355 FXUS61 KBOX 231103 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 703 AM EDT TUE APR 23 2013 .SYNOPSIS... A COASTAL STORM TRACKING SOUTHEAST OF NANTUCKET WILL BRING A CHILLY RAIN TO EASTERN NEW ENGLAND TODAY AND INTO TONIGHT. DRIER AND MILD WEATHER ARRIVES WED. A QUICK MOVING COLD FRONT WILL PASS THROUGH WED NIGHT INTO THURSDAY. MAINLY DRY AND SEASONABLY COOL WEATHER RETURNS FRIDAY AND INTO THE WEEKEND THANKS TO A STRONG HIGH PRESSURE SYSTEM. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 700 AM UPDATE... BULK OF THE FORECAST REMAINS ON TRACK THIS MORNING. INCREASED POPS TO CATEGORICAL ACROSS THE CAPE AND ISLANDS AS IT IS RAINING CURRENTLY. EXPECT PRECIP TO SPREAD NORTHWARD OVER THE NEXT FEW HOURS AS COASTAL LOW APPROACHES. INCREASED WINDS ACROSS THE SOUTH COAST...CAPE AND ISLANDS AS PRESSURE GRADIENT IS INCREASING. OTHERWISE MADE MINOR TWEAKS TO ACCOUNT FOR CURRENT CONDITIONS. PREVIOUS DISCUSSION... TODAY... MODEL ISENTROPIC SURFACES SHOW STRONG LIFT...GREATER THAN 60 MB PER HOUR...MOVING UP PARTS OF EASTERN MASSACHUSETTS MOST NOTABLY ACROSS CAPE COD AND ISLANDS. SOUTHERN STREAM SHORTWAVE ALONG THE MID ATLANTIC COAST IS SUPPORTED BY 105 KNOT JET OVER NEW ENGLAND. THE ENTRANCE REGION TO THIS JET WILL BE OVER NEW ENGLAND TODAY AND PROVIDE ENOUGH UPPER VENTING TO SUPPORT STRONG LIFT AND RESULTING RAINFALL PRODUCTION. PRECIPITABLE WATER VALUES BETWEEN 1 AND 1.5 INCHES ARE DRAWN NORTH BY THE SHORTWAVE AND ASSOCIATED SURFACE LOW. SO EXPECT EXPECT A DEVELOPING RAIN SHIELD OVER THE REGION WITH FOCUS ON THE CAPE AND ISLANDS. POTENTIAL FOR 1.5 TO 2.5 INCHES OF RAIN ON THE CAPE/ISLANDS WITH 0.5 INCH TO 1 INCH OVER EASTERN MASS. LIGHT PCPN POSSIBLE IN THE CT VALLEY/EAST SLOPE AREA. THERE IS SOME CONCERN FOR URBAN/POOR DRAINAGE FLOODING ON THE CAPE...BUT WE WILL ALSO NEED TO MONITOR THE NEW BEDFORD-FALL RIVER-CRANSTON AREA ESPECIALLY IF RADAR SHOWS THE HEAVY RAIN AREA SHIFTING A LITTLE FARTHER WEST. ALTHOUGH WINDS ARE INCREASING...ALL MODELS SHOW THE STRONGEST WIND REMAINING ALOFT AND MOSTLY OFFSHORE. NO WIND HEADLINES ANTICIPATED AT THIS TIME. THE EAST FLOW OFF COASTAL WATER WITH SST IN THE MID 40S SHOULD HOLD EASTERN MAX TEMPS TO THAT LEVEL. WEST OF WORCESTER THE EAST WIND WILL BE A DOWNSLOPE WIND INTO THE CT VALLEY...AND THERE WILL BE LESS PCPN...SO TEMPS SHOULD BREAK 50 IN THAT AREA. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... ALL MODELS SHOW COASTAL LOW PRESSURE MOVING UP THROUGH 40N/70W AND CONTINUING RAIN OVER OUR EASTERN AREAS. STABILITY INDICES...ESPECIALLY THE TOTALS AND LI...SHOW POTENTIAL FOR THUNDER OVER THE CAPE/ISLANDS AFTER MIDNIGHT AND EXTENDING OVER EASTERN MASS/RI BY MORNING. SUCH CONVECTION WOULD INCREASE HOURLY PCPN RATES AND INCREASE POOR DRAINAGE FLOODING POTENTIAL. MODEL QPF CONTINUES TO FOCUS MOST OF THE PCPN OVER RI/EASTERN MASS/MERRIMACK VALLEY OF NH. THIS CONSENSUS AND GEOGRAPHY...THE WORCESTER HILLS...SUGGESTS A SHARP MOISTURE GRADIENT ON THE WESTERN EDGE OF THE RAIN SHIELD. THE LOW MOVES NORTHEAST TO THE MARITIMES LATE TUESDAY NIGHT/WEDNESDAY. THE ECMWF AND GGEM ARE SLOWER IN DOING THIS THAN ARE THE NAM AND GFS...BUT ALL SUGGEST A PERIOD OF DRYING AND PARTIAL CLEARING ON WEDNESDAY. EQUIVALENT MIXING TEMPS OF 6-8C WOULD SUPPORT MAX TEMPS IN THE UPPER 60S AND LOWER 70S. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... HIGHLIGHTS... * COLD FRONT WILL PUSH THROUGH WED NIGHT INTO THURS * WEAK WAVE ON FRIDAY * STRONG HIGH PRESSURE FOR THE WEEKEND CONFIDENCE LEVEL/MODEL GUIDANCE... HIGH CONFIDENCE IN FORECAST THROUGH THE WEEKEND. 00Z MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON PRECIPITATION TIMING AND FRONTAL PASSAGES. HIGH CONFIDENCE THAT A COLD FRONT WILL PUSH ACROSS SNE BY WED NIGHT INTO THURSDAY...MODERATE CONFIDENCE ON PRECIPITATION AMOUNTS. UPPER LEVEL LOW ON FRIDAY WILL PUSH A WEAK WAVE OVER THE NORTH HALF OF THE REGION. HIGH CONFIDENCE ON BUILDING HIGH PRESSURE FROM FRIDAY EVENING INTO EARLY MONDAY MORNING THANKS TO SURFACE HEIGHTS APPROX 2-3 STANDARD DEVIATIONS IN BOTH THE GFS AND EC ENSEMBLES. DETAILS... WED NIGHT INTO FRIDAY... STRONG UPPER LEVEL TROUGH WILL BRING TWO WAVES OF ENERGY THROUGH SNE. THE FIRST WILL OCCUR WED NIGHT INTO THURS DEVELOPING A SURFACE LOW NORTH OF VT/NH AND PUSHING IT NORTHEASTWARD. THIS WILL DRAG A COLD FRONT ACROSS SNE WED NIGHT. THIS FRONT HOWEVER REALLY LOSES ITS MOISTURE AS IT MOVES THROUGH THE INTERIOR. BELIEVE THE BEST AREA TO SEE ACCUMULATING AMOUNTS WILL BE OUT WEST...WITH SCT SHOWERS ACROSS THE CENTRAL PART OF THE CWA. AS WE GET CLOSER TO THE EAST COAST...DEWPOINTS ARE A TAD HIGHER AND WITH SOUTHWESTERN FLOW...MORE MOISTURE IS ADVECTING INTO THE MID-LEVELS...SO EXPECT PRECIP TO BE MORE ABUNDANT ACROSS THE EAST COAST BY EARLY THURS MORNING. EXPECTING LESS THAN A 0.25 INCHES OF PRECIP AS THIS FRONT WILL BE MOVING QUITE QUICKLY. THERE IS A CHANCE FOR SOME ISOLATED THUNDER WITH THIS SYSTEM...YET THE POSSIBILITY OF STRONG STORMS IS QUITE LOW. THE SECOND WAVE THAT ROUNDS THE TROUGH WILL MOVE THROUGH SNE BY THURS NIGHT INTO FRIDAY MORNING. THIS SYSTEM AM LESS CONFIDENCE ABOUT AS THERE IS PLENTY OF DRY AIR ALOFT AND HIGH PRESSURE IS QUICKLY BUILDING BEHIND IT...PUSHING IT MORE NORTHWARD TOWARDS NORTHERN NEW ENGLAND. BELIEVE THAT PERHAPS SCT SHOWERS ARE POSSIBLE...BUT MORE LIKE SPRINKLES IN AREAS NORTH OF THE MASS PIKE. THE WEEKEND... AS THE TROUGH MOVES OFFSHORE...HIGH PRESSURE WILL BUILD IN FOR THE WEEKEND. ZONAL FLOW ALOFT WILL TRY TO PUSH A FEW WAVES THROUGH SNE...BUT BELIEVE THE AREA WILL BE TO DRY SO PERHAPS JUST PASSING CLOUDS. THIS HIGH PRESSURE SEEMS TO BUILD OVER SNE FOR SOME TIME AND MODELS ARE HAVING A HARD TIME ON WHEN TO PUSH IT OUT OF THE REGION FOR EARLY NEXT WEEK. REGARDLESS...EXPECT MOST CLEAR SKIES AND TEMPS IN THE MID TO UPPER 60S. