087
FXUS61 KLWX 161840
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
240 PM EDT THU JUL 16 2026
WHAT HAS CHANGED
WE HAVE EXPANDED THE HEAT ADVISORY AS HUMIDITY IS SUBSTANTIALLY
HIGHER TODAY. CONFIDENCE IS INCREASING FOR MULTIPLE ROUNDS OF
THUNDERSTORMS AND POTENTIAL SEVERE WEATHER ON SATURDAY.
KEY MESSAGES
- 1) HOT AND HAZY CONDITIONS PERSIST THROUGH FRIDAY WITH A
CHANCE OF A COUPLE STRONG STORMS THROUGH THIS EVENING.
- 2) A STRONG COLD FRONT BRINGS THE THREAT OF SEVERE WEATHER
SATURDAY, POSSIBLY LINGERING INTO SUNDAY TO THE SOUTH.
- 3) HIGH PRESSURE BRIEFLY RETURNS MONDAY, THEN ANOTHER STRONG
FRONTAL SYSTEM CROSSES MID NEXT WEEK.
DISCUSSION
KEY MESSAGE 1...HOT AND HAZY CONDITIONS PERSIST THROUGH FRIDAY
WITH A CHANCE OF A COUPLE STRONG STORMS THROUGH THIS EVENING.
HUMIDITY HAS REMAINED VERY ELEVATED THIS AFTERNOON, RESULTING IN
WIDESPREAD HEAT INDICES OF 100 TO 109. EXPECT REDUCED MIXING DUE
TO SMOKE ALOFT. HEAT ADVISORIES ARE IN EFFECT UNTIL 8PM FOR MUCH
OF THE AREA, WITH ONLY A SLOW DROP IN TEMPERATURES THIS EVENING.
SATELLITE DATA HAS STARTED FLOWING AGAIN AS OF EARLY THIS
AFTERNOON. THIS REVEALS A LARGE AND RATHER THICK PLUME OF SMOKE
EMANATING FROM WILDFIRES IN CANADA. THE THICKEST SMOKE IS ON THE
COOL SIDE OF A FRONT DRAPED OVER PA TO NJ, WITH A SECONDARY WEAK
BOUNDARY DANGLING DOWN THE WEST SIDE OF THE CHESAPEAKE BAY
(ENHANCED BY THE BAY BREEZE).
THIS CONGLOMERATE OF BOUNDARIES, ACCENTUATED BY DIFFERENTIAL
HEATING ALONG THE EDGE OF THE THICKER SMOKE, MAY BE ENOUGH TO
IGNITE A FEW THUNDERSTORMS OVER NORTHERN TO CENTRAL MD HEADING
INTO THIS EVENING. GIVEN STRONG INSTABILITY (MLCAPE 3000-4000
J/KG), DCAPE (1000-1500 J/KG), AND ~40 KTS EFFECTIVE BULK SHEAR,
ANY STORMS THAT FORM COULD PRODUCE VERY GUSTY WINDS. LARGE HAIL
CAN'T BE RULED OUT GIVEN AMPLE CAPE, SUFFICIENT SHEAR, AND MID-
LEVEL LAPSE RATES AROUND 7 C/KM.
THE FRONT WILL DROP SOUTH TONIGHT. NORTH TO NORTHEAST WINDS IN
ITS WAKE WILL ADVECT DRIER AIR, BUT THICK HAZE AND SMOKE INTO
THE REGION. AIR QUALITY WILL BECOME POOR AS A RESULT THROUGH
FRIDAY. VISIT AIRNOW.GOV FOR THE LATEST AIR QUALITY FORECASTS
FROM THE SUBJECT MATTER EXPERTS AT STATE ENVIRONMENTAL AGENCIES.
THE FRONT LOOKS TO STALL NEAR/SOUTH OF I-64. A COUPLE OF
THUNDERSTORMS MAY TRY TO POP UP LATER IN THE AFTERNOON NEAR THE
APPALACHIANS AIDED BY OROGRAPHIC LIFT, BUT OTHERWISE HAZY AND
DRY CONDITIONS WILL CONTINUE. TEMPS RISE INTO THE 90S FOR MUCH
OF THE AREA, BUT LOWER HUMIDITY SHOULD KEEP HEAT INDICES BELOW
THE CENTURY MARK ACROSS THE BOARD.
BEGINNING LATE FRIDAY EVENING, THE BOUNDARY WILL RETURN NORTH AS
A WARM FRONT. AN INCREASE IN 925-850 HPA FLOW OF 20-30 KTS
ACROSS THE BOUNDARY WILL ADVECT IN ADDITIONAL MOISTURE. THIS
SETUP MAY RESULT IN AT LEAST WIDELY SCATTERED THUNDERSTORMS BY
EARLY SATURDAY MORNING. GIVEN THE INCREASE IN LOW-LEVEL MOISTURE
AND FLOW, A STRONGER/ROTATING STORM OR TWO CAN'T BE RULED OUT.
