113
FXUS61 KLWX 161549
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
ISSUED BY NATIONAL WEATHER SERVICE STATE COLLEGE PA
1149 AM EDT WED SEP 16 2026
WHAT HAS CHANGED
THE FORECAST REMAINS ON TRACK SO NO MAJOR ADJUSTMENTS WERE
NECESSARY. THE PRIMARY PERIOD OF UNCERTAINTY CONTINUES TO BE
SUNDAY INTO EARLY NEXT WEEK AS A FRONTAL SYSTEM MEANDERS NEARBY.
THIS IS REFLECTED IN A HIGHLY UNCERTAIN TEMPERATURE FORECAST.
KEY MESSAGES
- 1) TURNING WARMER WITH A RETURN OF SHOWER AND THUNDERSTORM
CHANCES FOR THE SECOND HALF OF THE WORK WEEK.
- 2) UNSETTLED BUT UNCERTAIN PATTERN THIS WEEKEND INTO EARLY
NEXT WEEK.
DISCUSSION
KEY MESSAGE 1...TURNING WARMER WITH A RETURN OF SHOWER AND
THUNDERSTORM CHANCES FOR THE SECOND HALF OF THE WORK WEEK.
TODAY WILL PROVIDE ONE MORE DAY OF DRY WEATHER BEFORE THE
PATTERN TURNS MORE ACTIVE FOR LATTER PORTIONS OF THE WORK WEEK.
CANADIAN HIGH PRESSURE REMAINS OVER THE EASTERN SEABOARD BUT HAS
CONTINUED TO ADVANCE CLOSER TO THE ATLANTIC COASTLINE. GIVEN
THE RIDGE AXIS IS NOT DIRECTLY BISECTING THE LOCAL AREA, SOME
WEAK ONSHORE GRADIENTS HAVE ALLOWED FOR LIGHT WINDS OVERNIGHT.
AS OF 07Z/3 AM, MOST LOCATIONS ARE SITTING IN THE UPPER 50S TO
LOW 60S. THIS DOES COME WITH SOME POCKETS OF MID 60S ACROSS
WASHINGTON, D.C. AND BALTIMORE, AS WELL AS NEAR RIVER/BAY
INFLUENCES ALONG AND EAST OF I-95. SKIES DO REMAIN CLEAR GIVEN
THE PRESENCE OF HIGH PRESSURE. A FEW AREAS OF PATCHY FOG MAY
DEVELOP AHEAD OF DAYBREAK, ESPECIALLY ACROSS MOUNTAIN VALLEYS
AND OTHER LOW-LYING SPOTS.
RELATIVE TO EARLY IN THE WEEK, TEMPERATURES WILL RETURN TO ABOVE
AVERAGE FOR MID-SEPTEMBER. THIS IS IN RESPONSE TO THE BUILDING
OF MID/UPPER HEIGHTS AS SOUTHERN U.S. RIDGING FLEXES NORTHWARD.
AN EXPANSIVE MID-LEVEL 594-DM RIDGE IS FORECAST TO EXTEND FROM
THE SOUTHERN PLAINS AND GULF COAST REGION UP TO THE MID-ATLANTIC
STATES. SOME ENSEMBLE GUIDANCE EVEN SHOW THE DEVELOPMENT OF A
600-DM CONTOUR OVER THE MID-SOUTH. THESE POSITIVE HEIGHT
ANOMALIES WILL RUN AROUND 2 TO 2.5 SIGMA ABOVE CLIMATOLOGY.
ALTHOUGH THERE IS TREMENDOUS WARMING ALOFT, THIS DOES NOT FULLY
REFLECT AT THE SURFACE. WHILE CONDITIONS WILL BE WARM, HIGH
TEMPERATURES SHOULD BE CONFINED TO THE MID/UPPER 80S, WITH A FEW
LOW 90S ACROSS THE ALLEGHENY MOUNTAIN VALLEYS. A SHIFT TO
SOUTHERLY GRADIENTS ALSO AIDS IN INCREASING HUMIDITY, BUT
CERTAINLY NOT OPPRESSIVE BY ANY MEANS. THE FORECAST DOES STAY
DRY WITH SUBSIDENCE ALOFT KEEPING SKIES MOSTLY SUNNY.
CANADIAN HIGH PRESSURE BECOMES CENTERED JUST OFF THE ATLANTIC
COAST TONIGHT. AT THE SAME TIME, AN APPROACHING COLD FRONT IS
EXPECTED TO BRIEFLY STALL OVER THE OHIO VALLEY THROUGH THURSDAY
MORNING/AFTERNOON. TONIGHT WILL YIELD A GRADUAL INCREASE IN
CLOUDS, PARTICULARLY NORTH OF I-66/U.S. 50. THE ADDED CLOUDS AND
CONTINUED SOUTHERLY WINDS CARRIES OVERNIGHT LOWS IN THE LOW/MID
60S. THURSDAY ALSO OFFERS THE NEXT OPPORTUNITY FOR SHOWERS AND
THUNDERSTORMS. THIS LARGELY FOCUSED WEST OF U.S. 15, AND
ESPECIALLY TOWARD THE SHENANDOAH VALLEY AND POINTS WESTWARD.
