029
FXUS61 KGYX 010028
AFDGYX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
828 PM EDT TUE JUN 30 2026
WHAT HAS CHANGED
RECENT RUNS OF THE HRRR SUGGEST AN MCS OVER ONTARIO WILL TRACK
ACROSS THE AREA LATE TONIGHT INTO WEDNESDAY MORNING AND WILL BE
WEAKENING AS IT DOES SO. MODEL SOUNDINGS SHOW CONVECTION WILL BE
ELEVATED, WHICH SHOULD PRECLUDE ANY SEVERE WIND THREATS, BUT
TRENDS WILL NEED TO BE MONITORED OVERNIGHT. HAVE REFINED POPS
BASED ON RECENT HI RES GUIDANCE AND UPDATED THE AVIATION
SECTION FOR THE 00Z TAFS.
KEY MESSAGES
1. THE HOT AND HUMID CONDITIONS BEGIN ON WEDNESDAY, AND
CONTINUE THROUGH AT LEAST FRIDAY ACROSS NORTHERN NEW ENGLAND.
THE HEAT PEAKS ON THURSDAY, WITH ONLY A GRADUAL COOL DOWN
EXPECTED INTO THE WEEKEND. NIGHTTIME LOWS IN THE 70S OFFER
LITTLE RELIEF, AND RESULT IN ACCUMULATED HEAT STRESS.
2. STARTING LATE TODAY THROUGH THE END OF THE WEEK THE
INGREDIENTS WILL BE THERE FOR THUNDERSTORMS, SOME OF WHICH COULD
BE STRONG TO SEVERE. SPC HAS A MARGINAL RISK FOR SEVERE STORMS
FOR AT LEAST A PORTION OF OUR AREA LATE TODAY THROUGH THURSDAY.
3. CHANCES FOR AFTERNOON SHOWERS AND THUNDERSTORMS WILL REMAIN
IN THE FORECAST THROUGH THE HOLIDAY WEEKEND AND INTO EARLY NEXT
WEEK, BUT EXTREME HEAT LOOKS TO BREAK WITH THE PASSAGE OF A COLD
FRONT LATE WEEK.
DISCUSSION
KEY MESSAGE 1 DESCRIPTION...
THE HEAT AND HUMIDITY REMAINS ON TRACK FOR THE NEXT FEW DAYS.
WATCHES HAVE BEEN UPGRADED TO WARNINGS AND ADVISORIES FOR MOST
AREAS. A HEAT ADVISORY IS IN EFFECT FOR PARTS OF MAINE ON
WEDNESDAY, AND AN EXTREME HEAT WATCH IS IN EFFECT FOR THURSDAY
WHEN THE HIGHEST TEMPS ARE EXPECTED.
OVERALL THINKING HASN'T CHANGED FROM THE LAST FEW DAYS. THERE
REMAINS SOME UNCERTAINTY ON THE TIMING OF CLOUD COVER AND RIDGE
ROLLERS' EFFECT ON TEMPERATURES THROUGH THE NEXT FEW DAYS, WHICH
IS DISCUSSED IN MORE DETAIL IN KEY MESSAGE 2. THESE HOLD THE
POTENTIAL TO KEEP TEMPS LOWER THAN EXPECTED SHOULD THEY ARRIVE
IN THE LATE MORNING TO EARLY AFTERNOON TIMEFRAME, BUT WITHOUT
THEM HIGHS ARE LIKELY TO REACH THEY'RE FORECASTED LEVELS.
ONE OTHER FACTOR WE'RE WATCHING THAT COULD LIMIT TEMPERATURES
IS SOME WILDFIRE SMOKE FROM THE WESTERN US, WHICH WOULD LESSEN
THE AMOUNT OF SOLAR RADIATION REACHING THE SURFACE. ALMOST OF
THIS SMOKE WILL REMAIN ELEVATED, BUT SOME OF IT COULD MAKE ITS
WAY TO THE SURFACE AROUND CLUSTERS OF SHOWERS AND THUNDERSTORMS.
