866
FXUS61 KLWX 021419
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1019 AM EDT FRI MAY 2 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 EARLY NEXT WEEK. HIGH PRESSURE WILL LIKELY RETURN AT LEAST
BRIEFLY FOR THE MIDDLE OF NEXT WEEK BEFORE ANOTHER COLD FRONT
APPROACHES THE AREA THURSDAY.
NEAR TERM /THROUGH TONIGHT/
A FEW SCATTERED SHOWERS ARE NOTED OVER THE HIGHER ELEVATIONS OF
EASTERN WEST VIRGINIA. THESE SHOWERS COULD FALL APART THROUGH
THE REST OF THE MORNING AS DEWPOINT TEMPERATURES ARE EXPECTED TO
DROP A COUPLE OF DEGREES THROUGH THE DAY. ADDITIONAL SHOWERS AND
A FEW THUNDERSTORMS COULD ERUPT DURING THE AFTERNOON WITH
DAYTIME HEATING AND A WEAK TROUGH OF LOW PRESSURE. MODEST CAPE
AND MODERATE TO STRONG DCAPE WITH INVERTED-V PROFILES MAY BE AN
INDICATION THAT THUNDERSTORMS THAT DO DEVELOP IN OUR REGION
DURING THE PEAK TIME OF HEATING COULD HAVE LOCALLY DAMAGING WIND
GUSTS. HIGHS WILL BE WELL INTO THE 80S AND APPROACHING 90 IN A
FEW PLACES. THE BEST CHANCE FOR THESE THUNDERSTORMS WILL BE
ALONG AND WEST OF I-81.
PREVIOUS DISCUSSION...
WEAK HEIGHT FALLS WILL SPREAD ACROSS THE REGION OVERNIGHT, BUT
WITH THE LOSS OF HEATING AND LACK OF OTHER LARGER SCALE FEATURES
ACTIVITY OVERNIGHT SHOULD BE SPOTTY. AREAS EAST OF I-95 INTO
SOUTHERN MD WHERE HUMIDITY IS A BIT HIGHER COULD HAVE A BETTER
CHANCE AT A SHOWER OR PERHAPS A THUNDERSTORM TONIGHT, WITH
ANOTHER AREA OF POTENTIALLY HIGHER PROBABILITIES OF SHOWERS AND
A THUNDERSTORM OR TWO OUT NEAR THE APPALACHIANS A BIT CLOSER TO
THE AFOREMENTIONED APPROACHING SURFACE COLD FRONT.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
PREVIOUS DISCUSSION...
SATURDAY, THE UPPER TROUGH APPROACHING FROM THE WEST WILL BEGIN
TO CUT OFF AS IT APPROACHES THE REGION. MORE APPRECIABLE HEIGHT
FALLS/PVA ALONG WITH A NOTABLE UPTICK IN LOW-LEVEL MOISTURE
SHOULD BE ABLE TO FORCE NUMEROUS TO WIDESPREAD SHOWERS AND AT
LEAST SCATTERED THUNDERSTORMS. THERE ARE SOME QUESTIONS AROUND
THE EXTENT OF CLOUD COVER AND SUBSEQUENT HEATING, WHICH WILL
AFFECT THE AMOUNT OF INSTABILITY/CAPE AVAILABLE. MID-LEVEL LAPSE
RATES ARE MODEST (6.0-6.5 C/KM), SO AT LEAST AROUND 1000 J/KG
OF CAPE SHOULD BE ABLE TO DEVELOP JUST FROM THAT AND THE
INCREASE IN LOW-LEVEL MOISTURE. IF MORE HEATING IS REALIZED,
THEN CLOSER TO 2000 J/KG COULD DEVELOP. GIVEN 30-40 KTS OF
EXPECTED EFFECTIVE BULK SHEAR, STORMS MAY VERY WELL ATTAIN
ORGANIZATION INTO EITHER SMALL CLUSTERS/LINES, OR EVEN
SUPERCELLS. IF HEATING IS MORE MUTED BY CLOUD COVER, THEN MORE
INTENSE UPDRAFTS WILL LIKELY BE LIMITED WITH SEVERE WEATHER
BEING RELATIVELY SPOTTY AND ISOLATED. BUT, MORE HEATING AND
INSTABILITY COULD LEAD TO HIGHER COVERAGE OF STRONG TO SEVERE
THUNDERSTORMS SATURDAY AFTERNOON INTO SATURDAY EVENING. ACTIVITY
SHOULD GRADUALLY WEAKEN AFTER DARK WITH THE LOSS OF DAYTIME
HEATING, BUT THE DEEP TROUGH AND SURFACE COLD FRONT APPROACHING
FROM THE WEST COULD KEEP AT LEAST SOME SHOWERS AND STORMS GOING
INTO THE NIGHT. SOME GUIDANCE INDICATES INCREASED CONVERGENCE
BETWEEN I-81 AND I-95 AMID INCREASING PWATS SATURDAY NIGHT,
WHICH COULD LEAD TO LOCALIZED HIGHER RAINFALL TOTALS. ONGOING
DROUGHT SHOULD TEMPER A MORE WIDESPREAD FLOOD THREAT, BUT ANY
LOCALIZED HEAVIER RAINFALL AMOUNTS FALLING IN A SHORT PERIOD
OVER SENSITIVE BASINS (PARTICULARLY NEAR COMPLEX TERRAIN) COULD
RAISE THE PROSPECT OF ISOLATED FLOODING POTENTIAL.
