Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
384 FXUS61 KLWX 141837 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 237 PM EDT Sun Jul 14 2024 .SYNOPSIS... A surface trough will linger east of I-95 through midweek while high pressure remains offshore. The surface trough will be overtaken by a cold front late Wednesday into Thursday. This front will then stall to the south through the end of the week. && .NEAR TERM /THROUGH TONIGHT/... Several regions of agitated cu are developing across the region, with the most notable in the vicinity of the Bay Breeze east of I-95. This is where SPC has placed a Level 1 out of 5 for SVR WX (MRGL Risk), mainly due to effective shear of 30-35 kts. Microbursts look like the biggest threat, though mid-level lapse rates are rather poor (~5C/km) so updrafts may struggle to grow. There is a decent overlap in high magnitudes of SFC based CAPE with a relative max in vorticity along the bay. Moisture convergence is noted as well with PWs around 1.6-1.8", so any storm can produce localized heavy rain. 12Z RAOB from IAD along with ACARS data at local airfields show abundant dry air just off the surface, hence why most locations haved mixed Tds down into the upper 50s west of the Blue Ridge. Still hot, but a dry heat. Tds in the 60s for most of the region to the east of the Blue Ridge. Most storms will dissipate through the evening. 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/... For the start of the workweek, the Bermuda high will likely begin to break down and allow for increased moisture and humidity locally. Highs will be right around 100 degrees for many areas, especially along and east of the Blue Ridge on Monday. Have upgraded the Excessive Heat Watch for Monday into an Excessive Heat Warning for the DC and Baltimore metros along with the northern portions of the Shenandoah Valley into the eastern panhandle of West Virginia. Elsewhere, heat advisories are in effect for tomorrow afternoon and evening. 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. However, there is likely a residual lee sfc trough in the vicinity of the mountains that will act as another forcing/convergence mechanism. It will be worth monitoring this trend over the next day or so if a more widespread severe potential will reside locally. As of now, SPC has most of the area in a Level 1 out of 5 for SVR WX (MRGL Risk) Monday. An Excessive Heat Watch has been issued for Tuesday for most of the area aside from the Blue Ridge and Alleghenies. Another day of heat indices between 100-110F is likely. Showers and thunderstorm are possible again Tuesday, though more uncertainty wrt coverage compared to Monday. Overnight lows will drop down into the upper 60s to low to mid 70s further east towards the waters. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... A cold front will slowly approach from the Ohio River Valley Wednesday, then cross the region heading into Thursday. This front will intersect a very hot, humid, and moderately unstable airmass over the Mid-Atlantic. Flow aloft remains modest until Wednesday night, though it may be sufficient enough given the heat and CAPE present to result in at least loosely organized thunderstorms capable of heavy downpours and gusty winds. Timing uncertainties with the front, CAPE/shear overlay, and mesoscale details preclude higher confidence in any potential severe weather threat. The front will drift slowly south and stall through the end of the week. Showers and a few thunderstorms are possible especially south of I-66/US-50 Thursday closer to the front, though temperatures and humidity look to be notably lower. The front (and some heat and humidity) return northward heading into next weekend. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... 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. Sub-VFR conditions are possible briefly in TS Wed PM-Thu. S winds become NW generally AOB 10 kts outside of TS. && .MARINE... Main change to the marine forecast was the introduction of the potential for SMWs this afternoon and evening. Background winds will turn more southerly later this evening. Additional SMWs are possible in any thunderstorms Monday and Tuesday afternoon and evening. Better coverage/confidence appears to be on Monday, though some uncertainty remains. Southerly to southwesterly flow may approach SCA levels ahead of a cold front Wednesday. Showers and a few thunderstorms are likely as the front crosses late Wednesday into Thursday, some of which may produce gusty winds. && .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 Warning from 11 AM to 8 PM EDT Monday for DCZ001. Excessive Heat Watch from Tuesday morning through Tuesday evening for DCZ001. MD...Excessive Heat Warning from 11 AM to 8 PM EDT Monday for MDZ003-006-008-011-013-014-016>018-504-506>508. Excessive Heat Watch from Tuesday morning through Tuesday evening for MDZ003>006-008-011-013-014-016>018-502>508. Heat Advisory from 11 AM to 8 PM EDT Monday for MDZ004-005-502- 503-505. VA...Excessive Heat Warning from 11 AM to 8 PM EDT Monday for VAZ027>031-053>055-057-527. Excessive Heat Watch from Tuesday morning through Tuesday evening for VAZ026>031-037>040-050-051-053>057-501-502- 505-506-526-527. Heat Advisory from 11 AM to 8 PM EDT Monday for VAZ025-026- 036>040-050-051-056-501-502-504>506-526. WV...Excessive Heat Warning from 11 AM to 8 PM EDT Monday for WVZ051>053. Excessive Heat Watch from Tuesday morning through Tuesday evening for WVZ050>053-055-502-504. Heat Advisory from 11 AM to 8 PM EDT Monday for WVZ050-055-502- 504-506. && $$ SYNOPSIS...DHOF NEAR TERM...CPB SHORT TERM...CPB LONG TERM...DHOF AVIATION...DHOF/CPB MARINE...DHOF/CPB TIDES/COASTAL FLOODING...LWX CLIMATE...LWX