285
FXUS61 KLWX 061309
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
909 AM EDT MON JUL 6 2026
WHAT HAS CHANGED
HAVE EXPANDED THE FLOOD WATCH A BIT FARTHER TO THE WEST DUE TO A
BROAD ZONE OF CONVERGENCE AND EASTERLY UPSLOPE FLOW.
KEY MESSAGES
- 1) A RISK OF A FEW SEVERE THUNDERSTORMS AND SPOTTY FLASH
FLOODING CONTINUES THROUGH TUESDAY.
- 2) SEASONABLE TEMPERATURES RETURN MID TO LATE WEEK DESPITE
CONTINUED CHANCES FOR DIURNAL SHOWERS AND THUNDERSTORMS.
DISCUSSION
KEY MESSAGE 1...A RISK OF A FEW SEVERE THUNDERSTORMS AND SPOTTY
FLASH FLOODING CONTINUES THROUGH TUESDAY.
MOST OF THE CONVECTIVE ACTIVITY THAT DEVELOPED NEAR THE
CHESAPEAKE BAY IN THE FEW COUPLE HOURS CONTINUES TO MOVE ACROSS
THE DELMARVA PENINSULA. WITH LIGHT WINDS AND SATURATED LOW-
LEVELS, SOME LOW CLOUDS HAVE DEVELOPED IN THE I-81 CORRIDOR, AS
WELL AS THE I-95 CORRIDOR NEAR AND NORTHEAST OF WASHINGTON DC
INTO BALTIMORE MD. TEMPERATURES ARE SLOWLY RISING THROUGH THE
70S INTO THE 80S WITH DEW POINTS IN THE LOW TO MID 70S.
THE CURRENT FRONTAL ANALYSIS CONTINUES TO PLACE A STALLED
BOUNDARY JUST SOUTH OF THE MASON-DIXON LINE. THIS FRONT WILL
MEANDER ABOUT THE REGION THE NEXT 24 TO 36 HOURS, OFTEN BEING
SHIFTED AROUND BY CONVECTIVE-SCALE PROCESSES. THE PATTERN ALOFT
FEATURES A VERY BROAD POSITIVELY-TILTED TROUGH STRETCHING FROM
THE UPPER GREAT LAKES DOWN TOWARD THE OZARKS. AS THIS TROUGH
EDGES EASTWARD, A SERIES OF IMPULSES WILL CONTINUE TO RIDE OVER
THE MENTIONED SURFACE BOUNDARY. THERE IS SOME HINT OF THIS
UPPER TROUGH WEAKENING, BUT ITS REMNANTS WOULD SLOWLY MIGRATE
EASTWARD TO THE ATLANTIC COAST DURING THE NEXT COUPLE DAYS. ALL
IN ALL, THIS WILL LEND ITSELF TOWARD ADDITIONAL ACTIVE WEATHER
DAYS OVER THE MID-ATLANTIC REGION.
FOR TODAY, THERE IS A THREAT FOR BOTH ISOLATED SEVERE
THUNDERSTORMS AS WELL AS INSTANCES OF FLASH FLOODING. WHILE THE
STORM PREDICTION CENTER FEATURES A MARGINAL RISK ACROSS THE
ENTIRE AREA, THE WEATHER PREDICTION CENTER MAINTAINS A SLIGHT
RISK FOR FLASH FLOODING. THE OVERALL THERMODYNAMIC PROFILE HAS
GRADUALLY SHIFTED OVER TOWARD MORE OF A HEAVY RAIN SIGNATURE
VERSUS WIDESPREAD SEVERE STORMS. INSTABILITY COMES DOWN WITH A
TALL/SKINNY CAPE PROFILE WITH HIGH FREEZING LEVELS/DEEP WCLS
WHICH IS SUPPORTIVE OF VERY HEAVY/WARM RAIN PROCESSES. THE
TROPICAL NATURE OF THE AIR MASS WILL CARRY PRECIPITABLE WATER
VALUES INTO THE 2 TO 2.25 INCH RANGE. FORECAST SOUNDINGS SHOW
LIGHT LOW-LEVEL EASTERLIES WHICH OCCURS BENEATH WEAK WESTERLIES.
THIS WILL FAVOR SOME VERY SLOW CELL MOTIONS AND THUS A RISK FOR
FLASH FLOODING. THERE IS CONCERN FOR STORMS TO STALL OR "LOCK
ON" TO TERRAIN OR MESOSCALE BOUNDARIES LIKE OUTFLOW AND BAY OR
RIVER BREEZES, FURTHER INCREASING POTENTIAL FOR HEAVY RAINFALL.
