Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 010011 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 811 PM EDT Fri Sep 30 2016 .SYNOPSIS... Upper level low pressure gradually lifts north toward the Great Lakes tonight into Saturday, with a frontal boundary pushing across the area tonight into Saturday. The upper low then gradually pushes northeast through the Saint Lawrence Valley Saturday night into Sunday with drier air building into the region from the west. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... The Delmarva is presently getting a much need break from heavy rain, which has totaled up to 6-12" across DE/Lwr MD Ern Shore over the past 48 hours. This water will result in rising main stem rivers through the evening and potentially through at least Saturday. Follow the latest flood warnings for more details. Current GOES WV imagery continues to depict a stubborn anomalous upper low over central KY. A plume of deep moisture extends from off the SC/GA coast nwd into central NC/s-central VA, and nw across the central Appalachians. Another plume to the east has pushed offshore brining the need break in rain to the Delmarva. Showers and embedded tstms are developing are streaming nwd into the Piedmont/I-95 corridor. This activity is being triggered by the combination of the aforementioned moist plume/mid-level theta-e ridge, a push of mid-level dry air on the wrn flank of the moisture stream, a spoke of shortwave energy rotating around the upper low. The interaction of the push of dry air into the moist airmass will create some convective instability aloft. Strong mid-level flow (55- 65kt at 500mb) will result in strong deep layer shear. This combination could trigger some strong to marginally severe tstms this afternoon and evening, which is reflected in the marginal outlook from SPC. The main threats are hail and locally strong wind gusts. The main limiting factor will be the lack of SB/BL CAPE with an in situ wedge airmass in place. The greater threat through the afternoon/evening will be the potential for flooding over central VA where 1hr FFG is only 0.5-1.0" after Wednesday evenings excessive rain. A Flash Flood Watch has been issued through midnight to account for this. The best coverage will be from the I-95 corridor westward through the evening. Showers/tstms will gradually lift northeastward this evening into early Saturday morning as the mid-level theta-e boundary lifts to the ne. Anomalous PW values cling toward the coast through Saturday morning. Shower/tstm coverage is not clear at this time for the Lower Ern Shore late tonight into Saturday morning. However, these areas are very sensitive to any additional rainfall, so a short-term flash flood watch may be necessary depending on the areal coverage of pcpn. Drying inland late this evening through the overnight with some breaks in the clouds possible over the southern Piedmont. Mild again with lows in the mid to upper 60s. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... Drier air continues to entrain into the upper low Saturday as it fills and lifts northward, then northeastward Saturday night through Monday. The result will be gradually improving conditions. Addition energy lifts over the region in southwest flow aloft, so can`t rule out iso-sct showers along the coast Saturday aftn, with a lesser probability Sunday afternoon. Sky conditions also improve with a partly cloudy sky inland, but remaining mostly cloudy near the coast Saturday, before becoming partly cloudy Sunday and Monday. Highs Saturday range from the upper 70s to low 80s, but less humid as dewpoints drop into the upper 50s to low 60s inland. Highs Sunday and Monday will again be in the upper 70s to low 80s, with lows in the low/mid 60s. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... The long term period will see a return of an onshore flow that prevailed during much of the past week. a stationary front will be situated well off the Mid Atlantic Coast with a strong surface high over southeast Canada rebuilding over the Eastern Seaboard. Upper level ridging will slowly breakdown during the week as a strong upper level trough moves across the Northern Great Plains. There will be 20 to 40 percent chances for showers especially over eastern portions of the area with highest chances Wednesday through Thursday night. Hurricane Matthew may influence portions of the area late in the week. Although the track is is expected that its greatest impact will be in the marine area. Check with the National Hurricane Center for updates and details. High temperatures are forecast to range through the 70s with Tuesday likely being the warmest day. Low temperatures will generally be in the 60s. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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Low pressure system continues over the Tn Valley and frontal system along the Atlantic coastal area. The combination continues to produce a strong moisture feed up the east coast and over the Mid Atlantic region. Most of the convection that developed during the afternoon/evening has subsided but some activity remain over central Virginia and the Piedmont region during the early evening. The threat of rain for most of the TAF sites tonight is minimal but overcast MVFR/IFR conditions are likely with a moist atmosphere and lots of rain falling during the day. Moisture moving up the coast may affect SBY by early morning so expect them to see some -RA overnight into Sat and possibly through the day. The trend suggests improving conditions for inland areas as drier air moves into the region and VFR conditions should generally prevail on Sat into Sun.
