Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 241849 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 250 PM EDT Fri Mar 24 2017 .SYNOPSIS... An area of high pressure anchored offshore will extend west into central NC through Saturday. A weakening upper disturbance will cross our region on Sunday. && .NEAR TERM /THROUGH TONIGHT/... As of 250 PM Friday... Air mass modification underway as sly low level flow has advected a warmer and slightly wetter air mass into central NC. This is evident by dewpoints currently in the 40s (versus the teens and 20s from Thursday). Temperatures have rebounded into the 60s, near 70 over the Sandhills. Extensive mid level cloudiness which covered much of the western Piedmont this morning has thinned out, while scattered- broken cu has developed, primarily south of highway 64. An area of high pressure at the surface was anchored offshore. Circulation around this feature was ushering the warm moist air into our region. Aloft, an area of high pressure stretched from the northern Gulf into the Carolinas. These features will drift slowly east and weaken with time tonight into Saturday. With the uptick in low level moisture, there is a higher threat for patchy fog and/or low clouds late tonight into early Saturday morning. The moist layer is relatively shallow and the lift is very weak, so no precip should occur. Overnight temperatures will be rather mild compared to recent nights. Lows should be in the upper 40s to around 50. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... As of 250 PM Friday... Warming trend continues Saturday as the high continues to drift away from our region, while an area of low pressure lifts from the southern Plains into the mid MS Valley. The approach of this feature will deepen our sw flow, increasing the moisture advection. This will lead to increasing cloudiness. While the atmosphere moistens, little if any lifting mechanisms noted to generate precip, aside from afternoon heating, Saturday through Saturday evening. Still, could see an isolated shower or two over the southern Piedmont but probability and coverage is too remote at this time to mention in the forecast. The warming air mass will translate to afternoon temperatures in the 70-75 degree range. Clouds will thicken and lower across the area Saturday night. This blanket of clouds will trap the heat gained Saturday, resulting in overnight temperatures in the 50s. A lead s/w ahead of the main low pressure system over the mid MS Valley will support a band of showers that will cross the mountains overnight, and may be in vicinity of the Yadkin River just prior to daybreak. Will retain the slight chance PoP over our western periphery late Saturday night. && .LONG TERM /SUNDAY THROUGH FRIDAY/... As of 240 PM Friday... A deep low pressure system will lift northeast into the Great Lakes Sunday. Its associated cold front will be weakening and essentially stalling as it edges up against the mountains Sunday and the parent low moves further northeast. This will result in central NC being nicked by only a glancing blow from the stronger dynamic regime associated with the upper system. So, despite our increasingly warm and moist airmass, convection will be favored northwest, with progressively smaller chances heading southeast. Some areas east of I95 may not see any activity at all. Will also maintain small chances for thunder west during the afternoon as instability will be modest and the east will be strongly capped in proximity to the Bermuda high offshore. Highs will reach the low to mid 70s, but the northeast may struggle to reach upper 60s due to heavier cloud coverage and potential shower activity. Warm and moist airmass remains in place in return flow around the Bermuda high with isolated convection on Monday and highs mostly in the upper 70s. A rather weak, but more southerly tracking short wave will be approaching from the west on Tuesday to increase our chance of convection somewhat due to its moving through during the heat of the day. Not seeing forcing that would readily signal potentially strong or well-organized convection, though, so will maintain 40-50 chance PoPs. Tuesdays highs will again climb way up into the 70s, with some lower 80s likely across the southern tier. Highs will again reach upper 70s Wednesday, but only isolated showers look doable in weak westerly low level flow and upper ridging over the area. Cooler high pressure makes a surge down the Atlantic coast on Thursday, with a backdoor cold front threatening to make it as far south as central NC, but low confidence in picking a model solution at this point. We will concurrently have a more southerly low pressure system taking shape over the southern Midwest which would feed moisture into the frontal zone and potentially give us a rain period Thursday night and Friday. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... As of 100 PM Friday... High pressure at the surface and aloft will gradually weaken and drift east through Saturday night. This will allow an area of low pressure to approach from the west Saturday night and Sunday. The southerly flow ahead of the low will advect a moist air mass into our region, leading to probabilities of MVFR conditions due to low clouds and fog late tonight-early Saturday morning, and again Saturday night into Sunday morning. The sub VFR parameters may linger well into the morning hours before lifting into VFR criteria during the afternoon. The threat for showers appear minimal through Saturday, though the potential appears higher for late Saturday night into Sunday. Periods of MVFR/IFR ceilings and visibility due to fog appear probable Sunday night through Wednesday. The highest threat for scattered showers will be on Tuesday when another upper disturbance passes primarily to our north. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...mlm AVIATION...WSS

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