214
FXUS61 KLWX 040116
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
916 PM EDT WED JUN 3 2020
SYNOPSIS
A COLD FRONT WILL STALL OUT JUST NORTH OF THE MASON-DIXON LINE
TONIGHT BEFORE RETREATING TO THE NORTH AS A WARM FRONT THURSDAY.
A SERIES OF UPPER-LEVEL DISTURBANCES WILL PASS THROUGH THE AREA
THURSDAY AND FRIDAY. A STRONGER COLD FRONT WILL THEN SWEEP
ACROSS THE AREA LATE SATURDAY, WITH CANADIAN HIGH PRESSURE
BUILDING IN FOR SUNDAY AND MONDAY.
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
A WEAK COLD FRONT WILL STALL JUST NORTH OF THE MASON-DIXON LINE
TONIGHT. SHOWERS AND THUNDERSTORMS THAT HAVE DEVELOPED AHEAD OF
THE BOUNDARY OVER PA, HAVE MOSTLY DISSIPATED AS THEY MOVED INTO
OUR AREA DUE TO A DOWNSLOPING WESTERLY FLOW. INHIBITION WILL
INCREASE OVERNIGHT DUE TO THE LOSS OF DAYTIME HEATING. AN COUPLE
SHOWERS CANNOT BE RULED OUT (PERHAPS A RUMBLE OF THUNDER NEAR
THE APPALACHIANS) ACROSS THE POTOMAC HIGHLANDS INTO NORTHERN VA,
NORTHERN MD, AND EASTERN WV. HOWEVER, MUCH OF THE TIME WILL BE
DRY ACROSS THESE AREAS.
WARM AND HUMID CONDITIONS WILL PREVAIL, WITH LOWS IN THE 60S
OVER THE POTOMAC HIGHLANDS TO THE LOWER AND MIDDLE 70S IN
DOWNTOWN WASHINGTON AND BALTIMORE.
SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/
THE AFOREMENTIONED FRONT REMAINS STALLED TO THE NORTH ON
THURSDAY, KEEPING THINGS WARM AND HUMID DURING THE AFTERNOON. A
WEAK SHORTWAVE APPROACHES FROM THE WEST DURING THE AFTERNOON
WHICH WILL LEAD TO FORMATION OF SHOWERS AND STORMS OVER THE
HIGHER ELEVATIONS. WITH HIGHS STILL NEAR 90, AND DEW POINTS
SLIGHTLY HIGHER, INTO THE MID 60S, CAPE VALUES SHOULD EXCEED
1000 J/KG AT LEAST. HOWEVER, SOME GUIDANCE SHOWS UPWARDS OF 2000
J/KG. EITHER WAY, LOOKS UNSTABLE ENOUGH FOR THUNDERSTORMS, GIVEN
THE FORCING ALOFT, PAIRED WITH A SURFACE TROUGH IN THE LEE OF
THE APPALACHIANS. FLOW WILL NOT BE AS STRONG ALOFT HOWEVER,
WHICH MAY LIMIT THE SEVERE THREAT A BIT. HOWEVER, COULD SEE SOME
PULSE TYPE THUNDERSTORMS, WHICH COULD CERTAINLY BRING SOME
DAMAGING WINDS. SPC HAS THE AREA IN A MARGINAL RISK FOR SEVERE
STORMS DURING THE AFTERNOON AS A RESULT.
IN ADDITION TO THE SEVERE THREAT, THERE WILL BE A THREAT FOR
SLOWER MOVING STORMS, WHICH COULD LEAD TO ISOLATED INSTANCES OF
FLOODING. FLOW WILL BE PARALLEL TO THE STALLED FRONT AND ALSO
WEAKENING OVERALL, AS MENTIONED PREVIOUSLY. THIS COULD POSE AN
ISOLATED FLOODING RISK. WPC HAS OUR REGION IN A MARGINAL RISK
FOR EXCESSIVE RAINFALL TOMORROW AS WELL. HIGHS WILL BE A BIT
LOWER DUE TO MORE CLOUDS AND BETTER CHANCE OF RAIN, BUT STILL
NEAR 90.
PREVIOUS DISCUSSION: SHOWER/STORM ACTIVITY THURSDAY EVENING
SHOULD DIMINISH OVERNIGHT AS THE SHORTWAVE PUSHES EAST AND
INSOLATION ENDS. LOWS WILL REMAIN MUGGY, IN THE 60S TO NEAR 70.