THE TIMING OF TODAY'S CONVECTION LOOKS VERY MESSY OVERALL AND
RATHER UNCERTAIN IN ANY ONE LOCATION. GENERALLY SPEAKING, ALL
SIGNS POINT TOWARD DESTABILIZATION OF THE BOUNDARY LAYER AND
RESULTANT CONVECTIVE INITIATION OVER THE HIGHER TERRAIN BY THE
EARLY/MID AFTERNOON. GIVEN MINIMAL CAPPING, OTHER MESOSCALE
FEATURES LIKE THE LEE-SIDE TROUGH AND RIVER/BAY BREEZES WILL
ALSO BE SITES FOR CONVECTIVE INITIATION. BASED ON OUTPUT FROM
THE 00Z/06Z HIGH-RESOLUTION SUITE, EVOLUTION OF THE CONVECTION
COULD BE RATHER CHAOTIC. THIS WOULD INCLUDE ACTIVITY SPAWNING
OFF COLLIDING OUTFLOWS, REPEAT ACTIVITY, AND POSSIBLE TRAINING
IN A WEST-EAST FASHION GIVEN UNIDIRECTIONAL ZONAL FLOW. FLOOD
WATCHES HAVE BEEN ISSUED FOR THE THREAT OF FLASH FLOODING. THE
AREA OF GREATEST CONCERN WOULD BE ALONG THE I-95 CORRIDOR, AND
OTHERS IMPACTED BY HEAVY RAINFALL THE PAST 24 TO 48 HOURS (I.E.,
PARTS OF MADISON, GREENE, MONTGOMERY, HOWARD, PENDLETON AND
ALLEGANY COUNTIES).
WHERE THIS FRONTAL ZONE LIES ON TUESDAY WILL DICTATE THE LEVEL
OF THREAT FOR ADDITIONAL ACTIVE WEATHER. THE FORECAST SUGGESTS
THIS BOUNDARY SHOULD LIE ALONG I-66 DURING THE MORNING HOURS
BEFORE SAGGING SOUTHWARD TO THE VIRGINIA/NORTH CAROLINA BORDER
BY THE NIGHT. THUS, THERE IS SOME RISK FOR ADDITIONAL CONVECTION
WHICH INCLUDES A FEW SEVERE STORMS AND FURTHER FLASH FLOODING.
MARGINAL RISK AREAS ARE BEING ADVERTISED FOR BOTH THE SEVERE
AND FLOOD THREATS WITH THIS SYSTEM. MAINLY OVERCAST SKIES AND
NORTHEASTERLY ONSHORE WINDS SHOULD HOLD TEMPERATURES BELOW
AVERAGE INTO TUESDAY. FORECAST HIGHS WILL BE IN THE UPPER 70S TO
MID 80S, WITH UPPER 60S TO 70S FOR MOUNTAIN LOCALES.
KEY MESSAGE 2...SEASONABLE TEMPERATURES RETURN MID TO LATE WEEK
DESPITE CONTINUED CHANCES FOR DIURNAL SHOWERS AND THUNDERSTORMS.
THE EARLY WEEK FRONTAL BOUNDARY IS FORECAST TO PUSH DOWN INTO
THE CAROLINAS BY MID-WEEK BEFORE SHEARING OUT SHORTLY AFTER.
THERE IS DECENT MODEL AGREEMENT IN THE PATTERN ALOFT WHICH
FAVORS THE STRONGER BELT OF WESTERLIES BEING ACROSS NEW ENGLAND
INTO SOUTHEASTERN CANADA. THIS PLACES THE LOCAL AREA ON THE
SOUTHERN FLANK OF THESE WINDS, AND THUS A MORE SLOW MOVING,
CONVECTIVELY AIDED SHORTWAVE PATTERN. THIS IS WHERE MODEL
AGREEMENT BREAKS DOWN AS EACH 00Z DETERMINISTIC PLACES NOTABLE
SHORTWAVE TROUGHS IN VARIABLE LOCATIONS. AS A SERIES OF
VORTICITY MAXIMA ADVANCE TOWARD THE EASTERN SEABOARD, THESE
COULD EASILY BE AN IMPETUS TOWARD DIURNAL CONVECTIVE
DEVELOPMENT. THUS, EXPECT A PATTERN THAT IS MORE SEASONABLE IN
NATURE FOR EARLY/MID JULY, BUT ALSO WITH A THREAT FOR DAILY
SHOWERS AND THUNDERSTORMS. HOWEVER, STORM ORGANIZATION WILL
LIKELY NOT BE LIKE RECENT DAYS. FORECAST HIGHS RETURN TO THE 90
DEGREE MARK BY THURSDAY AND FRIDAY, BUT WITH PERHAPS A GRADUAL
COOL DOWN BY THE UPCOMING WEEKEND.