KEY MESSAGE 2...A STRONG COLD FRONT BRINGS THE THREAT OF SEVERE
WEATHER SATURDAY, POSSIBLY LINGERING INTO SUNDAY TO THE SOUTH.
AN UNSEASONABLY STRONG UPPER TROUGH AND EMBEDDED SHORTWAVE/JET
STREAK WILL PIVOT NEAR AND NORTH OF THE AREA SATURDAY. STRONG
HEIGHT FALLS ASSOCIATED WITH THIS TROUGH, COUPLED WITH HIGH
LOW-LEVEL MOISTURE CONTENT AND MODEST MID-LEVEL LAPSE RATES WILL
LIKELY RESULT IN STRONG INSTABILITY, PERHAPS EVEN IF CLOUD
BREAKS ARE MUTED BY EARLY DAY PRECIP. THE STRONG DEEP LAYER FLOW
WILL LEAD TO EFFECTIVE SHEAR MAGNITUDES OF 30-40 KTS, HELPING TO
ORGANIZE STORMS THAT DEVELOP IN THE VICINITY OF A PRE-FRONTAL
SURFACE TROUGH IN THE WAKE OF ANY MORNING ACTIVITY. LOW-LEVEL
FLOW WILL BE A BIT WEAKER DURING THE DAY, SO ALTHOUGH TRANSIENT
SUPERCELL STRUCTURES ARE POSSIBLE, THE MAIN RISK SHOULD BE
DAMAGING WIND GUSTS AND PERHAPS LARGE HAIL AS OPPOSED TO
TORNADOES. THIS COULD CHANGE IF THE EFFECTIVE WARM FRONT
LINGERS OVERHEAD.
DEPENDING ON STORM COVERAGE, TEMPS COULD REACH WELL INTO THE 90S
SATURDAY. WITH HIGH HUMIDITY, HEAT INDICES MAY APPROACH 100.
HEADING INTO SATURDAY EVENING, LOW-LEVEL FLOW INCREASES AGAIN
AHEAD OF THE APPROACHING SYNOPTIC COLD FRONT ASSOCIATED WITH
THE AFOREMENTIONED UPPER TROUGH. THIS SENDS PWATS HURDLING TO
OVER 2.2" AND KEEPS CAPE ELEVATED WELL INTO THE EVENING. THE
EXPECTATION IS FOR A STRONGLY FORCED LINE OF STORMS TO DEVELOP
IN THE UNSTABLE AIRMASS FROM THE EASTERN GREAT LAKES INTO THE
UPPER OHIO VALLEY (I.E. WESTERN NY/PA INTO OH/WV). THIS LINE OF
STORMS MAY BE SLOW TO WEAKEN AS IT TREKS INTO THE AREA FROM THE
NORTHWEST THROUGH THE EVENING, ESPECIALLY IF THERE IS MODERATE
TO STRONG INSTABILITY LEFT (DEPENDS ON EARLIER ACTIVITY). THE
MAIN THREAT AT THIS POINT WOULD APPEAR TO BE GUSTY TO DAMAGING
WINDS AND HEAVY RAIN DUE TO MULTIPLE ROUNDS OF STORMS. HIGH
INSTANTANEOUS/SUB-HOURLY RAIN RATES WOULD BE PLAUSIBLE IN THIS
SETUP. IF ANY DISCRETE ACTIVITY DEVELOPS IN THE EVENING AHEAD OF
THE LINE AS THE LLJ INCREASES, THERE MAY BE A RISK FOR LARGE
HAIL AS WELL AS A COUPLE TORNADOES, PARTICULARLY IN AREAS FOR
SURFACE FLOW IS BACKED (I.E. NEAR/EAST OF I-95 NEAR ANY BAY
BREEZE BOUNDARIES, INCREASING SRH). SOME GUIDANCE SUCH AS THE
NAM12/RRFS-A HAS THE SIGTOR PARAMETER IN THE 1-3 RANGE SATURDAY
EVENING IN THIS ENVIRONMENT.
ACTIVITY SHOULD WANE DURING THE OVERNIGHT HOURS SATURDAY AS THE
FRONT AND ASSOCIATED CONVECTION DROP SOUTH AND THE ATMOSPHERE
GRADUALLY STABILIZES. THE FRONT WILL PROBABLY END UP NEAR OR
SOUTH OF I-64, WITH ANY REMAINING SEVERE THREAT LATER ON SUNDAY
ENDING UP NEAR AND SOUTH OF THE EFFECTIVE FRONTAL BOUNDARY.
