Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
526 FXUS61 KLWX 141404 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1004 AM EDT Sun Jul 14 2024 .SYNOPSIS... High pressure will continue to build across the southeast today into the middle portion of the workweek, leading to a return of hot and humid conditions locally. A cold front arrives Wednesday into Wednesday night, leading to potentially unsettled weather. High pressure returns by late week into the weekend. && .NEAR TERM /THROUGH TONIGHT/... An area of upper ridging will continue to influence the region today. Did increase MaxTs for today a degree or two given latest obs and trends in 12Z guidance. Bermuda high pressure off to the east will allow Td`s to stay in the upper 60s to low 70s for today. This should keep heat headlines away for today in this area, with some places east of the Blue Ridge Mountains getting closer to the threshold, with mid to upper 90s expected. Cannot completely rule out an area further east reaching/exceeding criteria for an hour or two but confidence is low at this time especially given the potential for showers/thunderstorms to initiate by 16/17Z and produce cooling (relatively speaking) outflows. Additionally, a few isolated to scattered showers and thunderstorms will be possible with the return of heat and humidity across the area later today. Most of the area should stay mostly dry throughout the day but if a storm gets going, weak flow aloft may keep it going for a while and bring some appreciable rainfall to the outlooked area in a drought. Lows will fall back into the upper 60s out west to low to mid 70s further east towards the waters tonight with mostly dry conditions expected. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... No major changes to the short term. Maintained the Excessive Heat Watch for Monday and issued a new watch for the same areas plus the lower elevations of the northern Alleghenies on Tuesday. Otherwise, previous discussion follows... For the start of the workweek, the Bermuda high will likely begin to break down and allow for increased moisture and humidity locally. Heat indices will be approaching at least Heat Advisory criteria, if not Excessive Heat Warning criteria. Highs right around 100 degrees will be possible for many areas, especially along and east of the Blue Ridge on Monday, with heat indices reaching 105 to 110 F where the Excessive Heat Watch resides. Shower and thunderstorm chances return for the afternoon and evening hours on Monday. There is some uncertainty with storm severity that day as a result of decaying MCS dropping down from the Great Lakes will play an important role in the potential for any severe thunderstorms Monday afternoon. It will be worth monitoring this trend over the next day or so if a more widespread severe potential will reside locally. Additional heat headlines are becoming increasingly likely on Tuesday as well. The last few days, most models had the highest dewpoints on Tuesday, leading to the highest heat indices but there maybe a small decrease in the Td`s compared to the last few days but nonetheless it will still be dangerously hot out there. Showers and thunderstorm chances will persist for the afternoon and evening hours before dissipating. Overnight lows will drop down into the upper 60s to low to mid 70s further east towards the waters. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... An upper trough descending from Canada will drive a cold front toward the area Wednesday. Even if the front is delayed, falling heights will offer a better chance for convective initiation along the terrain and lee trough during the afternoon, progressing east through the evening. Flow aloft doesn`t appear particularly strong, but may be enough when combined with the forcing and instability to produce a localized severe storm risk. With the ridge being suppressed along with increasing clouds, Wednesday may be a few degrees cooler than Tuesday. However, dew points may be a touch higher, so heat index values of 100-110 remain possible, especially east of the Blue Ridge. The position of the front will be important for convective initiation Thursday. The highest chances will be across central Virginia to southern Maryland, but it`s possible most activity will be south of the CWA. Should enough instability develop, increased shear due to the orientation of the trough could support stronger storms. It is more likely that temperatures will return closer to normal Thursday with the front