000 FXUS61 KCAR 081910 AFDCAR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CARIBOU ME 310 PM EDT TUE JUL 8 2008 .SYNOPSIS... A COLD FRONT WILL SLOWLY APPROACH FROM THE NORTHWEST TONIGHT. SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS THE STATE TOMORROW...ESPECIALLY IN THE AFTERNOON. HIGH PRESSURE WILL BUILD OVER THE REGION AGAIN FRIDAY FOR IMPROVED CONDITIONS. && .NEAR TERM /THROUGH TONIGHT/... CLEAR TO PARTLY CLOUDY SKIES COVER MOST OF THE AREA EARLY THIS EVENING AS HIGH PRESSURE OFF THE MID ATLANTIC COAST CONTINUES TO CARRY VERY WARM AND HUMID AIR ACROSS THE REGION. A WEAK FRONTAL BOUNDARY SEEMS TO BE LOCATED BETWEEN CENTRAL MAINE AND SOUTHWESTERN MAINE DIVIDING 70 DEGREE DEW POINT AIR TO THE SOUTH FROM 60 DEGREE DEWPOINT AIR TO THE NORTH. THUNDERSHOWERS POPPING IN NORTHERN PARTS OF WESTERN NEW ENGLAND MAY DRIFT ALONG THIS BOUNDARY EARLY THIS EVENING BRINGING SOME THUNDERSTORMS TO SOUTH CENTRAL AREAS. A MORE VIGOROUS SHORTWAVE CAN BE SEEN APPROACHING NORTHERN NEW YORK STATE. ALTHOUGH THIS WAVE IS PROGGED TO FLATTEN OUT AND WEAKEN AS IT MOVES INTO OUR AREAS LATER THIS EVENING...THERE MAY STILL BE ENOUGH ENERGY TO SPAWN A FEW MORE THUNDERSTORMS AROUND. THEREFORE...KEPT SCATTERED TRW INTO THIS EVENING MAINLY OVER WESTERN AREAS. FOG OVER THE WATERS IS EXPECTED TO EDGE BACK NORTH INTO SOUTHERN DOWNEAST LOCATIONS OVERNIGHT AS SURFACE WINDS BECOME A BIT MORE SOUTH TO SOUTHWESTERLY. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... TOMORROW PROMISES TO BE AN ACTIVE DAY ACROSS MAINE. THE STORM PREDICTION CENTER HAS PLACED PORTIONS OF CENTRAL MAINE IN A SLIGHT RISK OF SEVERE CONVECTION. EXAMINATION OF THE SYNOPTIC AND MESOSCALE PATTERN REVEALS THIS THREAT TO BE JUSTIFIED. AN UPPER LEVEL TROF OVER THE NORTHERN GREAT LAKES WILL DRIVE A SURFACE LOW PRESSURE CENTER AND ASSOCIATED COLD FRONT EASTWARD OVERNIGHT TONIGHT. BY LATE MORNING ON WEDNESDAY...THIS FRONT WILL BE ON THE WESTERN DOORSTEP OF THE STATE. ASSESSMENT FORCING MECHANISMS FOR TOMORROW IS TRICKY. SYNOPTIC SCALE FORCING...AS ASSESSED BY Q-VECTOR CONVERGENCE...IS WEAK AT BEST. HOWEVER...THE RIGHT REAR QUADRANT OF A JET STREAK MAKES ITS ARRIVAL OVER THE STATE BY LATE AFTERNOON. THIS COULD PROVIDE SOME HELP FOR LIFTING. INSTABILITY AS MEASURED BY CAPE APPEAR TO BE RATHER IMPRESSIVE FOR NORTHERN MAINE. SBCAPE...MLCAPE AND MUCAPE ALL APPEAR TO BREAK THE 1500 J/KG MARK ALONG A THIN AXIS FROM GREENVILLE TO HOULTON IN THE AFTERNOON. EXAMINATION OF MODEL DERIVED SOUNDING INDICATE THAT THIS INSTABILITY IS MORE PREVALENT IN THE LOWER LEVELS THAN THE MID-LEVELS DUE TO WARMER TEMPERATURES ALOFT. THIS