098
FXUS61 KLWX 291943
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
343 PM EDT MON JUN 29 2026
WHAT HAS CHANGED
HEAT ADVISORIES HAVE BEEN ISSUED FOR TUESDAY FOR THE UPPER
POTOMAC RIVER VALLEY. SMALL CRAFT ADVISORIES HAVE BEEN ISSUED
FOR TUESDAY AFTERNOON AND NIGHT. HELD OFF ON EXTREME HEAT
WATCHES FOR NOW GIVEN WEDNESDAY LOOKS TO BE MORE IN THE ADVISORY
REALM, WITH HIGHER POTENTIAL FOR WARNING-LEVEL BEYOND 72 HOURS.
KEY MESSAGES
- (1) SIGNIFICANT HEAT WAVE BUILDS THROUGH THE WEEK.
- (2) POTENTIAL FOR SEVERE THUNDERSTORMS INCREASES LATE THIS
WEEK THROUGH THE WEEKEND.
DISCUSSION
KEY MESSAGE 1...SIGNIFICANT HEAT WAVE BUILDS THROUGH THE WEEK.
INCREASING SUBSIDENCE IN THE WAKE OF AN EARLIER FRONTAL PASSAGE
HAS KEPT ANY SHOWER AND THUNDERSTORM ACTIVITY TO A MINIMUM AS OF
19Z/3PM EDT. WITH A BIT MORE HEATING, THAT MAY BE ENOUGH TO GET
A FEW WIDELY SCATTERED SHOWERS OR A BRIEF THUNDERSTORM OR TWO
MAINLY WEST OF US-15 (FOCUSED TOWARD THE HIGHER TERRAIN WHERE
ADDED OROGRAPHIC LIFT IS PRESENT).
DRY WEATHER AND CLEARING SKIES WITH LIGHT SOUTHEAST WINDS ARE
EXPECTED OVERNIGHT. LINGERING LOW-LEVEL MOISTURE COULD LEAD TO
AREAS OF FOG SOUTHWEST OF THE POTOMAC RIVER WHERE LOW-LEVEL
MOISTURE IS EXPECTED TO BE MOST ROBUST. LOW TEMPERATURES WILL
DROP INTO THE 60S FOR MOST OF THE REGION.
TUESDAY...
A STRONG RIDGE ALOFT BEGINS TO BUILD IN EARNEST ON TUESDAY,
CENTERED OVER THE OHIO RIVER VALLEY. AT THE SURFACE, HIGH
PRESSURE SETTLES OVER THE EAST COAST. THIS MARKS THE START OF
WHAT MAY TURN OUT TO BE THE MOST SIGNIFICANT HEAT WAVE IN OVER A
DECADE FOR MUCH OF THE REGION (THINKING ABOUT THE HEAT IN 2012).
THE BUILDING RIDGE AND CORRESPONDING LOW-LEVEL THERMALS SUPPORT
HIGH TEMPERATURES IN THE LOWER 90S. HIGHER LOW-LEVEL MOISTURE IS
EXPECTED TO BEGIN ADVECTING IN FROM THE WEST, AND SHOULD REACH
THE UPPER POTOMAC RIVER VALLEY (EASTERN WV, WESTERN MD) BY PEAK
HEATING WITH DEW POINTS INTO THE LOWER 70S POOLED IN THE VALLEYS.
THIS SUPPORTS HEAT INDEX VALUES AROUND 100 FOR A FEW HOURS. HAVE
ISSUED A HEAT ADVISORY FOR THIS REASON.
FURTHER EAST, DRY AIR JUST ABOVE THE SURFACE COUPLED WITH
ONSHORE FLOW OFF RELATIVELY COOLER WATER IS EXPECTED TO KEEP
HIGH TEMPERATURES A DEGREE OR TWO LOWER WITH DEW POINTS DROPPING
DOWN INTO THE LOWER TO MIDDLE 60S. LOWER HEAT INDICES ARE
FORECAST AS A RESULT, AND THEREFORE THERE ARE NO HEADLINES ALONG
OR EAST OF I-81 AT THE MOMENT FOR TUESDAY. SHOULD HEATING OR
MOISTURE (OR BOTH) TREND UPWARDS MORE QUICKLY, THIS MAY HAVE TO
BE RE-EVALUATED. LOW TEMPERATURES TUESDAY NIGHT WILL ONLY DROP
INTO THE UPPER 60S TO LOWER 70S AS HUMIDITY INCREASES AREAWIDE.
