Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 231725 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 125 PM EDT Sun Apr 23 2017 .SYNOPSIS... A frontal boundary becomes nearly stationary across the Carolinas today. A strong low pressure system will cross the region through midweek...and bring periods of moderate to heavy rainfall to the region Monday and Tuesday. && .NEAR TERM /THROUGH TONIGHT/...
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Pcpn moving more east than northeast as it advances from the SW. Still some BINOVC / thinning across the north due to the high moving east across PA. Think the pcpn eventually wins out as afternoon progresses so adjusted grids a bit. Main change was to change from a convective pcpn form to more stratiformed since we are on the cool side of the developing low (i.e. rain vs shwrs). Remaining cool with highs 55-60. PVS DSCN: Late morning MSAS has low pressure over nrn GA with the cold front extending east to near ILM then offshore. AKQ fa wedged in as high pressure to the north provides a cool NE wind. Rain associated with the first wave has diminished to some light rain over the south, even some BINOVC across the north. However, moisture from the second wave already making a beeline for the region from the SW. Thus, expect a cloudy, cool and increasingly wet afternoon ahead as this moisture overspreads the region. Exception will be across the lwr MD eastern shore where any rain will not arrive until late. Highs 55-60, coolest over the piedmont due to the developing in- situ wedge. Thunder chcs just about NIL due to the cool and rather stable airmass.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... A cloudy and wet period to begin the work week. Periods of mdt to hvy rainfall expected Monday night and Tuesday. QPF btwn 1.5 to 3.5 inches (highest across the southern third of the area). Models in general agreement that aforementioned upr-level low cuts off as it tracks SE across the southeast and the coastal Carolinas. System then takes on a neg tilt Mon night that spawns a coastal low off the se coast Monday. Resultant strong coastal front will be conducive for heavy rainfall across the southeast CONUS, which will eventually move in our direction Late Monday night and Tuesday. Look for mainly cloudy skies with periods of mdt to locally hvy rainfall Mon/Tue as copious amounts of deep Atlantic moisture gets entrained north and rotates around the system. Thus, confidence remains high enough to go with likely to categorical pops each period. Kept high pops but low chc thunder along the coast. Highs Mon in the mid 50s-mid 60s except 65-70 sern coastal areas. Lows Mon nite in the upr 40s-lwr 60s. Highs Tue in the lwr 60s-lwr 70s. Hydro wise, no flood headlines anticipated attm with numerous breaks in between bouts of rain expected. Do expect some healthy rises in local river by early next week, especially if the heavy rainfall falls over the headwaters. Given the forecasted QPF and after coord with the RFC, expect minor flooding at Lawrenceville on the Meherrin River by Tue. Again, this based on QPF so plenty of time to adjust if needed. Rain tapers off from south to north Tuesday night as the upper low pivots offshore and NE of the Delmarva overnight into Wednesday morning. Early morning lows 55-60. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Long term period will feature a trend towards drier and warmer conditions. For Tue night, mid-level cutoff low and associated sfc low start to progress offshore, with some pcpn psbl on the backside of the systm. PoPs range from 20-40%. Warming trend then commences for Wed as deep SWly flow develops across the eastern seaboard, lasting through the end of the week with temps in the 70s Wed reaching the 80s most areas Thu and Fri. && .AVIATION /18Z SUNDAY THROUGH THURSDAY/...
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High pressure moving east across PA is keeping RIC/SBY VFR attm but MFVR conditions across the south with -ra movg east. Expect MVFR ST to become dominate cloud coverage across the entire area as the slug of rain overspreads the region. SBY will be the last to go MVFR probably closer to 00Z. After that expect widespread MVFR/IFR CIGS in areas of rain/fog for the rest of the forecast period as the system is slow to develop off the se coast. Gusty NE winds (15-25 kts at times) along coastal TAF sites. OUTLOOK...A well organized low will linger just off the Mid Atlantic coast through mid week before lifting ne and away from the area. Expect a continuation of MVFR and IFR conditions along with areas of rain/fog through Tues, slowly ending west to east Tues night. MVFR/VFR expected later in the week as high pressure moves in.
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&& .MARINE... Northeast flow prevails over the marine area, between high pressure building into the Northeast and low pressure over the Southeast. Speeds are generally 15-20 knots, with marginal SCA conditions in the bay. Waves generally 2-3 feet and seas 3-6 feet (highest southern coastal waters). High pressure builds in from the northwest today as low pressure remains over the Southeast. Gradient winds relax later this morning into the afternoon, resulting in a brief lull in SCA conditions. Longer reprieve expected in the upper Bay, so have opted to drop the headlines mid morning. In the southern bay, marginal SCA conditions expected today with occasional gusts to 20-23 knots. Gusts of 20-25 knots also expected in the sound and southern coastal waters today. Seas average 4-6 feet. High pressure slides offshore tonight as low pressure slides toward the Southeast coast. The result will be an uptick in northeast winds tonight, with speeds of 15-25 knots. Gusts up to 30 knots in the coastal waters. Seas increase to 5-8 feet. Am concerned guidance is not handling the northeast flow and long period swell the best, so have opted to go above guidance on wave heights. There is the potential for high surf conditions as well, but there remains some uncertainty so have held off on high surf headlines. SCA headlines return for the rivers late tonight. Low pressure slides off the Southeast coast Monday and deepens. Strongest gradient winds begin to expand northward Monday, with speeds of 15-25 knots expected from the mouth of the bay northward. A brief lull is possible for the sound Monday. Seas remain 5-8 feet, but subside to 4-6 feet in the southern coastal waters. Waves 3-6 feet (highest in the mouth of the bay). Low pressure slowly lifts along the Southeast coast Tuesday and offshore the Mid-Atlantic coast Tuesday night. Onshore flow and SCA conditions persist. Seas build upwards of 6-9 feet Tuesday. Flow becomes northerly Tuesday night as speeds diminish at or below 15 knots as the low lifts over the waters. Seas subside to 4-6 feet late Tuesday night. Waves 1-2 feet. The low weakens and lifts away from the region Wednesday as sub-SCA conditions return. Seas forecast to drop below 5 feet late Wednesday. The next front approaches the waters Friday. && .TIDES/COASTAL FLOODING... Tidal departures are averaging 1 to 1.5 feet early this morning thanks to persistent onshore flow. Tidal departures will build today through midweek as onshore flow prevails ahead of an approaching area of low pressure. Majority of the tidal locations in the bay and Atlantic coast will reach action stage today and tonight, but no minor flooding is anticipated at this time. However, tidal departures increase to 1.5 to 2 feet Monday. Minor coastal flooding is expected during high tide Monday night and again on Tuesday, especially in the lower Chesapeake Bay and Atlantic waters. Depending on the exact track of the low, high end minor to low end moderate coastal flooding is possible Tuesday night. Departures subside Wednesday as low pressure lifts along the Northeast coast and flow becomes offshore. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from midnight tonight to midnight EDT Monday night for ANZ635>637. Small Craft Advisory until 6 AM EDT Tuesday for ANZ632-634-650- 652-654-656-658. Small Craft Advisory until 6 AM EDT Monday for ANZ633. Small Craft Advisory from 6 PM this evening to 6 AM EDT Tuesday for ANZ630-631. Small Craft Advisory from 6 PM this evening to midnight EDT Monday night for ANZ638. && $$ SYNOPSIS...MAM NEAR TERM...MPR/MAM SHORT TERM...MPR/MAM LONG TERM...MAS AVIATION...MAM/LSA MARINE...SAM TIDES/COASTAL FLOODING...

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