Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221054 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 655 AM EDT Tue May 22 2018 .SYNOPSIS... A moist and unsettled air mass will hold across central NC through mid week. A cold front will drop into the area from the north late Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 315 AM Tuesday... The subtle backdoor boundary noted on the latest surface analysis over NE NC is expected to wash out near or soon after daybreak, leaving us in a light SW flow pattern with an initially weak but sharpening lee trough. A few light showers persist over central NC early this morning, a function of weak waves tracking NE around the Bermuda ridge, although nocturnal stabilization and overturning have greatly diminished activity since the past evening. The remaining showers should track NE out of the forecast area later this morning as a band of lower PW now extending NW-SE over SC pivots NE into NC. Rising heights over the lower Miss Valley and adjacent Gulf States region combined with a weak mid level shortwave trough crossing the Great Lakes will turn the weak steering flow to a slightly drier westerly direction, contributing to a brief relative lull in precip for a good portion of the day over central NC. Passage of a weak perturbation through central/E NC from mid morning through early afternoon is expected to result in a short enhancement of shower coverage over the NE CWA during that time, so have retained chance pops in the NE from late morning through early afternoon, with generally dry weather elsewhere until late this afternoon. The aforementioned Great Lakes trough brushing by to our NW and N and the preceding DPVA into W and N NC late today into tonight should prompt scattered convection, moving into the W CWA after 5 pm as a surface cold front accompanying the mid level trough approaches from the NW. Soon after trending pops down and out from the NE CWA, pops will then trend back upward late over the W and far NW CWA, spreading over the rest of the W and N sections of the forecast area overnight with the slow arrival of dynamic forcing for ascent, supported by a strengthening mid level flow and resulting improvement in deep layer shear. Expect highs today in the mid to upper 80s, although longer-lasting stratus and showers in the far NE CWA this morning/early afternoon may hold maxes there in the lower 80s. Following persistence with partly to mostly cloudy skies tonight, expect highs from the mid 60s to around 70. -GIH && .SHORT TERM /Wednesday through Wednesday night/... As of 330 AM Tuesday... Expect scattered showers/storms across the W and N CWA Wed morning in tandem with the sharpening surface lee trough and the DPVA preceding the shortwave trough moving through the Northeast and interior Mid Atlantic region. This initial shear axis will continue moving ESE with strengthening and veering mid level flow, while the surface cold front moves into the NE CWA late in the afternoon. In addition to the strengthening deep layer shear from the WNW to 30-35 kts, models are indicating good destabilization during the mid to late afternoon, primarily across the north half. Probably the biggest question mark however is how quickly the morning convection pushes E and S. If this activity departs by mid afternoon, there could be enough recovery in the afternoon with residual low level moisture and minor mid level drying/cooling, such that surface CAPE values reach into moderate to strong instability categories. The NAM Nest wind profile shows veering and strengthening with height through 800 mb, with subtle backing 800-600 mb, and given the expected CAPE, large hail along with damaging winds are possible, mainly across the N Piedmont and N/C Coastal Plain. Again, though, this is dependent upon there being sufficient recovery in the afternoon. Will include a mention of possible severe storms across the N and NE CWA Wed afternoon/early evening. The storms should slowly decrease in intensity as they slide SE Wed night, with the cold front dropping SSE through much of NC overnight. Expect highs Wed in the mid 80s. Lows once again in the mid 60s to around 70, with some cooler dewpoints starting to work into N NC late. -GIH && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 330 AM Tuesday... There may be a break in the wet weather to begin the long term on Thursday as a front pushes through the southern portion of the state, leaving the northern half of the forecast area under high pressure and relatively dry. High pressure will remain northeast of the area keeping perception chances confined to the southwestern Piedmont through Friday before the high exits to the east and out to sea. Highs during this time in the mid 80s with lows in the mid to upper 60s. The moisture transport from the south returns once again for the weekend aided by the Bermuda high and a developing low pressure system in the Gulf of Mexico. At this time, it is uncertain as to how quickly the return of moisture will be able to produce precipitation over the area, and so Saturday is up in the air as far as rainfall is concerned. This is mainly because of the uncertainty in the development and track of the Gulf low. Despite these differences remaining on Sunday, it may not matter as a plume of moisture from the south is expected to ramp up convection once again over the Carolinas. This feature will remain in place through Monday and thus the end of the long term forecast. While Saturday temperatures will reach the upper 80s with some possible breaks in the clouds, expected overcast on Sunday and Monday will help bring temperatures back down into the low 80s. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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As of 655 AM Tuesday... MVFR/IFR conditions at RDU/RWI are expected to lift to VFR by 14z, with considerable mid and high clouds lingering overhead through the day. Despite VFR conditions then dominating after 14z areawide, scattered showers and storms with brief MVFR conditions are possible near RDU/RWI in the 16z-20z time frame, after which time this activity should be shifting to the NE toward/into VA. After 20z, showers/storms are then possible near INT/GSO as an upper trough approaches from the NW. This risk will persist until 01z before any showers/storms in the Triad slowly decrease in coverage and intensity through the end of the TAF valid period. But VFR conditions should dominate through 12z Wed. Looking beyond 12z Wed, the aforementioned approaching mid level trough and associated surface cold front will bring showers/storms across the NW sections including INT/GSO by late morning. This convection will increase in coverage and strength by midday, with a good chance of showers/storms at all sites 17z-22z Wed. Sub-VFR conditions and gusty/erratic winds are possible within and near any showers/storms. Convection will decrease slowly Wed night as the cold front drops southward through the area. Thu through Sat are likely to be mostly dry and VFR as high pressure builds in from the north, although FAY may see a few afternoon showers. Also, sub-VFR fog/stratus are possible early Sat morning with increasing low level moisture over the region. -GIH
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...Hartfield

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