Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 291807 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 207 PM EDT SUN MAY 29 2016 .SYNOPSIS... Tropical Depression Bonnie will linger along the South Carolina coast today, and will slowly track northeast along the Coastal Carolinas through the middle of the week. && .NEAR TERM /THROUGH TONIGHT/... Late morning analysis indicating TD Bonnie now located just inland of Charleston SC (was downgraded from a tropical storm at 8 am). Please continue to refer to discussions/forecasts issued by the National Hurricane Center for the track on TD Bonnie. Upper level ridge remains in place well off the mid Atlantic coast, and has been slowing/limiting the coverage of precip acrs the NE 1/2 of the CWA thus far this morning. However, with the warm/humid, modified tropical airmass now rapidly overspreading the region in tandem with increasing forcing, scattered to numerous showers have now pushed north from ne NC and into southern VA. Models in good agreement with an inverted sfc trough is developing and will continue to strengthen acrs the I-95 corridor this aftn. WV/IR imagery and radar trends support Likely to Categorical POPS this aftn for most areas, though it will take a few more hrs (until after 18-19Z acrs NE zones). Models suggest the highest POPS/categorical will tend to shift inland from the coast after 18Z, with high-end chc POPS persisting along the SE coast. Not much in the way of lightning activity so far, but will probably see at least scattered TSTMS later in the aftn and through the evening. Main issue today will be locally heavy rain, noting 12Z sounding from MHX at 2.18 PWAT (1.68 at WAL per 12Z). Steering flow today looks to be S to SSE and will need to monitor showers/storms closely for training due to high precip rates and potential localized flooding. Temps not expected to rise much if at all from current readings in the upper 70s/lower 80s (and will avg in the mid 70s in areas of heavier rain). TD Bonnie or it`s remnant low is very slow to weaken acrs SC and get slowly transported NE tonight as broad, Upper level troughing pushes in from the SW. Bulk of widespread and heavy precip may weaken for awhile in the evening or shift to far western portions of the CWA, but expect to see it regenerate overnight into Mon morning as increasing lift returns after midnight which will be further enhanced by upper divergence provided by RRQ of upper jet. Given the setup, there`s no avoiding the likelihood of a sharp QPF gradient across the area, owing to moisture/best lift likely becoming focused along the trough axis. A swath of 1-2" (locally higher amounts) appears likely given the moist airmass (PW 2-2.25) and aforementioned lift, maximized along the boundary. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... TD Bonnie (or her remnants) look to linger along the SC coast into Monday aftn/evening along the coast. Continued warm and humid with highs in the upper 70s/lower 80s on Memorial Day. With the sfc boundary/trough axis sliding toward the coast by midday, areal coverage of pcpn becomes a bit less widespread by afternoon, especially out west in the piedmont. Thus, while pops remain elevated they are a bit lower than today, ramping from sct (30-40%) far west to likely (60-70%) along the coastal plain, coincident with lingering boundary. Models seem a bit better resolved with handling the meandering remnants of Bonnie along the NC coast on Tuesday/Tuesday night. Slower solution makes a bit more sense considering that there really isn`t any synoptic feature present to kick it out to the NE as GFS wanted to do in previous cycles. The WPC-blended solution we`ve been following for a few cycles now does reflect this preference, and will continue to depict higher chc pop along the coast closer to the low, with a lower (more diurnally-driven) pop well inland. Temps remain near to a bit above climo despite mostly cloudy sky. Highs Tuesday in the low 80s inland, upper 70s to low 80s along the coast. Remaining variably cloudy and mild with lows in the 60s Tuesday night. