929
FXUS61 KLWX 180121
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
921 PM EDT WED AUG 17 2022
SYNOPSIS
AN UPPER LEVEL LOW WILL REMAIN OFF TO THE NORTH BRINGING COOLER
WEATHER AND CONTINUED CHANCES FOR PRECIPITATION THROUGH EARLY
THURSDAY. HIGH PRESSURE WILL BUILD OVER THE REGION THURSDAY
THROUGH THE EARLY PARTS OF THIS WEEKEND. A SURFACE LOW IS
EXPECTED TO FORM ALONG A STALLED BOUNDARY OVER SE US AND PASS
OFF TO SOUTH OF THE REGION THIS WEEKEND. A STRONGER COLD FRONT
WILL IMPACT THE REGION BY EARLY NEXT WEEK BRINGING THE NEXT
CHANCE FOR STRONG THUNDERSTORMS.
NEAR TERM /UNTIL 9 AM THURSDAY MORNING/
9:15 PM UPDATE: SHOWERS AND THUNDERSTORMS ARE CONTINUING TO
DIMINISH ACROSS THE AREA FROM NORTH TO SOUTH. A FEW SHOWERS AND
RUMBLES OF THUNDER REMAIN NEAR THE NORTHERN NECK AND LOWER TIDAL
POTOMAC RIVER. THESE WILL CONTINUE TO DISSIPATE OVER THE NEXT
HOUR OR SO. BEHIND THESE SHOWERS, CLEARING SKIES AND CALM
CONDITIONS EXPECTED FOR THE REMAINDER OF THE OVERNIGHT HOURS.
THE UPPER LOW WILL CONTINUE TO MOVE FURTHER NORTH ACROSS THE
NORTHEAST AND EVEN INTO THE PROVINCES OF CANADA LATER TONIGHT.
PREVIOUS DISCUSSION FOLLOWS:
CLOUDS WILL START BREAKING UP OVERNIGHT WITH WINDS SLOWLY BECOMING
LIGHT AND VARIABLE. THE COMBINATION OF LIGHT WINDS AND CLEAR SKIES
MAY LEAD TO SOME ISOLATED INSTANCES OF DENSE FOG FOR AREAS WEST
OF THE BLUE RIDGE MTNS. MODEL GUIDANCE HAS WIDESPREAD DENSE FOG
IN AREAS IN THE SHENADOAH VALLEYS AND WESTWARD WHICH SUGGESTS
THAT DENSE FOG MAY BE POSSIBLE OVERNIGHT BUT CONFIDENCE REMAINS
LOW. OVERNIGHT LOWS WILL BE COOL IN THE MID TO UPPER 50S TO
LOWER 60S.
SHORT TERM /9 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/
THE UPPER LEVEL LOW WILL LIFT NORTHEASTWARD, AWAY FROM OUR
REGION ON THURSDAY AS WEAK RIDGING BUILDS IN FROM THE WEST. A
WARMING TREND THAT WILL CONTINUE INTO THIS WEEKEND WILL BEGIN ON
THURSDAY. RISING HEIGHTS ALONG WITH INCREASING SOUTHERLY
ADVECTION WILL LEAD TO TEMPERATURES TRENDING UP INTO THE MID 80S
ON THURSDAY AND INTO THE UPPER 80S BY FRIDAY. MAINLY DRY
CONDITIONS ARE EXPECTED FOR MOST OF THE REGION ON THURSDAY BUT
AN ISOLATED SHOWER COULD FORM ALONG THE ALLEGHENY FRONT DUE TO
LOCAL TERRAIN CIRCULATIONS AND CONVERGENCE.
