EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 930 AM PST SUN FEB 4 2001
...SYNOPSIS...
HIGH PRESSURE ALOFT AND OFFSHORE FLOW WILL BRING RECORD AND
NEAR-RECORD HIGHS TODAY. SOME CANYONS AND PASSES WILL BE WINDY. A
COOLING TREND WILL BEGIN MONDAY AS ONSHORE FLOW RETURNS. A TROUGH OF
LOW PRESSURE WILL MOVE THROUGH AROUND WEDNESDAY AND BRING
BELOW-NORMAL TEMPERATURES...SOME CLOUDS AND BREEZY CONDITIONS.
...DISCUSSION...
AN UNSEASONABLY STRONG 587 HEIGHT LIES OVERHEAD...AND ACARS OUT OF
SAN SHOWS A 17 DEG C TEMP AT 850 MB. WITH PRESSURE GRADIENTS ABOUT 2
MB OFFSHORE FROM THE LOWER DESERTS AND 6+ FROM THE UPPER
DESERTS...TODAY SHOULD HAVE RECORD HIGH TEMPS IN NUMEROUS LOCATIONS.
COOLING SHOULD START MONDAY ALONG THE COAST AS THE FLOW BECOMES
ONSHORE BY AFTERNOON...THOUGH 850 MB TEMPS DO NOT DECREASE UNTIL
TUESDAY...SO MTNS/DESERTS SHOULD BE AS WARM MONDAY AS TODAY.
THE WIND ADVISORY WILL CONTINUE...THOUGH I EXPECT WINDS TO DECREASE
BY THIS AFTERNOON...BASED ON EXPECTED GRADIENTS AND OUTPUT FROM
IVORY'S SANTA ANA PROGRAM. A FEW GUSTS BETWEEN 45 AND 55 MPH HAVE
OCCURRED WITHIN THE LAST HOUR AT RIALTO HELIPORT AND IN NW SAN
BERNARDINO.
THE TROUGH FOR MAINLY WEDNESDAY WILL HAVE TO BE WATCHED. 12Z AVN IS
LACKING IN MOISTURE...MAYBE TOO MUCH SO. GIVEN A LOW OF THAT
STRENGTH...EVEN IF IT HAS AN INLAND TRACK...WE SHOULD SEE ENOUGH
ONSHORE FLOW AND CYCLONIC FLOW TO QUICKLY SPIN UP A DEEP MARINE
LAYER WITH ASSOCIATED DRIZZLE OR LIGHT SHOWERS. WE WILL EVEN THINGS
OUT TEMPERATUREWISE RELATIVE TO NORMAL BY HAVING A PERIOD OF
BELOW-NORMAL TEMPERATURES TUE-THU. ANOTHER SYSTEM COULD AFFECT US
TOWARDS THE END OF THE WEAK IN FAST NW FLOW.
THE CURRENT ZONE FORECASTS LOOK OK...SO NO UPDATE IS EXPECTED.
.SAN 000
.SAN...WIND ADVISORY TODAY FOR CAZ048-057-058...SEE LAXNPWSAN.
MAXWELL
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 845 AM PST SUN FEB 4 2001
COMPOSITE SATELLITE IMAGERY CONTINUES TO SHOW A PATTERN CHANGE OVER
THE NEXT FEW DAYS AS THE LONGWAVE RIDGE THAT HAS BEEN OVER THE WRN US
FOR THE PAST SEVERAL WEEKS RETROGRADES WWD TO 150W-160W. THE
MODELS...BOTH IN THE SHORT TERM AND IN THE MEDIUM RANGE...HAVE BEEN
HAVING DIFFICULTIES HANDLING DETAILS IN SHORT WAVE FEATURES DURING
THIS PERIOD OF TRANSITION.
IN THE SHORT TERM...A WARM OCCLUSION HAS MOVED RAPIDLY EWD THROUGH
WRN WA AND APPEARS TO BE NOW MOVING ACROSS THE CASCADES. PER
SATELLITE IMAGERY AND ACARS REPORTS...THE AXIS OF A ENE-WSW ORIENTED
120-130KT 300MB JET STREAK SITS FROM NEAR KUIL TO N OF KGEG WITH
CLOUDS AND PCPN ENHANCED IN ITS RIGHT REAR QUADRANT FROM THE CENTRAL
CASCADES TO JUST OFF THE NW OREGON COAST. SHORT TERM MODELS MOVE A
HANG BACK TROUGH FROM THE PARENT LOW OVER CENTRAL VANCOUVER ISLAND
ACROSS WRN WA ABOUT 00Z. EXPECT OROGRAPHIC PCPN AND CONVERGENCE ZONES
TO FORM BEHIND THIS TROUGH AS THE FLOW BECOMES WNW AND THE AMS
DESTABILIZES. WILL ISSUE A GALE WARNING COAST FOR NW FLOW BEHIND
TROUGH AS SUPPORTED BY BUOY 46036.
RADAR AND OBSERVATIONS SHOW HEAVIEST PRECIPITATION STEVENS PASS SW TO
KAST WITH IMPRESSIVE 0.15 INCH PER HOUR ACCUMULATION RATES. SNOW
LEVELS ARE ABOVE WHITE PASS TO THE S WITH SOME INDICATION THAT
SNOQUALMIE AND POSSIBLY STEVENS WILL CHANGE TO RAIN AS GRADIENTS
SWITCH TO WLY BEHIND THE FRONT AND TEMPS NOW 4500-5500 FEET AT OR A
BIT ABOVE FREEZING PER AVALANCHE DATA AND AIRCRAFT SOUNDINGS OUT OF
SEATAC. A PCPN LULL EXPECTED BEHIND THE OCCLUSION AS SEEN ON RADAR
BEHIND THE FRONT AND AHEAD OF SHOWER BAND APPROACHING COAST. 6-10
INCHES OF SN FELL IN THE MAJOR PASSES PAST FEW HOURS VERIFYING SNOW
ADVISORY...WITH MORE EXPECTED TONIGHT WITH OROGRAPHIC PCPN AND
CONVERGENCE ZONES. WITH AMS DESTABILIZING AND DRYING ALOFT WILL KEEP
AMOUNTS TONIGHT IN THE ADVISORY RANGE. GIVEN LULL AND AFTN RISE IN
FREEZING LEVELS WILL NOT ISSUE HEAVY SNOW WARNING FOR THE CASCADES.
IN THE EXTENDED EXPECT TIMING OF FAST SE MOVING SHORTWAVES TO
CONTINUE TO CAUSE FORECAST PROBLEMS. CURRENT BROAD BRUSH LOOKS GOOD
FOR NOW. WILL CLOSELY EVALUATE 12Z MODELS TO SEE IF MORE DETAIL CAN
BE ADDED DAYS 3-4 PERIOD IN AFTN FORECAST PACKAGE.
UIL 963 SEA 663 OLM 662 ALBRECHT
.SEW...GALE WARNING STRAIT AND COAST.
.SMALL CRAFT ADVISORY ADMIRALTY INLET...CAMANO ISLAND TO POINT
ROBERTS...AND PUGET SOUND/HOOD CANAL.
.SNOW ADVISORY WEST SLOPES CASCADES/PASSES AND OLYMPICS THROUGH
TONIGHT.
.KATX...VCP21/CSR21...OPERATIONAL.