Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
558 FXUS62 KRAH 271939 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 339 PM EDT Thu Apr 27 2017 .SYNOPSIS... A cold front will approach the mountains from the west late this afternoon and evening, then stall out and dissipate over the Mid- Atlantic tonight. A moist southerly return flow on the western periphery of a strengthening Bermuda high will prevail Friday through the weekend. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
-- Changed Discussion --
As of 330 PM Thursday... A surface cold front, associated with a shortwave moving over the Great Lakes, extends south through central Tenn and AL/MS this afternoon, with a prefrontal convection along a trough over eastern Tenn and another area of severe storms further east in central GA. Despite a strong, dry capping inversion near 780mb, noted on the 12Z/27th GSO raob, RAP soundings and SPC mesoanalysis showing sufficient moistening from the south between 700mb and 925mb to remove the cap, with a narrow axis of MLCAPE around 1000 J/KG working north along with 65F+ dewpoints. There`s a lot of cirrus over the western Piedmont, and the holding back of temps in the mid 70s may be enough hinder better destablization. Lapse rates aloft are relatively weak, so the CAPE is thin, but effective deep layer shear will increase to 40-50kt, supportive of supercells (Supercell Composite increases to 8-10), though that threat should diminish to the east with loss of heating. HRRR runs have been consistent in showing the Tenn Valley convection crossing the mountains into the western and northern Piedmont areas as the better jet forcing associated with the shortwave lifting into the Great Lakes passes by, and then some additional showers or isolated storms popping up in the south withing the axis of higher dewpoints and theta e. There may continue to be some showers or isolated storms to develop overnight as the cold front (or the associated trough and convergence) moves east through central NC, but the severe threat should end by 10 or 11pm. With increasing low-level moisture, expect overnight lows in the mid/upper 60s and some patchy stratus early tomorrow morning.
-- End Changed Discussion --
&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
As of 330 PM Thursday... In the wake of the upper wave lifting through the Great Lakes, the sub-tropical ridge will expand across the Southeast Friday into the weekend. Strong heating, with thicknesses approaching 1420m on Saturday, will leave to highs in the upper 80s Friday and upper 80s/low 90s on Saturday. A strong cap will limit any convection to the seabreeze on Friday, where the cap will be weaker owing to strong heating, but dry air will ultimately limit the coverage storms. Lows Friday night in the mid to upper 60s. Strong instability will develop on Saturday as an elevated mixed layer advectS across the region, deflect to the north a bit by the mid-level ridge. MLCAPE as high as 3000 J/KG is forecast by both the NAM and GFS. The threat of severe storms will be conditions upon convective development, which will be hindered by dry mid-level air (which will also support 1000 J/KG of DCAPE) and the lack of a focus, other than the terrain induced differential heating. Models do indicate a shallow tropopause disturbance/jet emerging off the GOMEX saturday, which given the strong instability could be enough to offer some forcing. However, confidence is low at this point. Lows Sat night will be in the upper 60s.
-- End Changed Discussion --
&& .LONG TERM /SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
As of 330 PM EDT Thursday... The subtropical ridge will retreat a bit on Sunday and especially Monday as an upper low lifts of the southern Plains. the associated cold front and convection are forecast to move into central NC Monday night, later than in prior forecasts, with limited instability and and forcing as it moves east. The front will also serve to knock temps back to more seasonal values, with highs in the 70s and lows in the 50s for midweek. Some uncertainty develops midweek, as the front is forecast to stall over the region and may be the focus for some unsettled weather as another shortwave or two swing through the longwave trough generally over the eastern US.
-- End Changed Discussion --
&& .AVIATION /19Z THURSDAY THROUGH TUESDAY/... As of 115 PM Thursday... VFR conditions prevail this afternoon with a 8-12kt southwest wind gusting to near 20kt in some spots. An area of showers and storms out ahead of a cold front will move into central NC from the west this evening,and while the intensity and coverage should weaken as they move east, there may be continued development of showers all the way east to RDU/RWI/FAY overnight as the primary cold front finally tracks east across the area. Brief MVFR/IFR conditions can be expected in any shower or storm, with low confidence in timing and location. IFR stratus looks to also be a possibility late tonight (08Z-12Z). VFR is expected to return by mid-morning Friday as strong high pressure aloft expands over the region. Outlook: A very summer-like pattern through the weekend with sub-VFR stratus possible during the early morning hours, scattering out by 15Z, and isolated afternoon convection being focused mainly around GSO/INT. Otherwise, expect the best overall potential for convection Monday evening/night in assoc/w a cold front /squall line/ progged to track eastward through the Carolinas. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...VINCENT NEAR TERM...SMITH SHORT TERM...SMITH LONG TERM...SMITH AVIATION...SMITH

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.