056
FXUS61 KLWX 190119
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
919 PM EDT SAT JUL 18 2026
WHAT HAS CHANGED
A LINE OF SHOWERS AND THUNDERSTORMS ARE APPROACHING FROM THE
NORTHWEST WITH A FLOOD WATCH IN EFFECT UNTIL 2AM. OTHERWISE, THE
FLOOD WATCH TO THE EAST, SEVERE THUNDERSTORM WATCH, TORNADO
WATCH, AND HEAT ADVISORY HAVE ALL BEEN CANCELLED WITH THE THREAT
HAVING DIMINISHED.
KEY MESSAGES
- 1) HOT AND HUMID CONDITIONS WITH A RISK OF SEVERE
THUNDERSTORMS TODAY.
- 2) THUNDERSTORM CHANCES MAY LINGER ACROSS SOUTHERN PORTIONS OF
THE AREA AS THE FRONT STALLS TO THE SOUTH SUNDAY AND MONDAY.
- 3) A STRONG COLD FRONT AND TROUGH OF LOW PRESSURE MAY BRING
SEVERE WEATHER TUESDAY AND/OR WEDNESDAY.
DISCUSSION
KEY MESSAGE 1...HOT AND HUMID CONDITIONS WITH A RISK OF SEVERE
THUNDERSTORMS TODAY.
UPDATE 01Z: A LINE OF SHOWERS AND THUNDERSTORMS APPROACH FROM
THE NORTHWEST WITH A FLOOD WATCH REMAINING IN EFFECT FOR WESTERN
MD AND MINERAL COUNTY WV UNTIL 2AM. THE AIRMASS OVER THE
FORECAST AREA HAS STABILIZED CONSIDERABLY FROM EARLIER WITH THE
LINE SHOWING SIGNS OF WEAKENING AS IT APPROACHES. THAT BEING
SAID, SOME MODEL GUIDANCE CONTINUES TO SHOW A FLOODING THREAT.
WILL CONTINUE TO MONITOR AS THE PRECIPITATION GETS CLOSER AND
WILL REEVALUATE THE WATCH LATER THIS EVENING. PREVIOUS
DISCUSSION BELOW.
15Z MESOANALYSIS INDICATES A CORRIDOR OF (EVEN
HIGHER) THETA-E AIR AT 925-850 HPA APPROACHING THE APPALACHIAN
CREST. A SURFACE TROUGH ROUGHLY ALONG I-81 IS EVIDENT IN SURFACE
ANALYSIS. AS THE LOW-LEVEL MOIST PLUME APPROACHES FROM THE WEST
AND INTERACTS WITH THE SURFACE TROUGH, ANTICIPATE STEADY TO
RAPID EXPANSION OF THUNDERSTORMS IN THE VICINITY OF THE BLUE
RIDGE BY 1-2PM.
UPSTREAM CONVECTIVE DEVELOPMENT IS ALREADY WIDESPREAD OVER SW
PA, OH AND WV. SEE NO REASON GIVEN THE ENVIRONMENT THAT THIS
WON'T CONTINUE TO EXPAND AS IT PRESSES EASTWARD GIVEN THE VERY
HUMID AND UNSTABLE AIRMASS IN PLACE.
REGARDING THE FLOOD THREAT, INDIVIDUAL STORM CELLS WILL LIKELY
BE MOVING GIVEN FLOW ALOFT, BUT THE FLOW IS ORIENTED PARALLEL TO
THE LIFTING MECHANISM (NEARBY WARM FRONT). BACK-BUILDING CELLS
OR CLUSTERS (POSSIBLY TRANSIENT HP SUPERCELLS) AS WELL AS
MULTIPLE ROUNDS ARE POSSIBLE. AREAS WITH LOWER FFG AND IN
COMPLEX TERRAIN AROUND WESTERN MD WOULD BE OF PARTICULAR
CONCERN, AND A WATCH IS IN EFFECT THERE UNTIL 2AM. TO THE EAST,
THERE MAY BE A HINT DOWNSLOPING/RAIN SHADOW, WITH MOST MODEL
QPFS SHOWING A RELATIVE MIN BETWEEN THE ALLEGHENIES AND I-81.
