Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 250708 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 308 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 /through Tonight/... As of 305 AM Monday... ...Dangerously hot conditions expected today across much of central NC... An area of high pressure centered aloft over the Carolinas will maintain the hot and dry conditions today. Low level thicknesses around 1440m Sunday are projected to inch upward to 1443/44m this afternoon, supportive of max temps in the mid-upper 90s. Surface dewpoints mixed out quite a bit in the northwest Piedmont Sunday afternoon with mid-late afternoon dewpoints in the mid 60s. While expect sfc dewpoints to mix out again, do not think that they will go as low as Sunday afternoon. Thus, should see heat index values around 105 degrees over most of central NC, excluding the nw Piedmont. Thus, little change required to the current heat advisory. Cannot rule out the potential for an isolated t-storm, mainly across the far south. However, considering the pocket of warm air aloft(as per 00Z GSO sounding), convective inhibition will be high. Thus,will refrain from mentioning an isolated t-storm for now. Tonight, very warm and muggy conditions will persist with most places not dropping below 80 degrees until after midnight. Min temps generally in the mid 70s. && .SHORT TERM /Tuesday and Tuesday night/... As of 305 AM Monday... Tuesday, a minor s/w approaching from the west will weaken the upper high overhead. This lowering of heights, the approach of the slightly cooler air aloft associated with the s/w, and a sfc tough over the Piedmont may be enough to allow for the development of isolated-scattered afternoon convection, mainly north of the I-40/85 corridor late Tuesday afternoon-evening. Elsewhere, presence of the upper ridge should inhibit convective development south of highway 64. Low level thicknesses projected to be just as warm Tuesday as today. Thus, will forecast max temps comparable to today in the mid to upper 90s. Another heat advisory may be warranted for most of the region. Any convection occurring early Tuesday evening across the north should quickly dissipate after sunset. Continued warm and muggy with overnight temps only cooling into the mid-upper 70s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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As of 3 AM Monday... Wednesday through Wednesday night: The remnants of a weak cold front will settle southward into northern portions of the area on Wednesday into Wednesday night eventually merging with a surface trough over the area. Meanwhile, the strong mid level ridge currently over the area will be located off the Southwest U.S. Coast by Wednesday. This will leave central NC on the southern fridges of the better westerlies for Wednesday. Given the the weak boundary will reside across northern portions of the area and potential for weak impulses to move across the area in the westerly mid level flow, expect we will see scattered to locally numerous showers and storms Wednesday afternoon/evening. Locations across the north will stand the best chance of seeing convection (closer to the actual boundary where better coverage is expected). With central NC on the southern fringe of the better westerly mid level flow (maybe around 20-25 kts at 500 mb across the north) we may see some multi-cell clusters of storms. Given this and expected mlcape values of around 1500 J/KG or higher during the afternoon into the evening and expected frontal zone placement we may see a better chance for severe storms on Wednesday than past days (especially across the northern half of the area). Though hard to time disturbances/mcv`s from upstream convection can and will have and impact on the eventual convective chances and placement. High temps on Wednesday are again expected to be above normal despite increasing chances for storms. Expect high temps to range from the lower to mid 90s north/northwest to the mid to upper 90s elsewhere, with heat index values from around 100 north to around 103-105 degrees southeast. Lows Wednesday night are expected to generally be in the mid 70s. Thursday through Sunday: Isolated to widely scattered showers and storms are expected each afternoon/evening through Saturday as the mid level ridge to our south/southeast is expected to bulge northward a bit late week into the first half of the weekend. This should result in high temps continuing to run in the mid to upper 90s for highs, with perhaps a few sites touching 100 by late week. This combined with a continued moist low level air mass (especially to the east of the lee side trough expected over the area) will allow for heat index values of around 100+ across the southern/southeastern half of the area which may result in additional heat advisories even if we dont reach heat index values of 105 degrees, thanks to the prolonged stretch of heat and humidity. The mid/upper level ridge is expected to shift eastward as s/w energy is expected to track across the Great Lakes into the Northeastern U.S next weekend. This should result in another weak frontal zone approaching central NC from the north by Sunday, yielding and increasing chance of mainly afternoon/evening convection. High temps by Sunday are expected to generally be in the lower to mid 90s. Low temps for the period are expected to generally be in the mid to upper 70s.
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&& .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...WSS SHORT TERM...WSS LONG TERM...BSD AVIATION...WSS

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