National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Sterling, VA

-- Highlight Changed Discussion --

-- Discussion containing changed information from previous version are highlighted. --262FXUS61 KLWX 191824AFDLWXArea Forecast DiscussionNational Weather Service Baltimore MD/Washington DC224 PM EDT Wed Jun 19 2024.SYNOPSIS...High pressure will remain anchored offshore through the week,resulting in a prolonged period of heat. The hottest days willbe Saturday and Sunday.&&.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
High pressure will remain directly overhead through Thursdaypromoting large scale subsidence/sinking motion and noconvection in the local area. Given the position of the high,low-level flow will be off the Atlantic. This coupled with aslight increase in high-level cirrus will result in slightlylower temperatures than those of the past view days. Tds arealso fcst to drop today potentially below 60F and remain in thecomfortable range through Thursday. No heat headlines plannedfor today or Thursday. Lows will remain near or above 70.
-- End Changed Discussion --&&.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
-- Changed Discussion --
High pressure will drift westward Friday while sfc to 850 mbhigh moves further inland causing winds to veer more from thesouth or southwest direction, coming from a continentaltrajectory as opposed from oceanic direction. Temperatures onFriday are expected to soar into the upper 90s and may approachthe century mark across western areas. Heat Advisories may beneeded for western areas. Still keeping fcst dry for mostFriday, though cannot rule out isolated convection across theMason-Dixon.
-- End Changed Discussion --&&.LONG TERM /SATURDAY THROUGH WEDNESDAY/...The hottest temperatures of the ongoing heat wave are anticipatedthis coming weekend, with daytime highs climbing into the mid-upper90s. Some locations may even reach 100 on Sunday. Dewpoints willalso increase into the upper 60s and lower 70s, making it feel morehumid. Peak heat indices in excess of 100 look to be a good bet formuch of the forecast area this weekend. There will also be lesserrelief at night, with lows only dropping into the mid-upper 70s tothe east of the Blue Ridge.Gradual height falls aloft combined with daytime heating may lead toa few pop up afternoon or evening thunderstorms on Saturday, butoverall coverage is expected to remain low. By Sunday into Monday,an upper trough will approach from the Great Lakes, leading toincreased chances for afternoon and evening thunderstorms.Ensemble guidance shows a fair amount of variance with respect tothe timing of this disturbance and its associated cold frontalpassage, but the majority of solutions show the front passingthrough Monday. Depending on the timing of this system, therecould be a threat for severe thunderstorms as flow aloft increasesatop a very hot and humid airmass. If the front were to progressslower and hold up to our north, it could potentially be very hot(near 100) again Monday, but more solutions than not show the frontpassing through sometime Monday, leading to slightly coolerconditions (highs in the lower 90s). There`s a greater consensusamongst guidance that we`ll be within a post-cold frontal airmass byTuesday, leading to dry conditions. It will still be hot however,with highs forecast to be in the lower 90s.&&.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
-- Changed Discussion --
Lots of high clouds today and Thursday, then clear on Friday.SE winds around 10kt during the day becoming light south duringthe night.Prevailing VFR conditions and southerly winds are expected at theterminals on both Saturday and Sunday. A pop up afternoon or eveningthunderstorm may be possible either day.
-- End Changed Discussion --&&.MARINE...A few hours (2-4 hrs) of SCA gusts are possible each eveningacross the southern waters. Otherwise, S to SE winds 10 to 15kt.Winds may reach low-end SCA values in channeled southerly flow bothSaturday and Sunday afternoon/evening. SMWs may also be needed forany thunderstorms that move over the waters.&&.CLIMATE...Hot temperatures are expected much of this week and especiallythis coming weekend. The hottest days appear to be Friday throughSunday when several records could be in jeopardy. Below is a listof record high temperatures for Jun 21st, 22nd, and the 23rdand the year the record was set, and the current forecast hightemperatures for those days. RERs are only issued for DCA, IAD,BWI, and MRB, but other sites are shown for reference. Friday Jun 21stClimate Site Record High Forecast HighWashington-National (DCA) 99F (2012) 95FWashington-Dulles (IAD) 98F (1988) 97FBaltimore (BWI) 100F (2012+) 95FMartinsburg (MRB) 102F (1931) 94FCharlottesville (CHO) 99F (1933) 96FAnnapolis (NAK) 100F (1988) 90FHagerstown (HGR) 97F (1923) 96F Saturday Jun 22ndClimate Site Record High Forecast HighWashington-National (DCA) 101F (1988) 97FWashington-Dulles (IAD) 99F (1988) 97FBaltimore (BWI) 100F (1988) 95FMartinsburg (MRB) 102F (1933) 93FCharlottesville (CHO) 101F (1933) 98FAnnapolis (NAK) 101F (1988) 91FHagerstown (HGR) 100F (1988) 95F Sunday Jun 23ndClimate Site Record High Forecast HighWashington-National (DCA) 98F (1988) 98FWashington-Dulles (IAD) 96F (1988) 99FBaltimore (BWI) 97F (2010) 98FMartinsburg (MRB) 100F (1934) 95FCharlottesville (CHO) 100F (1894) 100FAnnapolis (NAK) 98F (1988) 95FHagerstown (HGR) 98F (1988) 96F&&.LWX WATCHES/WARNINGS/ADVISORIES...DC...None.MD...None.VA...None.WV...None.MARINE...None.&&$$SYNOPSIS...LFRNEAR TERM...CPBSHORT TERM...CPBLONG TERM...KJPAVIATION...KJP/CPBMARINE...KJP/CPBCLIMATE...LFR