Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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620 FXUS62 KRAH 051612 RRA AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1211 PM EDT Sun May 5 2024 .SYNOPSIS... A quasi-stationary front across the area this morning will retreat northward through the afternoon as a series of mid and upper-level disturbances traverse the area. A low amplitude shortwave trough will progress east into the area late Monday and into Tuesday, bringing additional chances of showers and storms. Drier conditions are expected by mid week, leading to increasing heat as upper level ridging returns. && .NEAR TERM /THROUGH TONIGHT/... As of 1030 AM Sunday... * An area of showers associated with an MCV will move northeast across the Piedmont through early afternoon. * Convection including some thunderstorms focuses across the east and northeast areas this afternoon with less active conditions and widely scattered showers and storms elsewhere. The latest water vapor satellite imagery and morning RAOB data/regional radar VWP data shows a well defined vortex/MCV that is tied to convection that moved across northeast GA/Western SC last evening. This feature is located across the southern Piedmont of NC, just northeast of KCLT this morning and is driving the cluster of showers and embedded heavier rain across much of Stanly, western Moore, Randolph and western Chatham Counties. At the same time, the surface boundary lingering across the region since yesterday retreated west overnight and extends from south-central VA to near KTDF, just east of KBUY to near KCLT. West of the boundary winds are northeast to northwesterly with dew points in the lower 60s and low clouds with IFR to LIFR CIGS of 2-900 feet. East of the front it`s a warmer and more humid air mass with dew points in the mid to upper 60s, a southeast wind, and higher cloud bases with some breaks of sunshine in the Coastal Plain near Clinton, Goldsboro and Rocky Mount. The air mass has become weakly unstable southeast of the front with MLCAPE values now near and just in excess of 500 J/Kg in a tongue extending from eastern SC north into the Sandhills and eastern Piedmont. The band of showers extending from southwest to northeast across the western Piedmont this morning will continue for the next few hours, but as the MCV rides northeast, the more widespread rain/showers should lift northeast across Chatham, Alamance and Orange counties into Durham and Person Counties with shower activity waning in the subsidence to the west and southwest. In addition, scattered showers will develop over the next hour or two across northeast SC, Sandhills and southern Coastal Plain and spread northeast. This convection is more apt to become deeper and support some thunderstorms toward early to mid afternoon. By mid to late afternoon the focus for convection will likely shift northeast across the central and northern Coastal Plain near Rocky Mount and Roanoke Rapids. Given the modest mid level lapse rates and weak to possibly moderately unstable airmass, a few stronger storms are possible. Further west, it will trend less active with a widely scattered shower or possibly a storm during the afternoon. Highs today will range from the lower/mid 70s across the Triad and VA border areas to the upper 70s to around 80 in the east and southeast. Upper level forcing wanes this evening and overnight with some weak mid level ridging extending across the area. The axis of deepest moisture slips east slightly but PW values remain near 150% of normal overnight. Can`t rule out an isolated shower overnight and there is a signal for convection that may develop in far western NC to hold together and move into the western Piedmont as it fades late this evening. Otherwise, clouds will thicken up again tonight and it will be muggy. Overnight lows will range in the lower to mid 60s. -Blaes && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 330 AM Sunday... ...Elevated Rain/Storms Chances Again Monday... The southern stream shortwave trough associated with the expansive MCS over the southern Plains and Texas will become increasingly sheared as it ejects eastward across the middle MS and Tn Valley Monday afternoon and then across the central and southern Appalachians and into mid-Atlantic region Monday evening and night. Renewed moisture advection ahead of this wave will lead to a resurgence of anomalous moisture into the region with PWATs 1.6-1.8, near record daily maximum. Stronger daytime heating should result in more robust instability of 1000-2000 J/Kg across the area. There is the potential for an area of deep moist convection(DC) to propagate east into and across the area during the afternoon and early evening, with additional development