HIGH PRESSURE IS FORECAST TO BUILD OVER OUR REGION LATE THURSDAY AND
REMAIN IN PLACE THROUGH FRIDAY. DRY AND NEAR AVERAGE CONDITIONS
SHOULD CONTINUE ON FRIDAY BUT THE NEXT CHANCE FOR WIDESPREAD SHOWERS
WILL COME LATE FRIDAY INTO SATURDAY. A COASTAL LOW IS FORECAST TO
FORM IN SOUTHERN STREAM ENERGY OVER SE US AND LIFT NORTHEASTWARD
THROUGH THE SOUTHERN MID-ATLANTIC LATE FRIDAY INTO SATURDAY.
DEPENDING ON THE TRACK OF THIS SURFACE LOW, OUR REGION COULD
EXPERIENCE SOME PRECIPITATION OVER THE SOUTHERN HALF OF OUR
REGION EARLY ON SATURDAY. THERE REMAINS A LOT OF UNCERTAINTY ON
THE TIMING AND POSITIONING OF THE SURFACE LOW AND HOW FAR NORTH
PRECIPITATION WILL REACH EARLY THIS WEEKEND.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
A BROAD TROUGH IS LOCATED OVER THE GREAT PLAINS AND WILL BEGIN TO
SLOWLY MOVE EASTWARD THROUGH THE LONG TERM PERIOD. AN UPPER LEVEL
LOW WILL DEVELOP OVER THE GREAT LAKES ON SUNDAY. THROUGHOUT THE LONG
TERM PERIOD, WE WILL REMAIN IN THE EASTERN PORTION OF THE TROUGH
BRINGING SOUTHERNLY FLOW AND INSTABILITY. TEMPERATURES WILL BE
SEASONABLE WITH HIGHS IN THE 80S AND LOWS IN THE 60S TO 70S.
A SHORTWAVE WILL MOVE NORTHEAST OVER THE MID-ATLANTIC REGION
SATURDAY MORNING. THERE WILL BE PLENTY OF MOISTURE IN THE ATMOSPHERE
WITH PRECIPITABLE WATER VALUES NEARING 2 INCHES. SHOWERS AND
POSSIBLY A FEW THUNDERSTORMS ARE FORECASTED. SOME MODELS HAVE
INCREASED PRECIPITATION TOTALS WHICH COULD LEAD TO HYDRO ISSUES.
AFTER THE PASSING OF THE SHORTWAVE, THERE WILL BE TIME FOR DIURNAL
DRIVEN SHOWERS AND THUNDERSTORMS SATURDAY AFTERNOON.
THE UPPER LEVEL LOW CENTERED OVER THE GREAT LAKES WILL BEGIN
TRACKING EASTWARD SUNDAY AND INTO NEXT WEEK. A FEW SHOWERS AND A
POSSIBLE THUNDERSTORM CANNOT BE RULED OUT DUE TO DIURNAL HEATING,
BUT THE CHANCE FOR HAZARDOUS WEATHER IS DECREASED COMPARED TO
SATURDAY AND THE REST OF THE LONG TERM PERIOD.
GOING INTO THE WORK WEEK, CHANCES FOR HAZARDOUS WEATHER INCREASE ON
MONDAY. AS THE AFOREMENTIONED TROUGH MOVES CLOSER TO THE AREA,
INSTABILITY, MOISTURE, AND FLOW ALOFT WILL INCREASE. SOUTHERLY FLOW
WILL PROVIDE PLENTY OF MOISTURE WITH PRECIPITABLE WATER VALUED
GREATER THAN 2 INCHES. OF THE LONG TERM PERIOD, MONDAY HAS THE
GREATEST THREAT FOR HAZARDOUS WEATHER INCLUDING STRONG THUNDERSTORMS
AND ISOLATED FLOODING. THERE IS A CHANCE OF DIURNALLY DRIVEN SHOWERS
AND THUNDERSTORMS ON TUESDAY, BUT THERE IS STILL UNCERTAINTY ABOUT
THE DETAILS GIVEN HOW FAR OUT IT IS.
