Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
068 FXUS61 KLWX 240117 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 917 PM EDT Sun Jun 23 2024 .SYNOPSIS... A cold front will pass east of the area Monday leading to drier weather and lowering humidity. High pressure briefly returns Tuesday before another surge of excessive heat and humidity Wednesday as high pressure pushes offshore. Another cold front will approach the area late Wednesday into Thursday bringing additional chances for showers and thunderstorms. && .NEAR TERM /THROUGH MONDAY/... Not sure how much convection will occur tonight ahead of the frontal passage especially given lack of showers on radar this evening and steady downward trend in lightning across the Appalachians. Have kept isold/low end sct PoPs for the overnight period, but it appears most places will stay dry overnight except in the mountains where chances look a little higher. Frontal passage is expected around 12Z with sharp drying expected through the day Monday. Temperatures will still be around 90, but with lowering humidity through the day. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... By Monday morning, the surface cold front will be nearly through the area, with any lingering showers and storms quickly exiting southern Maryland. While temperatures will still be a little above normal in the mid 80s to near 90, dew points falling into the 50s and a gusty northwest wind will likely feel refreshing compared to the weekend. A few showers may linger through midday along the Allegheny Front as the primary upper trough axis passes. As the wind abates Monday night, lows will range from the mid 50s in the mountains to 60s in most other places. The surface high will translate through on Tuesday and move to the southeast Tuesday night. Comfortable dew points in the mid to upper 50s remain through the day, although temperatures will rebound a little to the upper 80s and lower 90s. A light southerly flow and potential clouds will result in a slightly warmer night. There is a slight chance weakened convection from the Ohio Valley makes a run at the Appalachians toward Wednesday morning. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Excessive heat and humidity briefly return Wednesday ahead of a cold front that will bring more widespread chances for showers and thunderstorms across the region. Overall the synoptic pattern becomes a bit more amplified as high pressure shifts offshore and the next piece of upper level shortwave energy moves south from the Great Lakes into the Mid-Atlantic region. With high pressure pushing offshore south/southwesterly flow will increase which means a return of the excessive heat and humidity. Temperatures will surge back into the mid to upper 90s with heat index values around or over the 100 degree mark east of the Blue Ridge Wednesday afternoon. Some uncertainty remains in regards to the temperatures due to the progression of the next shortwave trough and incumbent cold front from the Ohio River Valley. 12z synoptic/ensemble guidance suggests the development of convection Wednesday afternoon across the western half of the forecast area before advancing east Wednesday evening into Wednesday night as the cold front sweeps in. Added heat and humidity will allow for increased instability across the region lending a limited potential for severe weather. Current CSU learning machine probabilities and the SPC discussion in the Day 4 timeframe also back up this notion although confidence is medium at this time. Additional shower and thunderstorm chances are possible especially east of the Blue Ridge Thursday as the front and upper level trough slowly push through the remainder of the area. With that said, extra cloud cover and a front overhead will lead to cooler temperatures in the mid to upper 80s. Broad high high pressure will return from the north Friday delivering mostly dry conditions, seasonable temperatures, lower humidity, and light onshore flow. The high slides off the New England coast late Friday into Saturday allowing south to southwesterly flow to return along with a warm front from the south. Some uncertainty remains in the placement of this boundary in relation to an area of low pressure tracking across the northern Great Lakes region. For now, opted to hold low end precipitation chances Saturday afternoon and evening especially in areas west of the Blue Ridge. Additional showers and thunderstorms are likely Sunday as the next cold front approaches the region. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... The wind shift to the W/NW with the cold front will occur toward sunrise Monday morning. Gusts up to 25 kt will be possible through the day with a developing cu field. High pressure will result in lighter winds Monday night into Tuesday. Prevailing VFR conditions are expected Wednesday through Friday. Showers and thunderstorms may lead to brief restrictions on both Wednesday and Thursday afternoons as a cold front slowly moves through the area. The highest coverage of storms looks to be on Wednesday with activity mainly along and east of the corridor Thursday. Winds will be out of the southwest Wednesday with gusts up to 20 knots. West to northwest winds return in the wake of the front THursday into Friday. && .MARINE... The cold front will pass through Monday morning with a wind shift to the northwest. The wind forecast has trended upward for Monday, with advisories added for all waters. Gusts of 20-25 kt are likely, with a few gusts to 30 kt not out of the question. Winds gradually subside Monday night, but advisories will likely continue. High pressure builds across the area Tuesday, with light west winds becoming southerly by Tuesday night. An SCA may be needed for the bay Tuesday night due to southerly channeling. Some southerly channeling could occur over the middle and lower waters Wednesday ahead of an approaching cold front from the Ohio River Valley. SCA level winds look to return to portions of the waters Wednesday afternoon into early Thursday as a cold front passes through. Winds will diminish throughout the day Thursday in northwest flow as high pressure builds back into the region. Sub SC- level winds are expected with high pressure Friday. && .CLIMATE... Very hot temperatures are expected on Wednesday. Several records could be in jeopardy, as seen below. Below is a list of record high temperatures for Jun 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 Climate Site Record High Forecast High Washington-National (DCA) 101F (1952) 98F Washington-Dulles (IAD) 95F (1998) 98F Baltimore (BWI) 99F (1954+) 98F Martinsburg (MRB) 102F (1943) 92F Charlottesville (CHO) 99F (1998) 98F Annapolis (NAK) 98F (1952) 94F Hagerstown (HGR) 98F (1954+) 95F && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ530>534- 537>543. Small Craft Advisory until midnight EDT tonight for ANZ535-536. Small Craft Advisory from 6 AM to 6 PM EDT Monday for ANZ535- 536. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...ADS LONG TERM...EST AVIATION...ADS/LFR/EST MARINE...ADS/LFR/EST CLIMATE...LFR