Area Forecast Discussion
Issued by NWS Sterling, VA
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Issued by NWS Sterling, VA
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-- Discussion containing changed information from previous version are highlighted. --444 FXUS61 KLWX 182355 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 755 PM EDT Tue Jun 18 2024 .SYNOPSIS... High pressure will remain anchored offshore through the week, resulting in a prolonged period of heat. The hottest days will be Friday, Saturday, and Sunday. && .NEAR TERM /THROUGH WEDNESDAY/...-- Changed Discussion --The few lingering afternoon showers dissipated very early this evening. The cu field has mostly collapsed as diurnal heating abates, and with that the Heat Advisory has also been cancelled. Dry conditions overnight as the center of an upper high drifts north and settles overhead. Lows tonight settle into the 60s for most, with 70s metros and immediate shoreline.-- End Changed Discussion --&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... Center of upper high will be overhead Wednesday and Thursday promoting large scale subsidence/sinking motion and inhibiting t-storm development everywhere. Guidance indicates slightly lower temps and dewpoints Wednesday likely as a result of low- level flow coming off of the Atlantic Ocean and not from a continental trajectory. Moderating a few degrees Thursday as the ridge shifts back south. && .LONG TERM /FRIDAY THROUGH TUESDAY/... Upper level ridging along the East Coast will flatten out as we head into the weekend. As this occurs, the 850 hPa high will shift to our south, which will cause 850 hPa flow to turn southwesterly. This will result in a more continental source region for the airmass and even hotter temperatures. High temperatures in the mid-upper 90s appear likely Friday through Sunday, with 100 degrees not entirely out of the question. Dewpoints will also increase into the upper 60s to lower 70s during that time, causing it to feel more humid than preceding days. Heat indices in excess of 100 appear likely during that time for much of the forecast area. There will be lesser relief at night as well, as overnight lows increase into the middle to upper 70s by the weekend to the east of the Blue Ridge (upper 60s to lower 70s further west). The combination of rising surface temperatures and dewpoints, along with decreasing temperatures aloft as the upper ridge breaks down will lead to an increase in instability, decrease in capping, and a return to thunderstorm chances each afternoon and evening. Thunderstorm activity is expected to remain relatively isolated on Friday, and primarily confined to locations west of the Blue Ridge. Thunderstorms coverage should increase slightly on Saturday as mid- level heights continue to slowly fall. Most model guidance shows a well defined upper trough tracking through the Great Lakes sometime during the Sunday-Monday timeframe, but there`s variance in timing between the individual models. As large scale ascent associated with that trough increases, so will the coverage of afternoon and evening thunderstorms. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...-- Changed Discussion --VFR conditions tonight through the end of the week. SE winds around 10kt during the day becoming S around 5kt at night. Prevailing VFR conditions and southerly winds are expected at the terminals on Friday and Saturday. A stray afternoon or evening thunderstorm can`t be ruled out either day.-- End Changed Discussion --&& .MARINE...-- Changed Discussion --SCA conditions continue through very late evening in the middle to lower Chesapeake Bay and Lower Tidal Potomac, where frequent gusts to 20 knots are expected. Elsewhere, occasional gusts to 20 knots are possible this evening. South to southeast winds prevail through much of the week. Winds may near low-end SCA levels in channeled southerly flow during the afternoon/evening hours on both Friday and Saturday.-- End Changed Discussion --&& .TIDES/COASTAL FLOODING... Persistent southerly flow continues, and tidal anomalies are hovering near one foot above normal. Sensitive areas will reach action stage around times of high tide. && .CLIMATE... Hot temperatures are expected much of this week and especially this coming weekend. The hottest days appear to be Friday through Sunday when several records could be in jeopardy. Below is a list of record high temperatures for today Jun the, 21st, 22nd, and the 23rd and the year the record was set, and the current forecast high temperatures for those days. RERs are only issued for DCA, IAD, BWI, and MRB, but other sites are shown for reference. Tuesday Jun 18th Climate Site Record High Forecast High Washington-National (DCA) 97F (1944) 91F Washington-Dulles (IAD) 94F (2018+) 93F Baltimore (BWI) 97F (1957+) 92F Martinsburg (MRB) 99F (1943) 92F Charlottesville (CHO) 96F (2014+) 93F Annapolis (NAK) 96F (1957) 87F Hagerstown (HGR) 95F (1957) 94F Friday Jun 21st Climate Site Record High Forecast High Washington-National (DCA) 99F (2012) 97F Washington-Dulles (IAD) 98F (1988) 98F Baltimore (BWI) 100F (2012+) 96F Martinsburg (MRB) 102F (1931) 95F Charlottesville (CHO) 99F (1933) 97F Annapolis (NAK) 100F (1988) 91F Hagerstown (HGR) 97F (1923) 97F Saturday Jun 22nd Climate Site Record High Forecast High Washington-National (DCA) 101F (1988) 99F Washington-Dulles (IAD) 99F (1988) 99F Baltimore (BWI) 100F (1988) 98F Martinsburg (MRB) 102F (1933) 96F Charlottesville (CHO) 101F (1933) 99F Annapolis (NAK) 101F (1988) 93F Hagerstown (HGR) 100F (1988) 97F Sunday Jun 23nd Climate Site Record High Forecast High Washington-National (DCA) 98F (1988) 96F Washington-Dulles (IAD) 96F (1988) 97F Baltimore (BWI) 97F (2010) 95F Martinsburg (MRB) 100F (1934) 92F Charlottesville (CHO) 100F (1894) 97F Annapolis (NAK) 98F (1988) 91F Hagerstown (HGR) 98F (1988) 94F + indicates that value has been reached on multiple years, with the year displayed being the most recent. && .LWX WATCHES/WARNINGS/ADVISORIES...-- Changed Discussion --DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 1 AM EDT Wednesday for ANZ532>534- 537-540-541-543.-- End Changed Discussion --&& $$ SYNOPSIS...CPB NEAR TERM...KRR/CPB SHORT TERM...CPB LONG TERM...KJP AVIATION...KRR/CPB/KJP MARINE...KRR/CPB/KJP TIDES/COASTAL FLOODING...CPB CLIMATE...LWX