Forecast Discussions mentioning "ACARS", "MDCRS", or "AIRCRAFT" received at FSL on 01/26/02

A SURFACE CYCLONE WAS ANALYZED OVER SOUTHERN ONTARIO JUST EAST OF LAKE SUPERIOR. THIS CYCLONE WILL KEEP THE WINDS UP TO THE 15 TO 20 MPH RANGE OVER THE FORECAST AREA TONIGHT. THERE IS SIGNIFICANT WARM AIR ADVECTION AT 850 MB AT 0000 UTC. THE ACARS SOUNDING FROM ORD AT 123 UTC SHOWS A SMALL INVERSION BELOW 800 MB. WILL RAISE THE WINDS TO 15 TO 20 MPH UNTIL MORNING AND RAISE THE LOWS VERY LITTLE.

.CHI...GALE WARNING SRN 1/3 LAKE MICHIGAN.

WHW



NO REAL CONCERN WITH THE SHORT TERM FORECAST. WE HAVE LOWERED WINDS A BIT IN THE SOUTHEAST. OTHERWISE...AFTER EXAMINING MORNING ACARS AND RAOB SOUNDINGS CURRENT FORECAST LOOKS TO BE ON TRACK.

.ICT...NONE. COX



.SYNOPSIS...A COLD AND UNSTABLE AIR MASS ASSOCIATED WITH A TROUGH OF LOW PRESSURE OFF THE COAST WILL REMAIN OVER WESTERN WASHINGTON THROUGH SUNDAY...WITH LOWLAND SNOW SHOWERS. THE TROUGH WILL MOVE INLAND LATER SUNDAY ALONG WITH A WEAK SURFACE LOW. THE LOW WILL TRACK SOUTHEAST THROUGH WESTERN WASHINGTON DRAWING COLDER AIR DOWN OVER THE AREA. THIS COMBINED WITH THE TROUGH MOVING INLAND WITH GIVE THE AREA A BETTER CHANCE OF MORE WIDESPREAD BUT LIGHT SNOW ACCUMULATIONS SUNDAY AFTERNOON AND NIGHT SEATTLE SOUTHWARD. HIGH PRES WILL BUILD OVER THE AREA MONDAY FOR A SHORT DRYING TREND.

.DISCUSSION...SATELLITE IMAGERY SHOWS THE LEADING EDGE OF THE COLD UNSTABLE AIR MASS REACHING THE COAST AT 20Z. ACARS SOUNDINGS OVER KSEA HAVE 850 MB TEMPS ALREADY DOWN TO -6C AND COLDEST AIR STILL OFFSHORE. NO THUNDERSTORMS YET BUT WITH 500 MB TEMPS COOLING 5-10C TONIGHT TO BELOW -35C WILL KEEP CHANCE OF THUNDERSTORMS IN THE FORECAST. CONVECTIVE TEMPERATURES IN THE MID 30S AND LIFTED INDEXES NEAR 0 SATURDAY TO MAINTAIN MENTION OF THUNDERSTORMS. AVALANCHE DATA SITES ONLY REPORTING A FEW HUNDREDTHS AN HOUR AT 21Z BUT SATELLITE IMAGERY STILL SHOWS GOOD DOWNSLOPE ALONG THE EAST SLOPES OF THE CASCADES. WILL KEEP SNOW ADVISORY GOING FOR TONIGHT. COLD UNSTABLE AIR MASS SLOWLY MOVING OVER THE AREA TONIGHT AND REMAINING THROUGH SUNDAY AS THE UPPER LEVEL TROUGH DIGS OFFSHORE. MODEL 850 MB TEMPS STILL -7 OR 8C FOR THE WEEKEND WITH FREEZING LEVEL DROPPING BELOW 1000 FEET TONIGHT AND STAYING BELOW 1000 FEET THROUGH THE WEEKEND. THIS PUTS THE SNOW LEVEL NEAR THE SURFACE. NO REAL ORGANIZED VORT LOBES MOVING THROUGH THE AREA BUT WITH AIR MASS SO UNSTABLE WILL HAVE TO KEEP POPS ABOVE LIKELY CATEGORY. THE BEST CHANCE FOR ACCUMULATIONS WILL COME DURING THE LATE NIGHT AND EARLY MORNING HOURS...WITH HEAVIER SHOWERS...AND ON THE HIGHER TERRAIN 300 FEET AND ABOVE. WILL ISSUE A SNOW ADVISORY TONIGHT FOR THIS SCENARIO. INTERESTING PATTERN DEVELOPING ON SUNDAY AS UPPER LEVEL TROUGH BEGINS TO MOVE INLAND AND WEAK SURFACE LOW THAT DEVELOPS ALONG THE LEE SIDE OF VANCOUVER ISLAND LATE SATURDAY TRACKS INLAND KSEA SOUTHWARD AT 00Z. THIS WILL TURN THE SURFACE GRADIENTS NORTHERLY OVER THE NORTHERN PORTION OF THE STATE AND DEVELOP A WEAK AREA OVER CONVERGENCE NEAR AND JUST TO THE NORTH OF THE SURFACE LOW. STILL PLENTY OF MOISTURE OVER THE AREA AT THIS TIME. THIS LOOKS LIKE THE BEST CHANCE TO GET MORE WIDESPREAD SNOW ALTHOUGH WITH WEAK FORCING AMOUNTS LOOK SIMILAR TO THE SHOWER SCENARIO OF TONIGHT THROUGH SUNDAY MORNING...1 TO 2 INCHES. TROUGH MOVES THROUGH THE AREA AFTER 06Z MONDAY WITH DRYING NORTHERLY FLOW ALOFT AND SURFACE GRADIENTS GOING INCREASING OFFSHORE. .EXTENDED...WILL KEEP DRY PATTERN GOING THROUGH THE MIDDLE OF THE WEEK AS UPPER LEVEL RIDGE REMAINS OFFSHORE WITH NORTHERLY FLOW ALOFT OVER THE AREA. MODELS BRING A WEAK SHORTWAVE OVER THE TOP OF THE RIDGE LATE TUESDAY BUT THE MODELS ARE GETTING SLOWER AND WEAKER WITH THIS SYSTEM IN THE LAST COUPLE OF RUNS. THIS LOOKS WAY OVERDONE WITH LITTLE MOISTURE SOURCE FOR THIS SYSTEM AND COMING OVER THE TOP OF THE RIDGE SHOULD ALSO WEAKEN IT. UPPER LEVEL PATTERN BECOMING MORE ZONAL LATE IN THE WEEK WITH A PAIR OF WEATHER SYSTEMS MOVING THROUGH THE AREA THURSDAY AND FRIDAY. MRF ENSEMBLES SHOWING A LOT OF VARIABILITY SO CONFIDENCE IN THE EXTENDED NOT HIGH. felton UIL 8888 SEA 8888 OLM 8888

