Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 201947 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 247 PM EST Mon Feb 20 2017 .SYNOPSIS... High pressure will extend along the East Coast through early Tuesday. A weakening upper-level disturbance will cross the Southeast states Tuesday night into Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 950 AM Monday... Forecast is on track. Plentiful sunshine is a near certainty beneath dry high pressure at the surface and deep ridging and stable/warm air aloft. Observed thicknesses are higher than yesterday morning by around 10 m, although they shouldn`t rise quite as high through the afternoon as they did yesterday, given that the surface ridge will be building down the Eastern Seaboard. Temps are already in the mid 50s to lower 60s, comparable to yesterday`s pace, so still expect highs from around 70 NE to the low-mid 70s elsewhere, with light winds veering from NE to E then SE through the day. -GIH Earlier discussion from 315 AM: A narrow upper level ridge extending from the eastern Gulf into southern Ontario coupled with a dry air surface ridge building southward along the East Coast will maintain mostly clear skies, and very mild conditions for this time of year. While the low level flow is northerly, it`s a neutral flow, meaning little if any cold air advection. Thus, afternoon temperatures should be fairly comparable to Sunday`s, in the 70-75 degree range. Tonight, the low level flow becomes ely as the parent high to our north moves a little farther to the east. This ely flow will advect moisture off the Atlantic and into central NC. Due to the upslope component of the flow, the rising/lifting of the moisture should cause a layer of stratus clouds to develop late tonight/early Tuesday morning in vicinity of the Yadkin River Valley, possibly spreading into our western counties including the Triad region. This moisture band is fairly narrow so no precipitation should be generated from these clouds. Elsewhere, expect mostly clear-partly cloudy skies, with patchy fog possible. Overnight temperatures will vary from the upper 30s-around 40 northeast to the mid 40s over the far south and west. -WSS && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 315 AM Monday... Tuesday, the low level ely flow will advect a cooler air mass into central NC, resulting in afternoon temperatures 4-6 degrees cooler than today`s high temperatures. In addition, expect to see more clouds, though still partly sunny. Tuesday night, the low level flow will continue to slowly veer to a south-southeast direction in response to the departure of the high pressure system and the approach of an area of low pressure from the southwest. The tightening pressure gradient will enhance the low level sly flow and attendant warm air advection, leading to increase isentropic lift/upglide and the possibility of a few showers breaking out overnight night across the western Piedmont. Additional lift may be supplied by increasing divergence aloft. Thus, have tweaked PoPs up 10-15 percent from the previous forecast with chance PoPs covering portions of the western/southern Piedmont after 06Z Wednesday. If model trends continue or remain consistent, solid chance/low end likely PoPs may be warranted. At this time, not anticipating rainfall amounts of any significance, with amounts of just a few hundredths expected. Overnight temperatures near 50-lower 50s. && .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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As of 247 PM Monday... The pattern begins to change for midweek and although we stay warm, a wetter pattern will bring more clouds and some chances for rain late in the week. That being said no day looks like a washout at this point and rainfall totals for the week look only to be about a half an inch at the most with some locations receiving very little rain. Temperatures will remain in the 60s and 70s throughout the period. To break it down further, Wednesday will bring our fist chance for rain as a low pressure system in the Gulf of Mexico dives southeastward towards the Florida Peninsula. As a surface high sinks southward, central NC will be on the northern fringes of this system and any rain that does occur will be a result of some isentropic lift and moisture advection from the south. Best chances will be in the western part of the forecast area. On Thursday a developing low pressure system to the west will establish a warm front along our northern border and begin to advect northward. As a result, best chances for any appreciable rain Thursday will be along the VA border counties. For the most part Friday looks dry as the low to the west tracks northeastward into the Great Lakes. As it does so frontogenesis will occur just west of the Appalachians as a cold front moves into North Carolina Saturday morning and across our area by Saturday late afternoon/evening. This may be our best chance for rain during the long term with a non-zero chance of some Thunder, especially in the southeast where some better instability may be allowed to develop. Behind the front, high pressure moves in for Sunday signaling a return to clear skies and dry weather.
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&& .AVIATION /18Z Monday through Saturday/... As of 112 PM Monday... High confidence in VFR conditions areawide through at least this evening, as high pressure builds in from the north, topped by warm and stable air aloft. Mostly just high clouds based above 18000 ft AGL are expected through tonight and Tuesday across the area, however at INT/GSO, increasing low level moisture within stable low levels late tonight may result in a few low clouds based below 900 ft AGL and perhaps shallow MVFR fog 08z-12z tonight. Elsewhere, no low clouds/fog are expected tonight. Winds will stay light from the NE, trending to ESE areawide over the next 24 hours, but speeds will be a bit stronger at RWI/FAY this afternoon. Looking beyond 18z Tue, VFR conditions will hold through Tue evening. We will see a chance for late-night and early-morning sub- VFR fog/stratus repeat areawide each day through the remainder of the week. MVFR to IFR conditions with a few showers are possible late Tue night through Wed as an upper trough crosses the region. A cold front will cross the area Sat, bringing a chance for showers and MVFR cigs. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS/BLS NEAR TERM...Hartfield/WSS SHORT TERM...WSS LONG TERM...Ellis AVIATION...Hartfield is the U.S. government's official web portal to all federal, state and local government web resources and services.