AVIATION /01Z THURSDAY THROUGH MONDAY/
VFR CONDITIONS ARE EXPECTED FOR THE TERMINALS TONIGHT WITH LIGHT
WINDS. LIGHT WINDS AND CLEAR SKIES MAY LEAD TO SOME ISOLATED
INSTANCES OF DENSE FOG, MAINLY AFFECTING THE MRB AND CHO
TERMINALS. MVFR TO IFR VISIBILITIES WILL BE POSSIBLE AT MRB
BETWEEN 6Z AND 13Z TOMORROW. WINDS ARE EXPECTED TO BEGIN OUT OF
THE WEST TO NORTHWEST THIS AFTERNOON AND THEN SLOWLY BECOME MORE
SOUTHWESTERLY BY THURSDAY AFTERNOON. PATCHY DENSE FOG WILL BE
POSSIBLE AGAIN THURSDAY EVENING WITH MRB MAINLY AT RISK FOR
OVERNIGHT RESTRICTIONS. VFR CONDITIONS AND LIGHT WINDS ARE
EXPECTED FOR FRIDAY.
SUB-VFR CONDITIONS MAY BE POSSIBLE SATURDAY MORNING WITH THE
POSSIBILITY OF SHOWERS AND STORMS. VFR CONDITIONS ARE EXPECTED
SATURDAY AFTERNOON AND SUNDAY, BUT AFTERNOON SHOWERS AND STORMS ARE
POSSIBLE.
MARINE
SUBSCA CONDITIONS EXPECTED THROUGH THURSDAY. SMALL CRAFT
ADVISORIES MAYBE NEEDED ON FRIDAY DUE TO A WEAK CHANNELING FLOW.
WINDS WILL LIKELY STAY BELOW SCA LEVELS SATURDAY AND SUNDAY WITH THE
EXCEPTION BEING DURING STORMS. IN THE EVENT OF A LOCALIZED STORM,
INCREASED WINDS ARE POSSIBLE. THUNDERSTORMS ARE POSSIBLE SATURDAY
MORNING WITH POTENTIAL FOR GUSTY WINDS.
TIDES/COASTAL FLOODING
COASTAL FLOODING IS ONGOING OR EXPECTED FOR A FEW AREAS
(ANNAPOLIS, ST. MARYS, DC SW WATERFRONT), YIELDING COASTAL FLOOD
ADVISORIES TO BE HOISTED. ST. MARYS LOCATION HAS REACHED MINOR
FLOOD STAGE AS OF 8 PM WITH THE EXPECTATION OF THE OTHER TWO
SENSITIVE LOCATIONS TO HIT MINOR FLOOD STAGE TONIGHT AND INTO
THE OVERNIGHT HOURS. ANOMALIES ARE COMING DOWN A BIT WHICH MAY
KEEP DC SW WATERFRONT FROM TOUCHING MINOR BUT WE WILL CONTINUE
TO MONITOR THE TRENDS OVER THE NEXT SEVERAL HOURS. AFTER
TONIGHT, ANOMALIES CONTINUE TO COME DOWN AND ALLEVIATE TIDAL
FLOODING CONCERNS FOR THE FORESEEABLE FUTURE.
LWX WATCHES/WARNINGS/ADVISORIES
DC...COASTAL FLOOD ADVISORY UNTIL 3 AM EDT THURSDAY FOR DCZ001.
MD...COASTAL FLOOD ADVISORY UNTIL 2 AM EDT THURSDAY FOR MDZ014.
COASTAL FLOOD ADVISORY UNTIL 10 PM EDT THIS EVENING FOR MDZ017.
VA...NONE.
WV...NONE.
MARINE...NONE.
SYNOPSIS...JMG/ADM
NEAR TERM...JMG/ADM
SHORT TERM...JMG
LONG TERM...AVS
AVIATION...AVS/JMG/ADM
MARINE...AVS/JMG/ADM
TIDES/COASTAL FLOODING...ADM
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