DECREASES THE HAIL THREAT SOMEWHAT. ALSO OF INTEREST IS THE FACT THAT CAPE VALUES ARE ALL PREDICATED ON SURFACE HEATING IN THE EARLY MORNING. THIS COULD BE AN ISSUE SINCE NOCTURNAL CONVECTION WILL BE SWINGING THROUGH NORTHERN NY AND VT OVERNIGHT. THIS MAY SEND DEBRIS CLOUDS IN THE MID AND UPPER LEVELS OUR WAY IN THE MORNING. IF SO...WE WILL NEVER REALIZE THE CAPES MENTIONED ABOVE. MOISTURE PRAMETERS ARE ALSO CAUSING A BIT OF CONCERN. IN ADDITION TO SEVERE CONVECTION...FLASH FLOODING MAY BE AN ISSUE. PRECIPITABLE WATER VALUES FROM THE MORNING SOUNDINGS AT CARIBOU AND PORTLAND ARE 1.40 AND 1.38 INCHES RESPECTIVELY. THESE ARE EXPECTED TO JUMP UP TO NEARLY 2.0 INCHES TOMORROW. STORMS TOMORROW ARE EXPECTED TO FIRE ALONG A VERY CONFINED ZONE FROM GREENVILLE TO HOULTON. PROPAGATION VECTORS OF NEW CELL DEVELOPMENT DOES SEEM TO BE LARGE IN ENOUGH TO PREVENT BACK BUILDING. HOWEVER...TRAINING OF STORMS COULD BE A PROBLEM. THIS WILL NEED TO WATCHED CLOSELY. IN SUMMARY...CONVECTION COVERAGE IN THE FORECAST WILL BE HIGHEST FOR CENTRAL ZONES. ENHANCED WORDING FOR HEAVY RAIN...GUSTY WINDS AND SMALL HAIL WILL BE ADDED IN THIS SAME AREA AS WELL. LESSER COVERAGES AND MORE SUBDUED WORDING FOR EXTREME NORTHERN AND COASTAL ZONES SEEMS PRUDENT. BEYOND TOMORROW NIGHT...LINGERING SHOWERS IN THE NORTH AND OVER COASTAL WATERS FOR THURSDAY...OTHERWISE CONDITIONS ARE MUCH IMPROVED ON FRIDAY AS HIGH PRESSURE MOVES INTO THE AREA. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... GMOS LOADED FOR THE EXTENDED RANGE. ONLY MINOR TWEAKS WERE MADE. OTHERWISE ALL ELSE APPEARS TO BE THE SAME AS THE MORNING FORECAST ASSESSMENT. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... NEAR TERM: VFR CONDITIONS MAY LOWER TO MVFR ACROSS THE NORTH LATE TONIGHT AND WILL LIKELY LOWER TO IFR OR LIFR DOWNEAST AS FOG AND LOW STRATUS EASE BACK INLAND. SHORT TERM: THERE IS A SLIGHT RISK F SEVERE CONVECTION ACROSS THE STATE OF MAINE. CONVECTIVE ACTIVITY IS EXPECTED TO INCREASE AFTER 16UTC. PLEASE CHECK TERMINAL FORECASTS FOR SPECIFIC TIMING. THUNDERSTORMS WILL BE ESPECIALLY STRONG IN THE AFTERNOON...WITH HEAVY RAIN AND GUSTY WINDS. && .MARINE... NEAR TERM: WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SCA TONIGHT. EXPECT FOG TO PERSIST OVER THE WATERS AND TO DRIFT NORTH INTO THE BAYS TONIGHT. SHORT TERM: CONDITIONS ARE NOT EXPECTED TO BREAK SCA CRITERIA. FORECAST WAS LOWERED DUE TO KNOWN BIAS. OTHERWISE ALL ELSE LOOKS GOOD. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...NONE. && $$ NEAR TERM...BLOOMER SHORT TERM...LERICOS LONG TERM...LERICOS AVIATION...BLOOMER MARINE...BLOOMER/LERICOS