MUCH WORK WAS DONE FROM THE NBM STARTING POINT TO KEEP FORECAST
TEMPS AND HEAT INDICES WITHIN REASONABLE RANGES GIVEN THE 850MB
TEMPERATURE FORECASTS AND SURFACE DEW POINTS. WEDNESDAY
FEATURES A SEA BREEZE ALONG THE MAINE COAST, OFFERING RELIEF
AFTER A WARM MORNING TO THE IMMEDIATE COAST. A SEABREEZE LOOKS
UNLIKELY AWAY FROM THE MIDCOAST ON THURSDAY, AND LEAST LIKELY ON
FRIDAY WITH A WEST WIND.
OVERNIGHT LOWS IN THE MID TO UPPER 70S ARE EXPECTED ACROSS
SOUTHERN NEW HAMPSHIRE WEDNESDAY NIGHT THROUGH FRIDAY NIGHT,
WITH LOWS STILL IN THE 70S ELSEWHERE. HOWEVER, WITH ANY
CONVECTION THAT DOES PASS THROUGH, A QUICK DROP INTO THE UPPER
60S TO LOW 70S WOULD BE EXPECTED.
SO AT THIS STAGE, THE HEADLINES PRIMARILY TELL THE STORY ON THE
HEAT'S PROGRESSION. NEAR RECORD HIGH TEMPERATURES ARE EXPECTED
EACH DAY, WITH WIDESPREAD HEAT INDICES IN THE 105-110 RANGE IN
THE WARNING AREAS, AND UP TO 104 IN THE ADVISORY AREAS. THE
LONG DURATION OF THE HEAT EVENT MAKES IT MORE IMPACTFUL THAN
SOME OF THE SINGLE HOT DAYS WE'VE SEEN IN RECENT YEARS. A
GRADUAL DECREASE IN TEMPS IS EXPECTED THROUGH THE WEEKEND AND
EARLY NEXT WEEK AS A TROUGH BEGINS TO HAVE MORE INFLUENCE ON
NORTHERN NEW ENGLAND.
KEY MESSAGE 2 DESCRIPTION...
FOR THE NEXT SEVERAL DAYS EXTREME HEAT (DETAILED IN KEY MESSAGE
1) IS GOING TO AID IN PROVIDING THE INGREDIENTS FOR SEVERE
WEATHER. EACH AFTERNOON CAMS SHOW AMPLE CAPE DEVELOPMENT
(GREATER 1000 J/KG), STEEP LOW LEVEL LAPSE RATES (7 TO 8 C/KM),
AND BULK SHEAR 35 TO 50 KNOTS. NOT TO MENTION THE INCREASING
DEWPOINTS PROVIDING PLENTY OF BUOYANCY. HOWEVER, WHAT THE MODELS
ARE LACKING IS MUCH IN THE WAY OF LIFT, A KEY COMPONENT FOR
CONVECTIVE INITIATION. MODELS ALSO HAVE SOME THOUGHTS ON LATER
TIMING OF THE CONVECTIVE WAVES AS WELL, WHICH WOULD LOWER THE
SEVERE RISK. THE BOTTOM LINE IS THAT WHILE LACK OF LIFT MAY KEEP
COVERAGE LOW, ANYTHING THAT GETS ITSELF TOGETHER CERTAINLY HAS
THE POTENTIAL TO QUICKLY BECOME SEVERE. I WILL BREAK DOWN THE
DAILY DETAILS IN THE NEXT PARAGRAPHS.
THIS AFTERNOON, TWO DISTINCT MCSS ARE VISIBLE ON RADAR MOVING
THROUGH ONTARIO DOWNSTREAM OF THE RIDGE. AT THE TIME OF THIS
WRITING THE LEADING MCS IS JUST ABOUT TO THE U.S. BORDER AND
SHOULD BE CROSSING INTO UPSTATE NEW YORK SHORTLY. THE LAST FEW
RUNS OF THE CAMS HAVE TRENDED TOWARD THE BULK OF THIS STAYING TO
OUR WEST WITH MAYBE A FEW SHOWERS AND STORMS ABLE TO SNEAK INTO
WESTERN NEW HAMPSHIRE. THE OTHER THING WE WILL HAVE TO WATCH
THIS AFTERNOON AND EVENING IS THE SEABREEZE AS THAT CAN BE A
GOOD SOURCE OF LIFT, BUT AGAIN WOULD MOST LIKELY NOT BE A SOURCE
OF WIDESPREAD CONVECTIVE INITIATION AND ONLY RESULT IN JUST A
FEW STORMS THAT MAY QUICKLY BECOME STRONG TO SEVERE. THE SECOND
MCS, JUST NOW CRESTING THE RIDGE AT THE TIME OF THIS WRITING,
LOOKS LIKE IT WILL ARRIVE IN OUR AREA AS THE RIDGE AXIS SLOWLY
SHIFTS EASTWARD. HOWEVER, TIMING ON THE LATEST CAMS SUGGEST THIS
OCCURS IN THE VERY EARLY HOURS OF WEDNESDAY MORNING. SO, WHILE
IT IS POSSIBLE SOME LOCATIONS, ESPECIALLY ALONG THE
INTERNATIONAL BORDER GET WOKEN UP BY SOME IMPRESSIVE NOCTURNAL
CONVECTION, THAT TIME OF THE DAY IS NOT LIKELY TO LEND ITSELF TO
SEVERE WEATHER.
