AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 726 AM EDT WED JUL 16 2014 .SYNOPSIS... A SLOW MOVING FRONTAL BOUNDARY WILL BRING PERIODS OF SHOWERS AND THUNDERSTORMS THROUGH WEDNESDAY. A FEW STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE DURING THIS TIME...ALONG WITH HEAVY RAIN AND POSSIBLY LOCALIZED FLASH FLOODING. DRY AND LESS HUMID WEATHER ARRIVES THU AND FRI...POSSIBLY LINGERING INTO SAT BEFORE THE RISK OF RAIN SUNDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... * HIGH CONFIDENCE IN HEAVY RAIN/POTENTIAL FLASH FLOODING TODAY * ISOLATED SEVERE WEATHER REMAINS POSSIBLE ACROSS EASTERN NEW ENGLAND...BUT LOW CONFIDENCE 7 AM UPDATE... A TALE OF TWO FORCING MECHANISMS THIS MORNING. TO THE W...A SLOW MOVING COLD FRONT HAS STARTED WORKING ITS WAY INTO WRN MA AND CT...AND WILL CONTINUE A SLOW E MOVEMENT THROUGH THE DAY AND EVENING HOURS TONIGHT. IT/S LIKELY TO NOT BE OFFSHORE UNTIL THE EARLY MORNING HOURS TOMORROW. OUT AHEAD...A BAND OF HEAVY RAIN/THUNDERSTORMS ARE FORMING ALONG THE AXIS OF A MODERATE LLJ AND UPPER LVL JET STREAK. THE MAIN ISSUE WITH THESE WILL BE HEAVY RAIN...AS MORE CONVECTION FIRES OFF OF THE DELMARVA AND NJ COASTLINES. WILL NEED TO CONTINUE TO MONITOR THROUGH THE DAY PRIMARILY FOR HEAVY RAIN...ALTHOUGH SPC DOES CONTINUE TO HIGHLIGHT A 5 PERCENT CHANCE FOR STRONG WINDS. HOWEVER...THIS IS ONLY LIKELY IF MORE INSTABILITY CAN BE REALIZED. SPEAKING OF THIS INSTABILITY...ITS LIKELY TO BE MUCH LOWER THAN YESTERDAY THANKS TO A FAIR AMOUNT OF CLOUDS AND SLOW BUILDING OF DRY AIR ALOFT FROM THE W. ADJUSTED TEMPS/DWPTS...BUT ALSO TRIED TO BETTER TIME POPS WITH THIS UPDATE...USING A BLEND OF THE HRRR/NAM. PREVIOUS DISCUSSION... LATEST MESOANALYSIS STILL SHOWS UP TO 600 J/KG MOST UNSTABLE CAPE VALUES ACROSS EASTERN MA AND RI EARLY THIS MORNING. THUS...CANNOT COMPLETELY RULE OUT A STRAY SHOWER OR THUNDERSTORM DURING THE PREDAWN HOURS. EXPECTING MOST OF SOUTHERN NEW ENGLAND TO REMAIN DRY THROUGH DAYBREAK. THE GREATEST RISK FOR SHOWERS OR THUNDERSTORMS SHOULD BE ACROSS SOUTHEAST MA. THE SECOND MOST AT RISK AREAS WILL BE THOSE ALONG AND WEST OF THE CT RIVER. HEAVY RAINFALL AXIS SHIFTS TO EASTERN NEW ENGLAND TODAY AS A SLOW MOVING COLD FRONT AND A LOW LEVEL JET MOVE EAST. STILL ENOUGH INSTABILITY TO SUPPORT ISOLATED TO SCATTERED THUNDERSTORMS...WHICH WILL ENHANCE RAINFALL RATES. TRAINING IS POSSIBLE DUE TO THE SLOW MOVEMENT OF THE FRONT...FURTHER INCREASING THE RISK FOR LOCALIZED FLOODING AND FLASH FLOODING. THE GREATEST SURFACE INSTABILITY...GENERALLY LESS THAN 1000 J/KG...WILL SHIFT TO EASTERN NEW ENGLAND TODAY. THERE IS MODEST 0-6KM SHEAR OF 30-40 KT...SO CAN NOT RULE OUT AN ISOLATED STRONG TO SEVERE THUNDERSTORM AS WELL. BUT CONFIDENCE IS LOW AS INSTABILITY MAY BE A LIMITING FACTOR. MID LEVEL DRYING MOVES IN FROM THE WEST LATE TODAY. WE ANTICIPATE SHOWERS TO END IN WESTERN NEW ENGLAND DURING THIS AFTERNOON...AND MAY ALSO SEE SOME SUNSHINE DEVELOPING IN THE CT VALLEY. HOWEVER... SHOWERS AND SCATTERED THUNDERSTORMS WILL PERSIST THROUGH MUCH OF THE DAY FARTHER EAST. TEMPERATURES WILL BE MOSTLY IN THE 70S DUE TO CLOUDS AND SHOWERS. A FEW LOCATIONS IN THE LOWER CT VALLEY MAY REACH AROUND 80. VERY HUMID ACROSS EASTERN NEW ENGLAND WITH DEWPOINTS AROUND 70...BUT BECOMING LESS HUMID IN THE WEST AS DEWPOINTS FALL THROUGH THE 60S AND POSSIBLY INTO THE 50S BY THIS EVENING. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... TONIGHT...SHOWERS AND THUNDERSTORMS LINGER ACROSS EASTERN MASSACHUSETTS AND RHODE ISLAND AHEAD OF A COLD FRONT THIS EVENING. THIS COLD FRONT SHOULD MOVE OFFSHORE BY SUNRISE THURSDAY...BRINGING AN END TO ANY LINGERING SHOWERS. THURSDAY...DRIER AND MORE SUNNY WEATHER BECOMES MORE PREVALENT AS WEAK HIGH PRESSURE ARRIVES. THERE IS NOT MUCH PUSH FOR THIS COLD FRONT...SO IT IS STILL EXPECTED TO SLOWLY MOVE EAST OF THE MA COASTAL WATERS DURING THE DAY. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... HIGHLIGHTS... * DRY WEATHER RETURNS THURSDAY NIGHT THROUGH SATURDAY * CHANCE OF SHOWERS POSSIBLE SUNDAY AND MONDAY 16/00Z MODEL GUIDANCE NOT SHOWING MUCH CHANGE FROM PREVIOUS THINKING FOR THIS PORTION OF THE FORECAST. AS MODELS REMAIN IN GENERALLY GOOD AGREEMENT...USED THE CONSENSUS TO TWEAK THIS PORTION OF THE FORECAST. THURSDAY NIGHT THROUGH SATURDAY...HIGH PRESSURE BUILDS INTO SOUTHERN NEW ENGLAND BRINGING DRIER...SEASONABLE WEATHER BACK TO THE REGION. EXPECT HIGHS GENERALLY IN THE LOW TO MID 80S AND LOWS IN THE 60S WITH PARTLY CLOUDY SKIES. SUNDAY AND MONDAY...HIGH PRESSURE STARTS TO MOVE OFFSHORE AS A WEAK UPPER TROUGH STARTS TO MOVE EAST OUT OF THE GREAT LAKES. THIS TROUGH...ALONG WITH AN APPROACHING WARM FRONT...WILL ALLOW FOR SHOWERS AND POTENTIALLY SOME THUNDERSTORMS TO DEVELOP. HOWEVER... NOT EXPECTING A WASHOUT AT THIS TIME.
Posted on: Wed, 16 Jul 2014 12:06:03 +0000
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