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&& .MARINE... Seeing a gradual downward trend in seas and waves in the mouth of Ches Bay. Will allow SCA for the Bay to expire at 400 PM as planned and keep remaining SCA flags unchanged with regard to previously determined end times. Main change has been increasing wind speeds over the waters from Fenwick Island to Chincoteague where sustained winds range from 10-20kt with gusts to around 25kt possible. These speeds are anticipated to diminish through this evening. Strong/anomalous sfc high pressure remains over sern Canada through tonight before weakening Sat aftn. Meanwhile, stacked low pressure over the Midwest will continue to drift north and slightly east during this same timeframe. This will translate into winds becoming more se through tonight and then more sly on Sat. Speeds will generally be aob 15kt during this time. Waves on Ches Bay will average 1-3ft tonight into Sat...while seas generally average 4-5ft until SCA expiration times when seas will then average 3-4ft during the same timeframe. Onshore 9-10 sec period swell should also be anticipated tonight through Sat aftn. Calmer marine conditions expected Sat night through Mon. Wind directions will be variable sw-w through Sun evening and then shift to a more nly direction Mon into early Tue. Winds are then expected to increase in response to a tightening pressure gradient caused by Hurricane Matthew (located off the Atlantic coast of FL) and another Canadian high pressure centered over se Canada/nrn New England Tue aftn into Wed night. Still a lot of uncertainty regarding Matthew`s storm track at this time, but the general trend will be for increasing onshore winds and continually building seas for the second half of next week. && .HYDROLOGY... River flooding is developing across the primary rivers of the MD Lower Eastern Shore due to recent heavy rainfall, mainly the Pocomoke and Nanticoke. This flooding will likely persist at least through Saturday. See the latest flood warnings (FLWAKQ) for more details. && .TIDES/COASTAL FLOODING... * Updated at 613 PM EDT. See numbered bullets below for additional details. Strong/anomalous sfc high pressure remains over sern Canada through tonight before weakening Sat aftn as stacked low pressure over the Midwest drifts north and slightly east during this same timeframe. This will translate into onshore/se winds through tonight and then more southerly (and decreasing) on Sat. As the winds shift and decrease, tidal anomalies will decrease incrementally by a few tenths of a foot with each passing high tide cycle. Several areas of concern are as follows: 1. Coastal flood warning for the MD Lower Eastern Shore on Ches Bay has been extended through 400 AM Sat morning (primarily based on tidal data for Bishops Head). The previous warning for the Nrn Neck has been transitioned into a coastal flood advisory and is now in effect through 400 PM Sat aftn. 2. Coastal flood advisory for wrn Ches Bay areas from Hampton Roads to the Middle Peninsula has been extended through 1200 PM Sat aftn. 3. Coastal flood advisory for Maryland Beaches and Ches Bay side of VA Eastern Shore will continue through 1100 AM Sat morning. 4. Coastal flood statement will be in effect for Virginia Beach and Eastern Currituck this evening as tide levels end up within 0.3ft of minor flooding thresholds. Nuisance flooding may be possible in the persistent onshore flow. * Surf zone forecast has ended for the season. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...Coastal Flood Advisory until 11 AM EDT Saturday for MDZ024-025. Coastal Flood Warning until 4 AM EDT Saturday for MDZ021>023. NC...None. VA...Coastal Flood Advisory until noon EDT Saturday for VAZ084>086- 095>097-523>525. Coastal Flood Advisory until 3 PM EDT Saturday for VAZ089-090- 093. Coastal Flood Advisory until 11 AM EDT Saturday for VAZ099-100. Flash Flood Watch until midnight EDT tonight for VAZ064-075- 076-081>083-511>522. Coastal Flood Advisory until 4 PM EDT Saturday for VAZ075>078. MARINE...Small Craft Advisory until 10 PM EDT Saturday for ANZ650-652- 654. Small Craft Advisory until midnight EDT tonight for ANZ656-658. && $$ SYNOPSIS...AJZ/SAM NEAR TERM...AJZ/SAM SHORT TERM...AJZ/SAM LONG TERM...LSA AVIATION...JEF/LSA MARINE...BMD HYDROLOGY... TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.