Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
338 FXUS61 KLWX 281905 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 305 PM EDT Fri Jun 28 2024 .SYNOPSIS... High pressure builds in from the west today before pushing offshore late tonight into Saturday morning. A warm front lifts through the region on Saturday which will bring showers and thunderstorms back to the region. A cold front will then push through on Sunday, bringing yet another chance for afternoon showers and thunderstorms. High pressure then returns for the early portion of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... High pressure centered off to the north is allowing for mostly dry conditions across the area this afternoon and evening. A mid-level cumulus field will continue throughout the day, especially further south, more distant from the area of high pressure. Cannot rule out a few isolated showers across portions of central VA later this afternoon and evening but the probabilities are pretty low. Afternoon highs will top out in the low to mid 80s for the lower elevations with slightly cooler temperatures across the mountains. Overnight lows will drop down into the mid to upper 60s with increasing clouds ahead of the next disturbance poised to affect the area for the weekend. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... The area of high pressure will move further east Saturday morning with a warm front approaching the Mid-Atlantic from the south. A much warmer airmass and increasing moisture will allow for increased precipitation chances by late Saturday afternoon and evening. The best opportunity for showers and thunderstorms will be confined mostly to areas along and west of the Blue Ridge and Catoctin Mountains with the best chances across our far northwestern counties. Increasing instability and shear across the aforementioned areas will allow for some of these storms to be strong to severe with the mostly likely hazards being damaging winds and an isolated tornado. Timing of the showers and storms being late in the evening may limit coverage of the precipitation but there still may be enough instability during the evening hours to allow for convective initiation. Highs on Saturday will top out in the upper 80s to low 90s. With the warm front passing through the area later in the day, overnight lows will only get down into the low to mid 70s for the lower elevations and upper 60s for the mountains. For Sunday, the associated cold front will cross through the area during the day. Instability may be a bit more favorable compared to Sunday with increasing dewpoints, especially across the far eastern areas. Strong to severe thunderstorms will be possible Sunday afternoon/evening, especially along and east of the Blue Ridge Mountains. The main hazard will be damaging winds and maybe some hail. The other story on Sunday will be the heat, as areas east of the Alleghenies will be in the low to mid 90s with heat indices getting close to or exceeding 100 degrees, especially across portions of central VA. There is still uncertainty with any potential for headlines to be issued given the potential convection and ongoing cloud debris that may limit the temperatures and heat indices getting to criteria. After the cold front passes during the day on Sunday, much cooler air will be ushered in with 50s and 60s across the lower elevations and even upper 40s possible across the Allegheny Front. && .LONG TERM /MONDAY THROUGH FRIDAY/... Strong high pressure will build across the area Monday and Tuesday. Temperatures will be slightly below normal with comfortable dew points in the 50s. The high will move offshore by Wednesday with warmer and more humid air starting to return. However, ridging aloft should limit convective chances, with only a small chance of showers and thunderstorms over the mountains. Heat and humidity return in earnest Thursday (Independence Day) and Friday with forecast high temperatures well into the 90s and dew points in the 70s (potentially resulting in heat index values over 100). While the main frontal zone will remain north and west of the area, the heights aloft will flatten. Combined with lee troughing, there will be enough forcing and instability for at least scattered shower and thunderstorm activity each day. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... Mostly dry conditions continue today as high pressure passes to the north. Winds will slowly turn out of the SE by late this afternoon with a brief lull before increasing late tonight. Onshore flow tonight into Saturday morning could bring some lowered CIGs along/east of the Blue Ridge, which could particularly impact CHO. Lowered VSBY is possible, but winds are expected to be prominent enough to keep fog threat pretty low. Sub-VFR conditions are likely Saturday with any showers and thunderstorms that move across the terminals. A warm front lifts through the area in the morning/afternoon with some shower activity expected, and more is expected in the afternoon and evening with the potential for strong to severe storms. Sub-VFR continue into Sunday with showers and thunderstorms expected with a cold frontal passage, though likely improve behind the cold front. No significant weather expected Monday through Wednesday as high pressure moves across the area. && .MARINE... SCAs remain in effect over the lower waters of the Potomac River and central Chesapeake Bay through the remainder of the day and into tonight. The remaining zones will see SCA winds build back in later this evening and through the overnight hours as a pressure gradient tightens across the Mid-Atlantic as high pressure moves further east. Winds strengthen late tonight into early Saturday with a warm front moving north. Additionally, any storms that develop Saturday could produce damaging wind gusts and need SMWs. There is a non-zero threat for waterspouts as well. Both of these threats seem greatest in the northern portions of the waters at this time. Northerly winds may continue to result in Small Craft Advisory conditions through Monday afternoon, with a diminishing trend overnight. Winds should be lighter Tuesday as high pressure moves over the area. Southerly winds develop Wednesday, with some potential for advisories, especially toward evening as channeling increases on the bay. && .TIDES/COASTAL FLOODING... With prevailing north to northeasterly winds, tidal anomalies remain low as they current average between 0.20 to 0.50 feet. Today`s winds shift to mainly east-southeasterlies which allow some rise in water levels. A large rise ensues over the weekend give the stretch of southerly flow. A number of tidal sites start to push into Action stage, with Annapolis and Havre de Grace currently forecast to hit minor late Saturday night/early Sunday. Expect a cold front to track through Sunday evening which helps usher much of the additional water back toward the south heading into the new work week. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 7 PM this evening to 8 AM EDT Saturday for ANZ530>533-535-538>542. Small Craft Advisory until 8 AM EDT Saturday for ANZ534-536- 537-543. && $$ SYNOPSIS...ADM NEAR TERM...ADM SHORT TERM...ADM LONG TERM...ADS AVIATION...ADS/ADM/CAS MARINE...ADS/ADM/CAS TIDES/COASTAL FLOODING...LWX