.SEW...SMALL CRAFT ADVISORY COAST...PUGET SOUND. SNOW ADVISORY CASCADES AND OLYMPICS. SNOW ADVISORY ABOVE 300 FEET NON MOUNTAINOUS AREAS.

.KATX...VCP21/CSR21...OPERATIONAL.



.SYNOPSIS...A COLD FRONT PASSED THROUGH WESTERN WASHINGTON THIS MORNING. A COLD AND UNSTABLE AIR MASS ASSOCIATED WITH A TROUGH OF LOW PRESSURE OFF THE COAST WILL MOVE OVER WESTERN WASHINGTON BEHIND THE FRONT THIS AFTERNOON AND REMAIN OVER THE AREA THROUGH THE WEEKEND...BRINGING A CHANCE OF LOWLAND SNOW SHOWERS.

.DISCUSSION...LOTS GOING ON THIS MORNING. SATELLITE IMAGERY AND SURFACE OBS INDICATE COLD FRONT NOW SOUTH AND EAST OF THE CWA. CONVERGENCE ZONE FORMED BEHIND THE FRONT OVER SNOHOMISH COUNTY WITH KPAE REPORTING SNOW FOR A COUPLE OF HOURS. CONVERGENCE ZONE HAS SHIFTED NORTH IN THE LAST HOUR WITH SNOW AT ARLINGTON. CONVERGENCE ZONE SHOULD DISSIPATE THIS AFTERNOON AS FLOW THROUGH THE STRAIT DIMINISHES WITH THE SURFACE TROUGH OFFSHORE MOVING CLOSER TO THE COAST. COLD UNSTABLE AIR MASS OFFSHORE WITH THE LEADING EDGE OF THE COLD AIR OVER CENTRAL VANCOUVER ISLAND. SATELLITE EXTRAPOLATION BRINGS THIS OVER WESTERN WASHINGTON AFTER 20Z. TEMPERATURES AREN'T GOING TO GET MUCH WARMER TODAY AND MODEL CONVECTIVE TEMPERATURES ARE IN THE LOWER 40S. WILL KEEP THE CHANCE OF THUNDERSTORMS IN THE FORECAST. ACARS SOUNDING OVER KSEA THIS MORNING HAVE 850 MB TEMPS OF -4C. MODELS DROP THE 850 MB TEMPS TO -8C TONIGHT WITH PLENTY MOISTURE MOVING OVER THE AREA IN THE SOUTHWESTERLY FLOW ALOFT. SURFACE GRADIENTS ARE WEEKLY ONSHORE WHICH WILL NOT HELP KEEP THE SNOW LEVEL UP. CURRENT FORECASTS FOR SNOW LEVEL NEAR THE SURFACE IN HEAVIER SHOWERS LOOKS GOOD. POSSIBLE 1 TO 2 INCH ACCUMULATIONS IN THE HIGHER HILLS IN THE LOWLANDS. TROUGH CONTINUES TO DIG OFFSHORE DURING THE WEEKEND WITH THE JET SAGGING SOUTH INTO NORTHERN CALIFORNIA DYNAMICS WEAKENING AND SHOWER ACTIVITY SHOULD DIMINISH. AIR MASS STILL COLD WITH 850 TEMPS REMAINING NEAR -8 THROUGH THE WEEKEND. MODEL 500 MB TEMPS BELOW -35C. CURRENT FORECAST HAS EVERYTHING COVERED. WILL MAKE LITTLE IN THE WAY OF CHANGES. ON THE HYDRO FRONT...UPPER REACHES OF THE CHEHALIS CRESTING AND WILL ISSUE FLOOD WARNING FOR THE CHEHALIS. JUST TRYING TO GET SHORT TERM RIGHT FOR NOW...WILL DEAL WITH EXTENDED THIS AFTERNOON. felton

UIL ++8 SEA 897 OLM 897

.SEW...SMALL CRAFT ADVISORY ALL WATERS EXCEPT ADMIRALTY INLET. SNOW ADVISORY CASCADES AND OLYMPICS.

.KATX...VCP21/CSR21...OPERATIONAL.