802
FXUS61 KGYX 050136 AAA
AFDGYX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GRAY ME
936 PM EDT SAT JUL 4 2009
SYNOPSIS
A COLD FRONT WILL EXIT THE REGION TONIGHT AS LOW PRESSURE MOVES
INTO THE MARITIMES. A WEAK SURFACE TROUGH WILL CROSS THE AREA ON
SUNDAY. WEAK LOW PRESSURE WILL SLOWLY CROSS NORTHERN NEW ENGLAND
SUNDAY NIGHT AND MONDAY....THEN EXIT THE SOUTHERN NEW ENGLAND
COAST TUESDAY. HIGH PRESSURE WILL BUILD OVER THE AREA FROM ONTARIO
WEDNESDAY AND THURSDAY. A WARM FRONT WILL CROSS THE REGION
FRIDAY...FOLLOWED BY A COLD FRONT SATURDAY.
NEAR TERM /THROUGH SUNDAY/
UPDATE
BEST UPPER LEVEL DIVERGENCE AND FORCING CONTINUES TO ROTATE INTO
NORTHERN MAINE. EXPECT SCT SHOWERS OVER MAINLY THE EASTERN HALF OF
THE FORECAST AREA TO PERSIST OVER THE NEXT FEW HOURS. WEAK RIDGING
WILL THEN BUILD INTO THE AREA MAKING FOR PLEASANT WEATHER
TOMORROW. DRY WESTERLY WINDS WILL HELP TEMPS DROP INTO THE 40S
IN THE MOUNTAINS AND THE LOWER 50S TOWARDS THE COAST TONIGHT. SH/13
PREVIOUS DISCUSSION
1002 MILLIBAR LOW WAS VICINITY OF GASPE PENINSULA WITH TRAILING
COLD FRONT THROUGH EASTERN SECTIONS OF FORECAST AREA AT 18Z.
COOLING ALOFT COMBINED WITH UPPER IMPULSE AND HEATING HAS RESULTED
IN PULSE STORMS ACROSS THE AREA WITH UP TO QUARTER SIZED HAIL
REPORTED. ACTIVITY WINDS DOWN BY EARLY EVENING WITH LOSS OF
HEATING AND AS IMPULSE EXITS QUICKLY TO OUR EAST.
SHORT TERM /SUNDAY NIGHT/
LINGERING CLOUDS AND SCATTERED SHOWERS ACROSS NORTHERN SECTIONS
WITH THE UPPER LOW...WHILE SKIES GRADUALLY BECOME MOSTLY CLEAR
ACROSS THE COASTAL PLAIN AND SOUTHERN SECTIONS. ON SUNDAY A WEAK
SURFACE TROUGH WILL PRODUCE MOUNTAIN CLOUDS AND MAY TOUCH OFF A
FEW SHOWERS. ELSEWHERE...A DRY DAY EXPECTED WITH A FEW AFTERNOON
BUILD UPS. OFFSHORE FLOW AND 850 MILLIBAR TEMPERATURES NEAR +9C
ALLOW MOST AREAS TO WARM WELL INTO THE 70S...WITH A FEW LOWER 80S
SOUTH. HIGHS ACROSS THE MOUNTAINS WILL BE CLOSER TO 70 AS CLOUDS
AND A FEW SHOWERS LIMIT HEATING.
LONG TERM /MONDAY THROUGH SATURDAY/
LOOKS LIKE A SUBTLE PATTERN CHANGE IS IN STORE FOR THE MIDDLE OF
THE UPCOMING WEEK...WITH THE THREAT OF A RETURN TO THE TROUGHING
IN THE MID LEVELS FOR LATE NEXT WEEK AND NEXT WEEKEND.
ANY CONVECTION SHOULD END SUNDAY EVENING...WITH CONVECTIVE
CLOUDINESS DISSIPATING AFTER THIS. SINCE THE GROUND HAS BEEN WET
AND WINDS WILL BE FAIRLY LIGHT...WOULD EXPECT PATCHY FOG TO
DEVELOP AGAIN. LOWS WERE BASED ON A BLEND MOS NUMBERS.