SOME EROSION OF THIS STRONG UPPER RIDGE WILL ALLOW DIURNAL
HEATING AND TERRAIN CIRCULATIONS TO FIRE OFF SOME SCATTERED
STORMS. AS CONVECTION PRESSES EASTWARD, THE INFLUENCE OF THE
STOUT RIDGE ALOFT SHOULD YIELD A WEAKENING TREND OF SUCH
ACTIVITY. HIGH TEMPERATURES ARE FORECAST TO RETURN TO NEAR 90
DEGREES, WITH THE COOL SPOT BEING IN THE MOUNTAINS WHERE MID 70S
TO LOW 80S WILL BE MORE COMMONPLACE. ABOVE AVERAGE TEMPERATURES
CONTINUE INTO THE NIGHT WITH LOWS IN THE MID 60S TO LOW 70S.
THE MENTIONED COLD FRONT SHOULD TRACK ACROSS THE LOCAL AREA
EARLY FRIDAY AS ANOTHER DOME OF STRONG HIGH PRESSURE APPROACHES
FROM SOUTHERN ONTARIO. POST-FRONTAL NORTHERLY WINDS PICK UP IN
EARNEST WITH AFTERNOON GUSTS TO AROUND 15 TO 20 MPH. IT WILL NOT
BE A COMPLETELY DRY FORECAST AS SHOWERS FORM AROUND THE EASTERN
PERIPHERY OF THE RETREATING UPPER RIDGE. THIS MOSTLY FOCUSES
OVER THE CENTRAL VIRGINIA PIEDMONT BACK TOWARD THE POTOMAC
HIGHLANDS. FRIDAY PRESENTS A COOLING TREND WITH FORECAST HIGHS
IN THE UPPER 70S TO MID 80S. WINDS GRADUALLY TURN MORE
NORTHEASTERLY AS HIGH PRESSURE BUILDS OVER SOUTHERN QUEBEC INTO
INTERIOR NEW ENGLAND. LOWS FALLS BACK INTO THE UPPER 50S TO MID
60S.
KEY MESSAGE 2...UNSETTLED BUT UNCERTAIN PATTERN THIS WEEKEND
INTO EARLY NEXT WEEK.
A HIGH LATITUDE TROUGH DIGGING ACROSS SOUTHEASTERN CANADA SHOULD BE
ENOUGH TO NUDGE THE UPPER RIDGE BACK TOWARD THE SOUTH-CENTRAL U.S.
BY THIS WEEKEND. THIS ALLOWS A COLD FRONT TO PUSH FURTHER
SOUTH INTO NORTH CAROLINA BY SATURDAY WHICH PROVIDES A COOLER
DAY WITH LESS HUMIDITY. HOWEVER, THIS REPRIEVE IS SOMEWHAT
BRIEF AND UNCERTAIN AS ADDITIONAL DISTURBANCES IN THE ATMOSPHERE
TRACK TOWARD THE AREA LATE IN THE WEEKEND, CAUSING THE FRONT TO
WAVER BACK AND FORTH NEAR THE REGION. THE OVERALL JET PATTERN
TURNS A BIT MORE COMPLEX AS AN ARRAY OF FEATURES ENTER THE
PICTURE. A BROAD UPPER LOW RETROGRADES ACROSS THE GULF. AT THE
SAME TIME, A MYRIAD OF SHORTWAVES WILL EJECT ACROSS THE CENTRAL
U.S. TOWARD THE MISSISSIPPI VALLEY. HOW THESE IMPULSES BEHAVE
ALONG WITH WHERE SURFACE FEATURES RESIDE WILL DICTATE ANY LOCAL
WEATHER IMPACTS. HOWEVER, ALL SIGNS POINT TOWARD A MORE ACTIVE
PATTERN BY SUNDAY INTO EARLY NEXT WEEK.
AVIATION /15Z WEDNESDAY THROUGH SUNDAY/
15Z TAF UPDATE FOR DCA, IAD AND BWI FEATURES ONLY VERY MINOR
CHANGES. PREDOMINANTLY VFR CONDS ARE EXPECTED AREAWIDE THROUGH
18Z THURS. EXPECT A LIGHT SOUTHERLY WIND OF 5-10 KTS THIS
AFTERNOON AND GENERALLY LIGHT AND VARIABLE WINDS TONIGHT. A
LIGHT SOUTHERLY BREEZE WILL DEVELOP AGAIN ON THURSDAY.