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. OVERVIEW... MVFR ACROSS WESTERN SITES...WHILE IFR CONDITIONS ARE MOVING ACROSS THE EASTERN ZONES. SHOWERS ACROSS ACK WILL MOVE NORTHWARD AND OVER SPREAD EASTERN NEW ENGLAND. LOW PROB OF LIFR IN VSBYS. THERE IS ALSO SOME UNCERTAINTY IN THUNDERSTORM POTENTIAL. BEST CHANCE IS ACROSS ACK AND THE CAPE THIS AFTERNOON AND TONIGHT. INCREASING EAST WIND WITH OFFSHORE BUOYS SHOWING GUSTS TO 30 KNOTS OFF MONTAUK POINT NY. EXPECT GUSTS NEAR 30 KNOTS ESPECIALLY ALONG THE COAST TODAY AND TONIGHT. MVFR/IFR CONDITIONS CONTINUE INTO TUESDAY NIGHT...THEN IMPROVE TOWARD WEDNESDAY MORNING. VFR WEDNESDAY. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. LOWERING CIGS AND VSBYS TODAY. LOW CONFIDENCE IN ISOLATED THUNDER TUESDAY AFTERNOON AND NIGHT. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. EXPECT MVFR CIGS TO CONTINUE THROUGH THE DAY. RAIN SHOULD REMAIN MOSTLY EAST OF BDL. OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY... WEDNESDAY NIGHT INTO THURSDAY...MODERATE CONFIDENCE. VFR FOR THE MAJORITY...QUICK MOVING COLD FRONT MAY LEAD TO MVFR/IFR IN SHOWERS. LOW PROB FOR ISO TSRA. THE THREAT FOR MVFR/IFR LINGERS...ESPECIALLY EASTERN HALF OF THE AREA INTO THURSDAY. FRIDAY INTO SUNDAY...HIGH CONFIDENCE FOR VFR. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. OVERVIEW...MODERATE TO HIGH CONFIDENCE THROUGH WEDNESDAY. SMALL CRAFT ADVISORIES WILL CONTINUE INTO TONIGHT WITH EAST GUSTS TO 30 KNOTS. THERE IS A LOW PROBABILITY OF GUSTS TO 35 KNOTS...BUT NOT ENOUGH TO GO WITH GALES AT THIS TIME. COASTAL LOW PRESSURE OFF THE CAROLINAS WILL MOVE UP THE COAST TODAY AND TONIGHT. PERIODS OF HEAVY RAIN WILL REDUCE VSBYS ON THE WATERS. WINDS SHIFT FROM EAST THROUGH NORTH TO WEST AS THE COASTAL LOW PASSES OFFSHORE LATER TONIGHT AND WEDNESDAY. SMALL CRAFTS LINGER ON THE SOUTHERN AND OUTER WATERS THROUGH WEDNESDAY EVENING. BUILDING SEAS TODAY WITH ROUGH SEAS CONTINUING THROUGH WEDNESDAY. OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY... MODERATE CONFIDENCE THROUGH THE PERIOD. WED NIGHT INTO THU...SCA WILL BE NEEDED. FRONTAL PASSAGE WITH WIND SHIFT FROM SW TO NW. WINDS MAY GUST UP TO 30KTS AHEAD OF FRONT. THERE IS A CHANCE OF SHOWERS WITH LOW PROB FOR ISO THUNDER. SEAS ABOVE 5 FT WILL LINGER THROUGH THURSDAY AND INTO EARLY FRI. FRI INTO SUNDAY...HIGH PRES BUILDS IN WITH DRY WEATHER AND GOOD VSBY. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT WEDNESDAY FOR ANZ232>234. SMALL CRAFT ADVISORY FROM NOON TODAY TO 2 AM EDT WEDNESDAY FOR ANZ230. SMALL CRAFT ADVISORY UNTIL 6 PM EDT WEDNESDAY FOR ANZ231-251. SMALL CRAFT ADVISORY UNTIL 2 AM EDT WEDNESDAY FOR ANZ236. SMALL CRAFT ADVISORY UNTIL 7 AM EDT THURSDAY FOR ANZ235-237- 250-254>256. && $$ SYNOPSIS...WTB/DUNTEN NEAR TERM...WTB/DUNTEN SHORT TERM...WTB LONG TERM...DUNTEN AVIATION...WTB/DUNTEN MARINE...WTB/DUNTEN