WEDNESDAY...
HEIGHTS AND TEMPERATURES INCREASE FURTHER ON WEDNESDAY, THOUGH
HEIGHT RISES SLOW A BIT LATE IN THE DAY INTO THE EVENING
ESPECIALLY IN THE VICINITY OF NORTHEAST MD FARTHEST AWAY FROM
THE CENTER OF THE RIDGE. SLP PATTERNS SHOW A SHARPENING LEE
PRESSURE TROUGH EAST OF THE APPALACHIANS ALONG MUCH OF THE EAST
COAST (ROUGHLY NEAR THE BLUE RIDGE MOUNTAINS LOCALLY). THE SETUP
SEEMS FAVORABLE WEDNESDAY AFTERNOON FOR THE SURFACE TROUGH AND
BAY BREEZE TO INTERACT, WHICH COULD SPARK A THUNDERSTORM OR TWO
MAINLY NORTHEAST OF THE POTOMAC (FARTHEST FROM THE RIDGE).
SHOULD ANYTHING DEVELOP, IT COULD BE QUITE STRONG GIVEN HIGH
LEVELS OF INSTABILITY. BUT, MOST WILL BE DRY.
VERY HIGH INSTABILITY ON WEDNESDAY IS DUE IN LARGE PART TO HIGH
LOW-LEVEL MOISTURE CONTENT. DEW POINTS/HUMIDITY MAY PEAK ON
WEDNESDAY, ALTHOUGH AIR TEMPERATURES PROBABLY DON'T PEAK UNTIL
THURSDAY-FRIDAY. THE COMBINATION OF MID TO UPPER 90S AIR TEMPS
AND LOW 70S DEW POINTS RESULTS IN SOLID HEAT ADVISORY CRITERIA
AREAWIDE. FOR THIS REASON, NO EXTREME HEAT WATCH (WHICH IS A
PRECURSOR TO AN ANTICIPATED WARNING-LEVEL EVENT) HAS BEEN
ISSUED. IF TRENDS IN EITHER LOW-LEVEL MOISTURE OR TEMPS (OR
BOTH) COME TO FRUITION, THIS MAY NEED TO BE RECONSIDERED
TONIGHT. EITHER WAY, IT WILL BE QUITE HOT.
THURSDAY THROUGH SATURDAY...
THE HEAT PEAKS LATE THIS WEEK INTO THE INDEPENDENCE DAY HOLIDAY.
TRENDS HAVE BEEN FOR A SLOWER BREAKDOWN OF THE RIDGE, WHICH
PUSHES THE HIGHEST THUNDERSTORM CHANCES INTO THE WEEKEND.
BARRING WIDESPREAD CONVECTION EARLIER FRIDAY AFTERNOON, AIR
TEMPS COULD BE SIMILAR TO THURSDAY. DEW POINTS WILL BE A BIT
LESS ON THURSDAY AS SLIGHTLY DRIER AIR ALOFT WORKS IN, BUT MAY
REBOUND A BIT FRIDAY. BOTH DAYS MAY SEE WIDESPREAD HEAT INDICES
WELL OVER 100, APPROACHING OR EXCEEDING 110 FOR THE I-95
CORRIDOR, NEAR THE CHESAPEAKE BAY, AND INTO THE CENTRAL VIRGINIA
PIEDMONT. WATCHES WOULD BE ISSUED FOR THIS ONCE IT IS WITHIN
THE 60-72 HOUR LEAD TIME WINDOW AS CONFIDENCE INCREASES FROM
POSSIBLE TO PROBABLE.
THE CHANCE OF THUNDERSTORMS INCREASES SATURDAY AS THE RIDGE
BEGINS TO BUCKLE. THIS ALL POINTS TOWARD TEMPS A COUPLE DEGREES
LOWER BUT WITH A POTENTIAL UPTICK IN HUMIDITY, RESULTING IN HEAT
INDEX VALUES THAT MAY ULTIMATELY BE SIMILAR TO THURSDAY AND
FRIDAY. IT WILL ALSO BE THE FOURTH DAY IN A ROW OF NEAR OR ABOVE
100 DEGREE TEMPS, OVERLAPPING A HOLIDAY, WHICH COULD BE VERY
IMPACTFUL. BEGIN PREPARING NOW FOR THE HEAT. VISIT THE WEBSITE
WEATHER.GOV/SAFETY/HEAT FOR PREPAREDNESS INFORMATION. REFER TO
THE CLIMATE SECTION BELOW FOR HEAT RECORDS.