AVIATION /13Z MONDAY THROUGH FRIDAY/
A COUPLE BANDS OF MVFR CIGS HAVE DEVELOPED, ONE NEAR I-81
AFFECTING MRB, AND THE OTHER ALONG I-95 NORTHEAST OF DC
AFFECTING THE BALTIMORE TAF SITES. A PERIOD OF IFR IS POSSIBLE
UNTIL ABOUT 14Z OR 15Z. DCA/IAD LIKELY STICK WITH A PERIOD OF
MVFR DURING THIS TIME, WITH CHO HAVING A BIT LOWER CHANCE OF
LOWER CIGS. WEAK GRADIENTS WILL MAINTAIN LIGHT WINDS WHICH WILL
BECOME VARIABLE AT TIMES. THE MAIN CONVECTIVE WINDOW IS BETWEEN
21Z-03Z THIS EVENING WHERE RESTRICTIONS ARE LIKELY AT TIMES.
SOME CONVECTION MAY LINGER A BIT LONGER BEFORE SHIFTING TOWARD
ANOTHER NIGHT OF LOW STRATUS (LIKELY IFR AGAIN).
FOR TUESDAY, THE MAIN FRONTAL ZONE SLOWLY BEGINS TO PULL SOUTH
OF I-66. HOWEVER, ITS CLOSE PROXIMITY WILL KEEP SHOWERS AND
THUNDERSTORMS IN THE PICTURE AGAIN. ADDITIONAL STORM-DRIVEN
RESTRICTIONS ARE POSSIBLE IN THIS ENVIRONMENT. EXPECT MAINLY
NORTHEASTERLY WINDS OVER THE AREA AS THIS BOUNDARY CONTINUES
PUSHING SOUTHWARD.
THEREAFTER, DIURNAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE EACH
DAY. WHILE VFR CONDITIONS SHOULD DOMINATE MUCH OF THE TIME, SOME
RESTRICTIONS ARE POSSIBLE IF THESE STORMS IMPACT THE TAF SITES.
WINDS TURN MORE SOUTH-SOUTHWESTERLIES BY THURSDAY BEFORE
SHIFTING TO WESTERLY ON FRIDAY.
MARINE
WEAK SUMMERTIME GRADIENTS WILL LARGELY KEEP THE MARINE ZONES
FREE OF SMALL CRAFT ADVISORIES. HOWEVER, ADDITIONAL DAYS OF
ACTIVE CONVECTION SHOULD LEAD TO A GREATER THREAT OF SPECIAL
MARINE WARNINGS. BESIDES THE GUSTY THUNDERSTORM WINDS, OTHER
HAZARDS WOULD INCLUDE FREQUENT LIGHTNING AND ANY OUTFLOW WINDS.
THE MOST ACTIVE PERIOD IS LIKELY THROUGH TUESDAY GIVEN A FRONTAL
ZONE NEARBY. AS THIS BOUNDARY SAGS SOUTHWARD TO THE CAROLINAS,
DAILY CONVECTION BECOMES LESS WIDESPREAD. HOWEVER, EXPECT A RAMP
UP BY LATE IN THE WORK WEEK AS A SLOW MOVING UPPER TROUGH NEARS
THE REGION. AFTER MULTIPLE DAYS OF MAINLY NORTH TO NORTHEASTERLY
FLOW, WINDS TURN MORE SOUTHERLY BY THURSDAY AHEAD OF THIS
APPROACHING TROUGH.
LWX WATCHES/WARNINGS/ADVISORIES
DC...FLOOD WATCH FROM 4 PM EDT THIS AFTERNOON THROUGH THIS EVENING
FOR DCZ001.
MD...FLOOD WATCH FROM 4 PM EDT THIS AFTERNOON THROUGH THIS EVENING
FOR MDZ003>006-008-011-013-014-016>018-503>508.
FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH THIS EVENING
FOR MDZ501-502-510.
VA...FLOOD WATCH FROM 4 PM EDT THIS AFTERNOON THROUGH THIS EVENING
FOR VAZ027>031-037>040-050-051-053>057-501-502-505>507-
526-527.
FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH THIS EVENING
FOR VAZ025-026.
WV...FLOOD WATCH FROM 4 PM EDT THIS AFTERNOON THROUGH THIS EVENING
FOR WVZ051>053.
FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH THIS EVENING
FOR WVZ050-055-502>504-506.
MARINE...NONE.
DISCUSSION...BRO/DHOF
AVIATION...BRO/DHOF
MARINE...BRO/DHOF
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page