PARAMETER-WISE WEDNESDAY LOOKS LIKE THE BEST CHANCE FOR SEVERE
WEATHER ON PAPER WITH MUCAPE VALUES ON THE CAMS COMING IN AT A
VERY RESPECTABLE 2000-3000 J/KG ALONG WITH THE AFOREMENTIONED
LAPSE RATES AND SHEAR THAT ARE MORE THAN SUFFICIENT AS WELL.
CURRENTLY WHAT WEDNESDAY LACKS IS A RELIABLE SOURCE OF LIFT AND
THIS IS VERY APPARENT ON THE LATEST RUNS OF THE CAM WHICH SHOW
VERY LITTLE IN THE WAY OF SHOWERS AND STORMS PRESENT. THE
NAMNEST IS CURRENTLY LATCHING ON TO ANOTHER LATE ARRIVING
SHORTWAVE, BUT IT IS STILL TOO EARLY TO SAY FOR SURE WHAT MIGHT
BE OUT THERE, AND WE MAY HAVE TO WAIT TO SEE THE WHITES OF ITS
EYES THIS TIME TOMORROW IF MORE MODELS DON'T TREND THAT WAY
BEFOREHAND. THIS LOOKS LIKE A VERY TOUCH AND GO TIME PERIOD SO
ANYONE WITH PLANS TO BE OUTDOORS WEDNESDAY AFTERNOON SHOULD
MONITOR THE FORECAST AND CONDITIONS CLOSELY.
IRONICALLY THURSDAY MAY BE THE DAY WITH THE BEST LIFT AS MODELS
PROG A COLD FRONT TO SWEEP THROUGH, BUT IT ALSO LOOKS LIKE
SEVERE PARAMETERS TAKE A DOWNWARD TURN AS THE RIDGE AXIS MOVES
DIRECTLY OVERHEAD. THE 30/12Z NAMNEST IS NOT DEPICTING MUCH MORE
THAN A FEW ISOLATED STORMS, BUT THIS IS ALSO GETTING NEAR THE
END OF ITS RUN. I WOULDN'T BE SURPRISED TO SEE ACTIVITY TREND
UPWARD WITH SUBSEQUENT RUNS, BUT ALSO WOULDN'T BE SURPRISED IF
IT ENDS UP BEING A SIMILAR DAY WITH LOW COVERAGE, BUT PLENTY OF
ROOM FOR ANY ORGANIZED CONVECTION TO QUICKLY STRENGTHEN.
KEY MESSAGE 3 DESCRIPTION...
THE 500 MB PATTERN TRANSITIONS TO ZONAL FLOW AFTER THE RIDGE
AXIS SLIDES EAST LATE WEEK. HOWEVER, HIGH PRESSURE STAYS FIRMLY
PLANTED OVER THE EAST COAST SO FRIDAY COULD STILL BE A VERY WARM
DAY IN SOUTHERN ZONES. NORTHERN ZONES ARE MORE LIKELY TO SEE
THE INFLUENCE OF THE ZONAL FLOW AS SHOWERS AND THUNDERSTORMS
REMAIN IN THE FORECAST THERE. THE HOLIDAY WEEKEND STILL LOOKS
WARM, BUT THE CONTINUED NORTHWESTERLY FLOW ON THE BACK SIDE OF
THE COLD FRONT SHOULD START TO BRING HIGH TEMPERATURES BELOW
EXTREME HEAT THRESHOLDS. THE CONTINUED NORTHWESTERLY FLOW MEANS
THAT SHOWERS AND THUNDERSTORMS REMAIN A POSSIBILITY SO KEEP AN
EYE AND AN EAR TO THE SKY DURING ANY OUTDOOR FESTIVITIES. THE
PATTERN DOSEN'T CHANGE MUCH GOING INTO EARLY NEXT WEEK OTHER
THAN SOME MODELS TRANSITIONING THE ZONAL FLOW INTO A TROUGH, BUT
EITHER WAY THIS WOULD RESULT IN UNSETTLED WEATHER, SO I WILL
JUST LEAVE IT AT THAT.
AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
THROUGH WEDNESDAY NIGHT...
MAINLY VFR PREVAILS, BUT SOME BRIEF PERIODS OF RESTRICTIONS WITH
SHOWERS AND STORMS ARE POSSIBLE TONIGHT INTO WEDNESDAY MORNING.
BEST CHANCES FOR THUNDER WILL BE BETWEEN 08Z AND 12Z AT HIE,
LEB AND PWM WHILE CONFIDENCE IS NOT HIGH ENOUGH TO PUT IN THE
TAF. MAINLY VFR WEDNESDAY ALTHOUGH CHANCES FOR SHOWERS AND
STORMS LATE WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT COULD BRING
LOCALIZED RESTRICTIONS. SOME MARINE FOG IS ALSO POSSIBLE AT RKD
TONIGHT. MORE WIDESPREAD FOG IS POSSIBLE WEDNESDAY NIGHT.
OUTLOOK...
THURSDAY-SUNDAY: GENERALLY VFR CONDITIONS ARE EXPECTED DURING
DAYLIGHT HOURS WITH TEMPO MVFR CONDITIONS POSSIBLE EACH
AFTERNOON IN SHOWERS AND THUNDERSTORMS. IFR CONDITIONS WILL BE
POSSIBLE EACH NIGHT IN FOG, BUT HOW WIDESPREAD IT GETS IS
UNCERTAIN.
MARINE
HIGH PRESSURE SETTLES SOUTH OF THE WATERS TONIGHT. SOME PATCHY
MARINE FOG IS POSSIBLE AT TIMES EAST OF CASCO BAY TONIGHT AND
INTO WEDNESDAY. A FEW WAVES TO AROUND 5FT ARE POSSIBLE ACROSS
THE FAR EASTERN WATERS IN SOUTHWEST FLOW LATE TONIGHT, AND THEN
AGAIN LATE TOMORROW. A RIDGE OF HIGH PRESSURE SETTLES OVER THE
WATERS FROM MIDWEEK ONWARD WHICH SHOULD KEEP WAVES AND WIND
GUSTS PRIMARILY BELOW SCA CONDITIONS.
CLIMATE
HIGH TEMPERATURE RECORDS AT LONG TERM CLIMATE SITES...
JULY 1ST 2ND 3RD
AUG 92 (1971) 93 (1963) 94 (2002)
PWM 93 (1971) 98 (1941) 95 (2002)
CON 99 (1913) 98 (1966) 102 (1966)
GYX WATCHES/WARNINGS/ADVISORIES
ME...HEAT ADVISORY FROM 11 AM WEDNESDAY TO 8 PM EDT THURSDAY FOR
MEZ007>009.
EXTREME HEAT WARNING FROM 11 AM WEDNESDAY TO 8 PM EDT FRIDAY
FOR MEZ012-018>020-023-033.
HEAT ADVISORY FROM 11 AM TO 8 PM EDT WEDNESDAY FOR MEZ013-014-
021-022-024>026.
EXTREME HEAT WATCH FROM THURSDAY MORNING THROUGH THURSDAY
EVENING FOR MEZ013-014-021-022-024>028.
AIR QUALITY ALERT FROM 10 AM TO 11 PM EDT WEDNESDAY FOR
MEZ023>028.
NH...HEAT ADVISORY FROM 11 AM WEDNESDAY TO 8 PM EDT THURSDAY FOR
NHZ001>003.
EXTREME HEAT WARNING FROM 11 AM WEDNESDAY TO 8 PM EDT FRIDAY
FOR NHZ004>015.
AIR QUALITY ALERT FROM 10 AM TO 10 PM EDT WEDNESDAY FOR NHZ013-
014.
MARINE...NONE.
DISCUSSION...BARON/CLAIR/SCHROETER
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