FARTHER TO THE EAST, THE METRO AREAS ARE TYPICALLY MORE
VULNERABLE TO BEGIN WITH. HERE, MULTIPLE ROUNDS OF STORMS WITH
SOME (BUT NOT AS STRONG AS FURTHER WEST) SIGNAL OF BACK-
BUILDING, AS WELL AS A CONGLOMERATION OF BAY/RIVER BREEZES,
OUTFLOW, AND THE NEARBY WARM FRONT, COULD STILL RESULT IN HEAVY
RAINFALL. THIS IS ANOTHER AREA TO BE MONITORED LATER TODAY, WITH
A FLOOD WATCH NOW IN EFFECT 2-8PM.
WITH SURFACE WINDS TURNING SOUTHERLY AND WINDS ALOFT TURNING
SOUTHWESTERLY, THERE SHOULD BE AN IMPROVEMENT IN SMOKE AND AIR
QUALITY FROM SOUTH TO NORTH THROUGH THE MIDDAY HOURS.
SKIES MAY NOT BECOME COMPLETELY SUNNY, BUT IT WON'T TAKE MUCH TO
WARM UP. IT WILL ALSO BE VERY HUMID WITH DEW POINTS IN THE LOWER TO
MID 70S. HEAT INDEX VALUES WILL LIKELY RANGE FROM 100-105 EAST OF
THE BLUE RIDGE AND MID TO UPPER 90S IN THE LOWER ELEVATIONS TO THE
WEST. A HEAT ADVISORY HAS BEEN ISSUED FOR THE I-95 CORRIDOR FROM
BALTIMORE SOUTHWARD. THIS AREA IS EXPECTED TO HAVE THE MOST HEATING
BEFORE STORMS ARRIVE, AND HIGHER DEW POINTS WILL LIKELY REMAIN
POOLED EAST OF A DEVELOPING LEE TROUGH IN THIS AREA.
WITH 30+ KT OF DEEP LAYER SHEAR, THE HOT AND HUMID AIRMASS WILL
RESULT IN SUBSTANTIAL INSTABILITY AND A FAVORABLE ENVIRONMENT FOR
SEVERE THUNDERSTORM DEVELOPMENT. A PRIMARY FOCUS FOR STORM
INITIATION AND/OR INTENSIFICATION WILL BE THE LEE TROUGH EAST OF THE
BLUE RIDGE. MOST CAMS HAVE STORMS DEVELOPING IN THIS AREA BY EARLY
TO MID AFTERNOON. STORMS WILL LIKELY ALSO DEVELOP WELL UPSTREAM IN
THE GREAT LAKES CLOSER TO THE SURFACE FRONT. WHAT HAPPENS IN BETWEEN
THESE FEATURES IS A BIT MORE UNCERTAIN, THOUGH ADDITIONAL
THUNDERSTORMS ARE CERTAINLY POSSIBLE GIVEN THE STRONG UPPER TROUGH
AND DEEPENING SURFACE LOW TO THE NORTH. SOME AREAS COULD SEE
MULTIPLE ROUNDS. THE PRIMARY HAZARD WILL BE DAMAGING WINDS, WITH
SOME CONSIDERABLE SWATHS OF DAMAGE POSSIBLE IN ANY SUSTAINED
SUPERCELLS OR LINEAR SEGMENTS. SOME ISOLATED LARGE HAIL IS POSSIBLE,
BUT MODEST MID LEVEL LAPSE RATES WILL BE A LIMITING FACTOR. A
TORNADO IS ALSO POSSIBLE, WITH THE GREATEST CHANCES IN NORTHEAST
MARYLAND WHERE LOW LEVEL FLOW WILL BE MORE FAVORABLE. FREQUENT
LIGHTNING AND HEAVY RAINFALL ARE LIKELY WITH ANY STORM. PRECIPITABLE
WATER VALUES SURGE TO GREATER THAN 2 INCHES. THE FLASH FLOOD THREAT
APPEARS TO BE ISOLATED AND LIMITED TO ANY AREAS WITH LOCALIZED
TRAINING OR REPEATING STORMS, AS OVERALL STORM MOTIONS SHOULD BE
PROGRESSIVE. THE QPF SIGNAL IS HIGHEST IN NORTHEAST MD.