bisecting the area. The front will likely stall southeast of the area through the end of the week as there won`t be enough upper support to suppress the strong Bermuda high. We will be on the cool side of the boundary, meaning temperatures will remain closer to normal. There is more uncertainty in regards to the frontal position and any subsequent waves of low pressure. Friday appears to have the minimum in rain chances as high pressure builds to the north and the front reaches its southern extent. Moisture will work back northward over the weekend as the high to the north retreats. && .AVIATION /14Z SUNDAY THROUGH THURSDAY/... VFR conditions are expected today into Monday with only an isolated chance for a thunderstorm or rain shower to impact the terminals briefly this afternoon and Monday afternoon. Winds will continue to be fairly light out of the south to southwest heading into Tuesday. Shower and thunderstorm chances look to decrease by Tuesday afternoon but still none-zero. VFR conditions will likely persist for much of the period. Thunderstorms will become likely Wednesday afternoon and evening as a cold front approaches the area. A chance of thunderstorms may linger into Thursday depending on the frontal position, with the highest chance at CHO. && .MARINE... Winds will turn more southwesterly earlier today and eventually southerly later this evening. Cannot rule out a few isolated showers and thunderstorms across the waters with winds remaining light. An SCA gust may be possible if any of these showers or thunderstorms strengthen locally. Small Craft Advisory conditions may linger into Wednesday for portions of the waters due to increased southerly flow ahead of a cold front. Thunderstorms will become likely during the afternoon and evening, which could contain strong winds. The front will slowly press south Thursday with a wind shift to the northwest. Another round of thunderstorms is possible Thursday depending on the frontal position, with the highest chance across southern Maryland (and to the south). && .TIDES/COASTAL FLOODING... Anamolies will be slightly elevated over the next several days with some more sensitive tidal locations reaching action stage. No minor flooding is expected over the next several tide cycles locally. && .CLIMATE... Here are some daily high temperature records during the July 15-17 timeframe next week. Records (RERs) are only issued for DCA, IAD, BWI, and MRB, but other sites are shown for reference. A `+` sign indicates multiple years currently hold that record. ***MONDAY, JULY 15TH, 2024*** LOCATION RECORD (YEAR) FORECAST Washington-National (DCA) 100F (1988) 101F Washington-Dulles (IAD) 98F (1995) 100F Baltimore (BWI) 102F (1995) 101F Martinsburg (MRB) 107F (1936) 98F Charlottesville (CHO) 102F (1954) 99F Annapolis (NAK) 101F (1995) 98F Hagerstown (HGR) 102F (1954) 98F ***TUESDAY, JULY 16TH, 2024*** LOCATION RECORD (YEAR) FORECAST Washington-National (DCA) 104F (1988) 101F Washington-Dulles (IAD) 104F (1988) 101F Baltimore (BWI) 104F (1988) 101F Martinsburg (MRB) 107F (1988) 100F Charlottesville (CHO) 102F (1988) 100F Annapolis (NAK) 98F (1997)+ 98F Hagerstown (HGR) 104F (1988) 100F ***WEDNESDAY, JULY 17TH, 2024*** LOCATION RECORD (YEAR) FORECAST Washington-National (DCA) 102F (1980) 97F Washington-Dulles (IAD) 100F (1997)+ 97F Baltimore (BWI) 101F (1988) 97F Martinsburg (MRB) 102F (1988)+ 94F Charlottesville (CHO) 100F (1988)+ 97F Annapolis (NAK) 100F (1900) 94F Hagerstown (HGR) 100F (1953)+ 95F && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Excessive Heat Watch from Monday morning through Monday evening for DCZ001. Excessive Heat Watch from Tuesday morning through Tuesday evening for DCZ001. MD...Excessive Heat Watch from Monday morning through Monday evening for MDZ003>006-008-011-013-014-016>018-503>508. Excessive Heat Watch from Tuesday morning through Tuesday evening for MDZ003>006-008-011-013-014-016>018-502>508. VA...Excessive Heat Watch from Monday morning through Monday evening for VAZ027>031-037>040-050-051-053>057-501-502- 505-506-526-527. Excessive Heat Watch from Tuesday morning through Tuesday evening for VAZ026>031-037>040-050-051-053>057-501-502- 505-506-526-527. WV...Excessive Heat Watch from Monday morning through Monday evening for WVZ051>053. Excessive Heat Watch from Tuesday morning through Tuesday evening for WVZ050>053-055-502-504. && $$ SYNOPSIS...ADM NEAR TERM...ADM/CPB SHORT TERM...ADM/CPB LONG TERM...ADS AVIATION...ADS/ADM MARINE...ADS/ADM TIDES/COASTAL FLOODING...LWX CLIMATE...LWX