SUNDAY, THE UPPER LOW BECOMES CUT OFF AS IT STALLS JUST WEST OF
THE APPALACHIANS. DEEP LAYER FLOW INCREASES AND MID-LEVEL LAPSE
RATES REMAIN MODEST AS FREEZING LEVELS LOWER. THIS COULD BE
FAVORABLE FOR SOME HAIL WITH ANY DEEPER THUNDERSTORM CORES,
ESPECIALLY WEST OF I-81 CLOSER TO THE UPPER LOW, THOUGH
WIDESPREAD CLOUD COVER COULD LIMIT THE AMOUNT OF INSTABILITY
NEEDED IN ORDER TO REALIZE A MORE WIDESPREAD SEVERE HAIL THREAT.
WEAKER LOW-LEVEL LAPSE RATES DUE TO THE CLOUDS AND COOLER
SURFACE TEMPERATURES MAY TEMPER A WIND THREAT AS WELL, BUT IF
MORE HEATING IS REALIZED, THEN MORE STRONGER STORMS WOULD BE
POSSIBLE AGAIN SUNDAY AFTERNOON AND EVENING. IN ADDITION, THERE
IS SOME POTENTIAL FOR TRAINING OF HEAVIER SHOWERS AND
THUNDERSTORMS PARTICULARLY EAST OF THE BLUE RIDGE TOWARDS I-95
WHERE IT LOOKS LIKE THE BEST OVERLAP OF LOW-LEVEL CONVERGENCE
AND HIGHER PWATS WILL EXIST. RECENT DROUGHT CONDITIONS SHOULD
TEND TO LIMIT THE OVERALL FLOOD THREAT, BUT ANY HEAVIER RAINFALL
AMOUNTS OVER HYDROPHOBIC BASINS (I.E. URBANIZED AREAS) COULD
RESULT IN SOME LIMITED FLOOD POTENTIAL.
LONG TERM /MONDAY THROUGH THURSDAY/
MODEL GUIDANCE IS IN GOOD AGREEMENT THAT THE LONG TERM PERIOD WILL
START OFF ON MONDAY WITH TWO LARGE UPPER LOWS OCCUPYING THE CONUS,
WITH ONE CENTERED OVER THE ROCKIES, AND THE OTHER CENTERED OVER THE
OHIO VALLEY. THE SUBTROPICAL JET WILL REMAIN WELL OFF TO THE SOUTH
OVER MEXICO, WHILE THE POLAR JET WILL RESIDE WELL OFF TO OUR NORTH
ACROSS CANADA. ANY TIME AN UPPER LOW IS INVOLVED IT'S A LOW
CONFIDENCE LONG RANGE FORECAST, LET ALONE TWO UPPER LOWS. AS A
RESULT, THERE IS A LOT OF SPREAD WITH RESPECT TO HOW THE LARGE SCALE
FLOW PATTERN WILL EVOLVE NEXT WEEK.
DESPITE THE HIGHER THAN NORMAL FORECAST UNCERTAINTY, ENSEMBLES ARE
IN GOOD AGREEMENT THAT THE FIRST UPPER LOW WILL REMAIN OFF TO OUR
WEST OVER THE OHIO VALLEY ON MONDAY. THIS WILL MAINTAIN SOUTH TO
SOUTHEASTERLY LOW-LEVEL FLOW, HELPING TO KEEP DEWPOINTS UP IN THE
LOW 60S. THE COMBINATION OF MOIST LOW LEVELS AND COOLING ALOFT
AS THE UPPER LOW APPROACHES WILL LEAD TO CLOUDY SKIES AND THE
DEVELOPMENT OF SHOWERS AND THUNDERSTORMS LOCALLY. WHILE ENSEMBLE
MEMBERS BEGIN TO DIVERGE BY TUESDAY, MOST STILL FAVOR THE
DEVELOPMENT OF SHOWERS AND THUNDERSTORMS WITH THE UPPER LOW
HANGING NEARBY.
