AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 355 AM EDT MON APR 18 2011 .SYNOPSIS... HIGH PRESSURE WILL BRING MAINLY DRY WEATHER MONDAY AFTERNOON. UNSETTLED WEATHER WILL RETURN MONDAY NIGHT THROUGH WEDNESDAY...BRINGING PERIODS OF CLOUDS AND SHOWERS. A COLD FRONT WILL PUSH THROUGH WEDNESDAY NIGHT...BRINGING DRIER BUT COOLER CONDITIONS FOR THE END OF THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE SHORTWAVE THAT BROUGHT THE SCATTERED SHOWERS TO THE REGION LAST EVENING HAS EXITED THE REGION. PARTLY TO MOSTLY SUNNY ARE EXPECTED ACROSS MUCH OF THE REGION INTO THE EARLY AFTERNOON. HIGH TEMPERATURES SHOULD BE RATHER SEASONABLE FOR THIS TIME OF YEAR...GENERALLY BETWEEN 55 AND 60. IT WILL FEEL A TAD COOLER AS BUFKIT SHOWING GUSTY WEST TO SOUTHWEST WINDS DEVELOPING OF 25 TO 30 MPH AT TIMES. WE SHOULD SEE SKIES BECOME MOSTLY CLOUDY FROM WEST TO EAST DURING THE MID TO LATE AFTERNOON HOURS. A FEW SPOT SHOWERS MAY POPUP TOWARDS 00Z TUESDAY TO THE NORTHWEST OF A BOSTON TO PROVIDENCE LINE...SO INCLUDED A 20 TO 30 POP TOWARDS THIS TIME ACROSS THAT AREA. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... TONIGHT... A WEAK COLD FRONT WILL SLOWLY PUSH SOUTH AND PROBABLY BE LOCATED NEAR THE SOUTH COAST BY 12Z TUESDAY. A WEAK WAVE OF LOW PRESSURE WILL RIDE ALONG THE FRONT AND PROBABLY BRING A FEW SHOWERS. CERTAINLY NOT EXPECTING A WASHOUT AND MUCH OF THE TIME SHOULD BE DRY IN A GIVEN LOCATION. THEREFORE...WILL CARRY JUST CHANCE POPS. AS FOR LOW TEMPERATURES...SIDED WITH THE WARMER GUIDANCE WITH A FAIR AMOUNT OF CLOUDS AROUND THE REGION. LOWS SHOULD MAINLY BE IN THE LOWER TO MIDDLE 40S WITH A FEW UPPER 30S POSSIBLE IN SOUTHWEST NH/NORTHWEST MA. TUESDAY... A SECOND WAVE OF LOW PRESSURE WILL BE RIDING ALONG THE FRONT WHICH SHOULD BE TO THE SOUTH OF OUR REGION. THIS WILL RESULT IN A MAINLY CLOUDY DAY AND ALSO THE THREAT FOR SHOWERS AT TIMES. APPEARS TO BE SOMEWHAT BETTER FORCING WITH THIS SECOND WAVE SO WILL GO WITH SOME LIKELY POPS. HOWEVER...WERE NOT EXPECTING A HEAVY RAIN EVENT FROM THIS SYSTEM. WITH THE FRONT MAINLY TO THE SOUTH OF OUR REGION AND AN ABUNDANCE OF CLOUDS...THINK TEMPERATURES WILL BE A BIT COOLER THAN TODAY. HIGHS SHOULD MAINLY BE BETWEEN 50 AND 55...BUT SOME COASTAL LOCATIONS MAY HOLD IN THE UPPER 40S WITH AN ONSHORE FLOW. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... TUESDAY NIGHT-WEDNESDAY... SHORTWAVE ALOFT MOVES ONSHORE ON THE PACIFIC COAST MONDAY. THE SHORTWAVE PICKS UP A SURFACE LOW OVER THE PLAINS TUESDAY AND DRIVES IT INTO THE GREAT LAKES WEDNESDAY. SOUTHWEST WINDS AHEAD OF THE LOW AT 950-850 MB PRODUCE INCREASED ISENTROPIC LIFT AS THEY RIDE OVER THE TOP OF THE COOLER MARINE EAST SURFACE FLOW OVER NEW ENGLAND. THIS SHOULD SUPPORT INCREASED CHANCE OF RAIN TUESDAY NIGHT INTO WEDNESDAY. THE STRONGEST WINDS ALOFT AND RESULTING LIFT ARE FORECAST TO MOVE THROUGH THE EASTERN LAKES AND ALONG THE CANADIAN BORDER. THEREFORE EXPECT