KEY MESSAGE 2...POTENTIAL FOR SEVERE THUNDERSTORMS INCREASES
LATE THIS WEEK THROUGH THE WEEKEND.
WITH THE INCREASE IN NEAR RECORD HEAT AND HUMIDITY COMES
ABUNDANT INSTABILITY. AFTER BUILDING UNTAPPED FOR SEVERAL DAYS,
CONVECTION MAY ERUPT LATE IN THE WEEK AS THE RIDGE BEGINS TO
SHIFT AND BREAK DOWN. THIS BEGINS TO HAPPEN IN A SUBTLE
(TRENDING SLOWER) SENSE FRIDAY, BUT REALLY GETS GOING THIS
WEEKEND. AT THE VERY LEAST, SCATTERED STRONG TO SEVERE
THUNDERSTORMS WITH FREQUENT LIGHTNING, DAMAGING WIND GUSTS,
HEAVY DOWNPOURS, AND PERHAPS HAIL SEEM PLAUSIBLE. THIS WOULD
PROBABLY BE CENTERED ON THE AFTERNOON AND EVENING HOURS WHEN
HEAT AND INSTABILITY ARE RELATIVELY HIGHER. SHEAR LOOKS QUITE
LOW, BUT IF ANY SUBTLE WAVES APPROACH THE REGION FROM THE WEST
AND NORTHWEST BETWEEN THE RIDGE TO THE SOUTH AND THE JET STREAM
TO THE NORTH, THIS COULD INCREASE SHEAR AND CONSOLIDATE STORMS
INTO MORE WIDESPREAD CLUSTERS.
PLAN AHEAD FOR ANY OUTDOOR ACTIVITIES THIS WEEKEND, AS THEY ARE
LIKELY TO BE INTERRUPTED BY STORMS AT SOME POINT. GIVEN THE HEAT
IN PLACE, SOME STORMS COULD BE QUITE INTENSE (IF THEY FORM).
FROM A HISTORICAL PERSPECTIVE, PROLONGED NEAR RECORD HEAT IN
SUMMER OFTEN ENDS IN A PERIOD OF STRONG STORMS.
AVIATION /18Z MONDAY THROUGH SATURDAY/
VFR CONDITIONS ARE FORECAST TO PERSIST THROUGH WEDNESDAY.
HOWEVER, SOME FOG MAY FORM ESPECIALLY NEAR MRB/CHO LATER TONIGHT
INTO TUESDAY MORNING. WINDS WILL BE LIGHT OUT OF THE SOUTHEAST
BEFORE TURNING OUT OF THE SOUTH LATER THIS EVENING. WINDS ARE
EXPECTED TO REMAIN OUT OF THE SOUTH ON TUESDAY, BEFORE BECOMING
SOUTHWESTERLY ON WEDNESDAY. AFTERNOON BAY BREEZES MAY CAUSE MORE
E/SE FLOW AT MTN AND POSSIBLY BWI. DRY WEATHER IS EXPECTED
THROUGH MID WEEK, THOUGH A POP UP T-STORM CAN'T BE RULED OUT
NEAR ANY BAY BREEZES (ESPECIALLY WEDNESDAY).
PREVAILING VFR CONDITIONS ARE EXPECTED THURSDAY THROUGH FRIDAY
MORNING. BEGINNING FRIDAY AFTERNOON AND EVENING, THUNDERSTORM
CHANCES INCREASE. SHOULD THUNDERSTORMS MATERIALIZE, SOME COULD
BECOME SEVERE. INTERMITTENT SUB-VFR CONDITIONS ARE POSSIBLE
FRIDAY INTO THE WEEKEND AS A RESULT, AS WELL AS CHANGES IN WIND
SPEED AND DIRECTION.
