Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
377 FXUS61 KLWX 300130 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 930 PM EDT Mon Apr 29 2024 .SYNOPSIS... Strong high pressure off the southeast U.S coast will result in near record warmth and mainly dry conditions today. Unseasonably warm temperatures continue Tuesday despite renewed chances for showers and thunderstorms as cold front crosses the region. Additional showers and thunderstorms are possible Wednesday for portions of the area as the front is slow to sink south and east. High pressure briefly returns Thursday into Friday before another cold front this weekend. && .NEAR TERM /THROUGH TUESDAY/... Mild conditions continue this evening, with most locations still in the upper 70s to lower 80s. Winds are out of the south at around 5-10 mph, and that should continue to be the case through the remainder of the night. Earlier showers and storms across Grant and Mineral counties have dissipated, leaving conditions dry across the entire forecast area. Skies are mostly clear at the moment, but high clouds will be on the increase through the night. With the southerly breeze in place, temperatures will remain mild through the night, with lows in the 60s for most (mid-upper 50s in the mountains). && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... Subtle relief from the early warm season heat arrives late Tuesday into Wednesday as an upper level trough and associated cold front cross the region. The front will bring renewed chances for showers and thunderstorms to the region on both Tuesday and Wednesday afternoons. 12z model guidance continues to show a slower front/upper level trough arriving late Tuesday afternoon before finally pushing south and east of the area Wednesday into Wednesday night. This will lead to several rounds of scattered to widespread shower and thunderstorm activity mainly during the diurnal periods. Activity will wane during the overnight hours before re-firing in the afternoon especially along and east of the boundary as it passes through. As for the threat of severe weather it remains low, but not zero. Instability will remain fairly low on the order of 500-1000 j/kg with 0-6km bulk effective shear values running 20-30 kts. Both SPC, CSU Machine Learning, and CIPS analogue products continue to back off on the threat for a widespread severe weather event. Even with that said, one or two storms could become strong given the antecedent conditions. Biggest threats with any storms Tuesday or Wednesday look to be wind gusts 40-50 mph, frequent lightning, and locally heavy rainfall (PWATS running 0.75-1.25 inches). High temperatures Tuesday will push back into the mid to upper 80s with 70s over the mountains/near the bay. Lows Tuesday night will fall back into the upper 50s and low 60s with areas of patchy fog that due see the rain. The main upper trough/front is forecast to be east of the area Wednesday. An additional shortwave trough and weak front will quickly follow in it`s wake Wednesday afternoon touching off additional showers and thunderstorms. The highest probabilities for precipitation will be along and east of the I-81 corridor. Drier conditions return as high pressure builds south from New England Wednesday evening and night. Highs Wednesday will push into the mid to upper 70s and low 80s with overnight lows in the mid to upper 50s. && .LONG TERM /THURSDAY THROUGH MONDAY/... A ridge of high pressure will remain firm and in control Thursday through midday Friday. This ridge will keep the region very warm and dry throughout the period. Highs Thursday will be low to mid 80 s. Highs Friday, due to some increasing clouds, will not be as warm with temperatures in the upper 70s. These numbers are still above average for early May. Increasing clouds and showers arriving from west to east late Friday into Friday evening will be in response to the ridge of high pressure gradually breaking down and mid-level disturbance riding up and over the ridge. Showers aren`t expected to be widespread but could be accompanied by a few thunderstorms, especially over the mountains and our far northwestern zones. The unsettled conditions of showers and additional thunderstorms could continue Friday night through Sunday, as multiple weak to modest mid-level disturbances continue their assault on the large ridge of high pressure in the east. With the expected cloud cover and precipitation throughout the weekend, temperatures will be more average or slightly below average. Any cooler temperatures will be compromised by any modest southerly flow around the backside of the ridge of high pressure. Highs Saturday and Sunday should be lower 70s for most, but cooler in the mountains. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... VFR conditions are expected to continue through tonight with strong high pressure centered off the southeast U.S coast. Dry conditions will prevail at most of the terminals. The next chance for sub-VFR conditions arrives with a cold front Tuesday afternoon and evening. This front will bring renewed chances for scattered showers and thunderstorms. The strongest storms will be capable of producing wind gusts over 35 knots, frequent lightning, and brief vsby reductions from locally heavy rainfall. Any shower or thunderstorm activity moves east of the area late Tuesday evening with a few spotty showers lingering Tuesday night into Wednesday morning. A few showers and thunderstorms remain possible Wednesday as an additional upper level trough and weak cold front push through. This will lead to a few scattered showers and perhaps a couple of thunderstorms at terminals mainly east of I-81. This activity quickly moves east of the area by Wednesday evening. Outside of shower/storm activity, VFR conditions are expected Tuesday and Wednesday. VFR conditions Thursday through Friday night. Any showers Friday afternoon or evening may bring a brief reduction in conditions to MVFR, but not everywhere will get showers. Winds southeast 5 to 10 knots Thursday and Thursday night. Winds southeast 10 to 15 knots Friday and Friday night. && .MARINE... Favorable marine conditions are expected through Tuesday morning as high pressure brings warm and dry conditions to the waters. Winds will remain out of the southwest tonight at 5-10 knots before increasing to 10 to 15 kts Tuesday with gusts up to 20 kts at times especially over the open waters Tuesday afternoon. A cold front is set to cross the local waters Tuesday afternoon and evening bringing scattered showers and thunderstorms. These storms will be capable of producing wind gusts of 35+ knots, frequent lightning, and locally heavy rainfall. Special Marine Warnings may be needed as these storms cross the waters late Tuesday afternoon into the evening. Showers and thunderstorms push east of the waters late Tuesday evening into Tuesday night. Winds will turn back toward the northwest at this point, but should remain below SCA levels during this time. Northwest winds may come close to SCA criteria Wednesday as a cold front pushes to the south. A thunderstorm is also possible. Winds will become southerly again Thursday and Friday. Marginal SCA conditions could occur in channeling on the bay in the evening/overnight each day. No marine hazards expected Thursday through Friday night. Winds southeast around 10 knots Thursday and Thursday night. Winds southeast 10 to 15 knots Friday and Friday night. && .TIDES/COASTAL FLOODING... Southwesterly winds are expected tomorrow, which may lead to an increase in water levels. No flooding is expected tomorrow, but more sensitive locations may reach Action stage. Water levels are expected to decrease again on Wednesday as winds turn out of the northwest. && .CLIMATE... Below is a list of record high temperatures for tomorrow, April 30th. Apr 30th Climate Site Record High Forecast High Washington-National (DCA) 92F (1942+) 87F Washington-Dulles (IAD) 86F (2017+) 85F Baltimore (BWI) 92F (1910) 87F Martinsburg (MRB) 91F (1974+) 84F + denotes that multiple years reached this value, but the depicted year is the most recent && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from noon Tuesday to midnight EDT Tuesday night for ANZ530>543. && $$ SYNOPSIS...EST NEAR TERM...KJP SHORT TERM...EST LONG TERM...KLW AVIATION...KLW/EST MARINE...KLW/EST TIDES/COASTAL FLOODING...KJP CLIMATE...LWX