329
FXUS61 KLWX 091917
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
317 PM EDT WED JUL 9 2025
SYNOPSIS
A SURFACE TROUGH WILL REMAIN ACROSS THE AREA THROUGH THURSDAY.
WEAK HIGH PRESSURE WILL BUILD OVER THE AREA FOR THE END OF THE
WEEK.
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
LOW-LEVEL TROUGH IS EXPECTED TO SHARPEN ACROSS THE AREA THROUGH
TONIGHT AS A SHORTWAVE-TROUGH APPROACHES FROM THE OH VALLEY.
THIS WILL PROVIDE STRONGER FORCING AND HELP SUSTAIN THUNDERSTORMS
LONGER INTO THE NIGHT TONIGHT. IN OTHER HAND, RECENT NUCAPS
DATA FROM 1717Z INDICATE THAT AIR MASS TODAY IS NOT AS UNSTABLE
AS IT WAS YESTERDAY. NOT SEEING THE 3500 J/KG CAPE THAT I SAW
YESTERDAY. NORTHEAST MARYLAND LOOKS PARTICULARLY MORE STABLE
AND LESS HUMID TODAY THAN YESTERDAY. THE 925-850 MB MOISTURE
AXIS IS ALSO FURTHER WEST TODAY AND EXTENDS UP THE I-81
CORRIDOR FROM AUGUSTA COUNTY VA UP THROUGH WINCHESTER,
MARTINSBURG, HAGERSTOWN INTO CHAMBERSBURG PA. THE RADAR TRENDS
INDICATE THAT THE CLUSTER OVER ROCKINGHAM COUNTY WILL LIKELY
MERGE EVENTUALLY WITH THE OTHER CLUSTERS APPROACHING THE
APPALACHIANS, POSING A FLOOD RISK OVER PARTS OF EASTERN WV.
GIVEN THESE TRENDS AND MOISTURE AXIS FURTHER WEST, HAVE EXPANDED
THE FLOOD WATCH TO COVER EASTERN WV AND WASHINGTON COUNTY MD.
WITH TIME, THIS MOISTURE AXIS IS EXPECTED TO SHIFT NORTHEAST ON
SSW WINDS. SO, EXPECT A LATER ONSET OF THUNDERSTORMS IN CENTRAL
AND NORTHEAST MD THIS EVENING WHEN COMPARED TO YESTERDAY. GIVEN
THE STRONGER FORCING, EXPECT THUNDERSTORMS TO LAST WELL INTO
THE OVERNIGHT HOURS, ESPECIALLY FOR THE I-95 CORRIDOR. OVERALL,
THE FLOOD RISK LOOKS HIGHER THAN THE SEVERE THREAT.
AFTER THE THUNDESTORMS EXIT LATE TONIGHT, EXPECT AREAS OF LOW
CLOUDS/FOG TO FORM.
SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/
LOW CLOUDS TO START THE DAY WILL KEEP TEMPERATURES AND
INSTABILITY DOWN THU. WEAKENING SURFACE TROUGH WILL RESULT IN
LESS FORCING FOR THUNDERSTORM DEVELOPMENT. EXPECT THUNDERSTORM
COVERAGE TOMORROW TO BE SIGNIFICANTLY LESS THAN TODAY.
STRENGTHENING LOW-LEVEL RIDGING FRI SHOULD RESULT IN A DOWNWARD
TREND IN AREAL COVERAGE OF CONVECTION.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
VERY LITTLE CHANGE TO WHAT IS A TYPICAL SUMMERTIME PATTERN ACROSS
THE REGION. SENSIBLE HEAT AND HUMIDITY WILL REMAIN ALONG WITH
DAILY SHOWER AND THUNDERSTORM CHANCES. THIS IS A RESULT OF ZONAL
FLOW ALOFT AND NO STRONG FRONTAL BOUNDARIES SET TO CROSS THE REGION.
OVERALL, A STAGNANT AIRMASS THAT WILL BE HARD TO FLIP UNTIL AT LEAST
THE MIDDLE OF NEXT WEEK.
SYNOPTICALLY, WILL CONTINUE TO MONITOR AN AREA OF LOW PRESSURE AND
SHORTWAVE TROUGH TRACKING ACROSS THE GREAT LAKES INTO EASTERN CANADA
THIS WEEKEND. THIS SHORTWAVE TROUGH COMBINED WITH A DISSIPATING
FRONTAL BOUNDARY WILL LEAD TO AN UPTICK IN SHOWERS AND THUNDERSTORMS
THIS WEEKEND INTO EARLY NEXT WEEK. ONCE AGAIN. IT WILL NOT BE
RAINING ALL THE TIME WITH AMPLE DRY TIME FOR PLANS IN BETWEEN.
HIGHEST COVERAGE WILL BE DURING THE AFTERNOON AND EVENING HOURS
THROUGH AT LEAST TUESDAY.