possible along convective outflow. Shear will increase slightly, with models indicating a pocket of enhanced shear of 25- 30kts along the potential DC feature. Thus, cannot rule out an isolated severe cluster or two Monday afternoon and evening. Storms intensity and coverage should decrease after sunset, with some lingers isolated showers possible Monday night. Highs 80-85. Lows in the 60s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... As of 1211 PM Sunday... Upper pattern for the extended: A short-wave will exit to our east early Tuesday, behind which mid-level ridging will build back over the southeast through late Wednesday. The ridge will de-amplify as a strong vort max digs into the Midwest Thursday, eventually ejecting eastward through the northeast US. This feature will induce increasingly swly flow aloft over central NC Friday into Saturday. Temperatures: Hot and humid conditions will persist Tuesday through Thursday under the anomalous mid-level ridge. The NBM still continues to highlight high probabilities for >90 degrees for locations south and east of Raleigh both Wednesday and Thursday (The GEFS, EPS, and GEPS are less enthused, but generally depict a similar geographic area with highest probabilities (10-30%)). Given dew points will peak in the upper 60s/lower 70s, heat indices will likely pop up into the mid 90s both Wednesday and Thursday afternoons. Thus, make sure to take frequent breaks in the shade and hydrate if spending a lot of time outdoors these days. Temps will "cool" off a bit Friday and into the weekend as the aforementioned upper vort max/trough dips into the southeast. Highs in the mid 80s are currently expected Friday, followed by mid to upper 70s on Saturday. However, these may need to be modified some as we get closer and guidance comes into better agreement/confidence increases. Precipitation: POPs will be lower Tuesday and Wednesday under general ridging aloft (and some nwly flow in the lower levels should lower PWAT a bit). However, can`t rule out some isolated/scattered diurnally driven showers/storms along any differential heating boundaries including late day sea breeze migration into our area. Some guidance depicts some energy aloft trickling through our area late Wednesday which could maybe generate a bit more activity. However, will keep POPs capped at low chance for now. As we progress into the Thursday through Saturday timeframe, there is some uncertainty wrt to the evolution of the aforementioned strong vort max/trough and an associated cold front. However, the general consensus among ensembles/deterministic output is that this upper feature does look strong enough to possibly induce an airmass change for our area later this weekend (i.e. a stronger cold front actually making it`s way to the coast). As such, showers and storms are likely ahead of and along the cold front as it moves through. While we`ll need a bit more updated model guidance to get into specifics, it does appear at this point that some severe storms will be possible Thursday and Friday as guidance suggests an uptick in mid-level lapse rates and bulk-layer shear in this time frame. Again, a bit too far out for specifics, but we`ll continue to monitor as we get closer to later next week. && .AVIATION /11Z SUNDAY THROUGH THURSDAY/... As of 640 AM Sunday... Upper level disturbances interacting with anomalously moist air in place will continue to result in adverse aviation conditions through the forecast period. A band of moderate showers with the potential for some embedded lightning currently over western and central Piedmont of NC will progress slowly eastward through the remainder of the morning and afternoon hours, and should impact all terminals through 21z. Additional showers and thunderstorms will likely develop outside of the primary band, but should be more scattered in nature through the remainder of the afternoon and evening. Expect gradual lifting of the widespread LIFR to MVFR as the front draped across the area begins to lift north. Outside of any convection, flight conditions should lift to VFR at KFAY and KRWI during the late morning and early afternoon. KGSO, KINT, and KRDU will also show some improvement, but could very likely remain MVFR through the afternoon and evening. Widespread LIFR to MVFR restrictions are expected to re-develop Sunday evening/night. Outlook: Scattered to numerous showers and storms are expected again Monday. Rain chances should become more diurnal and scattered in nature Tuesday and Wednesday. Continued moist air will support the potential for restrictions associated with widespread fog and/or low clouds each morning && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...BLAES SHORT TERM...CBL LONG TERM...Luchetti AVIATION...CBL