A SECONDARY CONCENTRATION OF THUNDERSTORMS WILL DEVELOP CLOSER TO
THE COLD FRONT NEAR THE GREAT LAKES. MOST GUIDANCE SHOWS THIS
ACTIVITY RAPIDLY WEAKENING AS IT APPROACHES THE AREA DURING THE LATE
EVENING, WITH SOME STRONGER STORMS POTENTIALLY REACHING THE
ALLEGHENY FRONT. THE REFS DOES SHOW A BIT MORE PERSISTENCE TO THESE
STORMS HOWEVER. EITHER WAY, THERE WILL BE A DRYING TREND THE SECOND
HALF OF THE NIGHT.
KEY MESSAGE 2...THUNDERSTORM CHANCES MAY LINGER ACROSS SOUTHERN
PORTIONS OF THE AREA AS THE FRONT STALLS TO THE SOUTH SUNDAY AND
MONDAY.
THE COLD FRONT WILL PUSH SOUTH THROUGH THE AREA SUNDAY. BY THE TIME
CONVECTION INITIATES, IT MAY LARGELY BE SOUTH OF THE FORECAST AREA.
HOWEVER, THERE IS ENOUGH UNCERTAINTY IN THE FRONTAL POSITION THAT
THE I-64 CORRIDOR IN CENTRAL VA COULD SEE SOME THUNDERSTORMS ON
SUNDAY. THE GREATEST RISK FOR SEVERE THUNDERSTORMS REMAINS SOUTH OF
THE AREA.
HIGH PRESSURE BRIEFLY BUILDING TO THE NORTH WILL BRING COOLER
TEMPERATURES SUNDAY AND MONDAY. THE FRONT WILL STALL TEMPORARILY BUT
BEGIN TO LIFT BACK NORTH MONDAY INTO MONDAY NIGHT. DEPENDING HOW
QUICKLY THIS OCCURS, SOME SHOWERS AND THUNDERSTORMS COULD MOVE BACK
INTO THE AREA.
KEY MESSAGE 3...A STRONG COLD FRONT AND TROUGH OF LOW PRESSURE
MAY BRING SEVERE WEATHER TUESDAY AND/OR WEDNESDAY.
A STRONG UPPER TROUGH AND COLD FRONT WILL CROSS THE REGION TUESDAY
INTO WEDNESDAY. THERE STILL REMAINS UNCERTAINTY IN TIMING AND
PLACEMENT OF UPPER TROUGH AND FRONT, ALONG WITH COVERAGE OF
CONVECTION EACH DAY. IT LOOKS AS IF THERE WILL BE SECONDARY COLD
FRONT TO FOLLOW THE FIRST FRONT SOMETIME MIDDAY WEDNESDAY INTO THE
AFTERNOON. AS WE GET CLOSER IN TIME EACH DAY, WE WILL HAVE A BETTER
FEEL FOR THIS CONVECTIVE PERIOD OF TIME IN THE MIDDLE OF THE WEEK.
SPC OUTLOOKS DENOTE ROUGHLY AT 15% RISK TUESDAY INTO WEDNESDAY FROM
WEST TO EAST, WITH VARIOUS ML/AI GUIDANCE A TICK OR TWO HIGHER THAN
THAT. DAMAGING WINDS WILL LIKELY BE THE PRIMARY THREAT WITH STORMS,
ALTHOUGH OTHER HAZARDS CANNOT BE RULED OUT PENDING THE PLACEMENT OF
THE TROUGH AND INGREDIENTS AT PLAY.
BEHIND THIS SYSTEM WILL BE LOWER HUMIDITY AND COOLER THAN NORMAL
TEMPERATURES FOR THE SECOND HALF OF NEXT WEEK WITH HIGH PRESSURE
RETURNING TO THE REGION.
AVIATION /00Z SUNDAY THROUGH THURSDAY/
SMOKE CONTINUES TO REDUCE VISIBILITIES. THESE CONDITIONS SHOULD
IMPROVE FROM SOUTH TO NORTH THROUGH MIDDAY AS SOUTHERLY WINDS
PICK UP, WHICH COULD POTENTIALLY GUST TO 20 KT THIS AFTERNOON.
