091
FXUS61 KGYX 232014
AFDGYX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
414 PM EDT WED JUL 23 2008
SYNOPSIS
AN UPPER LEVEL LOW PRESSURE SYSTEM WILL REMAIN PARKED TO THE WEST
THROUGH FRIDAY. WAVE ROTATING AROUND THIS SYSTEM WILL PROVIDE
AREAS OF HEAVY RAIN AND THUNDERSTORMS THROUGH FRIDAY...WITH
RAINFALL AMOUNTS IN EXCESS OF 2 INCHES POSSIBLE...ESPECIALLY IN
NEW HAMPSHIRE. A COLD FRONT WILL CROSS THE REGION EARLY FRIDAY...WITH
DRIER AIR BRIEFLY BUILDING IN BEHIND THE FRONT. FOR THE
WEEKEND...LOW PRESSURE WILL PASS TO THE NORTH...BRINGING A CHANCE
OF SHOWERS AND THUNDERSTORMS LATE SATURDAY INTO SUNDAY.
NEAR TERM /UNTIL 8 PM THIS EVENING/
ISOLATED SHOWERS EXITING OUT OF THE NORTHERN AREAS OF CWA THIS
AFTERNOON AS ANOTHER WAVE OF PRECIP OVER SOUTHERN NEW ENGLAND
MOVES N INTO NEW HAMPSHIRE. EXPECT HEAVIER PRECIP THROUGH EVENING
INTO OVERNIGHT WITH IMPULSES RIDING ALONG A STALLED BOUNDARY.
THE AIR MASS WILL BECOME MORE UNSTABLE THROUGH THE EVENING AS A
WARM FRONT SLOWLY LIFTS THROUGH THE AREA. POCKETS OF HEAVIER RAIN
WITH EMBEDDED THUNDERSTORMS ARE POSSIBLE FOR OUR SOUTHERN REGIONS.
SHORT TERM /8 PM THIS EVENING THROUGH THURSDAY NIGHT/
THE MAIN CONCERN WILL BE THE POTENTIAL FOR FLOODING...THOUGH
SEVERE WEATHER POTENTIAL IS ASSESSED AS WELL. MODELS EVER SO
SLOWLY CONVERGING ON A SOLUTION...WITH NAM/GFS/GEM/UKMET CONSENSUS
SHIFTING A TAD EAST ON THE 12Z RUN. EXPECT WARM FRONT TO LIFT
ACROSS THE REGION THIS EVENING...INCREASING PRECIPITABLE WATER
VALUES TO AS HIGH AS 2.00 INCHES. WINDS ALOFT INCREASING...WITH AN
UNSEASONABLY STRONG LOW LEVEL JET OF 50 KTS DEVELOPING AT 850 MB.
EXPECT WAVES OF CONVECTION TO RIDE ALONG THIS BOUNDARY THROUGH
THURSDAY NIGHT...FINALLY CUTTING OFF BETWEEN 06Z AND 12Z.
CONVECTIVE ELEMENT MAKES QPFS DIFFICULT. GENERALLY ACCEPT NAM/GFS
QPF BLEND OF 2 TO 4 INCHES ACROSS NEW HAMPSHIRE...WITH 1 TO 3
INCHES IN MAINE. HOWEVER...IF CONVECTIVE BANDS STALL ACROSS THE
SAME REGION...LOCALLY HIGHER AMOUNTS OF 6 INCHES ARE POSSIBLE.
WILL ISSUE A FLOOD WATCH FOR ALL BUT SOUTHEASTERN NEW HAMPSHIRE. SEE
HYDROLOGY SECTION FOR MORE ON FLOODING POTENTIAL.
FOR SEVERE WEATHER...WINDS ALOFT ARE ARE FORECAST TO INCREASE TO 50
KTS AT 850 MB FOR THURSDAY. WHILE BUFKIT SHOWS A STRONG
INVERSION...KEEPING THESE WINDS ALOFT FOR THE MOST PART...EMBEDDED
CONVECTIVE ELEMENTS COULD POTENTIALLY BRING THESE DOWN TO THE
SURFACE. FOR THE MOST PART...EXPECT WINDS NOT TO BE A
PROBLEM...HOWEVER WILL MONITOR RADAR FOR ANY SIGNATURE WHICH
SUGGESTS THESE WINDS MAY MAKE IT TO THE GROUND. SPC HAS US IN A
SLIGHT RISK.
USE NAM/GFS MOS BLEND FOR POPS AND TEMPERATURES...SLIGHTLY LEANING
TOWARDS THE NAM AS IT HAS HAD A SLIGHTLY BETTER HANDLE SO FAR.
LONG TERM /FRIDAY THROUGH TUESDAY/
500MB CLOSED LOW IS FORECAST TO LIFT BACK TO THE NW FRI-SAT...AND
THEN TRACK SLOWLY TOP THE...REACHING THE MARITIMES EARLY NEXT
WEEK. THIS WILL CONTINUE TO KEEP UNSETTLED WX OVER NRN NEW
ENGLAND INTO EARLY NEXT WEEK.
WAVES ALOFT...ROTATING AROUND THIS UPPER LVL LOW WILL DETERMINE
WHEN RAIN/THUNDER ACTUALLY OCCURS...AND MODELS NOT VERY GOOD ON
TIMING THIS FAR OUT. HOWEVER...BOTH GFS/NAM IN REASONABLE
AGREEMENT THAT WE/LL SEE A BIT OF BREAK LATE FRIDAY INTO EARLY
SAT...AND THAT ONE WAVE WILL WORK THRU LATE SAT AND INTO SUN...AND
THIS WILL BE WHEN THE BEST CHC FOR SHRA/TSRA WILL OCCUR IN THE
EXTENDED. AFTER THAT IT LOOKS AS IF THE WAVE TEND TO GET MORE
STRETCHED OUT AND WEAKER...SO ANY SHRA/TSRA LKLY TO BE MORE SCT
MON INTO TUE. CLOSED LOW LOOKS TO FINALLY FILL AND MOVE FAR ENOUGH
E BY MID-WEEK TO NO LONGER HAVE ANY REAL EFFECT ON THE CWA...BUT
SINCE MODEL PERFORMANCE WITH CLOSED LOWS IS SKETCHY...WILL HAVE TO
MAINTAIN SLT CHC POPS LATE IN THE FORECAST PERIOD.
