AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 405 PM EDT MON APR 18 2011 .SYNOPSIS... HIGH PRESSURE WILL BRING DRY...SEASONABLE CONDITIONS THROUGH THIS AFTERNOON. UNSETTLED WEATHER WILL RETURN TONIGHT THROUGH WEDNESDAY...BRINGING CLOUDS AND RAIN. A COLD FRONT WILL SWING THROUGH WEDNESDAY NIGHT. HIGH PRESSURE WILL BRING DRY BUT COOL CONDITIONS FROM THURSDAY THROUGH FRIDAY NIGHT. ANOTHER STORM MOVING OUT OF THE PLAINS WILL BRING MORE UNSETTLED WEATHER FOR MUCH OF THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... LITTLE CHANGE TO THE FORECAST EXCEPT SOME MODIFICATION TO HOURLY DEWPOINTS AND TEMPERATURES. USED MIXED T/TD TOOL TO ACCOMPLISH THIS AS A GUIDE. EXPECT PARTLY TO MOSTLY SUNNY SKIES INTO EARLY THIS 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 POP UP 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 TUESDAY NIGHT/... 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 /WEDNESDAY THROUGH MONDAY/... WEDNESDAY... FIRST QUESTION IS THE TIMING OF WARM FRONT PASSAGE...IF ANY. THE NAM KEEPS THE WARM FRONT SOUTH OF NEW ENGLAND THROUGH 18Z...THEN MOVES IT NORTH INTO AT LEAST SOUTHEAST MASS BY 00Z. THE GFS IS MORE PROGRESSIVE WITH SOUTHWEST FLOW TO THE SOUTH COAST BY 18Z AND TO ALL OF SOUTHERN NEW ENGLAND BY 00Z. THE 12Z ECMWF IS MOST PROGRESSIVE WITH SOUTHWEST FLOW TO THE NH BORDER BY 18Z. BASED ON THE UPPER FLOW AND WITH HIGH PRESSURE OVER QUEBEC/MARITIMES...WE FAVOR THE SLOWER NAM SOLUTION. TEMPERATURES ARE DRAWN FROM THE MET MOS VALUES. STRONGEST 850 MB WINDS...50 TO 75 KNOTS...ARE FORECAST TO MOVE ACROSS NORTHERN NEW ENGLAND WEDNESDAY. NO SURPRISE THAT THIS IS WHERE THE STRONGEST ISENTROPIC LIFT IS FORECAST. MUCH LIGHTER LIFT IS FORECAST ACROSS SOUTHERN NEW ENGLAND. HOWEVER LIFT OF 10 MB/HOUR IS FORECAST TO MOVE ACROSS NORTHWEST MASS/SOUTHWEST NH DURING THE MORNING...SO THIS PART OF OUR FORECAST AREA WILL HAVE THE BEST CHANCE OF RAIN IN OUR AREA. SATURATION CONTINUES THROUGH THE DAY AT 290K /ROUGHLY 900 MB/ BUT DRYING AT HIGHER LEVELS. WITH THIS IN MIND...WE USED LIKELY POPS SOUTH AND CATEGORICAL POPS NORTH. SECOND QUESTION IS TIMING OF COLD FROPA WEDNESDAY NIGHT. THE NAM BRINGS A WIND SHIFT FROM SOUTH TO WEST BETWEEN 06Z AND 12Z. NAM BRINGS TOTALS OF 45 TO 50 NORTH ACROSS OUR AREA DURING THE MORNING/MIDDAY BUT WITH VERY STABLE LI VALUES AND NO FORECAST CAPE. THIS MAY MEAN ELEVATED CONVECTION...OR POSSIBLY CONVECTION IF WE BREAK INTO THE WARM SECTOR. THESE VALUES THEN DIMINISH WEDNESDAY NIGHT. HAVE INCLUDED A CHANCE OF THUNDER IN THE FORECAST. THURSDAY... SUPPORTING UPPER LOW MOVES PAST WITH PVA AND A -24C COLD POOL. THIS SHOULD SUPPORT DIURNAL CLOUDS AND WIDELY SCATTERED SHOWERS. WEST FLOW AND COLD ADVECTION SHOULD ALLOW FOR DEEPER MIXING. 850 MB TEMPS OF -3C TO -5C SHOULD SUPPORT MAX TEMPS IN THE 50S...ESPECIALLY THE LOW TO MID 50S. WINDS AT 850 MB ARE FORECAST AT 30 TO 40 KNOTS...HIGHER IF THE NAM HAS A SAY...AND LAPSE RATES FAVOR MOST OF THIS MIXING TO THE SURFACE IN AFTERNOON GUSTS. FRIDAY... HIGH PRESSURE MOVES OVERHEAD. THIS SHOULD BE A FAIR DAY WITH LIGHT WIND. DEWPOINTS IN THE 20S AND LIGHT WIND SHOULD ALLOW MORNING TEMPS TO START COOL...IN THE UPPER 20S TO MID 30S. ONSHORE WINDS WILL KEEP THE COASTAL AREAS COOL DURING THE DAY...WITH UPPER TEMPS OF -1C TO -3C SUPPORTING MAX TEMPS IN THE 50S. INCREASING HIGH LEVEL MOISTURE WILL MEAN INCREASING HIGH CLOUDS ESPECIALLY IN THE AFTERNOON AND EVENING. FRIDAY NIGHT-SATURDAY... SOUTHERN STREAM SHORTWAVE