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... The remnants of Bonnie are progged to linger in the vicinity of the NC coast through Wednesday and Thursday. Main impacts from look to be lingering showers/thunderstorms along the coast/east of Interstate 95, w/ cooler temperatures, and north to northeast winds of 10 to 15 mph. A warm and humid air mass will remain in place over the local area with vorticity maxima associated with the mid level features providing modest forcing for ascent. Expect generally scattered showers and diurnally-driven thunderstorms. Subsidence between Bonnie`s remnants and an upstream cold front expected to limit showers/thunderstorms over the Piedmont Wed, with better chances Thursday as a warm front lifts northward over the central Appalachians. Highs in the low to mid 80`s and lows in the 60`s. Sky averages Partly Cloudy. Upstream trough and associated cold front reach the Central Appalachians Thursday night, either kicking the low off the coast or weakening the system over the region. Best chance for dry conditions appears to be Thursday night, before POPs ramp back up Friday as the front reaches the local area. Trough progged to deepen over the Ohio Valley Friday and Friday night, with the front slowing as it reaches the coast. Will keep 30-40% POPs into the weekend as unsettled conditions linger. Highs in the low to mid 80s Friday before cooling into the upper 70s to around 80. Lows in the 60`s. Sky averages partly cloudy to mostly cloudy. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... Moisture associated with T.D. Bonnie will continue to stream northward resulting in periodic MVFR cigs and vsbys in showers through the taf period. Some RW+ with brief gusts to 30 mph are possible next few hours as well based on current radar trends. Pcpn expected to become more widespread and stratiformed after 06z which is expected to result in local IFR cigs and vsbys in rain through 12z and possibly 18z. Thunder chances are rather low attm (no lightning observed through this writing) so thunder was kept out of the forecast for now. Best timing for any thunder would be through 00z. Outlook...low pressure to the north will push a cold front across the region Mon aftn/evening. This boundary will push the tropical moisture offshore by Tue morning. However the weakening/remnant tropical low pressure system is expected to linger invof the Carolina coast through the middle of the week and keep rain chances in the forecast during this time...highest chances along the coast. && .MARINE... Still no major impacts expected due to Tropical Depression Bonnie. Sfc high pressure across the nrn Mid Atlantic Region slowly erodes through the morning as Tropical Storm Bonnie tracks NNW twd the SC coast. Precip chances will be increasing through the day from south to north as wraparound rain bands from TS Bonnie move into the area. Thunderstorms will be possible this aftn/evening with periods of moderate to heavy rainfall and quick reductions to visibilities. Southeast winds aob 15kt will prevail today and tonight. Seas building to 3-4ft southern waters this morning...then all waters by this evening through Tue morning. Waves generally 1-2ft with up to 3ft possible in the mouth of Ches Bay due to persistent onshore swell from the Atlantic during this timeframe. A low pressure system tracking ewd above the Great Lakes in Canada is expected to drag a cold front through the region Mon aftn/evening and collect the initial batch of tropical rainfall, thus pushing it offshore by either late Mon night or Tue morning. A brief period of n winds are possible Tue morning, but will turn around to a ne-e direction by Tue aftn. However the weakening tropical system low pressure is expected to linger invof the Carolina coast through the middle of the week and keep rain chances in the forecast during this time. In addition, low stratus and periods of fog should linger over the waters Tue-Thu due to ample moisture present, persistent onshore winds, and no discernible weather features present to mix out the lower atmosphere. Next cold front approaches the waters on Thu and will help to kick the tropical system out to sea. This front is expected to cross the waters on Fri. Seas 2-4ft/waves 1-2ft (up to 3ft mouth of Bay) Tue-Thu. && .CLIMATE... The monthly rainfall total to date for May at Richmond is 8.41". May 2016 is currently the 6th wettest month of May on record at Richmond. There is a good chance for additional rain Today/Mon with the potential to end as the wettest May on record. Top 6 wettest months of May at Richmond 1. 9.13" 1889 2. 8.98" 1873 3. 8.87" 1972 4. 8.67" 1886 5. 8.59" 2003 6. 8.41" 2016 (to date) && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...LKB NEAR TERM...LKB SHORT TERM...LKB/MAM LONG TERM...SAM AVIATION...MPR MARINE...BMD CLIMATE...akq

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