Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 260708 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 307 AM EDT TUE JUL 26 2016 .Synopsis... Strong high pressure aloft will extend across the region through Wednesday, bringing a period of hot and humid conditions to central NC. The chances for afternoon storms will increase toward the end of the work week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 305 AM Tuesday... Today: Mid/upper level ridging continues over the area this morning with the mid level high centered across the Carolinas. Weak disturbances aloft continue to track around the mid/upper level ridge to the west and north of central NC. The center of the mid/upper level ridge is forecast to shift slightly to the southeast today, which will allow for a better chance of weak disturbances tracking around the ridge to affect northern portions of central NC this afternoon/evening. Once such disturbance is helping to support and area of showers drifting northward across northern GA/AL. This weak energy coupled with another weak disturbance located over the lower OH/TN valley region this morning will combine along with a weak surface trough across the area to produce isolated to widely scattered showers and storms this afternoon/evening (with better coverage likely to the north of our area). Given strong heating during the morning into the early afternoon hours we will likely see at least 2000 to 2500 J/KG of MLCAPE across the area today. Deep shear however looks fairly weak, with maybe 15 to 20 kts of westerly flow at 500 MB. This environment will be supportive of wet downbursts, with perhaps a few clusters of storms possible. Thus, the latest day one convective outlook from SPC has our far northern counties in a marginal risk for severe storms with possibly a few damaging wet downbursts. The main story today though will again be the relentless heat, with high temps expected to again range from the mid to upper 90s and heat index values ranging from near 100 NW to 104-107 elsewhere. Thus, will continue the heat advisory today from noon to 8 PM for all but the far Western Piedmont. Tonight: Most convection will generally die off by late evening with another warm night expected. Expect lows temps tonight to generally be in the mid to upper 70s. Can`t completely rule out additional weak disturbance tracking across northern portions of the area overnight, possibly sparking a shower or storm, though think any activity will be quite isolated as we should still be under the general influence from the nearby mid/upper level ridge.
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&& .SHORT TERM /Tuesday and Tuesday night/... As of 325 PM Monday... Shortwave energy over the central part of the country will push eastward into the OH valley toward the mid-Atlantic/Northeast through Tue night. While the primary bound of mid level westerlies will stay well to our north, this wave will help push both the surface frontal zone and the slightly deeper moisture (as noted on water vapor imagery) to the SSE toward NC, not quite reaching the NC/VA border but making enough southward progress to bring a scattered showers and storms to northern NC. Mid level lapse rates should be a bit better than today, in the 5.7-6.0 C/km range, although deep layer shear will remain minuscule as the mid-upper level ridge axis will continue to extend across the region. Model forecast CAPE values are expected to remain muted with the continued warmth aloft, particularly across the southern two-thirds of NC, closest to the ridge axis. Will bring in late-day low chance pops across the northern sections of the CWA Tue into early Tue evening, before coverage drops off through the evening with loss of heating. See little reason to depart from persistence regarding temps, with thicknesses remaining well above normal, topped by anomalously high temps and heights through the column, and high surface dewpoints holding at or above the low-mid 70s for a good portion of the day. Will retain highs in the mid-upper 90s, as statistical guidance supports, with lows again in the mid 70s. These temps again equate to heat indices near or above 105 over the south and east, so will go with another heat advisory for Tue for the same areas. These successive days of hot temps and high humidity without much recovery at night will exacerbate the risk of heat illnesses heading into mid week. -GIH && .LONG TERM /Thursday through Monday/... As of 300 AM Tuesday... Persistent upper level high over the Southeast U.S. will maintain hot conditions over central NC Thursday and Friday. Heating of the moist and moderately unstable air mass will support the development of isolated-scattered late afternoon-evening convection, mainly north of highway 64 where subtle height falls and presence of surface trough will occur. Low level thicknesses Thu still support max temps in the mid/upper 90s, and with sfc dewpoints in the low/mid 70s, potential for the continuation of heat advisory very possible. Thicknesses Fri lower 15-18m as the upper high begins to weaken, though this may be too aggressive as history suggest that the thicknesses may only lower 5-8m. Thus expect highs Friday back into the mid/upper 90s. Potential for more appreciable change in the weather pattern expected by Saturday-Monday as center of upper ridge shifts southward. This will allow weak upper disturbances to skirt across our area, especially across the north. This should lead to an uptick in the coverage of afternoon-evening convection. In addition, with more clouds/convection, should see max temps lower a few degrees with max temps generally in the 90-95 degree range. Presence of the surface trough and available moisture and instability will support additional convective development early next week. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... As of 150 AM Tuesday... 24-hr TAF Period: VFR conditions are generally expected to continue outside of some patchy morning sub-VFR fog/stratus (best chance at KRWI) and isolated to widely scattered showers and storms late this afternoon into the early evening (again best chance at KRWI). Otherwise, a mid/upper level area of high pressure over the region will help steer the main track of convection to the north and west of central NC, yielding VFR conditions with south to southwesterly winds at around 6 to 10 KTS. Looking ahead: VFR conditions will generally prevail through mid- week as an upper level ridge remains in place over the southern CONUS. Diurnal convection will become increasingly possible as the ridge weakens /week progresses/, with chances near climatology by late week into the weekend. && .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...BSD SHORT TERM...Hartfield LONG TERM...WSS AVIATION...BSD/Vincent

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