SPREAD IN ENSEMBLE GUIDANCE INCREASES SUBSTANTIALLY BY WEDNESDAY AND
THURSDAY, BUT MOST SOLUTIONS FAVOR A TREND TOWARD DRIER AIR AT LOW
LEVELS AND LESSER CHANCES FOR SHOWERS AND THUNDERSTORMS.
AVIATION /14Z FRIDAY THROUGH TUESDAY/
PREVIOUS DISCUSSION...
VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THIS EVENING.
THERE IS THE POTENTIAL FOR SOME LOWER CIGS TO DEVELOP MAINLY
OVER CENTRAL VA (NEAR KCHO) LATE TONIGHT INTO SATURDAY MORNING
(FL010-020), WITH SPOTTIER/BRIEFER MVFR CIGS POSSIBLE TO THE
NORTH DURING THIS TIME. WINDS WILL BE SW TODAY BECOMING S
TONIGHT; A FEW GUSTS TO NEAR 20 KNOTS ARE POSSIBLE THIS
AFTERNOON. SHOWER AND THUNDERSTORM COVERAGE LOOKS RATHER
ISOLATED TODAY, BUT FELT THE POTENTIAL WAS ENOUGH NOT JUST FOR
THUNDER BUT ALSO POTENTIALLY GUSTY WINDS IN/NEAR CONVECTION TO
MAINTAIN THE INHERITED PROB30S.
SUB-VFR CONDITIONS ARE LIKELY OVER THE WEEKEND AS AN UPPER LOW
APPROACHES FROM THE WEST RESULTING IN BOUTS OF SHOWERS,
THUNDERSTORMS, AND LOWER CEILINGS. WINDS WILL MAINTAIN A
SOUTHERLY HEADING THROUGH THE WEEKEND, WITH SOME MARGINAL LLWS
POSSIBLE AT NIGHT AS SURFACE WINDS DECREASE AND LLJS AROUND 35
KTS PIVOT OVERHEAD.
SUB-VFR CONDITIONS MAY BE POSSIBLE AT TIMES ON BOTH MONDAY AND
TUESDAY IN ASSOCIATION WITH BOTH LOW CEILINGS AND
SHOWERS/THUNDERSTORMS. WINDS WILL GENERALLY BE OUT OF THE SOUTHEAST
ON MONDAY, AND SOUTH TO SOUTHWEST ON TUESDAY.
MARINE
SOUTHWEST FLOW SHOULD KICK UP GUSTS TO AROUND 20 KNOTS
ESPECIALLY OVER THE NEAR SHORE WATERS THIS AFTERNOON. ALTHOUGH
GUSTS MAY TEND TO BE MORE OCCASIONAL AND LOCALIZED AT TIMES,
FELT SCAS WERE PRUDENT GIVEN THE WIND FIELD PRESENT AND THE
POTENTIAL OF SOMEWHAT ABRUPT/VARIABLE CONDITIONS CLOSER TO THE
MORE HEAVILY TRAVELED LAND/WATER INTERFACE THIS AFTERNOON.
HIGHER GUSTS ARE LIKELY TO MAINTAIN THEMSELVES OVER THE WIDER
WATERS OF THE MID BAY TONIGHT, WITH MORE WIDESPREAD SCA
CONDITIONS IN SOUTHERLY FLOW THIS WEEKEND.
AN ISOLATED SHOWER OR THUNDERSTORM IS POSSIBLE THIS AFTERNOON
AND EVENING, BUT MORE WIDESPREAD CONVECTION IS ANTICIPATED OVER
THE WEEKEND.
WINDS MAY NEAR SCA LEVELS WITHIN SOUTHEASTERLY FLOW ON MONDAY. SUB-
SCA SOUTHERLY WINDS ARE EXPECTED ON TUESDAY.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR MDZ008.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ530-
531-535-538-539.
SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ532-
533-536-537-540>542.
SMALL CRAFT ADVISORY UNTIL 6 AM EDT SATURDAY FOR ANZ534-543.
SYNOPSIS...DHOF
NEAR TERM...KLW/DHOF
SHORT TERM...DHOF
LONG TERM...KJP
AVIATION...KLW/DHOF/KJP
MARINE...KLW/DHOF/KJP
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