Area Forecast Discussion
Issued by NWS Wakefield, VA

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425 FXUS61 KAKQ 291223 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 823 AM EDT SUN MAY 29 2016 .SYNOPSIS...
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Tropical Depression Bonnie will approach the South Carolina coast this morning, and will meander along the Coastal Carolinas through midweek.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Bonnie now downgraded to a tropical depression along the SC coast as of the 8am NHC update. The current surface analysis continues to show high pressure well off the VA/NC coast, and ridging back into the Mid-Atlantic region. TD Bonnie (a minimal 30kt storm) is about 30mi SSE of Charleston, SC at 12z advisory. Aloft, strong upper level ridge centered offshore ridges back west into VA. Large-scale zone of weak subsidence continues to control the sensible weather locally, allowing dry conditions to hold on through late morning except acrs the far S/SW. Using the latest information/forecast from the NHC on Tropical Depression Bonnie...a general slow north track is expected today, before a jog to the ne occurs tonight into Monday. The system is expected to linger along the Carolina coast through Monday night. More uncertainty in track develops thereafter. Please continue to refer to discussions/forecasts issued by the National Hurricane Center. WV/IR imagery showing upper ridge beginning to lift to the e-ne over the past few frames as TD Bonnie, approaches the SC coast, and expect this trend to continue this morning. PW values AOA 2" further expand into srn VA by 15z and into the remainder of the CWA through the early afternoon hours. NCAR Ensembles and majority of probabilistic guidance favors ramping up pop into likely range across South Central VA and ne NC later this morning, before pcpn shield slides NNW, becoming focused along and just west of I-95 counties this afternoon along a developing inverted trough. Categorical pops remain in place over this area, with numerous rain showers expected falling moderate to heavy at times. Even with sky becoming overcast by late morning, highs will be rather mild considering surge of moist tropical airmass. Look for Maxima generally in the upper 70s swrn tier (SW of RIC), with highs in the upper 70s to lower 80s acrs the eastern 1/3 of the area.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
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The low is slow to weaken acrs the Carolinas and get slowly transported NE Sun night/Mon as upper level trough from the W tries to push through. The increasing support from the upper levels (enhanced by upper divergence provided by RRQ of upper jet) may lead to the most widespread precip for the entire event tonight. Aforementioned sfc trough nudges east, with h7 omega/lift fields per the both 00z/29 operational GFS and ECMWF supporting additional sct/numerous moderate to heavy showers in the modified tropical airmass. Precipitation appears as if it will be focused mainly along the i-95 corridor tonight, shifting just east of there for late tonight/early Monday. Have continued trend of nudging pops up in these areas, with broad stripe of categorical POPS in NE corner of the area, tapering to likely POPS farther south. 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 narrow swath of 1-2" (locally higher amounts) appears very possible given the moist airmass (PW 2-2.25) and aforementioned lift, maximized along the boundary. TD Bonnie (or her remnants) look to linger along the SC coast into Monday aftn/evening along the coast. Continued warm and humid with early morning lows 65-70 F Monday morning and 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.
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&& .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 /12Z SUNDAY THROUGH THURSDAY/...
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Sfc high pressure across the nrn Mid Atlantic Region slowly erodes through this morning as Tropical Depression Bonnie tracks NNW twd the SC coast. Precip chances will be increasing through today from south to north as wraparound rain bands from TD Bonnie move into the area. MVFR cigs and visibilities should become the dominant flight condition as the day progresses, especially late tonight into Mon as more steady rain overspreads the region. Thunderstorms will also be possible this aftn/evening and Mon aftn/evening with periods of moderate to heavy rainfall and additional reductions to cigs and visibilities. 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. 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. In addition, areas of fog and prolonged periods of low stratus at all TAF sites should be anticipated Mon night through Thu due to persistent onshore winds, ample moisture present and no discernible weather features to kick the system out to sea until a cold front approaches the region on Thu. This front is expected to cross the area on Fri.
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&& .MARINE...
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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.
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&& .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...MAM NEAR TERM...LKB/MAM SHORT TERM...LKB/MAM LONG TERM...SAM AVIATION...BMD MARINE...BMD CLIMATE...AKQ

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