Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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015 FXUS62 KRAH 271108 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 708 AM EDT Mon May 27 2024 .SYNOPSIS... Unseasonably warm and humid airmass will continue unsettled conditions through tonight. A series of cold fronts will move through central NC through mid week with high pressure building overhead for the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 415 AM Monday... ...There is a level 2 risk for severe storms today with another unseasonably warm and humid airmass in place... A pair of MCVs within the remnants of the MCS that moved through late last night is working its way through eastern NC with its trailing stratiform rain exiting the forecast area. Over the western Piedmont and Sandhills, scattered showers and isolated thunderstorms have developed where an area of enhanced 925-850mb moisture transport and WAA overlaps with a plume of 1000-1500 J/kg MUCAPE. Hi- Res guidance has done a fairly good job with this regime and is forecast to lift northeast through the Piedmont into the mid morning hours. Upstream over the lower Ohio and Tennessee Valley, an MCS is moving ESE with its apex along the SBCAPE gradient stretching from near Morristown TN into the southern Piedmont. Observational trends have begun to show gradual weakening of this system and nearly all Hi-Res guidance weakens this complex even further as it traverses the southern Appalachians towards daybreak. The remnant cold pool may initiate scattered showers and storms near the Triad shortly after sunrise within a moist and unstable airmass in place. There will likely still be some surface stability in place, but there will be sufficient elevated instability to tap into if the cold pool is deep/strong enough. This regime will track eastward through central NC with greatest coverage expected across the northern half tied to an MCV from weakening convection upstream. Beyond 15z, upscale growth in deeper convection will become increasingly possible especially over the Coastal Plain where weakening MLCIN will allow for any ongoing showers/storms to tap into 1500-2500 MLCAPE, 35-45 kts of 0-6km shear, and 150-250 0-3km SRH, resulting in increased organized convection. Whether this occurs within the forecast area or just to the east remains uncertain, but the best chance will be along and east of the US-1 corridor. These storms would be capable of all hazards including damaging winds, large hail, and an isolated tornado. This regime should shift east by early afternoon with a second rounds of storms possible within its wake. This round remains fairly uncertain given it depends on the ability for the boundary layer to recover enough to overcome drier air punching in aloft and stronger 500mb flow shifting east into eastern NC. If the airmass is able to recover or if the first round fails to materialize, the second round would additionally be capable of all hazards from the mid afternoon into the early evening hours before shifting east of the forecast area. A cold front is expected to move through the area early Tues morning, but the cooler air most likely will not make it completely through central NC before daybreak with another night in the mid/upper 60s to low 70s expected. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 305 AM Monday... Aloft, a s/w should track through SC Tue then out over the Atlantic Tue night as the base of the trough moves over central NC. Meanwhile at the surface, the cold front should be over the NC Piedmont by daybreak Tue, then continue eastward through the area through the day and offshore Tue night. Expect NW flow in the wake of the front Tue, however the arrival of cooler air may be delayed until Tue night. Cannot rule out a shower/storm over the southern/central Coastal Plain on Tue ahead of the cold front, but that activity will move out with the passage of the front and dry weather is expected area-wide Tue night. Highs Tue should generally range from low/mid 80s north and northwest to upper 80s south and southeast. Lows Tue night will depend on the arrival of cooler air, but for now expect upper 50s north to low/mid 60s south. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 230 AM Monday... An upper level trough will amplify as it progresses eastward over and through the mid-Atlantic and Carolinas. Several s/w disturbances will pass over the area as they swing through the trough, however for now they still appear relatively moisture-starved. The trough should shift offshore over the weekend, with the sub-tropical ridge slowly progressing eastward through the area behind it. At the surface, with the cold front offshore by early Wed, a trough may linger over central NC Wed before cool high pressure builds in from the west Wed night through Fri. The high should be over central NC Fri night/Sat. Forecast confidence decreases beyond Sat as model solutions diverge. For now, expect largely dry weather through Sat night, although will have to keep an eye on the passing s/w disturbances for potential precipitation development. Temperatures should be near normal for Wed, then near to below normal through the remainder of the forecast period. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... As of 700 AM Monday... Scattered to numerous showers have developed in multiple waves, the first moving just north of RWI with the second just now developing over the southern Piedmont and will track towards RDU through roughly 15z. Expect mostly showers with isolated thunder, but given the moist and unstable regime, have opted to TEMPO thunder given how easily this has been achieved in some convection this morning. A decaying MCS and outflow is currently traversing the southern Appalachians and working its way into the western Piedmont. Model guidance has continued to struggle with how this will impact GSO/INT so have kept status quo with TEMPO storm potential. Intensification is possible with eastward extent through the early afternoon, but unmodeled showers across the southern Piedmont may add complexities to the afternoon forecast. Southwesterly surface winds will become gusty by late morning at all TAF sites with gusts up around 25 kts. Afternoon showers and storms will again be possible, but will largely be dependent on the activity from earlier convection. Overnight fog/stratus may be possible, best chance FAY/RWI, ahead of a cold front approaching from the NW. Outlook: The first of several cold fronts will move through late Mon night into Tues morning with high pressure building in behind and VFR conditions expected through Fri. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Swiggett NEAR TERM...Swiggett SHORT TERM...KC LONG TERM...KC AVIATION...Swiggett