HIGHEST POPS TO OUR NORTH ESPECIALLY ON WEDNESDAY. SOME QUESTION AMONG THE MODELS AS TO HOW SOON/LATE THE WARM FRONT MOVES THROUGH SOUTHERN NEW ENGLAND. THE NORTHERN TRACK OF THE SURFACE LOW WOULD SUGGEST IT WILL HAPPEN AT SOME POINT...THE GFS SHOWS THE WIND SHIFT WEDNESDAY NIGHT BETWEEN 00Z AND 06Z WHILE THE NAM LIFTS IT THROUGH DURING WEDNESDAY AFTERNOON. THE 12Z GGEM IS CLOSE TO THE NAM. THIS HAS IMPLICATIONS FOR PCPN BEING EITHER A STEADY RAIN OR SHOWERY...AND IMPLICATIONS FOR MAX TEMP WITH COOLER VALUES IN THE MARINE FLOW NORTH OF THE WARM FRONT AND WARMER VALUES IN THE SOUTHWEST FLOW TO THE SOUTH. WE WENT WITH THE COOLER FRONTAL TIMING SIMILAR TO THE GFS. FOR TEMPERATURE WE USED A BLEND OF MOS WITH VALUES 50-55...THIS IS ABOUT 5F WARMER THAN THE COLDEST GUIDANCE VALUES. IF THE WARM FRONT MOVE NORTH OF US BY MID AFTERNOON THEN THE ACTUAL VALUES WILL BE 10-15 DEGREES HIGHER THAN OUR FORECAST. GFS AND GGEM MOVE THE LOW MOVES THROUGH QUEBEC WEDNESDAY NIGHT...AND THE NAM HINTS AT A SIMILAR TRACK PAST THE END OF ITS RUN. THE 12Z ECMWF DIFFERS BY BRINGING THE LOW ACROSS NEW ENGLAND. CURRENTLY FAVOR THE MORE NORTHERLY TRACK...WHICH WOULD SWING A COLD FRONT ACROSS NEW ENGLAND OVERNIGHT. STABILITY INDICES SHOW A POTENTIAL FOR THUNDER WITH TOTALS AROUND 50 AND MID LEVEL LAPSE RATES AT 6.5 TO 7.0C PER KM. THURSDAY... SURFACE LOW MOVES OFF TO THE NORTHEAST WHILE THE UPPER TROUGH MOVES ACROSS NEW ENGLAND. THIS WOULD MEAN LINGERING CLOUDS...ESPECIALLY DURING THE MORNING...WITH A CLEARING TREND IN THE AFTERNOON AS THE UPPER TROUGH MOVES OFF. INCREASING SUNSHINE AND COLD ADVECTION ALOFT WILL AID IN DEEPER MIXING THAT SHOULD REACH 850 MB. WINDS AT THAT LEVEL ARE FORECAST AT 35 TO 40 KNOTS ON THE GFS AND 30-35 KNOTS ON THE ECMWF. TEMPS ARE A BLEND OF HPC AND GMOS VALUES. FRIDAY... HIGH PRESSURE IN PLACE. FAIR WEATHER WITH LIGHT WINDS. TEMPS ARE A BLEND OF HPC AND GMOS VALUES. SATURDAY AND SUNDAY... LOW PRESSURE MOVES OUT OF THE PLAINS SATURDAY. THE GFS MOVES IT THROUGH THE GREAT LAKES SATURDAY...PUSHING A WARM FRONT THROUGH NEW ENGLAND SATURDAY NIGHT AND A COLD FRONT SUNDAY MORNING. THE 12Z ECMWF MOISTURE FIELDS INDICATE UNSETTLED WEATHER...BUT THE PRESSURE FIELDS ARE MUCH MORE VAGUE THAT THE GFS. ENOUGH CONSENSUS TO GO WITH CHANCE POPS FOR BOTH DAYS BUT LOW CONFIDENCE IN THE DETAILS AT THIS TIME. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT MEDIUM...30 PERCENT TO 60 PERCENT HIGH...GREATER THAN 60 PERCENT TODAY...HIGH CONFIDENCE IN VFR. WEST TO SOUTHWEST WIND GUSTS OF 20 TO 25 KNOTS. TONIGHT...MEDIUM CONFIDENCE. DESPITE AN ABUNDANCE OF MID LEVEL CLOUDINESS AND A FEW SHOWERS...VFR CONDITIONS WILL PROBABLY BE DOMINANT. HOWEVER...SOME MARGINAL MVFR CEILINGS AND VISIBILITIES MAY OCCUR AT TIMES. TUESDAY...MEDIUM CONFIDENCE. VFR TO MARGINAL MVFR BROKEN TO OVERCAST CEILINGS EXPECTED. THE BETTER CHANCE OF MVFR CONDITIONS WILL RESIDE IN THE AFTERNOON ALONG WITH SOME SHOWERS. KBOS TERMINAL...HIGH CONFIDENCE IN VFR TODAY. MEDIUM CONFIDENCE IN TAF TONIGHT AND TUESDAY. EXPECT VFR CONDITIONS TO DOMINATE TONIGHT AND TUESDAY...BUT A PERIOD OR TWO OF MVFR CEILINGS ARE POSSIBLE WITH THE BEST CHANCE ON TUESDAY. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... TUESDAY NIGHT-WEDNESDAY...CONDITIONS LOWERING TUESDAY NIGHT MVFR/IFR CEILINGS AND VSBYS IN RAIN/SHOWERS/FOG DURING THE OVERNIGHT AND ON WEDNESDAY. SUFFICIENT INSTABILITY FOR SCATTERED EMBEDDED THUNDERSTORMS WEDNESDAY AFTERNOON AND NIGHT. EAST WINDS DURING THE DAY SHIFTING TO SOUTH BRIEFLY WEDNESDAY NIGHT...THEN SOUTHWEST OVERNIGHT. MEDIUM CONFIDENCE. THURSDAY-FRIDAY...CONDITIONS IMPROVING TO VFR. WEST WINDS INCREASING THURSDAY WITH GUSTS AROUND 35 KNOTS...DIMINISHING THURSDAY EVENING. LIGHT WINDS FRIDAY. MEDIUM CONFIDENCE. && .MARINE... TODAY...SCA HEADLINES REMAIN POSTED FOR ALL WATERS AS BUFKIT SHOWS GOOD MIXING. THIS SHOULD YIELD WEST TO SOUTHWEST WIND GUSTS OF 25 KNOTS. TONIGHT...WINDS SHOULD DIMINISH BELOW SCA THRESHOLDS BY EARLY EVENING. HOWEVER...WILL NEED TO CONTINUE SCA FOR SEAS FOR ALL OF TONIGHT AS SEAS WILL REMAIN AT OR ABOVE 5 FEET IN THIS REGION. TUESDAY...WINDS SHOULD REMAIN BELOW SCA THRESHOLDS AS COLD FRONT PUSHES SOUTH OF MOST OF THE WATERS. HOWEVER...NORTH TO NORTHEAST WIND GUSTS UP TO 20 KNOTS ARE EXPECTED. SEAS WILL REMAIN AROUND 5 FEET ACROSS THE SOUTHERN OUTER-WATERS SO SCA HEADLINES MAY NEED TO BE EXTENDED. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... TUESDAY NIGHT-WEDNESDAY...WINDS AND SEAS BELOW SMALL CRAFT LEVELS TUESDAY NIGHT AND WEDNESDAY. WINDS AND SEAS INCREASE WEDNESDAY NIGHT WITH A COLD FRONT CROSSING THE WATERS...WIND SHOULD REACH 25-30 KNOTS AND SEAS 5-9 FEET ESPECIALLY ON THE SOUTHERN OUTER WATERS. SCATTERED THUNDERSTORMS WEDNESDAY AFTERNOON AND EVENING. THURSDAY...WEST WINDS INCREASING TO 30-35 KNOTS. LOW TO MEDIUM CHANCE THESE MAY REACH GALE FORCE FOR A FEW HOURS DURING THE DAY. SEAS WILL REMAIN 5-10 FEET. FRIDAY...WINDS AND SEAS BELOW SMALL CRAFT LEVELS. && .HYDROLOGY... RECENT SNOWMELT IN NORTHERN NEW ENGLAND AND RAINFALL HAS RESULTED IN MAINLY MINOR FLOODING ALONG PORTIONS OF THE CONNECTICUT RIVER. A FLOOD WARNING CONTINUES FOR THE CONNECTICUT RIVER AT NORTHAMPTON...THOMPSONVILLE...AND HARTFORD. THESE LOCATIONS ARE EXPECTED TO REMAIN IN MINOR FLOOD UNTIL FURTHER NOTICE. THE CONNECTICUT RIVER AT MIDDLETOWN MAY GO INTO LOW END MODERATE FLOODING THIS MORNING...SO WILL CONTINUE TO MONITOR IT CLOSELY. THE AREAL FLOOD ADVISORY FOR THE WILLIMANTIC RIVER AT COVENTRY HAS BEEN CANCELLED. THE RIVER HAS FALLEN BELOW FLOOD STAGE AND THE RIVER WILL CONTINUE TO RECEDE. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ230>234-236. SMALL CRAFT ADVISORY UNTIL 7 AM EDT TUESDAY FOR ANZ235-237- 254>256. SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ250. SMALL CRAFT ADVISORY UNTIL 5 PM EDT THIS AFTERNOON FOR ANZ251. && $$ SYNOPSIS...FRANK