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National Weather Service meteorologists use a wide variety of tools such as observations, satellite imagery, radar imagery, and computer models to aid in making forecasts. The Enhanced Area Forecast Discussion is intended to provide additional insight into our traditional Area Forecast Discussion (AFD) by including embedded links to some of the key tools used in the forecast process. These links are specific to the forecast issue of the day and are updated as the forecast discussion is updated. For comments or feedback please contact the Seattle WFO Webmaster For more information on the terms used in the Enhanced AFD, please see Frequently Asked Questions (updated 20 May, 2008). For help decoding the image legends, please see Legends Help. Previous Version ZCZC SEAGPHAFD 000 TTAA00 KSEA 141800 AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SEATTLE WA 915 AM PST TUE FEB 14 2012 .SYNOPSIS...AN UPPER LEVEL LOW PRESSURE SYSTEM WILL CROSS WESTERN WASHINGTON TODAY...THEN DROP INTO OREGON TONIGHT. HIGH PRESSURE WILL BUILD OVER THE AREA ON WEDNESDAY. A WEAK WEATHER SYSTEM WILL REACH THE REGION THURSDAY...FOLLOWED BY HIGH PRESSURE FRIDAY. A STRONGER FRONTAL SYSTEM WILL REACH WESTERN WASHINGTON FRIDAY NIGHT WITH AN UPPER TROUGH ON TAP FOR SATURDAY. && .SHORT TERM...A CLOSED UPPER LEVEL LOW IS DROPPING SOUTHEAST INTO THE SOUTH WASHINGTON COAST THIS MORNING. PRECIPITATION CONSISTS OF A STEADIER SHIELD OF RAIN SLIDING SOUTHEAST AHEAD OF THE LOW OVER THE OLYMPIC PENINSULA AND SOUTHWEST INTERIOR...AND AN AREA OF DEFORMATION ALLOWING SHOWERS TO PERSIST FURTHER NORTH (image). THE FRONTAL BOUNDARY HAS PASSED THROUGH THE SOUTH WASHINGTON COAST...AND COLD CU IS PILING IN BEHIND FROM THE WNW (image). ISOLATED THUNDERSTORMS HAVE BEEN ADDED FOR THE CENTRAL COAST AND LOWER CHEHALIS VALLEY TODAY...AREAS ON THE NORTHERN EDGE OF THE COLD POOL WITH LIFTED INDEX VALUES DIPPING BELOW ZERO. POPS FOR THE REST OF THE CWA HAVE ALSO BEEN NUDGED UP. SNOW LEVELS CLOSE TO THE COLD POOL (image) WILL LOCALLY FALL TO AROUND 1000 FEET IN HEAVY SHOWERS...MAINLY FOR THE HIGHER TERRAIN IN GRAYS HARBOR AND WESTERN LEWIS COUNTY. THE LOW WILL DROP SOUTH INTO OREGON BY 06Z THIS EVENING...WITH THE FLOW ALOFT BECOMING NORTHERLY. SHOWERS WILL TAPER QUICKLY FROM NORTH TO SOUTH ACROSS WESTERN WASHINGTON THIS AFTERNOON. THE UPPER LEVELS WILL DRY OUT BEGINNING LATER TODAY AND TONIGHT...BUT WITH WEAK GRADIENTS A SLOWER CLEARING TREND WILL TAKE PLACE FOR THE INTERIOR OVERNIGHT. A WEAK RIDGE BUILDING ON WEDNESDAY WILL PRODUCE DRY AND MOSTLY SUNNY WEATHER WITH HIGH TEMPERATURES NEAR OR A LITTLE BELOW NORMAL. THE NEXT FRONTAL SYSTEM APPROACHING FROM THE NORTHEAST PACIFIC WILL PLOW INTO THE RIDGE ON THURSDAY (image)...BRINGING RAIN AND MOUNTAIN SNOW. QPF DOES NOT LOOK PARTICULARLY HEAVY WITH THIS EVENT. SHOWERS WILL DIMINISH OVERNIGHT AS WEAK UPPER LEVEL RIDGING TAKES PLACE. DAMICO .LONG TERM...FRIDAY'S DRY FORECAST IS IN QUESTION. 12Z GFS AND NAM HAVE ABANDONED THE HEALTHY LOOKING RIDGE FOR FRIDAY...NOW SHOWING A FRONTAL SYSTEM MOVING ONTO THE COAST BY MID-AFTERNOON. LAST NIGHT'S CANADIAN SHOWS SOMETHING SIMILAR. WILL WAIT FOR THE 12Z ECMWF BEFORE GREATLY INCREASING POPS. BOTH THE GFS AND EURO HINT TOWARD WETTER WEATHER FRI NIGHT AS THE FRONT MOVES IN. THE FORECAST REMAINS UNSETTLED THROUGH THE REMAINDER OF THE WEEKEND AS THE UPPER LOW SPINS OVERHEAD. WITH A COOL/MOIST/UNSTABLE AIR MASS IN PLACE EXPECT MOSTLY CLOUDY SKIES...SCATTERED SHOWERS WITH TEMPS BELOW NORMAL. DAMICO/33 && .HYDROLOGY...FLOODING IS UNLIKELY DURING THE NEXT 7 DAYS. && .AVIATION...AN UPPER LOW W OF VANCOUVER ISLAND WILL CONTINUE MOVING SE AND WILL BE OVER SW WA BY LATE THIS AFTERNOON. SW FLOW ALOFT WILL BECOME ELY (image). THE SFC LOW AND ASSOCIATED OCCLUDED FRONT WILL ALSO MOVE ACROSS SW WA THIS AFTERNOON. THE AIR MASS WILL BECOME UNSTABLE OVER THE SW PORTION TODAY...RESULTING IN A RISK OF ISOLD TSTMS (image). CIGS WILL BE A CHALLENGE TODAY. IN GENERAL...ANTICIPATE CIGS TO BE AT OR ABOVE 5K FT BUT THERE WILL BE AREAS OF MVFR CIGS /1-3K FT/. KSEA...CIGS WILL CONTINUE TO BOUNCE AROUND THIS MORNING. CIGS SHOULD GENERALLY BE AT OR ABOVE 5K FT TODAY WITH OCCASIONAL CIGS NEAR 2K FT EXPECTED TIL ABOUT 2100 UTC. SLY WINDS OF 8 TO 14 KT WILL DECREASE AS THE DAY PROGRESSES. && .MARINE... A 1010 MB LOW OFF THE COAST OF VANCOUVER ISLAND AND ITS ASSOCIATED OCCLUDED FRONT WILL MOVE ACROSS THE COASTAL WATERS TODAY. THE AIR MASS WILL ALSO BE UNSTABLE OVER THE COASTAL WATERS FOR ISOLATED TSTMS THIS AFTERNOON (image). EXPECT VARIABLE AND GUSTY WINDS TO 25 KT WITH THE TSTMS. WEAK HIGH PRES WILL BUILD OVER THE AREA TONIGHT AND PERSIST THROUGH WED NIGHT. ANOTHER FRONTAL SYSTEM WILL AFFECT THE AREA ON THU. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...NONE. PZ...SMALL CRAFT ADVISORIES FOR HAZARDOUS SEAS ARE IN EFFECT FOR THE COASTAL WATERS THROUGH WED AFTERNOON. SMALL CRAFT ADVISORY FOR ROUGH BAR THROUGH WEDNESDAY AFTERNOON FOR THE GRAYS HARBOR BAR. && $$ WWW.WEATHER.GOV/SEATTLE |
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