MARINE
WINDS TURN SOUTHERLY THIS EVENING, AND COULD BRIEFLY NEAR LOW-
END SCA FOR A FEW HOURS AS THEY DO SO. BRIEF/MARGINAL NATURE OF
THIS THREAT WOULD BE COVERED WITH A MARINE WEATHER STATEMENT
VERSUS A SMALL CRAFT ADVISORY (SCA). WINDS REMAIN SOUTHERLY FOR
TUESDAY AND WEDNESDAY, WITH SCAS IN EFFECT TUESDAY AFTERNOON
AND NIGHT. ADDITIONAL SCAS MAY BE NEEDED WEDNESDAY.
WINDS LIKELY STAY BELOW SCA THRESHOLDS THURSDAY AND THROUGH THE
WEEKEND. THUNDERSTORM CHANCES OVER THE WATERS INCREASE FRIDAY
INTO THE WEEKEND, WHICH COULD BECOME SEVERE. SHOULD THESE
CONDITIONS MATERIALIZE, SPECIAL MARINE WARNINGS COULD BECOME
NECESSARY. WINDS GENERALLY FLOW SOUTH TO SOUTHWESTERLY.
CLIMATE
THERE IS A SIGNIFICANT HEAT RISK THIS WEEK. THE NUMBERS BELOW
AREN'T A FORECAST, BUT RATHER A REFERENCE FOR HISTORICAL CONTEXT
FOR COMPARISON. LATEST FORECAST: WEATHER.GOV/LWX.
==================================================================
*** ALL-TIME RECORD HIGHS ***
==================================================================
BALTIMORE 107 (SET ON JUL 10, 1936)
WASHINGTON 106 (SET ON JUL 20, 1930 + AUG 06, 1918)
STERLING-DULLES AIRPORT 105 (SET ON JUL 22, 2011)
BALTIMORE DOWNTOWN 108 (SET ON JUL 07, 2012 + JUL 22, 2011)
ANNAPOLIS 106 (SET ON AUG 06, 1918)
HAGERSTOWN 105 (SET ON JUL 14, 1954)
MARTINSBURG 112 (SET ON JUL 11, 1936)
CHARLOTTESVILLE 107 (SET ON SEP 07, 1954 + 3 OTHER TIMES)
==================================================================
*** ALL-TIME RECORD WARM LOWS ***
==================================================================
BALTIMORE 83 (SET ON AUG 05, 1930 + 2 OTHER TIMES)
WASHINGTON 84 (SET ON JUL 24, 2011 + 2 OTHER TIMES)
STERLING-DULLES AIRPORT 79 (SET ON AUG 08, 2007)
BALTIMORE DOWNTOWN 88 (SET ON JUL 02, 2011 AND JUL 10, 1993)
ANNAPOLIS 92 (SET ON JUL 07, 1994)
HAGERSTOWN 86 (SET ON JUN 15, 1899)
MARTINSBURG 86 (SET ON JUL 21, 1930)
CHARLOTTESVILLE 85 (SET ON AUG 07, 1918)
==================================================================
*** JULY MONTHLY RECORD HIGHS ***
==================================================================
BALTIMORE 107 (SET ON JUL 10, 1936)
WASHINGTON 106 (SET ON JUL 20, 1930)
STERLING-DULLES AIRPORT 105 (SET ON JUL 22, 2011)
BALTIMORE DOWNTOWN 108 (SET ON JUL 07, 2012 + JUL 22, 2011)
ANNAPOLIS 105 (SET ON JUL 21, 1930 + JUL 02, 1901)
HAGERSTOWN 105 (SET ON JUL 14, 1954)
MARTINSBURG 112 (SET ON JUL 11, 1936)
CHARLOTTESVILLE 107 (SET ON JUL 10, 1936 + JUL 20, 1930)
==================================================================
*** JULY MONTHLY RECORD WARM LOWS ***
==================================================================
BALTIMORE 83 (SET ON JUL 21, 1930)
WASHINGTON 84 (SET ON JUL 24, 2011 + 2 OTHER TIMES)
STERLING-DULLES AIRPORT 78 (SET ON JUL 24, 2010 + JUL 08, 2010)
BALTIMORE DOWNTOWN 88 (SET ON JUL 22, 2011 + JUL 10, 1993)
ANNAPOLIS 92 (SET ON JUL 07, 1994)
HAGERSTOWN 83 (SET ON JUL 24, 2010)