AS FOR SEVERE WEATHER, UNCERTAINTY REMAINS GIVEN THE PLACEMENT OF
THE WAVERING FRONT AND TIMING OF SHORTWAVE ENERGY AS IT PIVOTS
ACROSS. CURRENT CSU LEARNING MACHINE GUIDANCE, CIPS PATTERN
RECOGNITIONS, AND LONG RANGE NSSL PROBS ARE LEANING TOWARD THE
SATURDAY AND SUNDAY TIMEFRAME AS THE NEXT POTENTIAL PERIOD FOR
ORGANIZED CONVECTION. EITHER WAY THUNDERSTORMS WILL HAVE THE
POTENTIAL OF PRODUCING LOCALLY DAMAGING WINDS AND INSTANCES OF FLASH
FLOODING EACH AFTERNOON. THIS IS DUE LARGELY IN PART TO THE STAGNANT
WARM AND MOIST AIRMASS HANGING TOUGH OVER THE REGION. TEMPERATURES
THIS WEEKEND INTO EARLY NEXT WEEK WILL RANGE FROM THE MID TO UPPER
80S AND LOW 90S. HEAT INDICES WILL MAKE IT FEEL MORE LIKE THE MID TO
UPPER 90S.
BEYOND MONDAY, UNCERTAINTY CONTINUES IN REGARDS TO A POTENTIAL
FRONTAL PASSAGE. 12Z SYNOPTIC/ENSEMBLE GUIDANCE SHOW A COLD FRONT
EJECTING OUT OF THE MIDWEST AND OHIO RIVER VALLEY SOME TIME TUESDAY
INTO WEDNESDAY NEXT WEEK. THIS FRONT DOES NOT APPEAR CROSS UNTIL
THEN WITH A SECONDARY FRONT TO FOLLOW LATE NEXT WEEK. THE GFS TENDS
TO REMAIN MORE AGGRESSIVE IN HOLDING THE CURRENT PATTERN WHILE ECWMF
AND CANADIAN TURN THE PATTERN OVER MID NEXT WEEK.TEMPERATURES AND
PRECIPITATION WILL CONTINUE TO REMAIN ABOVE AVERAGE WITHIN THE BACK
HALF OF THE LONG TERM PERIOD.
AVIATION /19Z WEDNESDAY THROUGH MONDAY/
NUMEROUS TO WIDESPREAD SHOWERS AND THUNDERSTORMS ARE EXPECTED
LATE THIS AFTERNOON THROUGH THIS EVENING. HEAVY RAINFALL, FREQ
LIGHTNING AND REDUCED VSBY ARE THE MAIN THREATS. LOW CLOUDS FORM
LATE TONIGHT WITH IFR CIGS EXPECTED BEFORE MIXING/SCATTERING OUT
LATE THU MORNING. LESS T-STORM COVERAGE EXPECTED THU.
PREVAILING VFR CONDITIONS ARE EXPECTED SATURDAY THROUGH MONDAY. SUB-
VFR REDUCTIONS REMAIN POSSIBLE DURING THE AFTERNOON AND EVENING
HOURS AS A RESULT OF SHOWERS AND THUNDERSTORMS. WINDS WILL REMAIN
LIGHT OUT OF THE SOUTH AND SOUTHWEST SATURDAY BEFORE TURNING LIGHT
OUT OF THE WEST TO NORTHWEST SUNDAY.
MARINE
GRADIENT WINDS ARE EXPECTED TO INCREASE TONIGHT ACROSS THE
SOUTHERN WATERS WHICH MAY REQUIRE SCAS. OTHERWISE, HIGHER WINDS
AND WAVES CAN BE EXPECTED NEAR THUNDERSTORMS.
SCATTERED TO NUMEROUS THUNDERSTORMS LOOK TO IMPACT THE WATERS
ANYTIME AFTER 18-20Z/2-4PM THIS AFTERNOON. SPECIAL MARINE WARNINGS
WILL BE NEEDED TO COVER THIS THREAT WITH STORMS CAPABLE OF PRODUCING
SEVERE DOWNBURSTS WINDS AND HEAVY RAINFALL. HIGHEST COVERAGE OF
STORMS LOOK TO BE BETWEEN 4-9PM THIS EVENING BEFORE DIMINISHING
OVERNIGHT. ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE
THURSDAY AS THE FRONT STALLS NEARBY. WIND WILL BE THE PRIMARY THREAT
WITH STORMS ALONG WITH FREQUENT LIGHTNING AND HEAVY RAINFALL.
ADDITIONAL SMWS WILL BE NEEDED TO ENCOMPASS THIS THREAT. WINDS WILL
REMAIN LIGHT OUT OF THE SOUTH OUTSIDE OF THUNDERSTORMS, WITH
OUTFLOWS LIKELY DISRUPTING OPPORTUNITIES FOR SOUTHERLY CHANNELING
OUTSIDE OF THE OPEN WATERS.
SUB-SCA LEVEL WINDS ARE EXPECTED THROUGH THE UPCOMING WEEKEND
DESPITE A STALLED FRONT NEARBY. LIGHT SOUTHERLY WINDS ARE EXPECTED
FRIDAY AND SATURDAY WITH LIGHT WEST TO NORTHWESTERLY WINDS ON
SUNDAY. THUNDERSTORMS MAY BE POSSIBLE DURING THE AFTERNOON AND
EVENING HOURS, POTENTIALLY LEADING TO THE ISSUANCE OF SMWS.
LWX WATCHES/WARNINGS/ADVISORIES
DC...FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR DCZ001.
MD...FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR MDZ004>006-008-011-
013-014-016>018-503>508.
VA...FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR VAZ025>027-029>031-
036>040-050-051-053>057-501-502-505>508-526-527.
WV...FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR WVZ053.
MARINE...FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR ANZ530.
SYNOPSIS...LFR
NEAR TERM...LFR
SHORT TERM...LFR
LONG TERM...EST
AVIATION...LFR/EST
MARINE...LFR/EST
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