631
FXUS61 KGYX 031908
AFDGYX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
308 PM EDT MON AUG 3 2020
SYNOPSIS
BY LATER TONIGHT WILL START TO SEE SOME SHOWERS ASSOCIATED WITH
ISAIAS MOVING INTO THE REGION, WHICH WILL BECOME MORE NUMEROUS
DURING THE DAY ON TUESDAY. THE BRUNT OF THE STORM SHOULD HIT
TUESDAY NIGHT WITH STRONG WINDS AND LOCALLY HEAVY RAINFALL. THE
STORM EXITS TO THE NORTH EARLY WEDNESDAY, WITH MORE NORMAL TO
WARM TEMPERATURES AND LOWER HUMIDITY FOR THE END OF THE WEEK.
NEAR TERM /THROUGH TONIGHT/
MOISTURE WILL BEGIN TO SPREAD NORTH TONIGHT AHEAD OF TROPICAL
CYCLONE ISAIAS INTO WESTERN NEW HAMPSHIRE AS A DEEP SOUTHERLY
FLOW DEVELOPS OVER THE REGION. LOWS WILL REMAIN IN THE MID TO
UPPER 60S OVER SOUTHERN AREAS AS THIS MOISTURE ADVANCES INTO THE
REGION AT ALL LEVELS.
SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/
SHOWERS BECOME MORE NUMEROUS DURING THE DAY TUESDAY AS WINDS
INCREASE FROM THE SOUTH. PRECIPITABLE WATER LEVELS WILL BECOME
VERY HIGH ONCE AGAIN. THIS DEEP MOISTURE ADVECTING POLEWARD WILL
ALLOW FOR HEAVY SHOWERS. DESTABILIZATION OF THE ATMOSPHERE WILL
ALLOW FOR A FEW THUNDERSTORMS AS WELL.
AS ISAIAS CONTINUES TO TRACK NORTH, PLENTY OF SHEAR WILL BE
PRESENT. AN ISOLATED THUNDERSTORM OR TWO MAY LEAD TO THE
POSSIBILITY OF A TORNADO TUESDAY NIGHT AS THE SYSTEM TRACKS INTO
AND THROUGH OUR AREA. IN GENERAL, 12Z MODEL GUIDANCE SUGGESTS
THE TIMING OF THIS SYSTEM WILL BE FASTER THAN PREVIOUS RUNS WITH
MOST OF THE RAINFALL EXITING INTO CANADA BY WEDNESDAY MORNING.
SLIGHT WESTWARD ADJUSTMENTS CONTINUE FOR THE TRACK.
GUSTY SOUTH TO SOUTHEASTERLY WINDS WILL CONTINUE WITH THE
PASSAGE OF THE CYCLONE AS IT MOVES UP THE CONNECTICUT RIVER
VALLEY TUESDAY NIGHT. STRONGEST GUSTS WILL BE OVER THE SOUTH
FACING HIGHER TERRAIN AND THE SHORELINE.
LONG TERM /WEDNESDAY THROUGH MONDAY/
FIRST THINGS FIRST... WEDNESDAY SEES THE EXPEDITED DEPARTURE OF
TROPICAL STORM ISAIAS, OR ITS REMNANTS. BY THEN, THE SYSTEM
WILL BE UNDERGOING OR WILL HAVE UNDERGONE EXTRATROPICAL
TRANSITION AS A NORTHERN STREAM TROUGH OVER THE GREAT LAKES
SWINGS AN AXIS ACROSS THE NORTHEAST WEDNESDAY WITH A DRYING,
WESTERLY BREEZE IN ITS WAKE. LATEST MODEL GUIDANCE SUGGESTS THE
SHIELD OF STRATIFORM RAINFALL ASSOCIATED WITH THE SYSTEM IS MORE
OR LESS OUT OF OUR FORECAST AREA AND INTO NORTHERN MAINE BY
12Z/8AM WEDNESDAY; THERE REMAINS SOME UNCERTAINTY IN THE FORWARD
SPEED AND GENERAL TIMING OF THE TROPICAL SYSTEM WITH SIGNIFICANT
ACCELERATION EXPECTED AS IT TRAVELS UP THE COAST, BUT LATEST
MODEL GUIDANCE IS CONVERGING ON THE SYSTEM CENTER LOFTING INTO
THE LOWER ST LAWRENCE VALLEY BY 12Z. SOME WRAP AROUND MOISTURE
MAY GENERATE A FEW RAIN SHOWERS OVER THE MOUNTAINS DURING THE
DAY WEDNESDAY BEFORE DRYING ENTIRELY BY THAT NIGHT. SOME OF
THOSE SHOWERS MAY TRACK INTO THE LOWER ELEVATIONS, BUT WOULD BE
MINOR AND THERE ISN'T CONFIDENCE TO INCLUDE IN THE FORECAST FOR
NOW. TEMPERATURES WILL WARM INTO THE 70S AND 80S AS SKIES CLEAR
OUT WITH A WEST TO SOUTHWEST BREEZE AT ABOUT 10 KTS (AFTER
GUSTIER WINDS FROM THE STRATIFORM SHIELD EXIT TO THE NORTH).
BEYOND WEDNESDAY, THE LONG RANGE FORECAST LOOKS FAIRLY QUIET.
