Area Forecast Discussion
Issued by NWS Portland, ME

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KGYX 250807
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
407 AM EDT TUE AUG 25 2015

.SYNOPSIS...
HUMID AND UNSETTLED CONDITIONS WILL CONTINUE THROUGH MID WEEK. ON
A COLD FRONT WILL SLOWLY APPROACH FROM THE WEST TODAY...PROVIDING
A ROUND OF SHOWERS AND THUNDERSTORMS TODAY. THE FRONT STALLS OVER
THE AREA TONIGHT INTO WEDNESDAY AS WEAK LOW PRESSURE TRACKS
NORTHEAST ALONG IT...WITH MORE SHOWERS AND THUNDERSTORMS
EXPECTED. THE FRONT FINALLY EXITS THE REGION LATE WEDNESDAY.
ANOTHER ROUND OF SHOWERS IS POSSIBLE...MAINLY IN THE
MOUNTAINS...ON THURSDAY AS A SECOND COLD FRONT PUSHES THROUGH.
DIRER AND RELATIVELY COOLER AIR WILL MOVE IN AT THE END OF THE
WEEK AS HIGH PRESSURE BUILDS IN. AS THE HIGHS SETTLES SOUTH AND
EAST OF US OVER THE WEEKEND...LOOK FOR MAINLY FAIR WEATHER AND A
WARMING TREND.

&&

.NEAR TERM /THROUGH TODAY/...
THRU MORNING WE WILL SEE PLENTY OF FOG AND LOW CLOUDS. AND LIKE
YESTERDAY...AS WE HEAT UP THESE CLOUDS WILL GRADUALLY LIFT AND
SCATTER OUT. IT IS THESE BREAKS IN THE OVERCAST THAT WILL BE SO
IMPORTANT TO THE AFTERNOON FORECAST.

BOUNDARY LAYER IS CHARACTERIZED BY A WARM AND VERY MOIST AIR MASS
ENTRENCHED ACROSS THE AREA. DESPITE POOR LAPSE RATES ALOFT...EVEN
MARGINAL HEATING OF THIS LOW LEVEL AIR MASS WILL SUPPORT
DESTABILIZATION. THIS HEATING IS MOST LIKELY TO OCCUR IN
POCKETS...AS ONGOING CONVECTION FROM THIS MORNING SPREADS EXTRA
CLOUD COVER INTO THE AREA...AND WHILE MORNING FOG SLOWLY LIFTS. AT
THIS HOUR CONVECTION ALLOWING MODELS STRONGLY FAVOR BEST AIR MASS
RECOVERY TO OCCUR OVER SRN NH. AS THE DAY WEARS ON...A
MODEST...CYCLONICALLY CURVED H5 JET WILL WORK TOWARDS NEW ENGLAND.
SHEAR WILL CONSEQUENTLY INCREASE THRU THE DAY...AND PROVIDE MORE
THAN ENOUGH TURNING IN THE ATMOSPHERE FOR STORM ORGANIZATION. AS
UPPER LOW IS ONLY SLOWLY INCHING EWD...THERE WILL BE A BIT OF A
LACK OF FORCING OVERALL...SO STORM COVERAGE SHOULDN/T BE
WIDESPREAD.

PRIMARY THREAT WILL BE GUSTY WINDS...BOTH VIA WET MICROBURSTS OR
AS DEEP SWLY UNIDIRECTIONAL WINDS ALOFT INCREASE LATER IN THE
AFTERNOON. GIVEN TENDENCY FOR CONVECTION ALLOWING MODELS TO LEAN
TOWARDS SOMEWHAT DISCRETE STORM STRUCTURES LARGE HAIL CANNOT BE
RULED OUT...IN ADDITION TO AN ISOLATED TORNADO. THE LATTER IS
MITIGATED MAINLY BY THE WEAKER FLOW IN THE LOWEST 3 KM OF THE
ATMOSPHERE. THAT BEING SAID...A WARM FRONTAL FEATURE WILL BE
DRAPED ACROSS NH DURING THE AFTERNOON...SO NEAR AND JUST N OF THIS
BOUNDARY WILL BE A LOCALLY HIGHER TORNADO THREAT.

IN ADDITION TO THOSE STORM THREATS...DEEP SWLY FLOW WILL TEND
TOWARDS TRAINING OF INDIVIDUAL CELLS. THIS WILL COMPOUND AN
ALREADY MOIST ENVIRONMENT FAVORABLE FOR HEAVY RNFL...SO FLASH
FLOODING WILL BE JUST AS LIKELY THIS AFTERNOON.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
COLD FRONT WILL VERY SLOWLY PROGRESS ACROSS THE AREA
OVERNIGHT...SO THE THREAT FOR SHOWERS WILL LINGER ACROSS ERN ZONES
WELL INTO THE NIGHT. AGAIN GIVEN THE DEEP SWLY FLOW...THE TENDENCY
FOR TRAINING WILL CONTINUE AS WELL...AND HEAVY RNFL IS A
POSSIBILITY.

ONSHORE FLOW WILL CONTINUE...ESPECIALLY ACROSS ME...AND ALLOW
FOG/STRATUS TO REDEVELOP TONIGHT AHEAD OF THE FRONT. THE EXTENT OF
LOW CLOUDS WILL DEPEND ON HOW FAR E THE FRONT CAN ADVANCE...BUT
GENERAL MODEL CONSENSUS IS THAT ERN ZONES REMAIN DOWNSTREAM OF THE
BOUNDARY UNTIL WED. AGAIN WILL KEEP HIGHEST POP IN THE ERN ZONES
TO ACCOUNT FOR SLOW FRONTAL MOVEMENT.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
HIGH IMPACT WEATHER: NONE.

