593
FXUS61 KLWX 030756
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
356 AM EDT SAT MAY 3 2025
SYNOPSIS
A SLOW-MOVING COLD FRONT WILL APPROACH FROM THE MIDWEST THROUGH
TONIGHT, THEN GRADUALLY CROSS THE MID-ATLANTIC FROM WEST TO EAST
THROUGH TUESDAY. HIGH PRESSURE MAY FOLLOW BRIEFLY FOR WEDNESDAY.
ANOTHER FRONTAL SYSTEM AND AREA OF LOW PRESSURE MAY GRADUALLY
APPROACH THE REGION FROM THE TENNESSEE VALLEY LATE NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
EARLY MORNING GOES-16 IR/NIGHTTIME MICROPHYSICS RGB IMAGERY SHOWS
RATHER LARGE EXPANSES OF MAINLY CLEAR SKIES ACROSS MUCH OF THE
MID-ATLANTIC EAST OF I-81 AND ROUGHLY NORTH OF I-64. MID/HIGH
LEVEL CLOUDS LEFTOVER FROM PRIOR CONVECTION ARE STREAMING NNE UP
THE APPALACHIANS, WITH ANOTHER AREA OF CLOUDS OVER SOUTHERN VA
WORKING NORTH BUT DISSIPATING. THESE MAINLY CLEAR SKIES WILL
PLAY AN IMPORTANT ROLE IN HEATING AND THE EVOLUTION OF
CONVECTION LATER TODAY.
AS A LARGE AND DEEP UPPER-LEVEL LOW CUTS OFF OVER THE OHIO
VALLEY AND SLOWLY APPROACHES FROM THE WEST, A SURFACE COLD FRONT
WILL ENCROACH UPON THE APPALACHIANS BY TONIGHT. SUBSTANTIAL
HEIGHT FALLS AHEAD OF THESE FEATURES AMID A SEASONABLY WARM AND
HUMID AIRMASS WILL SET THE STAGE FOR AN ACTIVE 24 TO 48 HOURS.
HEATING MAY ALLOW STORMS TO BEGIN INITIATING AS EARLY AS
MIDDAY OR SHORTLY THEREAFTER, THOUGH SOME LINGERING SUBSIDENCE
OR CAPPING ALOFT MAY KEEP STRONGER UPDRAFTS AT BAY UNTIL MID
AFTERNOON. STORMS ARE MOST LIKELY TO INITIATE IN THE VICINITY OF
A SURFACE TROUGH ORIENTED ROUGHLY ALONG THE BLUE RIDGE AS OF
EARLY THIS MORNING.
COOLING MID-LEVEL TEMPS AND STRONG PVA/HEIGHT FALLS AS WELL AS
RER DYNAMICS OF THE ATTENDANT UPPER JET WILL OVERLAY ISENTROPIC
ADVECTION IN THE LOW LEVELS. MODEST MID-LEVEL LAPSE RATES OF
6-6.5 C/KM OVERTOP SURFACE TEMPS RISING WELL INTO THE 80S WITH
DEW POINTS INTO THE LOWER 60S IS LIKELY TO RESULT IN A BROAD
750-1250 J/KG MLCAPE BY MID AFTERNOON BETWEEN THE FOOTHILLS OF
THE ALLEGHENY AND POTOMAC HIGHLANDS WEST OF I-81 TO NEAR AND
JUST WEST OF I-95. WITHIN THIS BROAD ZONE, POCKETS OF LOCALLY
GREATER HEATING AND/OR SUBTLY HIGHER LOW-LEVEL MOISTURE POOLING
IN SOME VALLEYS OR IN THE LEE OF TERRAIN FEATURES COULD RESULT
IN LOCAL MAXIMA OF 1500-2000 J/KG MLCAPE, AS NOTED IN SOME HI-
RES GUIDANCE. THE FLOW IN THE 850-500 HPA LAYER WILL INCREASE TO
30-45 KTS THROUGH THE AFTERNOON INTO THIS EVENING, OFFERING THE
POTENTIAL OF STORM ORGANIZATION INTO LINES/CLUSTERS AND PERHAPS
TRANSIENT SUPERCELL STRUCTURES. GIVEN MODERATE DCAPE AND STEEP
LOW-LEVEL LAPSE RATES AS WELL AS POCKETS OF MID-LEVEL DRY AIR
(FAVORABLE FOR EVAPORATIONAL COOLING AND ACCELERATION OF
DOWNDRAFTS) AMID THE MODEST BACKGROUND FLOW, STRONG TO DAMAGING
STRAIGHT LINE WIND GUSTS WILL LIKELY BE THE PRIMARY THREAT WITH
THE MORE INTENSE UPDRAFTS/LINE SEGMENTS. FAVORABLE SHEAR AND
MODEST CAPE IN THE -10 TO -30 DEG C (HAIL GROWTH) LAYER COULD
RESULT IN SOME SEVERE HAIL WITH ANY PERSISTENT SEMI-DISCRETE
UPDRAFTS. THERE IS SOME CURVATURE TO THE LOW-LEVEL HODOGRAPH IN
MOST FORECAST SOUNDINGS, BUT MODEST WIND SPEEDS IN THE LOWEST 2
KM AGL MAY KEEP ANY TORNADO THREAT LIMITED/CONDITIONAL ON ANY
FAVORABLE STORM-SCALE BOUNDARY INTERACTIONS, OR PERHAPS
INTERACTION WITH ENHANCED ENVIRONMENTAL VORTICITY NEAR THE
SURFACE TROUGH OR JUST EAST OF HIGHER TERRAIN FEATURES (WHERE
SURFACE FLOW COULD BE SLIGHTLY ENHANCED PARALLEL TO THE RIDGES).
