Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
562 FXUS61 KLWX 241810 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 210 PM EDT Mon Jun 24 2024 .SYNOPSIS... High pressure will build back into the area through Tuesday bringing a brief reprieve to the excessive heat and humidity. High pressure pushes offshore Wednesday as another cold front approaches from the Ohio River Valley. The front will cross the area Wednesday afternoon into Thursday with the next chance for showers and thunderstorms. High pressure briefly returns from the north Friday before another series of fronts and increased heat this weekend. && .NEAR TERM /THROUGH TONIGHT/... An upper trough axis will pivot offshore through tonight, with high pressure building at the surface. Humidity has really fallen which will result in notably lower temperatures overnight tonight compared to the last couple of nights. Breezy conditions will subside this evening which will also aid in falling temperatures overnight. Lows are expected to range from the mid 50s to mid 60s, except around 70 in the major urban centers and right along major bodies of water. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... High pressure will pivot over the area Tuesday, then move offshore by Tuesday night. Humidity will remain low but temperatures may end up a degree or two higher than Monday. Warm air advection will cause an increase in clouds heading into Tuesday night, with perhaps a few showers or a thunderstorm approaching the Appalachians through the night. A sharpening upper trough and associated strong surface cold front will approach from the Ohio Valley Wednesday, then cross the region Wednesday night. Return flow ahead of this system will result in a surge of heat and humidity. Cloud cover as a result of upstream convection draws into question just how hot it gets, with some questions surrounding the quality of low- level moisture return as well. This results in uncertainty regarding the level of instability, although the potential is rather high given the ambient airmass. In addition, deep layer flow and shear will increase to 30 to 40 knots by Wednesday evening. All of this combined with increased ascent lends to the potential of strong to severe thunderstorms. This threat will need to be fine-tuned in the coming days as finer scale details come into focus, but a considerable severe weather episode is possible if conditions come together. && .LONG TERM /THURSDAY THROUGH MONDAY/... Heat and humidity return for the weekend along with additional shower and thunderstorm chances as a series of fronts push through the area. Calmer conditions are expected for the late week period as a cold front slowly exits south and east Thursday with high pressure building in briefly from the north Friday. A few showers and thunderstorms may linger along and east of the boundary (i.e east of the Blue Ridge) Thursday morning into early Thursday afternoon. The 12z GFS and ECWMF advertise a few spotty showers and thunderstorms mainly across central and eastern VA with high pressure building south from the Great Lakes region. As for temperatures Thursday, expect highs to drop back into the upper 80s and low 90s with dewpoints in the low to mid 60s. Additional relief arrives Thursday night as dewpoints fall into the 50s under light north to northwest flow. Lows Thursday night will range from the 50s and low to mid 60s west of US-15 to upper 60s and low 70s in the metros. High pressure continues to push eastward into the New England states Friday before pushing offshore Friday night into Saturday. This will allow for a light onshore flow component to converge against the Blue Ridge promoting a few showers and perhaps an isolated thunderstorm over the central/southern Blue Ridge (Shenandoah Valley/central VA Piedmont). Most locations will remain dry with temperatures once again in the mid to upper 80s and low 90s. Overnight lows Friday night will fall back into the upper 60s and low 70s areawide with increasing moisture as the flow turns toward the south. By the weekend, temperatures look to increase as a series of fronts push into the area. High pressure will continue off the New England coast Saturday with a warm front lifting into our region from the south. This front is in association with an area of low pressure moving across the northern Great Lakes into eastern Canada. With the warm front nearby, synoptic/ensemble guidance illustrates a few showers and thunderstorms mainly tied to areas along and west of the Blue Ridge. However, the highest probabilities of thunderstorms appears to be on Sunday as the warm front kicks north and the incumbent cold front follows from the Ohio River Valley. Some of these thunderstorms could be on the strong side given the recent Day 6/7 probabilities from CSU machine learning. SPC also makes a mention in their Day 4-8 discussion although confidence in how strong the storms will become and placement remains uncertain. Any rain that we do see will be beneficial at this point given the flash drought conditions. Highs this weekend will get back into the low to mid 90s with heat indices running close to or just shy of Heat Advisory criteria. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... VFR conditions are forecast through Wednesday morning. Gusty NW winds will persist until around 00Z before diminishing, then become SW Tuesday into Wednesday. A strong cold front will likely touch off some showers and thunderstorms Wednesday especially late into the day and into the night. && .MARINE... Gusty NW winds will continue into tonight before diminishing late. High pressure moves overhead tonight, then offshore Tuesday. Southerly channeling is likely Tuesday night, with gusty SW flow ahead of a strong cold front Wednesday. This front will likely deliver strong thunderstorms. && .TIDES/COASTAL FLOODING... Tidal anomalies decrease through Tuesday with NW flow. A return of southwest winds late Tuesday into Wednesday will bring another increase in water levels, although no flooding is forecast at this time. && .CLIMATE... Very hot temperatures are expected on Wednesday. Several records could be in jeopardy. Below is a list of record high temperatures for June 26th, the year the record was set, and the current forecast high temperatures for that day. A plus sign after the date signifies the record was set multiple times, with the most recent year indicated below. RERs are only issued for DCA, IAD, BWI, and MRB, but other sites are shown for reference. Wednesday Jun 26th Washington-National (DCA) 101F (1952) 98F Washington-Dulles (IAD) 95F (1998) 97F Baltimore (BWI) 99F (1954+) 98F Martinsburg (MRB) 102F (1943) 93F Charlottesville (CHO) 99F (1998) 97F Annapolis (NAK) 98F (1952) 94F Hagerstown (HGR) 98F (1954+) 93F && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 2 AM EDT Tuesday for ANZ530>534- 537>541-543. Small Craft Advisory until 8 PM EDT this evening for ANZ535- 536-542. && $$ SYNOPSIS...EST NEAR TERM...DHOF SHORT TERM...ADS/DHOF LONG TERM...EST AVIATION...DHOF/EST MARINE...DHOF/EST TIDES/COASTAL FLOODING...LWX CLIMATE...LWX