THE STALLED FRONT REMAINS NORTH OF THE REGION THROUGH FRIDAY
NIGHT, IN FACT LIKELY DISSIPATING AHEAD OF ANOTHER COLD FRONT
APPROACHING FOR SATURDAY. AIR MASS WILL REMAIN VERY WARM AND
HUMID, BUT SHORTWAVE ENERGY LOOKS LESS WITHOUT A SIGNIFICANT
SHORTWAVE OR VORT MAX IN THE VICINITY. THUS, WHILE
SHOWER/T-STORM RISK WILL CONTINUE FRIDAY AFTERNOON, ODDS LOOK
SLIGHTLY LOWER IN COVERAGE AND SIGNIFICANCE. HIGHS WILL AGAIN BE
NEAR 90. FRIDAY NIGHT WILL BE FAIRLY SIMILAR TO THURSDAY NIGHT
ASIDE FROM A BIT LESS STORM COVERAGE TO START THE NIGHT, WITH
LOWS AGAIN IN THE 60S TO NEAR 70.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
A COLD FRONT WILL APPROACH OUR REGION ON SATURDAY AS TROUGH ALOFT
DEEPENS INTO THE MID ATLANTIC. SOUTHERLY FLOW AHEAD OF THE FRONT
WILL ADVECT WARM AND MOIST AIR INTO OUR REGION, AND WITH ENOUGH
INSTABILITY AND DIURNAL HEATING, SHOWERS AND THUNDERSTORMS WILL BE
POSSIBLE OVER OUR AREA. THESE WILL BE MOVING OUT OF OUR AREA ON
SATURDAY EVENING/NIGHT AS THE FRONT MOVES ACROSS AND AWAY FROM US.
MID LEVEL TROUGH AXIS WILL MOVE AWAY FROM OUR AREA EARLY ON SUNDAY
AS HIGH PRESSURE BUILDS INTO OUR REGION FROM THE NORTHWEST AND MID
LEVEL RIDGING PUSHES INTO THE EASTERN CONUS. RIDGE WILL REMAIN IN
CONTROL THROUGH TUESDAY, KEEPING DRY CONDITIONS OVER OUR REGION,
THEN ANOTHER FRONT APPROACHES OUR AREA ON WEDNESDAY.
HIGH TEMPERATURES THROUGH THIS PERIOD WILL BE IN THE 80S ACROSS OUR
REGION, WITH LOWS IN THE 50S AND 60S.
AVIATION /01Z THURSDAY THROUGH MONDAY/
VFR CONDITIONS ARE EXPECTED FOR MOST OF THE TIME OVERNIGHT INTO
THURSDAY MORNING. HOWEVER, PATCHY FOG CANNOT BE COMPLETELY RULED
OUT. CONFIDENCE IS TOO LOW TO MENTION IN TAFS DUE TO HIGH AND
MID-LEVEL CLOUDS AROUND.
GENERALLY VFR CONDITIONS EXPECTED THURSDAY AND FRIDAY AS WELL,
BUT AFTERNOON THUNDERSTORMS POSSIBLE BOTH DAYS. CHANCES DECREASE
FRIDAY THOUGH COMPARED TO THURSDAY. WINDS WILL GENERALLY BE
LIGHT OUT OF THE SOUTH TO SOUTHWEST BOTH DAYS.
VFR EXPECTED ON SATURDAY WITH POSSIBLE SHOWERS AND THUNDERSTORMS
EXPECTED. THESE COULD BRING SOME RESTRICTIONS OVER THE TERMINALS.
VFR CONDITIONS EXPECTED ON SUNDAY AND MONDAY WITH HIGH PRESSURE IN
CONTROL.
MARINE
A WEST TO SOUTHWEST FLOW IS EXPECTED TONIGHT. WINDS MAY BE CLOSE
TO SCA CRITERIA ACROSS THE MIDDLE PORTION OF THE BAY AND LOWER
TIDAL POTOMAC RIVER, BUT CONFIDENCE FOR AN SCA IS TOO LOW SINCE
THE GRADIENT IS EXPECTED TO WEAKEN SLIGHTLY OVERNIGHT.
WIND SHOULD REMAIN BELOW SCA CRITERIA FOR MOST OF THE TIME
THURSDAY AND FRIDAY. HOWEVER, COULD SEE SHOWERS/STORMS EACH
DAY, WHICH COULD WARRANT SOME SHORT-FUSED HAZARDS.
GENERALLY SUB-SCA CONDITIONS EXPECTED SATURDAY INTO MONDAY. SHOWERS
AND THUNDERSTORMS ARE POSSIBLE ON SATURDAY.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR
ANZ530>533-535>542.
SYNOPSIS...CJL
NEAR TERM...BJL/CJL
SHORT TERM...CJL
LONG TERM...IMR
AVIATION...BJL/IMR/CJL
MARINE...BJL/IMR/CJL
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