PREVIOUS DISCUSSION BELOW....
WHILE CANADIAN HIGH PRESSURE HAS SLOWLY MOVED TOWARD THE
ATLANTIC COAST, ITS INFLUENCE WILL HELP MAINTAIN VFR CONDITIONS
INTO THURSDAY MORNING. GRADIENTS REMAIN WEAK WITH LIGHT
SOUTHERLY WINDS EXPECTED. AHEAD OF AN APPROACHING COLD FRONT,
SHOWERS AND THUNDERSTORMS RETURN TO THE FORECAST ON THURSDAY.
THE WESTERN TAF SITES WOULD SEE THE MOST LIKELY IMPACTS, WITH
CONVECTION LIKELY TO WEAKEN FURTHER TO THE EAST. OUTSIDE OF ANY
STORM DEVELOPMENT, VFR CONDITIONS CONTINUE ON THURSDAY WITH
SOUTHERLY WINDS AROUND 5 TO 10 KNOTS. A COLD FRONT MOVES THROUGH
THE REGION EARLY FRIDAY WHICH YIELDS A SHIFT TO NORTHERLY
WINDS. AFTERNOON GUSTS COULD APPROACH 15 TO 20 KNOTS, WITH ANY
STORM CHANCES BACK TOWARD CENTRAL VIRGINIA.
HIGH PRESSURE PASSING TO OUR NORTH SHIFTS WINDS OUT OF THE EAST TO
SOUTHEAST SATURDAY, TURNING SOUTHWESTERLY BY SUNDAY. OVER THE
WEEKEND, GUSTS UP TO 15 TO PERHAPS 20 KNOTS ARE POSSIBLE. IN
GENERAL, EXPECT PREDOMINANTLY VFR CONDITIONS TO PERSIST, BUT
FLIGHT CONDITIONS COULD DETERIORATE AS SHOWER AND THUNDERSTORM
POTENTIAL INCREASE LATE IN THE WEEKEND.
MARINE
EARLIER ELEVATED SOUTHERLY WINDS HAVE WEAKENED WITH MAXIMUM
GUSTS CURRENTLY AROUND 10 TO 15 KNOTS. CANADIAN HIGH PRESSURE
REMAINS NEARBY INTO TONIGHT WHICH WILL FAVOR TRANQUIL WEATHER
OVER THE WATERWAYS.
BY THURSDAY, THIS RIDGE EDGES OFFSHORE AHEAD OF THE NEXT COLD
FRONT. AHEAD OF THIS SYSTEM, SOUTHERLY WINDS INCREASE WHICH
COULD NEAR SMALL CRAFT ADVISORY LEVELS ON THURSDAY
AFTERNOON/EVENING. THIS IS PARTICULARLY THE CASE OVER WIDER
WATERS OF THE CHESAPEAKE BAY DUE TO SOUTHERLY CHANNELING. THE
COLD FRONT CROSSES THE WATERS EARLY FRIDAY WHICH SHIFTS WINDS
OVER TO NORTHERLY. BREEZY CONDITIONS IN THE WAKE COULD AGAIN
NEAR ADVISORY LEVELS. AS HIGH PRESSURE TRACKS ACROSS SOUTHERN
QUEBEC, MARINE WINDS TURN NORTHEASTERLY INTO FRIDAY NIGHT WITH
GUSTS AROUND 10 TO 15 KNOTS.
HIGH PRESSURE PASSING TO OUR NORTH SHIFTS WINDS OUT OF THE EAST TO
SOUTHEAST SATURDAY, TURNING SOUTHWESTERLY ON SUNDAY. OVER THE
WEEKEND, GUSTS UP TO 15 TO PERHAPS 20 KNOTS ARE POSSIBLE.
TIDES/COASTAL FLOODING
AS WINDS HAVE TURNED MORE SOUTH TO SOUTHEASTERLY, THE ONSHORE
FLOW HAS RAISED TIDAL ANOMALIES TO JUST BELOW 1 FOOT. THIS HAS
BEEN ENOUGH TO PUSH A FEW OF THE MORE SENSITIVE LOCATIONS INTO
THE ACTION STAGE. UNTIL THE COLD FRONT MOVES THROUGH EARLY
FRIDAY, WATER LEVELS WILL REMAIN SOMEWHAT ELEVATED. ALTHOUGH NO
TIDAL SITE IS SHOWN TO EXPERIENCE ANY COASTAL FLOODING, IT WILL
NEED TO BE MONITORED. THIS IS PARTICULARLY THE CASE AT
ANNAPOLIS, ESPECIALLY DURING THE HIGHER OF THE TWO ASTRONOMICAL
HIGH TIDES.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.
DISCUSSION...BRO/KVH
AVIATION...BRO/KVH/CTP
MARINE...BRO/KVH
TIDES/COASTAL FLOODING...BRO
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