OVERALL 500MB PATTERN TREND IS TO TREND AWAY FROM MORE AMPLIFIED
BLOCKY PATTERN AT THE START OF THE FORECAST PERIOD...TO LARGE
SCALE RIDGING BUILDING OVER THE ERN 2/3 OF THE CONUS AND TROUGHING
NEAR THE WEST COAST BY EARLY NEXT WEEK. INITIALLY...LARGE CLOSED
LOW SOUTH OF JAMES BAY WILL LIFT NE THU AND FRI...WITH ZONAL FLOW
TAKING OVER THE WEEKEND...AND FINALLY THAT RIDGE STARTS TO BUILD
IN EARLY NEXT WEEK. 850MB TEMPS WILL INCREASE FROM 8-10C AT THE
END OF WEEK TO 12-15C MON AND TUE.

SENSIBLE WEATHER WILL START WITH SHRA/TSRA SHIFTING EWD AND OUT OF
THE CWA WED EVENING...WITH A SLIGHT DROP IN RH/TEMPS WED
NIGHT. ANOTHER WAVE WILL ROTATE AROUND THE LOW ALOFT ON THU AND
PUSH ANOTHER COLD FRONT THRU ON THU...AND COULD SET OFF A SCT
SHRA...AND EVEN A TSRA...WHICH WILL PROBABLY BE LIMITED TO THE
NRN ZONES...WHICH WILL BE CLOSER TO THE BEST DYNAMICS...WHILE THE
COASTAL SHOULD STAY DRY IN DOWNSLOPE. BEYOND THAT LOOK FOR MAINLY
DRY AND GENERALLY FAIR WEATHER FRI-MON...ALTHOUGH A WEAK 500MB
WAVE PASSING N OF THE CWA COULD PRODUCE A FEW SHRA IN THE MTNS SAT
NIGHT OR SUN.

TEMPS WILL START NEAR NORMAL THU AND FRI...AT LEAST FOR
MAXES...OVERNIGHT LOWS MAY CONTINUE TO RUN SLIGHTLY ABV NORMAL WED
NIGHT INTO THU NIGHT BEFORE THE DRIEST AIR MOVES IN FRI...WITH
HIGHS IN THE 70S TO AROUND 80...AND LOWS IN THE 50S TO AROUND 60.
THE COOLEST NIGHT WILL PROBABLY BE FRI NIGHT INTO SAT MORNING WITH
LOWS DROPPING INTO THE 50S EVERYWHERE...AND MAYBE A FEW UPPER 40S
IN THE MTN VLYS. TEMPS WILL GRADUALLY WARM OVER THE WEEKEND AS
WARMER AIR MOVES IN ALOFT ON THE ZONAL FLOW...WITH HIGHS REACHING
INTO THE 80S IN MOST SPOTS BY MONDAY.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
SHORT TERM...AREAS OF LIFR IN FOG AND DRIZZLE WILL PERSIST THRU
MORNING ACROSS EXTREME COASTAL NH AND MUCH OF WRN ME. EXPECT VERY
GRADUAL IMPROVEMENT TODAY...BUT WITH COLD FRONT EDGING CLOSER
THERE WILL BE MORE AREAS OF MVFR THAN YESTERDAY AFTERNOON.

SHRA AND TSRA WILL ALSO CONTINUE TO FORM ALONG THE FRONT AND
BECOME MORE WIDESPREAD WITH DAYTIME HEATING. SHRA ARE LOOKING MORE
LIKELY AT NH TERMINALS THAN WRN ME AT THIS TIME...THOUGH
EVENTUALLY RNFL WILL WORK THRU BOTH STATES. TIMING AND LOCATION OF
TSRA REMAINS SOMEWHAT UNCERTAIN AT THIS HOUR...SO WILL START WITH
A PROB30 FOR NOW. FOG/STRATUS WILL MOVE BACK INTO THE COAST AFTER
00Z TONIGHT...ESPECIALLY ACROSS WRN ME.

LONG TERM...SOME AREAS OF FOG AND LOW CLOUDS WILL BE POSSIBLE WED
NIGHT...BUT PROBABLY NOT AS PREVALENT NOR AS IMPACTFUL AS THE LAST
FEW NIGHTS. AFTER THAT...THU-SAT WILL FEATURE MAINLY VFR...WITH
THE EXCEPTION OF VLY FOG EACH NIGHT.

&&

.MARINE...
SHORT TERM...WINDS AND SEAS EXPECTED TO REMAIN BELOW SCA
THRESHOLDS THRU WED. WIDESPREAD FOG AND LOW CLOUDS WILL PERSIST
THRU MORNING TODAY...SCATTERING OUT THIS AFTERNOON. IT SHOULD
RETURN AGAIN TONIGHT...MAINLY CONFINED TO COASTAL ME WATERS.

LONG TERM...MAY SEE SOME LINGERING LIGHT FOG WED NIGHT...BUT
OTHERWISE SEAS/WINDS WILL BE COMFORTABLY BLO SCA LVLS THU-SAT.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...NONE.
NH...NONE.
MARINE...NONE.

&&

$$

NEAR TERM...LEGRO
SHORT TERM...LEGRO
LONG TERM...CEMPA
AVIATION...CEMPA/LEGRO
MARINE...CEMPA/LEGRO



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.