HEIGHT FALLS AND MID-LEVEL FLOW STRENGTHEN TONIGHT, WITH
CONTINUED MOISTURE ADVECTION IN THE LOW LEVELS. THIS VERY WELL
MAY KEEP WIDESPREAD SHOWERS AND AT LEAST A FEW THUNDERSTORMS
GOING WELL INTO THE NIGHT, THOUGH THE SEVERE THREAT SHOULD
GRADUALLY WANE WITH THE LOSS OF DAYTIME HEATING AND AN
INCREASINGLY STABLE BOUNDARY LAYER. PWATS INCREASING TO
1.25-1.50 INCHES WITH STORM MOTIONS PARALLEL TO THE APPROACHING
COLD FRONT COULD AFFORD SOME TRAINING AND HEAVY RAIN POTENTIAL
TONIGHT. ONGOING DROUGHT CONDITIONS SHOULD LIMIT A MORE
SIGNIFICANT FLOOD THREAT, KEEPING THE RISK MARGINAL AND MOST
LIKELY RELEGATED TO HYDROPHOBIC (URBAN) BASINS, OR BASINS WITH
FLASHY COMPLEX TERRAIN. GUIDANCE DIFFERS ON EXACTLY WHERE ANY
HEAVIER RAINFALL TOTALS MAY FOCUS, BUT IN A BROAD SENSE THIS
LOOKS MOST LIKELY WEST OF I-95 AND EAST OF THE APPALACHIANS. IF
MORE WIDESPREAD ORGANIZED CONVECTION DEVELOPS THIS AFTERNOON AND
EARLY EVENING, THEN IT COULD RESULT IN A CONGLOMERATE OUTFLOW
AND SUBSEQUENT RENEWED CONVECTION SHIFTING FURTHER EAST CLOSER
TO THE MORE VULNERABLE URBAN BASINS TONIGHT, HOWEVER.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/
UNSETTLED WEATHER WILL CONTINUE SUNDAY AND MONDAY AS THE UPPER
LOW AND SURFACE COLD FRONT ONLY SLOWLY DRIFT WEST TO EAST ACROSS
THE MID-ATLANTIC. MID-LEVEL LAPSE RATES WILL STEEPEN A BIT,
PERHAPS EXCEEDING 7 C/KM BY MONDAY AFTERNOON. ENHANCED FLOW EAST
OF THE UPPER LOW WILL ALSO LINGER. THIS COULD SET THE STAGE FOR
MULTIPLE ROUNDS OF AT LEAST ISOLATED STRONG TO SEVERE STORMS,
WITH THE POTENTIAL FOR SOME LOCALLY HEAVIER RAINFALL TOTALS
GIVEN REPEAT/TRAINING POTENTIAL. COOLER MID-LEVEL TEMPS AND
LOWERING FREEZING LEVELS COULD RESULT IN AN UPTICK IN HAIL
POTENTIAL SHOULD DEEPER UPDRAFTS EVOLVE IN SUCH AN ENVIRONMENT
SUNDAY INTO MONDAY, AS WELL. LOW-LEVEL FLOW APPEARS TO BACK ON
MONDAY, WHICH COULD ALSO INCREASE SRH.
LONG TERM /TUESDAY THROUGH FRIDAY/
A NEARBY UPPER-LEVEL LOW WILL BRING SHOWERS AND THUNDERSTORMS
TO THE FORECAST AREA THROUGH TUESDAY EVENING. WHILE THERE
CONTINUES TO BE MODEL DISCREPANCY REGARDING THE LOCATION OF THE
UPPER LOW, GLOBAL MODELS INDICATE THE LOW TRACKING NORTHEAST
BETWEEN THE OHIO RIVER VALLEY AND GREAT LAKES REGION. AT THE
SURFACE, A COLD FRONT ASSOCIATED WITH A LOW PRESSURE SYSTEM WILL
MOVE THROUGH THE REGION ON TUESDAY. AS THE SURFACE LOW TRACKS
TO THE NE TOWARDS NEW ENGLAND, SURFACE HIGH PRESSURE BUILDS IN
FROM THE NORTHWEST. WHILE CONDITIONS DRY OUT OVERNIGHT TUESDAY
AND INTO WEDNESDAY, PRECIPITATION CHANCES LINGER THROUGHOUT THE
LONG TERM AS THE UPPER LOW REMAINS NEARBY AND THE AFOREMENTIONED
COLD FRONT STALLS TO THE SOUTH.
