Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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707 FXUS62 KRAH 031835 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 230 PM EDT Wed Jul 3 2024 .SYNOPSIS... Canadian high pressure centered just offshore the Middle Atlantic coast will linger over the Carolinas through tonight. A subtropical ridge will otherwise extend across the South Atlantic states through the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 217 PM Wednesday... Latest satellite observations show cumulus developing across the region as high pressure is centered off NJ coast. Upper level ridge over the Mid-Atlantic will slowly shift offshore by Thursday. Increased moisture levels moving into the region will result in dew points in the mid/upper 60s later this evening and into the low 70s by Thursday morning. Temperatures across the region this afternoon are in the mid to upper 80s with expectations for most areas to hit 90 degrees. Lows overnight will 3-6 degrees above average 68-71. Light southeast surface winds will slowly shift to SW by early Thursday morning. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 230 PM Wednesday.. A 595dm upper level ridge will extend from the Gulf Coast states NE toward the Mid-Atlantic on Thursday while surface high pressure continues to slip further offshore and allows moist southerly return flow to engulf the Carolinas. With southwesterly flow and deep mixing, dry adiabatic mixing technique yields mid to upper 90s for highs, which is on the higher side of guidance (equivalent to the 75th to 90th percentile range of the NBM) but not out of the realm of possibility. Thus will lean towards the higher side of guidance for highs. Deep mixing also suggests dewpoints will be able to mix out a little into the mid to upper 60s in a lot of areas, helping to keep heat indices in the low 100s for the most part. Will note that HeatRisk suggests moderate impacts, with much greater impacts Friday into Saturday. Regarding any convection, the stout mid-level cap that has been present this week will still be around early Thursday, weakening somewhat across the north as a trough moving into the Great Lakes tampers down the northern edge of the upper ridge. CAPE looks pretty limited due to the cap and mixing of dewpoints, but hires guidance suggests some isolated development on the mtn ridges and lee trough, perhaps migrating from SW VA toward the northern Piedmont along loosely-consolidated outflow. PW will also still be less than 1.5 inches, so the number of storms should also be limited. Thus the best chance of isolated storms should be from the Triad to Person County later in the afternoon and evening. Where storms do occur, the deep mixing and dry air will favor damaging winds as the greatest threat. Without better moisture available, convection is expected to wane quickly Thursday evening. Dewpoints will continue their background rise with the return flow, creeping into the lower 70s and keeping overnight lows in the low to mid 70s as well. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 225 AM Wednesday... Aloft, a potent northern stream s/w will move through the Great Lakes Fri/Fri night, as the longwave trough amplifies southward through the Plains and MS Valley. As the trough amplifies, the high over the Southeast US will be gradually pushed southeastward off the Southeast US coast Fri night/Sat. Another northern stream s/w will drop into the northern Plains and track eastward along the US/Canada border Sat/Sat night as the initial s/w lifts newd into Canada. As this second s/w moves through the Great Lakes Sun/Sun night, another disturbance will quickly drop ssewd through the northern Rockies and into the central Plains, helping further amplify the longwave trough through the southern Plains/lower MS Valley by Mon morning. All the while, central NC will remain situated between the trough to the west and the high to the east, with deep southwesterly flow prevailing. The fly in the ointment is the medium-range guidance picking up on a possible tropical low approaching the Carolina coast over the weekend. There is some uncertainty wrt this feature for Mon and Tue. Also on Sun/Sun night, Beryl is expected to make landfall along the western Gulf Coast, however exactly where that happens and when will determine what happens to the system as/where it moves inland early next week. There is still a lot of uncertainty in the forecast for Mon/Tue, but for now, it appears the longwave trough axis will generally remain west of the Appalachians through Tue, while s/w disturbances move through it. At the surface, a lee trough will remain in place through Sat, when a cold front will approach from the west. As of the latest model solutions, the front still appears to get hung up and generally wash out along the Appalachians Sat night, as Bermuda high pressure ridges westward. An area of low pressure will sit off the Southeast US coast Fri/Fri night, then weaken on Sat before the remnants of the low lift newd off the Carolina coast Sat night/Sun. possibly laying W-E through WV/VA Sun as high pressure lifts newd through the OH Valley and Northeast, but the front appears to stay north of central NC. Expect swly flow and the advection of warm, moist air into the area to take over once the ridge moves out Thu morning and prevail through at least Sat. The lee trough should once again strengthen over the area early next week. Temperatures will be above to well above normal through Tue. Latest forecast heat index values of 100-106 are expected across much of central NC for Fri and Sat. Sun and Mon heat index values max out around 100, mainly across the south, but may creep upward again on Tue. As for rainfall, the weather seems to be turning a bit wetter. As the mid-level ridge gradually gets suppressed south and the lee trough strengthens, expect more diurnally driven convection Fri through Tue, with higher chances/amounts as s/w disturbances clip the area. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... As of 120 PM Wednesday... VFR conditions expected for the 24 hour TAF period as high pressure dominants the region. While high pressure is centered just of the NJ coast, onshore flow is helping produce a nice Cu field across much of North Carolina. No restrictions are expected with a more widespread development of clouds across the area later tonight and into tomorrow morning. Winds will be overall light and variable, with onshore SE flow this afternoon slowly swinging to a SW flow by Thursday afternoon. Outlook: Sub-VFR conditions are possible in the NW by Thursday afternoon ahead of a tough moving into the region. Also, showers and storms will be possible Thursday afternoon in the NW with increasing chances spreading across Central NC Friday through early next week. && .CLIMATE... Record High Temperatures: July 4: KGSO: 98/1970 KRDU: 101/2012 KFAY: 98/2019 July 5: KGSO: 98/2012 KRDU: 102/1999 KFAY: 101/2002 July 6: KRDU: 102/2022 KFAY: 99/1990 Record High Minimum Temperatures: July 4: KGSO: 73/2018 July 5: KGSO: 74/1999 KRDU: 78/1902 KFAY: 77/2005 July 6: KGSO: 76/1999 KRDU: 79/1900 KFAY: 76/2017 July 7: KGSO: 73/2019 KRDU: 77/1900 KFAY: 78/2017 && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...CA SHORT TERM...bls LONG TERM...KC AVIATION...CA CLIMATE...RAH