AVIATION /19Z WEDNESDAY THROUGH MONDAY/
SHORT TERM...EXPECT CONDITIONS TO DROP QUICKLY WITH THE PASSAGE OF
A WARM FRONT...WHICH LIFT FROM SOUTH TO NORTH BETWEEN 00Z AND 06Z
TONIGHT. BEHIND THE FRONT...ALSO EXPECT LOW LEVEL WIND SHEAR TO
DEVELOP. THERE IS A CHANCE OF EMBEDDED THUNDERSTORMS THROUGH
THURSDAY...THOUGH MOST CONVECTION WILL BE ELEVATED.
LONG TERM...CONVECTION LOOKS TO REMAIN IN THE FORECAST RIGHT INTO
EARLY NEXT WEEK...HOWEVER...LOOKS LIKE THERE COULD BE A FRY PERIOD
FROM FRI AFTERNOON INTO SAT MORNING...WITH THE BEST CH FOR
SHRA/TSRA SAT AFTERNOON INTO SUN MORNING.
MARINE
SHORT TERM...ISSUED AN SCA FOR OUR OUTER WATERS...AS SEAS AND
EVENTUALLY WINDS ARE EXPECTED TO RISE. EXPECT SEAS TO REACH 5 FT
AROUND DAYBREAK...RISING THROUGH THE DAY AS WINDS PICK UP. WINDS
INITIALLY MARGINAL WILL LIKELY ALSO GUST TO 25 KTS OR GREATER ON
OUR OUTER WATERS LATE THURSDAY AFTERNOON AND EVENING. THEY BAYS
MAY NEED AN SMALL CRAFT ADVISORY LATER...BUT WILL NOT REACH SCA
CONDITIONS UNTIL LATER.
TRENDED BELOW WNA WAVE WATCH TONIGHT AND THURSDAY...BUT NUDGED WNA
UP LATE THURSDAY NIGHT...TRENDING TOWARDS THE NAM MODEL WHICH IS
SLOWER WITH THIS SYSTEM.
LONG TERM...SEAS WILL LKLY REMAIN NEAR OR ABOVE SCA LVLS INTO FRI
NIGHT...BUT SHOULD SUBSIDE AFTER THAT.
HYDROLOGY
EXPECT 2 TO 4 INCHES OF RAIN ACROSS NEW HAMPSHIRE...WITH 1 TO 3
INCHES IN MAINE. EMBEDDED AMOUNTS OF 6 INCHES ARE
POSSIBLE...THOUGH NAM/GFS BOTH KEEP THE AXIS OF HEAVIEST RAINFALL
JUST TO OUR WEST...DYNAMICS AND PRECIPITABLE WATER VALUES FORECAST
TO HIT 2 INCHES...SUPPORTS A WATCH FOR NEW HAMPSHIRE. ANY SHIFT
EASTWARD IN THE AXIS MAY REQUIRE EXPANDING THE WATCH...BUT FOR NOW
FEEL THE GREATEST RISK IS IN NEW HAMPSHIRE.
RFC FORECASTS ARE HEAVILY DEPENDANT ON QPFS. THOUGH RFC DID
FORECAST WITH 00Z DATA...VALUES RFC USED ARE ON TRACK WITH CURRENT
QPF FORECAST...SO EXPECT THESE TO BE FAIRLY REPRESENTATIVE. THE
MAIN ISSUES LOOK TO BE ON THE CONNECTICUT AND THE
PEMIGEWASSET...WITH SEVERAL OTHER RIVERS CLOSE. GIVEN THE 2 TO 4
INCHES OF QPF...ONLY MINOR FLOODING WOULD BE EXPECTED. IF LOCALLY
HIGHER AMOUNTS OCCUR...SIGNIFICANTLY HIGHER CRESTS ARE LIKELY. FOR
NOW...MINOR FLOODING IS THE MORE LIKELY SCENARIO...THOUGH THERE IS
A SLIGHT CHANCE THE AXIS OF HEAVY RAINFALL WILL SHIFT ACROSS NEW HAMPSHIRE.
FINALLY...DUE TO THE CONVECTIVE ELEMENT OF THIS EVENT...FLASH
FLOODING IS A POSSIBILITY. LOCALLY HEAVY RAINFALL MAY CAUSE
STREAMS AND FAST RESPONDING RIVERS TO RISE QUICKLY...PERHAPS
REQUIRING A FLASH FLOOD WARNING
FOR NOW
THE MAIN THREAT IS
SLOWER RESPONDING FLOODING...THUS A FLOOD WATCH INSTEAD OF A FLASH
FLOOD WATCH WAS ISSUED.
GYX WATCHES/WARNINGS/ADVISORIES
ME...NONE.
NH...FLOOD WATCH FROM THURSDAY MORNING THROUGH FRIDAY MORNING FOR
NHZ001>009.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM THURSDAY TO 8 AM EDT FRIDAY FOR
ANZ150-152-154.
SYNOPSIS...CEMPA
NEAR TERM...TAYLOR
SHORT TERM...APFFEL
LONG TERM...CEMPA
AVIATION...APFFEL
MARINE...APFFEL/CEMPA
HYDROLOGY...APFFEL
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