THE MID LEVEL PATTERN STARTS TO MAKE THE CHANGE AS THE CLOSED LOW
OVER ONTARIO AND QUEBEC STARTS TO OPEN UP AND LIFT OUT IN RESPONSE
TO RIDGING OVER THE INTERMOUNTAIN WEST. COOLER MID LEVEL TEMPERATURES
SHOULD SPARK AT LEAST SCATTERED CONVECTION MONDAY...AND AS THE MID
LEVEL SYSTEM CROSSES...STEERING WINDS WILL BECOME LIGHTER. WILL
NOT MENTION THIS IN THE FORECAST YET...BUT WILL HAVE TO WATCH FOR
SLOW MOVING CONVECTION TO POSSIBLY PRODUCE LOCALLY HEAVY RAINFALL.
THE CONVECTION SHOULD WANE MONDAY NIGHT...BUT REDEVELOP TUESDAY AS
THE LAST OF THE MID LEVEL SYSTEM EXITS. THE FINAL SPOKE AROUND THE
SYSTEM WILL PASS IN THE AFTERNOON...WITH COLD MID LEVEL TEMPERATURES.
THE BULK SHEAR REMAINS LIGHT...WITH A JET STREAK PASSING TO THE SOUTH.
THE BEST CHANCE OF CONVECTION SHOULD BE IN THE AFTERNOON...BUT
COVERAGE MAY END UP BEING LIMITED BY INSTABILITY.
AFTER THIS...THE MID LEVEL PATTERN TRANSITIONS THROUGH CYCLONIC
FLOW INTO A FLAT RIDGE FOR MID WEEK. BECAUSE OF THE CYCLONIC FLOW
(AND COOL MID LEVEL TEMPERATURES) CANNOT RULE CONVECTION OUT
COMPLETELY WEDNESDAY...BUT IT SHOULD BE LESS CONCENTRATED THAN
PREVIOUS DAYS. THE MID LEVEL RIDGING SHOULD RESULT IN DRY
CONDITIONS THURSDAY.
AFTER THIS...YET ANOTHER SHORT WAVE IN THE MID LEVELS DROPS INTO
THE FLOW AND STARTS TO CARVE OUT YET ANOTHER MID LEVEL TROUGH
ACROSS THE EAST. THE TIMING OF THE DETAILS FOR THIS BECAUSE LESS
CLEAR WITH TIME...BUT IT APPEARS AS THOUGH WARM AIR ADVECTION
INDUCED SHOWERS ARE POSSIBLE FRIDAY WITH A WARM FRONT. THE TIMING
OF SHOWERS NEXT SATURDAY WILL BE TIED TO THE POSITION OF A SURFACE
COLD FRONT...SO SHOWERS WERE MENTIONED THEN AS WELL.
AVIATION /02Z SUNDAY THROUGH THURSDAY/
SHORT TERM /THROUGH 23Z SUNDAY/...BRIEF MVFR THIS EVENING IN
SHOWERS AND THUNDERSTORMS...OTHERWISE VFR EXPECTED. BRIEF MVFR
POSSIBLE DURING THE DAY SUNDAY OVER MOUNTAIN SECTIONS IN SHOWERS.
LONG TERM...FOR THE MOST PART...VFR CONDITIONS DURING THE DAY
AND PATCHY IFR CONDITIONS ARE EXPECTED THROUGH TUESDAY...AS THE
LOW LEVEL PATTERN DOES NOT CHANGE MUCH. WOULD EXPECTED SCATTERED
CONVECTION MONDAY AND TUESDAY...WITH THE BEST ORGANIZATION TUESDAY
AFTERNOON.
A CLEANER AIRMASS IS EXPECTED FOR THE MIDDLE OF NEXT WEEK. THIS
SHOULD RESULT IN VFR DAYS AND PATCHY IFR ON FOG AT NIGHT...ESPECIALLY
AT KLEB AND KCON.
MARINE
SHORT TERM /THROUGH SUNDAY/...WESTERLY FLOW INCREASES BEHIND THE
COLD FRONT. HOWEVER...EXPECT WINDS AND SEAS TO REMAIN BELOW SCA
VALUES.
LONG TERM...WINDS AND SEAS SHOULD REMAIN BELOW SMALL CRAFT LIMITS
THROUGH THE PERIOD...AS THE SURFACE GRADIENT REMAINS WEAK. THE
FLOW SHOULD REMAIN WEAK AND ONSHORE THROUGH TUESDAY. AFTER THE LOW
DEPARTS TUESDAY EVENING....WEST WINDS COULD APPROACH 20 KNOTS FOR
A TIME TUESDAY NIGHT.
GYX WATCHES/WARNINGS/ADVISORIES
ME...NONE.
NH...NONE.
MARINE...NONE.
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