HIGH TEMPERATURES EACH DAY WILL BE IN THE 60S TO 70S WITH TUESDAY
BEING THE WARMEST DAY OF THE PERIOD. OVERNIGHT LOW TEMPERATURES WILL
BE IN THE 40S TO 50S EACH NIGHT, WITH THE EXCEPTION BEING WEDNESDAY
NIGHT WHEN THE METRO REGIONS STAY IN THE 60S.
ANOTHER UPPER-LEVEL LOW MAY APPROACH THE REGION BRINGING A
REJUVENATION OF UNSETTLED WEATHER LATE NEXT WEEK.
AVIATION /07Z SATURDAY THROUGH WEDNESDAY/
BOUTS OF SUB-VFR CONDITIONS ARE EXPECTED BEGINNING THIS AFTERNOON
AND LASTING RIGHT THROUGH EARLY NEXT WEEK. THIS IS DUE TO WAVES
OF SHOWERS AND THUNDERSTORMS AHEAD OF A SLOWLY APPROACHING UPPER
LOW. TIMING OF THE LOWEST CONDITIONS FROM CONVECTION IS A BIT
DIFFICULT, THOUGH SHOULD BE FOCUSED BROADLY ON THE AFTERNOON AND
EVENING HOURS EACH DAY. DURING THE OVERNIGHT HOURS, A SLIGHT
DECREASE IN SURFACE WINDS WITH ENHANCED FLOW AT A FEW THOUSAND
FEET COULD RESULT IN SPOTTY/MARGINAL LLWS. LOWER CIGS ARE ALSO
POSSIBLE IN THE INCREASINGLY MOIST LOW-LEVEL ENVIRONMENT LATE AT
NIGHT INTO THE MORNING HOURS EACH DAY. FLOW WILL BE MAINLY
SOUTHERLY WITH DAYTIME GUSTS TO AROUND 20 KTS POSSIBLE OUTSIDE
OF THUNDERSTORMS, BECOMING SOUTHEASTERLY MONDAY.
SHOWERS AND THUNDERSTORMS ON TUESDAY WILL LIKELY LEAD TO PERIODS OF
SUB-VFR CONDITIONS. SUB-VFR CONDITIONS ARE POSSIBLE AGAIN ON
WEDNESDAY WITH A CHANCE OF PRECIPITATION. SOUTHWEST WINDS ON TUESDAY
SHIFT TO NORTHWEST ON WEDNESDAY.
MARINE
SOUTHERLY GRADIENT WINDS WILL INCREASE TODAY, WITH A VERY
FAVORABLE SETUP FOR SOUTHERLY CHANNELING EXPECTED THIS AFTERNOON
INTO THIS EVENING. WINDS OF 25 TO 35 KNOTS OUT OF THE SOUTH A
FEW THOUSAND FEET ABOVE THE SURFACE WILL LIKELY BE DRAWN TOWARD
THE SURFACE BY SUBSIDENCE OVER THE COOLER WATERWAYS DUE TO
DEVELOPING BAY/RIVER BREEZES SINCE THE LAND/WATER TEMP
DIFFERENCE WILL BE 20+ DEG F THIS AFTERNOON. THIS DOWNWARD
TRANSPORT AND ENHANCEMENT FROM THE CHANNELING AND BAY/RIVER
BREEZE SHOULD OVERCOME SHALLOW STABILITY AND COULD EVEN RESULT
IN A FEW GUSTS NEAR GALE FORCE EARLY THIS EVENING OVER THE MAIN
CHANNEL OF THE CHESAPEAKE BAY. ENHANCED SOUTHERLY FLOW WILL
CONTINUE THROUGH THE DAY SUNDAY FOR AT LEAST PART OF THE WATERS,
WITH SOUTHEAST FLOW POSSIBLY NEARING SCA LEVELS MONDAY.
OTHERWISE, MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS ARE
ANTICIPATED OVER THE NEXT FEW DAYS, RESULTING IN THE POTENTIAL
FOR HAZARDOUS WINDS, WAVES, LIGHTNING, AND REDUCED VISIBILITY IN
HEAVY RAIN AT TIMES.
WINDS REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA BOTH TUESDAY AND
WEDNESDAY. SOUTHWEST WINDS ON TUESDAY SHIFT TO NORTHWEST ON
WEDNESDAY.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM THIS MORNING TO 8 PM EDT THIS
EVENING FOR ANZ530>532-535-536-538>540-542.
SMALL CRAFT ADVISORY FROM 6 AM THIS MORNING TO 6 PM EDT SUNDAY
FOR ANZ533-537-541.
SMALL CRAFT ADVISORY UNTIL 6 PM EDT SUNDAY FOR ANZ534-543.
SYNOPSIS...DHOF
NEAR TERM...DHOF
SHORT TERM...DHOF
LONG TERM...AVS
AVIATION...AVS/DHOF
MARINE...AVS/DHOF
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