KICKS A SURFACE LOW OUT OF THE PLAINS AND INTO THE GREAT LAKES BY SATURDAY. THIS IS A SIMILAR TRACK TO THE LAST STORM AND TO THE PROJECTED WEDNESDAY STORM. PER THE 12Z ECMWF...INCREASING ISENTROPIC LIFT IS EXPECTED TO REACH THE CONNECTICUT VALLEY LATER FRIDAY NIGHT WITH THE BEST LIFT CROSSING NEW ENGLAND SATURDAY MORNING. THE GFS IS ABOUT 6 HOURS FASTER WITH THIS LIFT. ALL THIS WILL MEAN INCREASING/THICKENING CLOUDS WITH CHANCE POPS FOR RAIN IN WESTERN AREAS LATE FRIDAY NIGHT AND ACROSS ALL AREAS ON SATURDAY. A COLD FRONT THEN SWINGS THROUGH SATURDAY NIGHT. THE VARIOUS TIMINGS WOULD BRING IT THROUGH AROUND 06Z. THIS WILL MEAN CHANCE POPS FOR SHOWERS...THEN DRYING TOWARD MORNING. SUNDAY-MONDAY... BOTH THE GFS AND ECMWF BUILD HIGH PRESSURE OVER THE NORTHEAST USA SUNDAY MORNING...THEN MOVE IT EAST IN THE AFTERNOON. THE SATURDAY NIGHT FRONT STALLS JUST SOUTH OF THE REGION...A LOW PRESSURE WAVE MOVES ALONG THE FRONT LATE SUNDAY/SUNDAY NIGHT. THIS WOULD BRING A CHANCE OF RAIN/SHOWERS BACK TO OUR AREA LATE SUNDAY AND SUNDAY NIGHT...TAPERING OFF MONDAY. LOW CONFIDENCE AT THIS TIME. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT MEDIUM...30 PERCENT TO 60 PERCENT HIGH...GREATER THAN 60 PERCENT TODAY...HIGH CONFIDENCE IN VFR CONDITIONS. EXPECT WEST TO SOUTHWEST WIND GUSTS 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 MAINLY AFTER MIDNIGHT. TUESDAY...MEDIUM CONFIDENCE. VFR TO BORDERLINE MVFR BROKEN TO OVERCAST CEILINGS EXPECTED. THE BETTER CHANCE OF MVFR CONDITIONS WILL OCCUR 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...WEDNESDAY THROUGH SATURDAY... WEDNESDAY...MVFR/IFR EXPECTED IN LOW CEILINGS AND RAIN/FOG. SCATTERED THUNDERSTORMS POSSIBLE IN THE AFTERNOON/EVENING. EAST WIND DURING THE DAY BECOMES WEST OVERNIGHT. MEDIUM CONFIDENCE. THURSDAY...VFR CONDITIONS. WEST WINDS AT SUSTAINED 20 KNOTS AND GUSTS 35 TO 40 KNOTS DURING THE DAY. MEDIUM TO HIGH CONFIDENCE. FRIDAY...VFR. HIGH CONFIDENCE. SATURDAY...CONDITIONS LOWERING TO MVFR/IFR IN LOW CEILINGS/RAIN/FOG. 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 TO 30 KT. 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...WEDNESDAY THROUGH SATURDAY... WEDNESDAY...WINDS JUST BELOW SMALL CRAFT LEVELS...BUT SEAS AT 5 TO 8 FEET ESPECIALLY ON THE OUTER WATERS. EAST WINDS DURING THE DAY WITH SOUTH WINDS ON THE SOUTHERN OUTER WATERS...ALL SHIFTING TO WEST WEDNESDAY NIGHT AS A COLD FRONT MOVES THROUGH. THURSDAY...WEST WINDS NEAR GALE FORCE DURING THE DAY...DIMINISHING IN THE EVENING. SEAS 5 TO 8 FEET ESPECIALLY ON THE OUTER WATERS...DIMINISHING LATE. FRIDAY...WINDS AND SEAS BELOW SMALL CRAFT LEVELS. SATURDAY...SOUTH WINDS INCREASING TO SMALL CRAFT ADVISORY SPEEDS. SEAS BUILDING TO 5 TO 8 FEET. && .FIRE WEATHER... DESPITE SIGNIFICANT RAINFALL SATURDAY NIGHT...THE FIRE HAZARD RISK WILL BE SLIGHTLY ELEVATED TODAY AS WINDS FREQUENTLY GUST TO 25 TO 30 MPH THROUGH MID AFTERNOON. MINIMUM RH VALUES WILL DROP TO THE 25 TO 35 PERCENT RANGE. && .HYDROLOGY... THE HEAVY RAINFALL FROM THIS PAST WEEKEND ALONG WITH RECENT SNOWMELT FROM NORTHERN NEW ENGLAND HAS CONTINUED TO CAUSE RIVER RISES ALONG SOME OF THE MAINSTEM RIVERS AND TRIBUTARIES. MINOR FLOODING CONTINUES 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 CLOSELY. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ230>234-236-251. SMALL CRAFT ADVISORY UNTIL 5 PM EDT TUESDAY FOR ANZ235-237- 254>256. SMALL CRAFT ADVISORY UNTIL 7 AM EDT TUESDAY FOR ANZ250. && $$ SYNOPSIS...WTB/FRANK