Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KRAH 210700 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 300 AM EDT Mon May 21 2018 .SYNOPSIS... A moist and slightly unstable air mass will remain entrenched across central NC through the middle of the week. && .NEAR TERM /THROUGH TONIGHT/... As of 210 AM Monday... Primary drivers of weather today include a weak backdoor surface front moving in from the north and minor mid level shear axes shifting in from the south. The latest surface map shows a fairly uniform air mass across much of the Carolinas and Southeast, albeit with lingering instability over the eastern CWA, and a weak backdoor front stretches W-E across central VA. This front is expected to drop southward into N NC this morning before washing out and ultimately dissipating as it starts to shift back N tonight. This front is more of a temporary wind shift, with minimal change in low level thicknesses, so impacts should be little more than weak low level mass convergence over the N Piedmont this afternoon. But this resultant forcing in tandem with afternoon heating and subsequent destabilization (tempered a bit by considerable mid and high clouds across the region) should allow scattered afternoon convection to be focused over the N Piedmont and N/C Coastal Plain starting in the mid afternoon, perhaps dropping into the Sandhills, S Coastal Plain and S Piedmont late afternoon into early evening, although this will depend to a large degree on cold pool propagation and a possible inland-moving sea breeze. While moderate CAPE is expected over the N and E CWA, other forcing mechanisms will be absent or very weak, including the aforementioned surface frontal convergence and subtle mid level waves tracking northward through the area between the offshore-centered mid level anticyclone and low pressure over the FL panhandle. Latest model runs are favoring pretty good convective coverage along the frontal zone, and will retain the trend up to likely pops across the N/E with lower coverage in the SW. Rather slow storm motion will raise the risk of locally higher rainfall totals. Storm intensity will be limited by the weak deep layer shear, although forecast soundings suggest elevated D-CAPE with potential for strong wind gusts, and high values of normalized CAPE favor high lightning activity. Expect highs in the low-mid 80s, with some upper 80s SW. Storms should decrease gradually in coverage and strength during the evening and into the overnight hours, although residual surface heat flux and high dewpoints necessitate keeping chance pops in through the night. Lows in the upper 60s to near 70 under mostly cloudy skies. -GIH && .SHORT TERM /Tuesday through Tuesday night/... As of 250 AM Monday... Today`s weak backdoor front should be mostly gone by Tue morning, leaving central NC within a light SW surface flow and light W mid level flow, as deep offshore ridging re-asserts its influence over the Southeast Coast. We will see passage of a mid level shortwave trough to our north Tue/Tue night, in conjunction with a surface trough crossing into the Mid Atlantic region Tue/Tue night NW to SE. Models depict a minimum in PW translating NE through the area during much of the day, and with a general lack in dynamic forcing for ascent and slightly lower forecast MUCAPE on the 3 km NAM with poor deep layer shear, storms may be fewer overall and focused across the far N and NW CWA, just ahead of the surface trough where CAPE will be greater (1500-2000 J/kg vs. the 500-1000 J/kg over much of the remaining CWA). Will have chance pops, highest N and W and lower SE, peaking in the afternoon. Pops should decrease in the evening and overnight, although will hold onto scattered showers over the NW through Tue night with an improving wind field resulting from digging of the mid level shortwave trough over the Northeast. Expect highs again in the low-mid 80s under partly to mostly cloudy skies. Lows Tue night in the upper 60s. -GIH && .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
As of 300 AM Monday... A continuation of the wet weather pattern is expected during the long term forecast with chances for rain each day of the forecast. A couple of features continue to drive this pattern including a frontal zone to the north of the area that is expected to remain close to our northern border and a low pressure system coming out of the Gulf of Mexico. While the frontal zone to the north with be a bigger player in the weather in the short term, a cold front is expected to pass through on Thursday. After this point attention will switch to the low coming out of the Gulf of Mexico as this feature is expected to bring large amounts of moisture transport to the Carolinas, especially late Memorial Day weekend. While it is unclear how this feature will ultimately evolve, a couple things remain true. We will have chances for showers and thunderstorms throughout the long term forecast. Temperatures will rise into the 80s each day with mid to upper 60s for lows.
-- End Changed Discussion --
&& .AVIATION /06Z MONDAY THROUGH FRIDAY/... As of 125 AM Monday... VFR conditions will dominate at central NC terminals through the next 24 hours, although there is a good chance of MVFR to IFR conditions 08z-12z this morning at FAY/RWI with a lower chance at RDU. Considerable mid level cloudiness based above 8 000 ft AGL is expected today through tonight, with scattered to periodically broken clouds based at 3 500 - 6 000 ft AGL this afternoon. Light winds and high humidity early this morning may induce development of stratocumulus based at 500-800 ft agl across the eastern sections in the hours before and around daybreak this morning. Scattered showers are possible near RDU/RWI 15z-18z, then scattered to numerous storms are possible 18z-00z later today at RDU/RWI/FAY, with a lower chance near INT/GSO. Shower/storm chances will decrease quickly after 00z. Looking beyond 06z Tue, VFR cigs/vsbys will dominate through Tue morning, with a slight chance of sub-VFR cigs 08z-12z. Another round of scattered showers/storms with local sub-VFR conditions is expected 18z-00z Tue. This pattern is expected to repeat through the week, with storm chances from mid afternoon through mid evening and low clouds or fog possible late each night through dawn. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...Hartfield is the U.S. government's official web portal to all federal, state and local government web resources and services.