE LOW AND ASSOCIATED
DEFORMATION BAND DROPS SWD.
LATE SUN-TUE LOOK DRY AND SEASONALLY COOL WITH NNE FLOW ALOFT.
.EXTENDED...
00Z AVN SIMILAR TO 12Z RUN AND LAST NIGHTS MRF IN INDICATING NEXT
SHORT WAVE TROUGH NOW ASSOCIATED WITH A 968 MB LOW IN THE BERING SEA
DIGGING FARTHER W THAN ECMWF OR PREVIOUS DAYS MRF RUNS. GIVEN THE
WAVELENGTH ACROSS THE PACIFIC...A SCENARIO SIMILAR TO LAST THURSDAY
NOT OUT OF THE QUESTION FOR WED OF NEXT WEEK AS COOL/DRY CONDITIONS
PREVAIL IN INTR WRN WA AND SHORT WAVE ENERGY TRIES TO DIG SWD ALONG
THE W COAST. WILL AWAIT THE COMPLET SUITE OF 00Z AVN/MRF SOLUTIONS
BEFORE MAKING CHANGES TO THE CURRENT DRY EXTENDED FORECAST.
UIL 9410 SEA 3100 OLM 6200 ALBRECHT
.SEW...SMALL CRAFT ADVISORY COAST FOR ROUGH BAR CONDITIONS.
.SMALL CRAFT ADVISORY FOR THE ENTRANCES TO THE STRAIT.
.KATX...VCP31/CSR31...OPERATIONAL.