National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Sterling, VA

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-- Discussion containing changed information from previous version are highlighted. --584FXUS61 KLWX 170755AFDLWXArea Forecast DiscussionNational Weather Service Baltimore MD/Washington DC355 AM EDT Mon Jun 17 2024.SYNOPSIS...
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High pressure will remain anchored offshore through the week. Awarm front will lift northeastward across the Mid-Atlantictoday, marking the beginning of a prolonged period of heat.
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A warm front arcing across West Virginia as of early thismorning will lift swiftly northeastward across the region today.This will leave an increasingly hot and humid airmass in itswake.Prior to ridging and associated subsidence building aloft,enough heat and instability should build in the vicinity of alee trough developing near/west of I-81. This will occur thisafternoon around the backside of the departing surface high, andmay result in scattered showers and thunderstorms. Given weaklow and mid-level flow, convection will move slowly and/or lockto nearby terrain, resulting in a localized heavy rainfallthreat. FFG is relatively high (2.5-4" in 1-3 hours), thoughslow storm motions and higher PWs could result in totals closeto these values in a reasonable high-end scenario. Given the dryantecedent conditions and the somewhat conditional nature ofthe threat, no Flood Watch has been issued at this time. Theincreased heat and steepening low-level lapse rates could alsoaid in a few localized strong downbursts/gusty to perhapsdamaging surface winds. Convection chances are highest near andwest of the Blue Ridge Mountains and south of US-50 from aroundmidday through early this evening.Elsewhere, a dry and hot day is expected. Humidity willincrease, but won`t be quite oppressive by early summer Mid-Atlantic standards. This should result in heat index valuesaround or a degree or two higher than the air temperatures -generally in the lower to middle 90s.Low temperatures tonight will be in the 60s to lower 70s under apartly to mostly clear sky.
-- End Changed Discussion --&&.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
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Ridging will build aloft Tuesday into Wednesday. Subsidencecould be weak enough to allow a few isolated showers orthunderstorms to develop near the Appalachians Tuesdayafternoon, but most of the time/area will just be dry and hot.Temperatures will trend upward a bit Tuesday, then decreaseslightly Wednesday as the center of the ridge reorients itselfto the north and low-level flow pivots to off relatively coolerwater. High temperatures in the upper 80s to middle 90s and lowsin the 60s to lower 70s are expected during this time.
-- End Changed Discussion --&&.LONG TERM /THURSDAY THROUGH SUNDAY/...
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Highly anomalous upper level ridging along the East Coast willslowly start to break down during the second half of the week, withflow aloft becoming more zonal in nature next weekend. As thisoccurs, the 850 hPa high to our northeast will also start to breakdown, allowing 850 hPa flow to shift from east-southeasterly onThursday, to southwesterly next weekend. As 850 hPa flow gains awesterly component, an increasingly continental airmass will moveover the region, leading to an increase in temperatures, despite thefalling heights aloft.The strong upper ridge should suppress any convection on Thursdayand Friday, leading to sunny skies both days. As temperatures riseat the surface and cool aloft, chances for popup afternoon andevening thunderstorms will return this coming weekend. Thunderstormactivity looks to remain relatively isolated on Saturday in theabsence of appreciable large scale forcing for ascent. By Sunday,height falls associated with a trough tracking through the GreatLakes may lead to greater chances for thunderstorms.The main story through the long term period will be the heat.Temperatures are expected to reach into the lower 90s on Thursday.The hottest temperatures of this week`s heat wave are expected tooccur on Friday, Saturday, and Sunday. High temperatures those daysshould make it into the mid-upper 90s, with around 100 possible insome spots. Overnight lows will also increase from the upper 60s tonear 70 on Thursday night, to the mid-upper 70s by Saturdaynight.
-- End Changed Discussion --&&.AVIATION /06Z MONDAY THROUGH FRIDAY/...
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VFR conditions are expected to prevail at the TAF sites throughat least the first half of the week. A shower or thunderstormcould approach KCHO/KMRB this afternoon or early evening. If itdoes, brief restrictions would be possible (as would patchy foglater tonight into early Tuesday morning). Winds will generallybe southerly to southeasterly at 6-12 kts with occasionaldaytime gusts to around 18 kts. Eastern terminal likelyexperience some river/bay breeze influence during the afternoonand early evening hours each day.VFR conditions and southerly winds are expected at the terminals onThursday and Friday.
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South to southeast winds will prevail through much of theupcoming week. Southerly channeling combined with bay/riverbreeze enhancements likely result in SCA level gusts eachafternoon and evening. Otherwise, dry and hot weather isexpected through the week.Low-end SCA level winds appear possible in channeled southerly flowduring the afternoon/evening hours of Thursday and Friday.
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Persistent southerly flow continues, and tidal anomalies arehovering near one foot above normal. This is enough to result innear minor flooding, particularly during the overnight high tidecycle near Annapolis the next couple of days.
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Hot temperatures are expected much of this coming week andespecially this coming weekend. We could see a few recordsbroken on Tuesday, but the hottest days appear to be Fridaythrough Sunday when several records could be in jeopardy. Belowis a list of record high temperatures for June 18th, 21st, and 22nd,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. Tuesday Jun 18thClimate Site Record High Forecast HighWashington-National (DCA) 97F (1944) 93FWashington-Dulles (IAD) 94F (2018+) 93FBaltimore (BWI) 97F (1957+) 92FMartinsburg (MRB) 99F (1943) 93FCharlottesville (CHO) 96F (2014+) 94FAnnapolis (NAK) 96F (1957) 88FHagerstown (HGR) 95F (1957) 94F Friday Jun 21stClimate Site Record High Forecast HighWashington-National (DCA) 99F (2012) 97FWashington-Dulles (IAD) 98F (1988) 98FBaltimore (BWI) 100F (2012+) 96FMartinsburg (MRB) 102F (1931) 95FCharlottesville (CHO) 99F (1933) 97FAnnapolis (NAK) 100F (1988) 91FHagerstown (HGR) 97F (1923) 97F Saturday Jun 22ndClimate Site Record High Forecast HighWashington-National (DCA) 101F (1988) 99FWashington-Dulles (IAD) 99F (1988) 99FBaltimore (BWI) 100F (1988) 98FMartinsburg (MRB) 102F (1933) 96FCharlottesville (CHO) 101F (1933) 99FAnnapolis (NAK) 101F (1988) 93FHagerstown (HGR) 100F (1988) 97F+ indicates that value has been reached on multiple years, withthe year displayed being the most recent.
-- End Changed Discussion --&&.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None.MD...None.VA...None.WV...None.MARINE...Small Craft Advisory from 10 AM this morning to 9 PM EDT this evening for ANZ530-538-539-542. Small Craft Advisory until 2 AM EDT Tuesday for ANZ531>534-537- 540-541-543.
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