Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 250538 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 138 AM EDT MON JUL 25 2016 .Synopsis... Strong high pressure aloft will extend across the region through early Wednesday, bringing a period of hot and humid conditions to central NC. The chances for afternoon storms will increase by mid week. && .Near Term /Overnight/... As of 915 pm Sunday... An expansive (albeit small amplitude) ridge aloft spanning ~10 degrees of latitude (30-40 degrees) from coast to coast will dominate the upper level pattern through mid-week, confining the primary belt of westerlies above 40 degrees latitude. Light/variable steering flow and synoptic subsidence overnight will leave central NC isolated from upstream convection/disturbances in a nocturnally stable thermodynamic environment otherwise unable to support convection. As a result, confidence is high in dry conditions overnight with lows in the mid 70s. -Vincent && .SHORT TERM /Monday through Monday night/... As of 255 PM Sunday... ...Heat Advisory in effect for much of Central NC from Noon to 8 pm EDT Monday... More of the same, with very warm temps aloft (approaching 3 standard deviations above normal) helping to limit instability and thus suppress most convection, with very weak deep layer shear. The stacked deep ridge axis will hold across NC, with a fairly dry column persisting, although models do indicate some moistening aloft just to our W and NW over the Appalachians. The HRRRX indicates scattered storms developing over the NC mountains by late morning Mon, and the larger-scale models support this, but with the very weak steering flow, these cells should meander very slowly to the E or SE during the afternoon, and may not quite reach the western CWA before daytime heating wanes. Will stick with no pops for now, although we may ultimately need a couple hours of isolated coverage very late in the day over the Triad. Statistical guidance and forecast thicknesses suggest highs once again in the mid-upper 90s, and while dewpoints should mix out somewhat during the day (although they did not mix out much today especially in the eastern CWA due in part to the very light low level winds), the heat index values are still likely to exceed 100 degrees over the eastern two-thirds of the forecast area, with some spots reaching or exceeding 105. Even if values don`t quite reach 105 Mon, the lack of much recovery at night (temps holding at 75-80 for a good portion of the nighttime hours) and the multiple successive days of hot/humid weather still support a heat advisory for tomorrow. Will place the advisory along and east of a line from Wadesboro to Siler City to Hillsborough to Roxboro. We should see the stagnant surface air of the last few days pick up a bit from the SW during the afternoon. Lows Mon night should once again be in the low-mid 70s. -GIH && .LONG TERM /TUESDAY THROUGH SUNDAY/... As of 210 PM Sunday... A low pressure system over eastern Canada moves offshore on Tuesday and leaves behind a frontal zone just north of the area. This boundary is not expected to move much for several days as high pressure over the southeast and westerly flow aloft maintain a hot and fairly stagnant pattern over central NC. The Piedmont trough is the only discernible boundary that remains over the area and could be the focus of some afternoon convection but not much in the way of severe weather to speak of. Wednesday and Thursday afternoons feature the best instability and shear comes up a little bit by late Thursday afternoon above 20 knots but confidence and timing at this point are very low. What is confident is that temperatures will remain hot with highs in the mid 90s every day through the long term and lows in the mid 70s. Dewpoints will also continue to be in the 70s. This will result in heat index values close to heat advisory criteria, especially in the south and east each day. && .Aviation /06Z Monday through Friday/... As of 138 AM Monday... Pockets of MVFR fog will develop across central NC between 09Z and 11Z, dissipating within an hour or two of sunrise. Otherwise, there is a high probability that VFR conditions will persist across central NC through Tuesday as an area of high pressure aloft remains overhead. There is a good probability that VFR conditions will persist through much of the remainder of the work week. Chances for afternoon- evening scattered convection will increase the later half of the week, along with the possibility of early morning fog and low clouds. && .RAH WATCHES/WARNINGS/ADVISORIES... Heat Advisory from noon today to 8 PM EDT this evening for NCZ007>011-024>028-040>043-074>078-083>086-088-089. && $$ SYNOPSIS...WSS NEAR TERM...Vincent SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...WSS is the U.S. government's official web portal to all federal, state and local government web resources and services.