Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
446 FXUS61 KLWX 140753 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 353 AM EDT Fri Jun 14 2024 .SYNOPSIS... A cold front approaching from the Ohio River Valley will cross the Mid-Atlantic tonight. High pressure will follow this weekend. A warm front will lift across the region Monday as high pressure shifts off the East Coast through next week. && .NEAR TERM /THROUGH TONIGHT/... Early morning radar and satellite imagery shows a mainly clear sky over the region, with the exception of some dwindling showers and clouds near northeastern Maryland. A few patches of river valley fog are possible through sunrise. Upstream, showers and thunderstorms were tracking across the Ohio River Valley while weakening. The upstream convection will continue to weaken through the morning hours. Remnant clouds and a subtle mid-level wave left in its wake will track across the area late this morning through early this afternoon. This may hamper heating somewhat, depending on the extent of any cloud cover. But, this feature may also sharpen a surface trough near the US-29 corridor. Despite the potential for some clouds for a time, ample surface heating should take place this afternoon. This will result in steep low-level lapse rates and a deeply-mixed boundary layer up to or even a little above 850 hPa. However, deep layer westerly flow (albeit light in the low levels) may cause surface dew points to drop and reduce convergence, casting uncertainty in thunderstorm coverage later today as a cold front and parent upper trough approach from the west. Coverage may tend to focus in a few different places: (1) along the surface trough, (2) near the PA line closer to better large scale forcing for ascent, and (3) near any terrain circulations in the vicinity of the Appalachians. Effective shear likely increases to 30-35 knots (highest north) by evening, so any deep convection that does develop will have the potential to organize into bands or multicell clusters. The main risk given the largely unidirectional flow and steep low-level lapse rates appears to be damaging wind gusts. Timing of thunderstorms is a bit uncertain, but should focus between 3 and 9 PM after the initial weak wave departs, heating maximizes, and the synoptic front/trough approach from the west. Additional shower activity or perhaps a thunderstorm or two may linger into the overnight hours as the parent upper trough pivots overhead. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... High pressure will build in this weekend in the wake of tonight`s cold front. Temperatures will be seasonable in the 80s with lower humidity expected. The chance of rain is near 0 through the weekend given deep dry air and large scale subsidence. Overnight low temperatures in the 50s and 60s are expected Saturday night, but Sunday night will be about 10 degrees warmer as high pressure moves offshore and a warm front approaches. && .LONG TERM /SUNDAY THROUGH THURSDAY/... A strong upper ridge is forecast to build over the Northeast and the northern mid-Atlantic early next week with ridge reaching maximum amplitude over the local area next Wednesday. As a result, hot and dry weather is expected all of next week. Some record highs appear possible, particularly Tue when records are in the mid 90s. Records on Wednesday and Thursday are higher in the upper 90s and will be more difficult to be broken. Some Heat Advisories or Heat Watches may become necessary at some point next week. Note that CPC has indicated the potential for a flash drought onset risk in their latest Days 8-14 Hazards Outlook valid Jun 21-27. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... Brief fog is possible near KMRB early this morning. Otherwise, prevailing VFR conditions are forecast through the weekend. Showers and a few thunderstorms may dot the region roughly 19Z-01Z (with possible lingering shower activity until 07Z or so), and this activity could bring brief restrictions and gusty winds. TS coverage is a bit uncertain given deep layer westerly flow which tends to limit things locally. However, steep low-level lapse rates could result in gusty and erratic surface winds even in seemingly weaker activity through this evening. Winds will be light out of the W/SW (230-290 at 4-7 kts) through about 17Z. Winds for most TAF sites may then pivot more to 190-220 through about 22Z as a surface trough sharpens. Further west at MRB, winds likely stay more westerly to the west of the trough. The wind direction appears more uncertain for IAD since the trough may be very close by. Winds shift to the W-NW-N through the evening as the cold front crosses, with a brief period of 15-20 kt gusts possible outside of any showers and thunderstorms. Northerly winds Saturday become northeast Saturday night, then east to southeast Sunday. Gusts of 15-20 knots are possible during the day Saturday. No sig wx is expected Mon or Tue. && .MARINE... Southerly channeling has decreased as of early this morning. Large scale flow will remain relatively light out of the south to southwest today, with air temperatures well above the water temperatures resulting in low-level stability. In spite of this, a strengthening surface trough just west of the waters will likely enhance flow just enough, and that combined with the afternoon bay breeze should be sufficient for a period of southerly gusts around 20 knots for the main channel of the Chesapeake Bay between Sandy Point MD and Smith Point VA (typical channeling area). A brief period of NW 15-20 knot gusts is possible in the wake of a cold front this evening, with gustier winds possible in shower or thunderstorm activity (may require Special Marine Warnings). Northerly winds likely gust 20-25 knots Saturday morning through early afternoon, before diminishing and becoming northeast Saturday night, then east to southeast Sunday through Sunday night. Dry weather is forecast this weekend. SCA conditions are possible all of next week due to southerly channeling and large water vs land temperature differences of nearly 20 degrees F. && .CLIMATE... High temperatures for next week. Below is a list of record high temperatures for June 17th, 18th, 19th, and the 20th and the year the record was set, and the current forecast high temperatures for those days. Daily temperature records are currently only maintained at DCA, IAD, BWI, and MRB. Others are shown for reference. Monday Jun 17th Climate Site Record High Forecast High Washington-National (DCA) 99F (2022) 93F Washington-Dulles (IAD) 96F (2022) 94F Baltimore (BWI) 96F (2022+) 92F Martinsburg (MRB) 98F (1939+) 91F Charlottesville (CHO) 97F (2022) 93F Annapolis (NAK) 96F (1939) 87F Hagerstown (HGR) 96F (1952) 92F Tuesday Jun 18th Climate Site Record High Forecast High Washington-National (DCA) 97F (1944) 95F Washington-Dulles (IAD) 94F (2018+) 95F Baltimore (BWI) 97F (1957+) 93F Martinsburg (MRB) 99F (1943) 92F Charlottesville (CHO) 96F (2014+) 93F Annapolis (NAK) 96F (1957) 89F Hagerstown (HGR) 95F (1957) 93F Wednesday Jun 19th Climate Site Record High Forecast High Washington-National (DCA) 99F (1994) 95F Washington-Dulles (IAD) 98F (1994) 95F Baltimore (BWI) 99F (1994) 93F Martinsburg (MRB) 96F (1994+) 92F Charlottesville (CHO) 97F (2018) 94F Annapolis (NAK) 96F (1993) 89F Hagerstown (HGR) 97F (1994) 94F Thursday Jun 20th Climate Site Record High Forecast High Washington-National (DCA) 99F (1931) 95F Washington-Dulles (IAD) 97F (1964) 96F Baltimore (BWI) 100F (1931) 94F Martinsburg (MRB) 98F (1931) 93F Charlottesville (CHO) 98F (1933) 94F Annapolis (NAK) 98F (1988) 89F Hagerstown (HGR) 98F (1931) 95F + indicates that value has been reached on multiple years, with the year displayed being the most recent. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 4 AM to 11 AM EDT Saturday for ANZ530>532-539>541. Small Craft Advisory from 2 PM this afternoon to 9 PM EDT this evening for ANZ532>534-537-542. Small Craft Advisory from 4 AM to 3 PM EDT Saturday for ANZ533- 534-537-542-543. && $$ SYNOPSIS...DHOF NEAR TERM...DHOF SHORT TERM...DHOF LONG TERM...LFR AVIATION...LFR/DHOF MARINE...LFR/DHOF CLIMATE...LFR