ADDITIONAL THUNDERSTORMS ARE LIKELY THIS AFTERNOON, ESPECIALLY FOR
THE METRO TERMINALS. COVERAGE IS A BIT MORE UNCERTAIN FOR CHO AND
MRB. TIMING IS ALSO A BIT UNCERTAIN, AND IT'S NOT OUT OF THE
QUESTION THERE COULD BE MULTIPLE ROUNDS. THUNDERSTORMS MAY BE STRONG
TO SEVERE WITH STRONG WINDS, HAIL, FREQUENT LIGHTNING, AND VERY
HEAVY RAIN. A POSSIBLY WEAKENING LINE OF STORMS MAY APPROACH DURING
THE LATE EVENING AS IT DROPS IN FROM THE NORTHWEST, BUT IT MAY
LARGELY FALL APART FIRST. WINDS WILL SHIFT BACK TO THE N AND NW
BEHIND THE COLD FRONT HEADING INTO SUNDAY. CHO MAY REMAIN CLOSE
ENOUGH TO THE FRONT TO SEE MORE THUNDERSTORMS SUNDAY AFTERNOON.
PREVAILING VFR CONDITIONS ARE EXPECTED MONDAY, THOUGH SOME GUIDANCE
HAS SHOWERS AND THUNDERSTORMS WORKING BACK NORTHWARD WITH A WARM
FRONT BY AFTERNOON OR MONDAY NIGHT.
POSSIBLE SUB-VFR CONDITIONS ON TUESDAY INTO WEDNESDAY. SHOWERS AND
THUNDERSTORMS COULD PUSH THROUGH MULTIPLE TIMES. WE WILL MONITOR THE
SET UP AS WE GET PAST THIS WEEKEND. WINDS SOUTHEAST TO SOUTH 5 TO 10
KNOTS TUESDAY. WINDS SOUTH TO SOUTHWEST 10 TO 15 KNOTS
WEDNESDAY.
MARINE
SOUTHERLY WINDS STRENGTHEN BY THIS AFTERNOON IN THE WAKE OF THE
WARM FRONT. ADVISORIES HAVE BEEN ISSUED FROM 11 AM TO 11 PM FOR
ALL WATERS, AND LINGERING FOR THE MID BAY THROUGH THE NIGHT.
STRONG TO SEVERE STORMS ARE POSSIBLE THIS AFTERNOON AND EVENING
AS WELL, WHICH MAY PROMPT SPECIAL MARINE WARNINGS.
LEFTOVER STORMS ON SUNDAY WOULD PROBABLY BE LIMITED TO AREAS AROUND
SOUTHERN MD, BUT TRENDS SUGGEST THEY WILL FORM FARTHER TO THE SOUTH.
OTHERWISE WINDS BECOME NORTHERLY IN THE FRONT'S WAKE, AND COULD
RESULT IN MARGINAL ADVISORY CONDITIONS.
EXPECT SUB-SCA LEVEL CONDITIONS SUNDAY NIGHT INTO MONDAY AS HIGH
PRESSURE BUILDS TO THE NORTH. SOUTHERLY CHANNELING MAY INCREASE
WINDS BY MONDAY NIGHT.
SCA CONDITIONS DUE TO SOUTHERLY CHANNELING COULD OCCUR TUESDAY INTO
WEDNESDAY AS A STORM SYSTEM AND TWO POSSIBLE COLD FRONTS PUSH ACROSS
THE REGION. WINDS SOUTHEAST 10 TO 15 KNOTS TUESDAY. WINDS SOUTH 10
TO 20 KNOTS GUSTS HIGHER WEDNESDAY.
TIDES/COASTAL FLOODING
INCREASING SOUTHERLY FLOW TODAY AND AGAIN ON TUESDAY COULD LEAD
TO WATER LEVELS APPROACHING MINOR FLOOD STAGE, ESPECIALLY AT
ANNAPOLIS. HOWEVER, CURRENT TRENDS SUGGEST LEVELS SHOULD FALL
SHORT OF FLOOD STAGE TODAY/TONIGHT.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR MDZ008.
FLOOD WATCH UNTIL 2 AM EDT SUNDAY FOR MDZ501-502-509-510.
VA...NONE.
WV...FLOOD WATCH UNTIL 2 AM EDT SUNDAY FOR WVZ503-504.
AIR QUALITY ALERT UNTIL MIDNIGHT EDT TONIGHT FOR WVZ050-055-
501>504.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR
ANZ530>533-535-536-538>542.
SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ534-537-543.
DISCUSSION...ADS/AVS/KLW/DHOF
AVIATION...ADS/KLW/DHOF
MARINE...ADS/KLW/DHOF
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