AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 328 AM EDT THU MAY 12 2011 .SYNOPSIS... AN OCEAN STORM WELL OFFSHORE WILL BRING COOL GUSTY NORTHEAST WINDS AND AREAS OF DRIZZLE TO EASTERN MASSACHUSETTS AND RHODE ISLAND THIS MORNING WITH SLOW IMPROVEMENT THIS AFTERNOON. THE CONNECTICUT VALLEY WILL BE DRY AND SEASONABLE. WEAKENING HIGH PRESSURE WILL BUILD ACROSS THE REGION TONIGHT AND FRIDAY WITH DRY AND SEASONABLE CONDITIONS. A WEAK BACK DOOR FRONT WILL CROSS THE AREA SATURDAY WITH SOME SHOWERS POSSIBLE. AN UNSETTLED PATTERN WILL CONTINUE INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... OCEAN STORM REMAINS WELL OFFSHORE BUT CONTINUES TO FEED CLOUDS DOWN THE MAINE COAST INTO EASTERN MASSACHUSETTS. ONE SHORTWAVE CIRCLING THE STORM IS MOVING THROUGH THE GULF OF MAINE SUPPORTING A SURGE OF CLOUDS DURING THE EARLY-MID MORNING. AS THIS SHORTWAVE TURNS SOUTH THIS MORNING THE CLOUDS SHOULD CEASE THEIR WESTWARD TREND AND START TO PULL EAST AGAIN. WESTERN SECTIONS SHOULD REMAIN MOSTLY CLEAR THROUGH THE DAY. THE NAM AND GFS CROSS SECTIONS SHOW LINGERING LOW LEVEL MOISTURE IN EASTERN SECTIONS...BELOW AN INVERSION BASE AT 850 MB. THIS MAY SLOW DOWN ANY CLEARING THIS MORNING. THE WARM MAY SUNSHINE SHOULD FRAY THE EDGES OF THE CLOUDS LATE IN THE MORNING AND BRING A CLEARING TREND FOR THE MIDDAY AND AFTERNOON. WE USED A BLEND OF NAM AND GFS SKY COVER FIELDS...WITH MANUAL ADJUSTMENTS FOR THIS MORNING TO MOVE THE WESTERN CLOUD EDGE FARTHER WEST. TEMPS AT 850 MB WILL BE AT 6-7C. FULL MIXING THAT TAPS THIS WOULD BRING MAX TEMPS IN THE UPPER 60S AND AROUND 70. THE ONSHORE FLOW IN EASTERN MASS AND RI WILL KEEP TEMPS THERE SEVERAL DEGREES COOLER. WE USED A BLEND OF MAV AND MET...THEN ADDED A DEGREE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... TONIGHT... HIGH PRESSURE RIDGE BUILDS OVER NEW ENGLAND LATE TODAY/TONIGHT. AS THE RIDGE TAKES CONTROL AND THE NORTHEAST FLOW BREAKS DOWN...THE POTENTIAL FOR CLEAR OR CLEARING SKIES WILL INCREASE. THE BIGGEST QUESTION MARK ON THIS CLEARING IS ACROSS THE CAPE AND ISLANDS...WHERE THE LOW LEVEL MOISTURE AND MARINE FLOW MAY HANG TOUGH. WE WILL KEEP 50-60 PERCENT COVER IN PLACE THERE WHILE BRINGING MOSTLY CLEAR SKIES TO THE REST OF SOUTHERN NEW ENGLAND. FRIDAY... AS WITH TONIGHT...THE FIRST QUESTION IS THE EXTENT OF ANY LOW CLOUDS ACROSS THE CAPE AND ISLANDS. WE WILL CONTINUE 50-60 PCT COVER IN THE SKY COVER GRIDS THERE. THE OTHER CONCERN IS CLOUDS FROM A FRONT WORKING SOUTH FROM CANADA. GIVEN THE STRENGTH OF THE RIDGE WE THINK ANY CLOUD INCREASE WILL BE SLOW. WE USED A BLEND OF NAM AND GFS SKY COVER WHICH BRINGS INCREASING CLOUDS TO THE NORTHWEST AREAS TOWARD EVENING. WARM SUN WILL BE AT ODDS WITH AN EASTERLY FLOW SO ONCE AGAIN WARMEST TEMPS WILL BE IN THE CT VALLEY AND HILLS WITH COOLEST TEMPS IN EASTERN MASSACHUSETTS. 850 MB TEMPS WARM 1-2C FROM TODAY...SO MAX TEMPS IN THE INTERIOR SHOULD REACH THE LOWER 70S WITH 60S EAST AND 50S ALONG THE COAST. WE USED A BLEND OF MOS VALUES...WHICH FITS THIS SCENARIO WELL. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... * DRY AND SEASONABLE CONDITIONS FRIDAY * MORE UNSETTLED WEATHER EXPECTED THIS WEEKEND AND INTO NEXT WEEK MODEL PREFERENCE... GOOD AGREEMENT AMONGST THE MODELS THROUGH SATURDAY WITH A FEW MORE SIGNIFICANT DIFFERENCES SUNDAY AND MONDAY. BY THE TIME WE REACH TUESDAY AND WEDNESDAY THERE ARE VERY DIFFERENT SOLUTIONS AMONG THE MODELS. GENERALLY SPEAKING WE WILL HAVE HIGH PRESSURE OVER THE REGION FRIDAY WITH THE POTENTIAL FOR A WEAK BACK DOOR FRONT MOVING ACROSS THE AREA SATURDAY. MOISTURE WITH THIS FRONT IS LACKING SO NOT EXPECTING A LOT OF RAIN WITH THIS FRONT...BUT COULD SEE SOME LIGHT SHOWERS FROM TIME TO TIME. SUNDAY AND MONDAY...HIGH PRESSURE MOVES OFFSHORE WHILE LOW PRESSURE IN THE GREAT LAKES/OH VALLEY APPROACHES THE AREA BUT THEN MOVES SOUTHWARD INTO THE SOUTHEAST CONUS. MODEL DIFFERENCES LAY IN HOW CLOSE THIS LOW PRES GETS TO SNE. WILL USE A BLEND OF THE ECMWF/GFS OR THE HPC GUIDANCE FOR THIS TIME PERIOD. TUESDAY AND WEDNESDAY IS WHEN WE SEE THE GREATEST DIFFERENCES BETWEEN THE MODELS. THE ECMWF TAKES THE LOW IN THE SOUTHEAST CONUS AND MOVES IT BACK UP INTO THE GREAT LAKES/OHIO VALLEY REGION WITH HIGH PRESSURE BUILDING ALONG THE COAST. MEANWHILE...THE GFS TAKES THE LOW AND MOVES IT UP THE COAST REACHING THE NJ COAST BY WEDNESDAY NIGHT. GIVEN THESE DIFFERENCES AND LOW CONFIDENCE IN ANY ONE SOLUTION...WILL STICK CLOSE TO WHAT WE ALREADY HAVE IN THE FORECAST. DETAILS... SATURDAY...A WEAK BACKDOOR FRONT WILL MOVE SOUTHWESTWARD ACROSS THE AREA. NOT A LOT OF PRECIPITATION IS EXPECTED WITH THIS FRONT...BUT IT CANNOT BE RULED OUT EITHER. WILL KEEP SLIGHT CHANCE POPS IN FOR THIS PERIOD TO ACCOUNT FOR THIS. OTHERWISE SLIGHTLY COOLER THAN NORMAL TEMPERATURES EXPECTED. SUNDAY THROUGH MONDAY...EASTERLY FLOW CONTINUES TO AFFECT SOUTHERN NEW ENGLAND AS LOW PRESSURE APPROACHES THE AREA AND HIGH PRESSURE MOVES OFFSHORE. COUPLED WITH WARM AIR ADVECTION...MORE RAIN IS EXPECTED...AND ALONG WITH IT MOSTLY CLOUDY TO OVERCAST SKIES. THIS LOW PRESSURE IS PROGGED TO MOVE SOUTHWARD INTO THE SOUTHEAST CONUS BY MONDAY NIGHT. TUESDAY AND WEDNESDAY...LOTS OF DISAGREEMENT AMONGST THE MODELS FOR THIS PERIOD. BEST FORECAST IS FOR MORE UNSETTLED WEATHER...WITH PRECIP AND CLOUDS FORECAST BY BOTH THE ECMWF AND THE GFS THOUGH THE DRIVING FORCES BEHIND SUCH WEATHER ARE A BIT DIFFERENT. CONTINUED WAA AND LOW PRES APPROACHING FROM THE OH VALLEY FOR THE ECMWF AND LOW PRESSURE MOVING UP THE COAST ON THE GFS. A LOW CONFIDENCE FORECAST FOR THIS TIME PERIOD TO BE SURE. && .AVIATION /07Z THURSDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT MODERATE...30 PERCENT TO 60 PERCENT HIGH...GREATER THAN 60 PERCENT TODAY...ONE MORE PUSH OF MARINE CLOUDS WEST OFF THE GULF OF MAINE. THIS WILL BRING 2500-3500 FOOT CEILINGS...VFR OR HIGH-END MVFR DURING THE MORNING. THE IMPULSE IN THE ATMOSPHERE CAUSING