KEY MESSAGE 3...HIGH PRESSURE BRIEFLY RETURNS MONDAY, THEN ANOTHER
STRONG FRONTAL SYSTEM CROSSES MID NEXT WEEK.
IN THE WAKE OF THE WEEKEND SYSTEM, RELATIVELY LOWER PRECIP
CHANCES ARE EXPECTED AS HIGH PRESSURE BRIEFLY SWINGS BY MONDAY.
GUIDANCE DIFFERS A BIT IN TIMING, BUT MOST MODELS SHOW ANOTHER
STRONG UPPER TROUGH AND COLD FRONT APPROACHING AND MOVING
THROUGH SOME TIME BETWEEN TUESDAY AND WEDNESDAY. DEPENDING ON
HOW THIS IS TIMED WITH THE DIURNAL CYCLE, AS WELL AS ANY IMPACTS
FROM THE LINGERING FRONTAL ZONE OFFSHORE (WHICH COULD CAUSE SOME
SINKING MOTION TO ITS WEST LOCALLY), ADDITIONAL STRONG STORMS
ARE POSSIBLE MID NEXT WEEK.
AVIATION /18Z THURSDAY THROUGH TUESDAY/
VFR AND MOSTLY DRY CONDITIONS WILL CONTINUE THROUGH EARLY THIS
EVENING. A POP UP THUNDERSTORM IS POSSIBLE AROUND 22Z OR 23Z
AROUND BWI/MTN, WITH MUCH LOWER PROBS AT THE OTHER TAF SITES.
A WEAK FRONT DROPS THROUGH TONIGHT, WITH THICK SMOKE FROM
CANADIAN WILDFIRES MOVING ACROSS THE REGION IN ITS WAKE. MVFR TO
INTERMITTENT IFR CONDITIONS ARE EXPECTED THROUGH FRIDAY IN
SMOKE. WINDS WILL VARY BETWEEN N/NW AND SW OVER THE NEXT FEW
DAYS AS THAT FRONT SITS NEARBY. A THUNDERSTORM CAN'T BE RULED
OUT NEAR THE MOUNTAINS FRIDAY AFTERNOON. SMOKE SHOULD DISPERSE
BY SATURDAY, BUT SUB-VFR IS LIKELY AT TIMES AS WAVES OF STORMS
TRAVERSE THE REGION BETWEEN EARLY SATURDAY MORNING AND LATE
SATURDAY EVENING.
PATCHY FOG OR LOW CIGS ARE POSSIBLE OVERNIGHT INTO THE MORNING
HOURS THIS WEEKEND. AFTER NUMEROUS STORMS SATURDAY, THE THREAT
SUNDAY SHIFTS TO NEAR OR SOUTH OF KCHO (AT LEAST THAT'S HOW IT
LOOKS AT THE MOMENT). GENERALLY MORE BENIGN WEATHER IS EXPECTED
FOR MONDAY.
MARINE
A PERIOD OF NORTHERLY WINDS GUSTING TO 20 KTS IS EXPECTED LATE
THIS EVENING INTO THE OVERNIGHT IN THE WAKE OF A FRONT. A
STRONG STORM IS POSSIBLE THIS EVENING AS THE FRONT CROSSES.
LOWERED VISIBILITY IN SMOKE CAN BE ANTICIPATED THROUGH FRIDAY.
STRONG STORMS ARE POSSIBLE SATURDAY WHICH MAY PROMPT SPECIAL
MARINE WARNINGS. SOUTHERLY WINDS FRIDAY NIGHT INTO SATURDAY
COULD APPROACH SCA LEVELS.
LIGHTER WINDS GENERALLY OUT OF THE NORTH ARE EXPECTED BEHIND
ANOTHER COLD FRONT SUNDAY INTO MONDAY. ANY STORMS ON SUNDAY
WOULD PROBABLY BE LIMITED TO AREAS AROUND SOUTHERN MD, BUT THERE
IS UNCERTAINTY IN JUST HOW FAR SOUTH THE FRONT GETS.
LWX WATCHES/WARNINGS/ADVISORIES
DC...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR DCZ001.
MD...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR MDZ003>006-008-
011-013-014-016>018-502>508.
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EDT FRIDAY
FOR MDZ008.
VA...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR VAZ027>031-040-
051-053>055-501-502-505-506-526-527.
WV...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR WVZ050>053-055-
502-504.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EDT FRIDAY
FOR ANZ530>534-537>543.
DISCUSSION...DHOF/CPB/EST
AVIATION...DHOF/CPB/EST
MARINE...DHOF/CPB/EST
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