878
FXUS61 KLWX 201417 AAA
AFDLWX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1017 AM EDT MON JUL 20 2026
WHAT HAS CHANGED
INCREASED SKY COVER AND RAISED MAXT SLIGHTLY. OTHERWISE, NO
CHANGES.
KEY MESSAGES
- 1) STRONG TO SEVERE THUNDERSTORMS ARE LIKELY TUESDAY, WITH
SOME THUNDERSTORM RISK LINGERING INTO WEDNESDAY.
- 2) COOLER THAN AVERAGE WITH MAINLY DRY CONDITIONS FOR THE END
OF THE WEEK AS HIGH PRESSURE BUILDS INTO THE REGION.
DISCUSSION
KEY MESSAGE 1...STRONG TO SEVERE THUNDERSTORMS ARE LIKELY
TUESDAY, WITH SOME THUNDERSTORM RISK LINGERING INTO WEDNESDAY.
HIGH PRESSURE POSITIONED OVER THE NORTHERN MID ATLANTIC/EASTERN
GREAT LAKES WILL PROVIDE BELOW NORMAL TEMPERATURES TODAY. MOST
CONVECTION SHOULD REMAIN SUPPRESSED TO THE SOUTH UNTIL LATE
AFTERNOON OR EARLY EVENING. THERE MAY BE A NOTABLE CUMULUS FIELD
HOWEVER.
AS THE HIGH DEPARTS THIS EVENING, A FRONT STALLED NEAR THE
VIRGINIA/NORTH CAROLINA BORDER WILL BEGIN TO LIFT NORTHWARD,
WITH MOISTURE AND ELEVATED INSTABILITY INCREASING FROM SOUTH TO
NORTH THROUGH THE NIGHT. THEREFORE, SOME SCATTERED SHOWERS AND
THUNDERSTORMS ARE POSSIBLE, ESPECIALLY THE SECOND HALF OF THE
NIGHT. CENTRAL VIRGINIA AND THE CENTRAL SHENANDOAH VALLEY COULD
SEE ACTIVITY EARLIER THIS EVENING, AND THERE ARE SOME
INDICATIONS OF HIGHER RAIN TOTALS FROM STORMS BECOMING LOCKED
ALONG THE TERRAIN.
TUESDAY IS THE GREATEST DAY OF CONCERN THIS WEEK. THE WARM FRONT
WILL LIKELY LIFT NORTH OF THE AREA TUESDAY MORNING, ALLOWING A
WARM AND HUMID AIRMASS TO OVERSPREAD THE AREA. A SEASONABLY
STRONG TROUGH WILL BE APPROACHING FROM THE WEST, PROVIDING
FORCING AND AT LEAST 30 TO 40 KT OF SHEAR. THIS COMBINATION
PROVIDES A FAVORABLE ENVIRONMENT FOR SEVERE THUNDERSTORMS, AND
IT APPEARS THE TYPICAL AFTERNOON AND EVENING TIME FRAME WILL BE
FAVORED FOR THE STRONGEST STORMS. SOME DETAILS REMAIN
UNRESOLVED, ESPECIALLY THE EFFECTS OF TODAY'S UPSTREAM
CONVECTION, ANY LINGERING LOCAL SHOWERS AND CLOUDS, AND IF THERE
WILL BE ANY FOCAL POINTS FOR GREATER STORM COVERAGE.
THUNDERSTORMS ARE ALSO LIKELY ACROSS THE OHIO VALLEY, AND THE
PROGRESSION OF THIS ACTIVITY COULD BE IN THE MIX AS
WELL. DAMAGING WINDS WILL BE THE PRIMARY HAZARD, ALTHOUGH LARGE
HAIL AND A TORNADO OR TWO ARE POSSIBLE IF SUPERCELLS DEVELOP.
RELATIVELY SPEAKING, THE TORNADO THREAT IS HIGHER TO THE NORTH
(AND NORTH OF THE CWA) CLOSER TO THE WARM FRONT.
WITH PRECIPITABLE WATER VALUES INCREASING (OVER 2 INCHES EAST OF
THE BLUE RIDGE), ANY STORM MERGERS AND TRAINING COULD RESULT IN
LOCALIZED FLASH FLOODING. THERE ARE MANY MESOSCALE DETAILS THAT
NEED TO UNFOLD, BUT ADDITIONAL ROUNDS OF SHOWERS AND
THUNDERSTORMS MAY CONTINUE THROUGH THE NIGHT AS THE COLD FRONT
APPROACHES AND A LOW LEVEL JET OVERSPREADS THE AREA. WHILE
SEVERE WEATHER STEADILY BECOMES LESS LIKELY, I COULD SEE A
LINGERING FLASH FLOOD THREAT, AS THE INGREDIENTS MAY BE IN PLACE
FOR SLOW MOVING OR TRAINING HEAVY RAINERS.
THERE IS SOME UNCERTAINTY WITH THE COLD FRONTAL POSITION BY
WEDNESDAY. WITH THE UPPER TROUGH OVERHEAD, ADDITIONAL SHOWERS
AND THUNDERSTORMS ARE LIKELY, ESPECIALLY EAST OF THE BLUE RIDGE.
