Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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709 FXUS62 KRAH 021340 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 940 AM EDT Tue Jul 2 2024 .SYNOPSIS... Canadian high pressure will move across and offshore the Middle Atlantic through Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 940 AM Tuesday... No major updates this morning as forecast is track. High pressure to the NE will continue to influence dry weather today with NE flow at the surface. Highs will range from 84-87 degrees across the region this afternoon. As of 330 AM Tuesday...A subtropical ridge will expand across the Southeast as a mid/upr-level anticyclone drifts from the lwr MS Valley ewd and over the TN Valley. Continued rising heights aloft and subsidence will result across the Carolinas. At the surface, Canadian high pressure now centered over NY/PA will drift sewd and reach the Middle Atlantic coast by 12Z Wed, while its associated ridge will continue to extend swwd across the Carolinas. The presence and influence of the deep layer ridging will favor continued deep dryness and stability over cntl NC, highlighted by a daily record minimum PW of just 0.48" observed at GSO last evening. Remarkably, that daily record minimum was preceded by a daily record maximum of 2.14" just 24 hours prior. Unseasonably low surface dewpoints mostly in the 50s this morning will likely decrease another several degrees with diurnal heating/mixing and result in another day of unseasonably low humidity values mostly in the 30th percentile, as temperatures warm into the mid-upr 80s beneath a mainly sunny sky. Mainly clear and calm tonight will then favor strong radiational cooling and below average temperatures in the upr 50s to mid 60s tonight. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 350 AM Tuesday.. A subtropical ridge over the Southeast may weaken a couple of decameters and retreat slightly, as convectively-generated disturbances, in quasi-zonal flow poleward of the ridge, develop and move from the cntl Plains and mid MS Valley ewd and across the OH Valley and cntl Appalachians. While associated height falls will be maximized across the OH Valley and nrn Middle Atlantic, 10-20 meter/12 hr falls will support some gradual weakening of the preceding strong subsidence inversion in place over cntl NC, especially Wed night. Some mid/high-level moistening and cloudiness may result Wed night, after high-based, diurnally-driven stratocumulus become scattered to broken Wed afternoon and dissipate through the evening. Otherwise, temperatures will moderate to slightly above average --highs in the upr 80s to lwr 90s and lows in the mid 60s to lwr 70s-- as increasingly-modified, Canadian surface high pressure drifts off the Middle Atlantic coast and directs sely to sly flow across cntl NC from late afternoon through overnight. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 225 AM Tuesday... Aloft, the mid-level anticyclone will sit over the Deep South through Thu night. A potent northern stream s/w will move through the northern Plains/upper MS Valley Thu/Thu night, picking up a weaker s/w moving through the central Plains into the mid-MS Valley. The mid/upper trough will amplify west of the Appalachians Fri/Fri night, as the s/w disturbances continue eastward through the Great Lakes and OH Valley. The high over the Deep South will be gradually pushed eastward through the Southeast on Fri and off the Southeast US coast Fri night/Sat the trough amplifies west of the Appalachians. As the initial s/w lifts newd into Canada on Sat, another northern stream s/w will drop into the northern Plains, tracking eastward along the US/Canada border into the Great Lakes Sat night/Sun. As this second s/w moves through the Great Lakes, the longwave trough will further amplify, extending from the s/w to the ARKLATEX by Sun night. 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. At the surface, a lee trough will set up and remain in place through Sat night, when a cold front will approach from the west. As of the latest model solutions, the front will largely wash out along the Appalachians Sat night, 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. Temperatures will be above to well above normal Thu through Mon. Latest forecast heat index values do creep back to around 105 again in a few spots on Thu, however the more widespread heat index values of 105 to 109 (across much of central NC) are expected Fri and Sat. Some lingering heat index values of 100-105 are possible across the south and east on Sun and Mon. As for rainfall, with central NC on the northern periphery of the ridge, some convection riding the ridge may move across the northern half of the area Thu aft/eve. Then as the mid-level ridge gradually gets suppressed south and the lee trough strengthens, expect more diurnally driven convection Fri, Sat, and Sun aft/eve, possibly continuing for Mon aft/eve as well. && .AVIATION /11Z TUESDAY THROUGH SATURDAY/... As of 700 AM Tuesday... The presence and influence of Canadian high pressure over the Middle Atlantic will favor VFR conditions in cntl NC through at least the next couple of days. Nely surface winds around the high may result in a few gusts into the teens to near 20 kts with diurnal heating this morning mainly at FAY, with light nely to ely winds expected otherwise and elsewhere. Outlook: A chance of showers/storms will exist over the wrn NC Piedmont (INT/GSO) Thu afternoon-evening and throughout cntl NC Fri through the weekend. && .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/MWS SHORT TERM...MWS LONG TERM...KC AVIATION...MWS CLIMATE...RAH