Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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230 FXUS62 KRAH 310550 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 150 AM EDT SUN JUL 31 2016 .SYNOPSIS... An upper level trough will cross the Northeast and Mid-Atlantic states through Monday, and then will slowly drifting offshore by Wednesday. A cold front will gradually approach our area from the northwest before stalling over the region early in the work week. && .NEAR TERM /THROUGH TONIGHT/... As of 930 PM Saturday... A couple of intense supercells affected the northern CWA earlier this evening, including one deep cell with tornadic signatures. While those storms lost strength quickly within poor mid level lapse rates and other cells stayed rather weak, the environment over the northeast CWA and all of eastern NC remains supportive of strong convection for a couple more hours. Favorable factors include lingering elevated instability with MUCAPE of 1500-2000 J/kg (although CINH has grown since sunset) and good low level shear (20+ kt 0-1 km), which have helped push the SCP values to 1-2. Upper divergence, albeit weak, is also providing larger scale support for lift, and deep layer effective shear is decent at 25-30 kts. Despite the stabilizing column, we should maintain small elevated instability through the night, within high PW well over 2.0". Will hold onto scattered pops east / isolated west for storms for another couple of hours before trending down to just isolated showers areawide overnight, a trend indicated by the latest CAM runs. Have nudged lows upward slightly based on trends and high-res guidance to 72-77. -GIH Earlier discussion as of 250 PM Saturday: Scattered showers and tstms have developed as expected across central NC, invof of the Piedmont trough, and to our west over and just east of the mountains. Aloft, SW flow persists across our area on the east side of a broad trough centered over the Ohio and Mississippi valleys. For the rest of this afternoon into this evening, the aforementioned showers and tstms will move east across our CWA, but given the scattered nature, not all locations will see rain, so for now will keep pops capped at 50%, implying the scattered coverage. As for storm intensity, latest mesoanalysis shows plenty of instability, esp from the US-1 corridor eastward, but shear is pretty weak, so look for mostly pulse storms, with perhaps some modest clustering north and northeast of Raleigh where the effective shear is the highest in our CWA. Given the instability, an isolated severe cell (wind or hail the main threats) can`t be ruled out, but given the weak shear, any severe cells won`t remain severe very long. Again, the best chance for a strong or severe cells will be north and northeast of Raleigh closer to the better shear. Look for shower/storm activity to wind down around midnight, with the remainder of the night partly cloudy. With little or no pattern or airmass change, will lean toward persistence for temps. Low`s tonight in the mid 70s. && .SHORT TERM /Sunday through Sunday night/... As of 250 PM Saturday... Sunday will start off much like today, with PC skies and isolated showers or sprinkles perhaps lingering on old outflow boundaries. Like today, isolated-to-scattered showers and tstms are expected to develop invof of the Piedmont trough during the early-to-mid afternoon. Then during the early evening, guidance is suggesting that a broken band of thunderstorms, first having formed over the mountains, will move east across our CWA. This band of tstms may have a little better coverage since it will be supported by a shortwave embedded in the SW flow. That shortwave is currently moving across the central plains. Despite this upper support, 0-6km shear is still progged to be aob 25 kt. So once again, most storms should remain below severe limits, but an isolated severe cell or two still can`t be ruled out given the instability. Speaking of instability, temps and dew points on Sunday will be similar to today, given that the airmass will have changed little. However, with slightly increased shower/storm coverage, our confidence of hitting heat advisory criteria in our eastern counties is not particularly high. For now, will forecast highs in the lower 90s and heat indices around 100. Nevertheless, it will still be uncomfortably hot, so folks need to continue exercising the heat precautions that we`ve been advertising. && .LONG TERM /Tuesday through Saturday/...
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As of 145 AM Sunday... Broad troughing aloft will prevail over the Carolinas and Mid- Atlantic early next week, transitioning to NW flow aloft mid-week as an upper level ridge re-strengthens over the lower MS river valley and Deep South, followed by ridging aloft mid/late next week as the aforementioned ridge builds E/NE over the Carolinas and Mid-Atlantic. With the above in mind, expect near normal temperatures early next week with temperatures rising above normal mid/late week as the aforementioned ridge builds over the region. With broad troughing aloft, expect near or above-normal chances for convection becoming somewhat more ambiguous in NW flow aloft by mid-week, then falling below normal (dry perhaps) late-week as the ridge builds over the region. With central NC situated on the southern periphery of the westerlies and eventually a period of NW flow aloft, a potential for organized severe weather may exist early to mid-week if small amplitude waves and/or upstream convection /MCVs/ progress into/across the region, particularly near peak heating. -Vincent
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&& .AVIATION /00Z Sunday through Thursday/... As of 730 PM Saturday... 24-Hour TAF period: Scattered showers and thunderstorms will locally reduce cigs and vsbys to MVFR or IFR category. Otherwise, expect VFR conditions and light and variable winds for the rest of the evening and overnight. Expect variable gusts around 20 kts near storms and/or thunderstorm outflows. Storms should dissipate after sunset. Similar conditions will prevail Sunday, with slightly higher chances for showers/storms resulting in gusty winds and locally reduced cigs and visbys. Looking ahead: Similar conditions through Tuesday with scattered afternoon/evening tstms and associated reduced flight conditions. Patchy morning fog possible as well. During the mid-week period, we may see decreased daily shower/storm chances as slightly drier air moves in the from the north. -NP && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield/np SHORT TERM...np LONG TERM...Vincent AVIATION...KC/np

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