WHILE SOME ADDITIONAL STRONG TO SEVERE THUNDERSTORMS CAN'T BE
RULED OUT IF THINGS TREND SLOWER, IT'S BEGINNING TO APPEAR THE
BEST PARAMETERS FOR THAT TO OCCUR WILL BE SHUNTED TOWARD
SOUTHEAST VIRGINIA.
KEY MESSAGE 2...COOLER THAN AVERAGE WITH MAINLY DRY CONDITIONS
FOR THE END OF THE WEEK AS HIGH PRESSURE BUILDS INTO THE REGION.
AN UPPER LEVEL TROUGH OF LOW PRESSURE WILL PIVOT ITS AXIS THROUGH
THE REGION THURSDAY. THIS WILL ALLOW FOR AN AREA OF HIGH PRESSURE
TO BUILD IN FROM THE WEST LATE THURSDAY THROUGH EARLY SUNDAY.
THE RESULT WILL BE MAINLY DRY CONDITIONS IN MOST AREAS WITH
TEMPERATURES 5 TO 10 DEGREES BELOW AVERAGE FOR THE THIRD WEEK OF
JULY. IT DOES LOOK AS IF THE HIGH WILL BEGIN TO BREAK DOWN THIS
WEEKEND. THE RESULT WILL BE AN INCREASE IN HUMIDITY AND DAYTIME
TEMPERATURES APPROACHING AVERAGE FOR JULY BY SUNDAY. MODEL
SPREAD INCREASES DURING THIS TIME IN REGARDS WHEN THE NEXT
CHANCE FOR RAIN COULD BE.
AVIATION /14Z MONDAY THROUGH FRIDAY/
HIGH PRESSURE PASSES NORTH OF THE AREA TODAY, WITH LIGHT NE
WINDS BECOMING SE BY THIS AFTERNOON. A WARM FRONT WILL APPROACH
FROM THE SOUTH TONIGHT. THIS WILL RESULT IN MVFR TO POSSIBLY IFR
CEILINGS SPREADING SOUTH TO NORTH. THERE WILL ALSO BE A CHANCE
OF SHOWERS AND THUNDERSTORMS, BUT COVERAGE UNCERTAINTIES RESULT
IN PROB30 TAFS FOR NOW.
CEILINGS WILL LIFT TUESDAY WITH GUSTY SOUTH WINDS DEVELOPING.
SHOWERS AND THUNDERSTORMS WILL BECOME LIKELY BY AFTERNOON, SOME
OF WHICH MAY BE SEVERE. ADDITIONAL ROUNDS OF SHOWERS AND
THUNDERSTORMS MAY LINGER INTO THE EVENING/NIGHT WITH POTENTIAL
FOR LOCALLY HEAVY RAIN. LOW CLOUDS OR FOG COULD FORM IN THE
WAKE. ADDITIONAL THUNDERSTORMS ARE POSSIBLE WEDNESDAY AFTERNOON
FOR THE METROS AND CHO DEPENDING ON HOW QUICKLY THE COLD FRONT
SWEEPS THROUGH.
VFR CONDITIONS THURSDAY AND FRIDAY. WINDS NORTH 5 TO 10 KNOTS
THURSDAY, BECOMING EASTERLY FRIDAY.
MARINE
NE WINDS BECOME SE BY THIS AFTERNOON. WINDS STRENGTHEN TONIGHT,
WITH CHANNELING OCCURRING ALONG THE BAY. A SMALL CRAFT ADVISORY
HAS BEEN ISSUED FOR FAVORED PORTIONS OF THE BAY FROM 8 PM UNTIL
5 AM. A WARM FRONT MAY BRING A FEW THUNDERSTORMS LATE TONIGHT.
THERE MAY BE A LULL IN THE WINDS TUESDAY MORNING, BEFORE
SOUTHERLY WINDS INCREASE DURING THE AFTERNOON. SMALL CRAFT
ADVISORIES WILL BE LIKELY THROUGH WEDNESDAY MORNING. SOME STRONG
TO SEVERE THUNDERSTORMS ARE ALSO LIKELY TUESDAY AFTERNOON AND
EVENING. THE COLD FRONT WILL CROSS ON WEDNESDAY AND COULD SPARK
A FEW MORE STRONG THUNDERSTORMS. WINDS WILL SHIFT TO THE NW THEN
N, WITH ADDITIONAL ADVISORIES LIKELY NEEDED THROUGH THURSDAY
MORNING.
WINDS SHOULD DECREASE THROUGH THURSDAY AS HIGH PRESSURE BUILDS
TOWARD THE AREA. WINDS NORTH BECOMING EAST 5 TO 10 KNOTS
FRIDAY.
TIDES/COASTAL FLOODING
INCREASING SE TO S FLOW FROM THIS EVENING INTO TUESDAY WILL
LEAD TO WATER LEVELS REACHING ACTION STAGES. ANNAPOLIS COULD
APPROACH MINOR FLOOD STAGE.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 5 AM EDT
TUESDAY FOR ANZ531>534-537-541-543.
DISCUSSION...ADS/LFR/KLW
AVIATION...ADS/LFR/KLW
MARINE...ADS/LFR/KLW
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