MARTINSBURG 86 (SET ON JUL 21, 1930)
CHARLOTTESVILLE 84 (SET ON JUL 22, 1930)
==================================================================
*** DAILY RECORD HIGHS | WARM LOWS ***
VALID: JUL 01
==================================================================
BALTIMORE 103 (1901) | 80 (1933 + 1901)
WASHINGTON 102 (1901) | 79 (1977)
STERLING-DULLES AIRPORT 96 (2012) | 72 (2017 + 3)
BALTIMORE DOWNTOWN 101 (2012) | 82 (2012)
ANNAPOLIS 103 (1901) | 79 (1945 + 1901)
HAGERSTOWN 100 (1901) | 74 (2017 + 1977)
MARTINSBURG 102 (1933) | 74 (1933)
CHARLOTTESVILLE 101 (2012 + 1945) | 78 (1901)
==================================================================
*** DAILY RECORD HIGHS | WARM LOWS ***
VALID: JUL 02
==================================================================
BALTIMORE 103 (1901) | 80 (1901)
WASHINGTON 101 (1898) | 79 (2012 + 1872)
STERLING-DULLES AIRPORT 98 (1966) | 75 (2022)
BALTIMORE DOWNTOWN 102 (1966) | 84 (2002)
ANNAPOLIS 105 (1901) | 80 (1901)
HAGERSTOWN 100 (1966) | 74 (2018 + 1901)
MARTINSBURG 102 (1933 + 1931) | 75 (1933 + 1901)
CHARLOTTESVILLE 100 (1954) | 76 (1910)
==================================================================
*** DAILY RECORD HIGHS | WARM LOWS ***
VALID: JUL 03
==================================================================
BALTIMORE 104 (1898) | 80 (1898)
WASHINGTON 101 (1966 + 2) | 80 (2018)
STERLING-DULLES AIRPORT 103 (1966) | 73 (2018 + 2)
BALTIMORE DOWNTOWN 102 (1997) | 82 (2018 + 1983)
ANNAPOLIS 100 (1901) | 84 (1896)
HAGERSTOWN 102 (1966) | 76 (2002)
MARTINSBURG 102 (1941 + 1911) | 74 (1980)
CHARLOTTESVILLE 100 (1966 + 1954) | 79 (1911)
PERIOD OF RECORD (POR) CONTEXT...
AREA (OBS SITE) RECORDS SINCE
------------------------------------------------------------------
BALTIMORE (BWI) JAN 1872
WASHINGTON (DCA) JUL 1872
STERLING-DULLES AIRPORT (IAD) JAN 1960
BALTIMORE DOWNTOWN (DMH) JUL 1950
ANNAPOLIS (NAK) JAN 1894
HAGERSTOWN (HGR) JAN 1899
MARTINSBURG (MRB) JAN 1891
CHARLOTTESVILLE (CHO) JAN 1893
TIDES/COASTAL FLOODING
INCREASING SOUTHERLY FLOW COULD CAUSE NEAR MINOR FLOODING
PARTICULARLY AT ANNAPOLIS AND POSSIBLY HAVRE DE GRACE, BOWLEY'S
QUARTERS AND ALEXANDRIA LATE TONIGHT INTO TUESDAY.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...HEAT ADVISORY FROM 11 AM TO 8 PM EDT TUESDAY FOR MDZ502.
VA...NONE.
WV...HEAT ADVISORY FROM 11 AM TO 8 PM EDT TUESDAY FOR WVZ050-055-
502-504-506.
MARINE...SMALL CRAFT ADVISORY FROM 5 PM TUESDAY TO 6 AM EDT WEDNESDAY
FOR ANZ530-534-539>541-543.AND SATURDAY
SMALL CRAFT ADVISORY FROM 2 PM TUESDAY TO 6 AM EDT WEDNESDAY
FOR ANZ531>533.
SMALL CRAFT ADVISORY FROM 5 PM TUESDAY TO 1 AM EDT WEDNESDAY
FOR ANZ535-538.
SMALL CRAFT ADVISORY FROM 2 PM TUESDAY TO 1 AM EDT WEDNESDAY
FOR ANZ536-537-542.
DISCUSSION...DHOF/KJP/SRT
AVIATION...DHOF/KJP/SRT
MARINE...DHOF/KJP/SRT
CLIMATE...DHOF
TIDES/COASTAL FLOODING...DHOF/BRO
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