HIGH PRESSURE BUILDS AT THE SURFACE OVER THE NORTHEAST CONUS
WITH PERSISTENT SW FLOW ALOFT AS A TROUGH HANGS BACK OVER THE
GREAT LAKES REGION AND RIDGING HOLDS OVER THE ATLANTIC. THURSDAY
WILL BE QUITE NICE WITH HIGHS IN THE 70S TO MID-80S AND LOWERED
DEW POINTS IN THE 50S UNDER MOSTLY SUNNY SKIES. AFTER THAT, A
WARM TREND CARRIES INTO THE START OF NEXT WEEK WITH STEADILY
INCREASING DEW POINTS. HIGHS WILL ONCE AGAIN APPROACH 90 OVER
INTERIOR/SOUTHERN LOCATIONS BY THE START OF NEXT WEEK. A FEW
SHORTWAVES CROSS TO THE NORTH THIS WEEKEND INTO NEXT WEEK WITH
AFTERNOON SHOWERS OVER THE MOUNTAINS POSSIBLE.
AVIATION /19Z MONDAY THROUGH SATURDAY/
SHORT TERM...PATCHY FOG IS POSSIBLE OVER A COUPLE OF THE
INTERIOR VALLEYS TONIGHT. OTHERWISE, CONDITIONS DETERIORATING
FROM WEST TO EAST LATE TONIGHT INTO TUESDAY AS SHOWERS AHEAD OF
ISAIAS MOVE NORTHEAST. LIFR CONDITIONS TUESDAY NIGHT IN HEAVY
SHOWERS.
LONG TERM...WESTERLY TO WSWERLY WINDS AT AROUND 10 KTS WEDNESDAY
WITH CONDITIONS IMPROVING TO VFR EARLY AS THE REMNANTS OF ISAIAS
LOFT NORTH OUT OF THE AREA. AFTERWARD... VFR PREVAILS WITH HIGH
PRESSURE MOVING INTO THE AREA.
MARINE
SHORT TERM...STRONG SOUTH TO SOUTHEASTERLY WINDS EXPECTED WITH
THE PASSAGE OF ISAIAS TUESDAY NIGHT. A TROPICAL STORM WATCH
REMAINS IN EFFECT. SEAS WILL BE BUILDING TO AROUND OR JUST OVER
10 FEET BY THE TIME OF HIGH TIDE TUESDAY NIGHT.
LONG TERM...THE REMNANTS OF ISAIAS WILL BE LOFTING NORTH INTO
THE ST LAWRENCE WEDNESDAY AND WELL AWAY FROM THE GULF OF MAINE,
ALLOWING SEAS TO GRADUALLY SUBSIDE. SEAS WILL LINGER AROUND 5 FT
OVER THE OUTER WATERS, ESPECIALLY TOWARD THE MAINE MIDCOAST,
INTO WEDNESDAY EVENING BEFORE HIGH PRESSURE BUILDS INTO THE
REGION. QUIET OVER THE WATERS FOR THE END OF THE WEEK AND
WEEKEND.
HYDROLOGY
SHOWERS AND THUNDERSTORMS COULD PRODUCE TORRENTIAL DOWNPOURS TUESDAY
AHEAD OF ISAIAS, BUT HEAVIEST RAINFALL IS LIKELY LATE TUESDAY
AND TUESDAY NIGHT. WESTERN AREAS CAN EXPECT THE HIGHEST
RAINFALL TOTALS, ESPECIALLY ACROSS THE HIGHER TERRAIN IN THE
MOUNTAINS WHERE SOUTHEASTERLY UPSLOPING MAY OCCUR. TWO TO FOUR
INCHES OF RAIN CAN BE EXPECTED THROUGHOUT THE REGION WITH
POTENTIALLY LOCALLY HIGHER AMOUNTS IN THE HIGHER TERRAIN. FLASH
FLOODING AND RIVER FLOODING WILL ALSO BE POSSIBLE WITH THIS
SYSTEM, HENCE A FLASH FLOOD WATCH HAS BEEN ISSUED.
TIDES/COASTAL FLOODING
A MODESTLY HIGH ASTRONOMICAL TIDE WILL OCCUR SHORTLY AFTER
MIDNIGHT TUESDAY NIGHT. AS THE REMAINS OF ISAIAS PASS BY TO OUR
WEST, A STRONG SOUTH TO SOUTHEASTERLY FLOW MAY COINCIDE WITH
THIS TIDE DEPENDING ON THE EXACT TIMING WITH THE SYSTEM.
BUILDING SEAS AND GUSTY ONSHORE WINDS MAY ALLOW FOR ABOUT A FOOT
OR SO OF STORM SURGE (CURRENT MODEL RUNS APPEAR TO HAVE A LOW
BIAS). THIS MAY LEAD TO LOCALIZED SPLASH-OVER ACROSS THE REGION
TUESDAY NIGHT. TIMING OF THE SYSTEM WILL CRITICAL.
GYX WATCHES/WARNINGS/ADVISORIES
ME...TROPICAL STORM WATCH FOR MEZ007>009-012>014-018>028-033.
FLASH FLOOD WATCH FROM TUESDAY AFTERNOON THROUGH LATE TUESDAY
NIGHT FOR MEZ007>009-012-013.
NH...TROPICAL STORM WATCH FOR NHZ001>015.
FLASH FLOOD WATCH FROM TUESDAY AFTERNOON THROUGH LATE TUESDAY
NIGHT FOR NHZ001>009-011-015.
MARINE...TROPICAL STORM WATCH FOR ANZ150>154.
CANNON/CASEY
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