Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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415 FXUS62 KRAH 140138 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 938 PM EDT Mon May 13 2024 .SYNOPSIS... A warm front will lift northward through the Southeast United States Tuesday morning, then lift along the Carolina coast Tuesday afternoon and evening. An area of low pressure over the Midwest will bring a cold front through Wednesday night to early Thursday, followed by high pressure for the end of the week Friday. && .NEAR TERM /THROUGH TONIGHT/... As of 930 PM Monday... No major changes to the forecast with the evening update, only slight tweaks to the temperatures to account for most recent observations and trends. The 00Z upper air analyses show plenty of moisture at H85 across much of central NC, while there was a strong gradient in H7 moisture from SW to NE across the area. A weak mid-level perturbation shows up at H5 over GA/SC, with sub-tropical ridging along the mid- Atlantic coast. Farther to the southwest, another perturbation, likely associated with the ongoing MCS, shows up at H25 and H5 over LA/MS. The strong mid-level closed low shows up invof Kansas City at H5. As of the 00Z surface analysis, high pressure continues to sit of the mid-Atlantic coast, while a stationary front remains draped along the Gulf Coast. The pair of MCSs are evident on GOES satellite imagery, one over FL and the other over the NW Gulf into LA/MS. Still expect isentropic ascent and some weak elevated instability tonight, favoring development of isolated/scattered showers, which should blossom over SC late tonight and spread NNE into central NC early Tue morning. Have kept forecast lows tonight in the upper 50s to low 60s. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... As of 250 PM Monday... A difficult forecast is in store Tue/Tue night, with uncertainty in regards to timing, duration, and intensity of showers, as well as severe potential. Synoptically speaking, the shortwave trough from Mon over the Midwest is forecast in most of the guidance to reach the southern Appalachians by early Wed, weakening as it moves east. At the surface, the stationary front over the deep south Mon will likely move north as a warm front into central GA and SC. The area of convection presently over southeast TX is forecast in much of the guidance to become a convective MCS somewhere over the deep south of LA/MS or western FL. Several of the models, including the high-res HRRR/ARW, indicate that as this convective MCS reaches the SE US Tue morning and afternoon, a remnant MCV could remain and possibly impact our SE counties Tue aftn/eve period. This remains to be seen and is uncertain. Nevertheless, the aforementioned storm complex could influence how much rain showers we get Tue morning, with the HRRR/ARW, for example, indicating scattered showers in the morning and the better chance of storms in the aftn/eve with the remnant MCV. The NSSL CAM, on the other hand, suggests stratiform rain in the morning, which could stabilize the atmosphere and limit convection later in the day. This certainly makes for a difficult forecast. Our current thinking favors isolated/scattered showers in the morning given lesser forcing aloft during this period. Better chances of showers and even some storms would be favored in the aftn/eve period as the mid-level trough inches closer and PW`s increase along with the 850 warm front getting into the Carolinas. As for the severe potential, SPC maintains a marginal risk across the southern Piedmont and Sandhills, but perhaps the better risk area could be from SW to NE over the eastern Sandhills to southern Coastal Plain to capture any remnant MCV and possible gravity wave favoring damaging wind potential or an isolated tornado. The NCAR Neural Network favors this region as well. Highs are tricky but we kept highs in the upper 60s to mid 70s. There could be a lull in showers and storms by the late evening, though guidance continues to hint at some storms over the higher terrain and over eastern TN possibly impacting the western Piedmont late Tue night in association with the trough and an attendant front/trough in the TN valley. This will also be near nocturnal stabilization so most activity would be isolated in nature. Lows in the 60s. && .LONG TERM /WEDNESDAY THROUGH MONDAY... As of 225 PM Monday... ...Unsettled Weather Pattern Potentially Continues Into the Weekend... Wednesday and Wednesday night: A compact shortwave trough centered over the TN Valley will progress slowly eastward through the region through Wednesday night. In the wake of the secondary/triple point sfc low and attendant warm front lifting north and east of the area, a lull in precip is looking increasingly probable through mid day, with a noticeable reduction in PWATs noted across the area during this time. However, favorable diurnal timing of the upper trough dynamics and surface front into the area from the west, should lead to a ramp up of convective rain chances during the afternoon and evening. Expected moderate destablization with deep layer shear of 30-40 kts would be sufficient to support a few strong to severe storm clusters, with the FV3/GFS ML probabilities maximized along and east of US 1 from 3-9 PM. Damaging wind gusts and large hail will be the primary threat. Rain chances will taper off west to east during the late evening and overnight hours. High will depend on breaks in cloud cover and timing of convective Wednesday afternoon; ranging from mid/upper 70s north to lower/mid 80s south. Lows in the upper 50s to lower 60s. Thursday and Thursday night: Drier conditions are expected on Thursday, through weak perturbations on the back-side of the exiting shortwave trough could result in some isolated showers and perhaps a rogue thunderstorm Thursday afternoon. Temps should be very comparable to Wednesday. Highs in the mid/upper 70s north to lower/mid 80s south. Lows in the upper 50s to lower 60s. Friday through Monday: Significant timing/phasing discrepancies persist wrt the eastward ejection of a southern stream shortwave trough from the SW US Thursday and into the SE US sometime during the second half of the weekend, or possibly delayed until early next week. Until the timing can be resolved, will advertise scattered showers and storms each day with a decent chance that we could see some convectively enhanced vorticity disturbances impacting the area, well in advance of the synoptic scale trough. Seasonable highs 80-85. Lows in the lower to mid 60s. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 815 PM Monday... An area of rain, associated flight restrictions, and gusty winds up to 25 kts will affect INT/GSO and vicinity this evening and interrupt VFR conditions otherwise and elsewhere in cntl NC for most of tonight. A separate area of rain/showers will develop across the srn Appalachians and Carolinas late tonight-early Tue, during which time MVFR-IFR conditions are expected to overspread cntl NC. Associated rain may become moderate to heavy in intensity at RDU, FAY, and RWI on Tue, especially where deeper showers and isolated storms will be possible Tue afternoon. Outlook: Sub-VFR conditions and possible fog will be possible early Wed. Another period of showers or storms are possible Wed aftn/eve, along with a chance of sub-VFR clouds early Thu. VFR should return Thu aftn, with the next chance of showers possibly Sat. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...KC/Kren NEAR TERM...KC/Kren SHORT TERM...Kren LONG TERM...CBL AVIATION...MWS/Kren