Forecast Discussion
Summary
SYNOPSIS
... Tropical Storm Ophelia will move northward across eastern North Carolina today and then away tonight. In its wake, quiet weather is expected through Sunday and Monday. High pressure ridging down from the north is expected to take hold by the middle part of next week, resulting in cloudy, damp, and cool weather.
NEAR TERM /THROUGH TONIGHT/... As of 6:35 AM EDT Saturday...The center of TC Ophelia remains just off the coast of Wilmington, NC with bands of sct light to moderate precip along and east of the I-77 Corridor. Bkn to ovc clouds continue to gradually expand westward and are currently covering roughly the eastern half of our CWA. At present, the gustier winds are largely confined to the I-77 Corridor with gusts in the 20 to 26 kt range, but I still expect the gusts to expand further west as the morning wears on. The continued NELY flow around the edge of TC Ophelia should keep the boundary layer pretty well mixed and prevent any fog from developing this morning except across the more sheltered sw NC mtn valleys. Low temps should bottom-out near or slightly below climatology.
Otherwise, this storm will keep gusty conditions across roughly the eastern half of the fcst area thru the afternoon. Wind speeds/ gusts are still expected to strengthen a bit across our eastern zones as we approach sunrise, but I still don't anticipate any gusts higher than 30 kts or so. Overall, QPF amounts have come down a bit across our NC Piedmont and Foothill zones with the highest amounts now less than an inch, which likely will not be enough for any significant flooding concerns. TC Ophelia will lift north of the area as it interacts with an upper level trof this afternoon/evening with precip coverage/amounts decreasing as the day wears on. Winds will also diminish by the evening as the center of the low lifts further northward and the pressure gradient weakens. Still expect high temps to approach normal values over our SW zones, with values as much as 8 to 10 degrees below normal across our extreme NE zones due to cloud cover and precip.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 308 AM Saturday...the back half of the weekend and early part of the new week look relatively benign even as a weak low and front might be hanging out along the southeastern edge of the forecast area. A weak mid/upper ridge is expected to build overhead in the wake of Ophelia, so we will lack mid/upper forcing and moisture will be paltry, thus the expectation of fair weather. Temps look nearly normal for Sunday, then maybe a category above normal for Monday, which should be the warmest of the stretch. Things start to deteriorate Monday night as a sfc ridge starts to nose down from the north and forms a weak cold air damming wedge east of the Appalachians beginning early Tuesday. Slight chances of rain are introduced over the mtns late Monday night as a weak upslope flow begins. The timing of this development could easily slip into Tuesday, though.
LONG TERM /TUESDAY THROUGH FRIDAY/... As of 233 AM Saturday...the medium range part of the forecast continues to look interesting and unusual. The guidance is in general agreement overall with a blocky upper pattern in the nrn stream that goes from an omega block to our north on Tuesday that evolves to a rex block for Wednesday and Thursday, before degenerating into something high-amplitude and positively-tilted with a ridge axis to our W/NW and a trof axis on the East Coast by the end of the week. What is unusual is how the guidance shows a sfc high over Quebec at the start of the period that manages to ridge all the way through/underneath the blockly upper mess and down the east side of the Appalachians as it slowly weakens and drifts to the lower Great Lakes through the period. The result is a weak cold air damming wedge that sets up on Tuesday over the area east of the mtns and remains largely intact thru the end of the period. No doubt it will have some isentropic upglide to thank for its existence, as that develops on Tuesday and forces light precip across much of the western Carolinas through the middle of the week. Precip probs ramp up through the chance range and maximize Wednesday afternoon in the likely range over the mtns/foothills. The upglide slowly wanes in the second half of the week and precip probs slowly diminish but never entirely go away until late Friday. The upshot is that the middle to late part of the week looks cloudy, damp, and cool with temps running 5-10 degrees below normal.