Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 010032 AFDRAH AREA FORECAST DISCUSSION National Weather Service Raleigh NC 832 PM EDT Sat Oct 31 2020 .SYNOPSIS... A coastal front and area of low pressure will develop and move into eastern NC and VA Sunday morning, while Canadian high pressure otherwise continues to extend southwestward across the interior Carolinas and middle Atlantic. A strong cold front will then cross the region late Sunday afternoon and early Sunday night. && .NEAR TERM /THROUGH TONIGHT/... As of 832 PM Saturday... No signif changes this evening. A strong nrn stream trough will amplify from s-cntl Canada and the cntl US sewd into the upr Great Lakes and mid MS Valley through 12Z Sun, with preceding strengthening swly flow aloft and 30-60 meter mid level height falls forecast across cntl NC late tonight. At the surface, 1033 mb, cP high pressure centered over srn New England and the nrn middle Atlantic will continue to extend swwd across the Carolinas. Meanwhile, a coastal front will develop/strengthen off the coast of the Carolinas, then retreat into the coastal Carolinas and sern VA by 12Z Sun. An area of 2500-6000 ft stratocumulus now expanding from SC and ern GA nwd into the srn NC Piedmont --in a regime of strong 925 warm/moist advection-- will continue to expand newd across cntl NC through midnight. Light nely to calm wind within the ridge axis, will favor a period of radiational cooling and low temperatures mostly in the mid-upr 40s reached prior to midnight. Temperatures will then likely steady and rise with the foregoing increasing clouds through Sun morning. Strengthening sely low level flow across the coastal frontal zone, and related strong low level WAA atop the ridge over the interior Carolinas, will also favor the development of widespread low overcast and patchy light rain across the NC Piedmont, where the approaching nrn stream trough will maximize deeper forcing for ascent. Associated developing and expanding low clouds and rain will consequently result in the onset of cold air damming over cntl NC through early Sun. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... As of 322 PM Sunday... High pressure overhead Sunday with a warm front to the south and shortwave trough to the northwest, gives a good chance for a CAD to develop in the Piedmont. The strong trough aloft will move east through the mid Atlantic region on Sunday. At the surface, a cold front will move across the area Sunday afternoon/evening. Ahead of the front, height falls associated with an upper level low to the north and along with isentropic lift will increase especially over the northern Piedmont early Sunday; and this will result in overcast skies and widespread showers across the region (beginning in the west and extending east over the day). PoPs were increased to likely-categorical as confidence has increased, whereas rainfall totals are still limited around a quarter inch on average across central NC. As warm moist air ascends across the top of the CAD in place, weak elevated instability may result in isolated thunder especially in the eastern half of central NC. On the other hand, a warm front will try and makes its way north but will be impeded by CAD which will result in surface based instability over eastern NC, perhaps as far west as the Coastal Plain. As the cold front moves out Sunday evening, cold air advection moving in will cause much colder air and gusty nwly winds to rush across the area. Winds in the evening and overnight hours will be 15- 20 kts with gusts up to 25-30 kts. While those strong winds will inhibit any development of frost, temperatures will likely fall to around freezing over the western Piedmont Monday morning, ranging to upper 30s in the Coastal Plain. With winds in the teens and cold temperatures in the low/mid 30s, there is a potential that central NC could see winds chills in the mid 20s to lower 30s Monday early morning. && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 230 PM Saturday... Primarily dry extended forecast for central NC with temperatures gradually moderating from below normal on Monday to at/above normal by the weekend. Frost/Freeze still a concern on Monday night with temperatures in the low to mid-30s area-wide. The upper level trough will shift offshore as the parent low lifts northeast through ME/Nova Scotia on Monday. Northwest flow will set up over the mid-Atlantic, with the pressure gradient relaxing and flow becoming more zonal Monday night. At the surface, high pressure over the ARKLATEX on Monday will slowly migrate eastward through the Deep South Monday night and Tuesday before moving northeast through the mid-Atlantic and over New England Tuesday night. With the continued breezy conditions on Monday, temperatures will feel chilly (mid 40s north to mid 50s south) despite temperatures topping out in the low to mid 50s from north to south. With the winds relaxing Monday night and the clear skies, temperatures will be the lowest of the season thus far, widespread low to mid 30s. A few of the usual cool spots could even dip below freezing Monday night. The surface high will continue ridging southwest into the mid-Atlantic as the high moves away from the Northeast US Wednesday and Thursday. An upper level shortwave will move through the Midwest mid-week, though medium-range model solutions begin to diverge beyond Thursday. Thus, forecast uncertainty increases for Friday and Saturday over central NC. An inverted coastal trough begins to amplify along the Carolina coast on Friday, with high pressure to the north and relatively lower pressure south. For now expect the forecast to remain dry, however the chances for rainfall across the Coastal Plain of NC may increase with time for Friday/Saturday. Normal temperatures for early November across central NC: Highs mid 60s NW to around 70 degrees SE and lows in the low to mid 40s. && .AVIATION /00Z SATURDAY THROUGH THURSDAY/... As of 832 PM Saturday... Through 00Z Monday: VFR conditions are expected across central NC through most of the overnight hours. The MVFR stratocu currently found across SC and GA will gradually lift nwd overnight, first overspreading the western Piedmont prior to 10Z, then spreading east while lowering of IFR cigs after 10Z as a cold front approaches the region. Look for IFR conditions with low cigs and scattered showers to gradually spread ewd across central between 10Z and 19Z Sunday as the cold front sweeps across the region. In the wake of the front, look for improving flt conditions with rising cigs. Otherwise, it`s worth noting that forecast soundings suggest a period of LLWS with 40kt of wind around 2k ft agl above light winds at the sfc. In the wake of the front, NW sfc winds will become gusty, thus more uniform gusty winds through the low levels. After 00Z Monday: VFR conditions are expected through much of the week with high pressure and drier airmass over the region. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...np/MWS SHORT TERM...CC LONG TERM...KC AVIATION...np

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