THE PUSH WILL MOVE SOUTH BY MIDDAY...SO EXPECT A CLEARING TREND MOST PLACES. THE CAPE AND ISLANDS MAY HOLD ON TO VFR OR HIGH-END MVFR CEILINGS THROUGH EVENING. STRONG GUSTY NORTHEAST WINDS WILL DIMINISH IN THE AFTERNOON. HIGH CONFIDENCE. TONIGHT...LINGERING VFR OR MVFR ON THE CAPE AND ISLANDS. VFR REMAINDER OF REGION. HIGH CONFIDENCE. FRIDAY...VFR. POSSIBLE MVFR EARLY ON THE CAPE AND ISLANDS. HIGH CONFIDENCE. KBOS TERMINAL... VFR CEILINGS THIS MORNING MAY FLIRT WITH HIGH-END MVFR...AROUND 2500 FEET...BUT ONLY BRIEFLY. CEILINGS THEN THIN AND BREAK MIDDAY AND AFTERNOON. MOSTLY CLEAR TONIGHT. INCREASING HIGH CLOUDS FRIDAY. NORTHEAST WIND WITH GUSTS 20 TO 25 KNOTS. OUTLOOK...FRIDAY NIGHT THROUGH MONDAY... SATURDAY...MEDIUM TO HIGH CONFIDENCE. MAINLY VFR. LOW PROBABILITY OF MVFR CONDITIONS IN ISOLD -SHRA. SUNDAY AND MONDAY...MEDIUM CONFIDENCE. MAINLY VFR WITH MVFR CONDITIONS OCCURRING IN LIGHT SHOWERS AND FOG. && .MARINE... TODAY...GALES LINGER AROUND NANTUCKET WITH 3 AM WINDS STILL GUSTING TO 35 KNOTS AT THE AIRPORT AND THE NANTUCKET BUOY GUSTING TO 33 KNOTS. WE WILL EXTEND THE GALES THERE FOR A COUPLE OF HOURS...BUT WINDS ARE DIMINISHING SO EXPECT THE HEADLINE TO DOWNSHIFT TO SMALL CRAFT ADVISORY BETWEEN 6 AND 8 AM. WINDS AROUND THE CAPE AND SOUTH COAST ARE GUSTING TO AROUND 25 KNOTS THIS MORNING WITH POTENTIAL FOR EXPANDED GUSTS DURING THE DAY. WINDS WILL BE TRENDING LIGHTER THROUGH THE AFTERNOON...BUT RESIDUAL NORTHEAST SWELLS WILL PERSIST. SO SMALL CRAFT ADVISORY FOR ALL WATERS TODAY. TONIGHT-FRIDAY... DIMINISHING WINDS AND SEAS AS HIGH PRESSURE BUILDS. SEAS WILL LINGER ABOVE 5 FEET ON THE OUTER WATERS THROUGH FRIDAY. OUTLOOK...FRIDAY NIGHT THROUGH MONDAY... SATURDAY...SEAS CONTINUE TO DIMINISH...FALLING BELOW 5 FEET DURING THE AFTERNOON. NORTHEASTERLY WINDS DIMINISH AND TURN TO THE SOUTHEAST. SUNDAY...SEAS REMAIN BELOW SCA THRESHOLDS DURING THE DAY THEN INCREASE OVERNIGHT. WINDS WILL REMAIN BELOW 25 KTS. MONDAY...SEAS INCREASE THROUGH MONDAY TO 5 TO 8 FEET. SOUTHEASTERLY WINDS REMAIN BELOW 25 KTS. && .TIDES/COASTAL FLOODING... NORTHEAST WINDS WILL DIMINISH TODAY. ASTRONOMICAL TIDES ARE TRENDING HIGHER...BUT AFTER THIS MORNING SEAS WILL BE TRENDING LOWER. EXPECT DIMINISHING BEACH EROSION THREAT AFTER THIS MORNING. SURGE VALUES WILL RANGE BETWEEN 1-1.5 FT /ADDED 0.5 FT TO STORM SURGE GUID/. HOWEVER TIDES REMAIN LOW ENOUGH TO PRECLUDE ANY COASTAL FLOODING. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...GALE WARNING UNTIL 6 AM EDT EARLY THIS MORNING FOR ANZ232. SMALL CRAFT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR ANZ233- 234. SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 4 PM EDT THIS AFTERNOON FOR ANZ230-236. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ231- 235-237. SMALL CRAFT ADVISORY UNTIL 6 PM EDT FRIDAY FOR ANZ250-251. GALE WARNING UNTIL 8 AM EDT THIS MORNING FOR ANZ254-255. SMALL CRAFT ADVISORY UNTIL 2 PM EDT FRIDAY FOR ANZ256. && $$