Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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456 FXUS62 KRAH 191705 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 105 PM EDT Sat Aug 19 2017 .SYNOPSIS... A cold front across the eastern Carolinas will linger tonight and then dissipate on Sunday as it retreats northwest. A strong cold front will approach the area on Wednesday and reach the coast on Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 1115 AM Saturday... The latest surface analysis shows the cold front moving east into the eastern Piedmont and approaching the Coastal Plain. Behind the front, surface dew points have fallen into the upper 60s across the northwestern Piedmont and around 70 in the northeast Piedmont. Further aloft, the 925 hPa trough was located near the I-95 region while a the 850/700 hPa trough lagged and was located in the western Piedmont. A prominent short wave trough at 500 hPa was moving across the OH and TN valleys this morning. Deep layer moisture across the region has decreased with precipitable water values ranging from 1.2 inches across the western Piedmont to 1.7 inches across the Coastal Plain. One of the main forecast concerns for the afternoon and this evening is the potential for scattered convection ahead of the front across the southern and central Coastal Plain and the Sandhills. While the atmosphere has become drier, the air mass ahead of the front will become weakly to moderately unstable this afternoon with eastward extent. The placement of the front and the localized convergence will dictate the the location of convection. Still fairly confident that any convection today will be confined to the eastern part of the CWA, east and especially southeast of I-95 with the greatest chances across Wayne, Sampson, and Cumberland counties. Any deep convection should largely dissipate by around sunset with a shower or too linger into the evening hours. Still, coverage will be limited, so no washouts are expected with PoPs ranging from 20-30%. While the wind field is notably stronger than previous days, winds are generally unidirectional from the southwest with the stronger flow well above the mixed layer. Thus, the threat of any severe weather is limited and should be confined to locations near and east of the front. The other issue this afternoon will be the temperatures and the heat index. Dew points this morning once again over performed and exceeded guidance with several stations reporting dew points of 78 and 79. With drier air aloft and drier air at the surface advecting into the region on northerly to northwesterly winds, dew points will come down this afternoon into the lower to mid 70s. This should preclude any need for a heat advisory although heat index values will reach 100 to 104 in spots and have added this to the HWO. Have adjusted maxes up a degree or two in the east with highs of 90 to 95 expected. Drier air tonight, especially across the Piedmont with dew points in the mid to upper 60s will result in a much less muggy night. Overnight lows will range from the upper 60s in the northwest Piedmont to the lower 70s in the Coastal Plain. -Blaes && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... As of 315 AM Saturday... Heights aloft will rise in the wake of the low-amplitude shortwave trough moving out of the region with a 594 dm upper level anticyclone strengthening over the SE US late Sunday into Monday. Meanwhile, front just south of the area will likely wash-out and become ill-define by Sunday evening. Can`t rule out isolated convection along the sea breeze across the far SE Zones, otherwise the warm air and resultant CAP aloft will put a lid on convection across central NC on Sunday. Highs in the lower to mid 90s with lingering low-level dry air again keeping heat indices below 100 F. Onset of southerly return flow Sunday night will mark the return of low-level moisture and warmer temps. Lows 70 to 75. .LONG TERM /MONDAY THROUGH THURSDAY/... As of 244 PM Friday... Monday: As continental high pressure begins to merge with an offshore surface high the question for Monday will be how much moisture is in the weak southerly return flow and what will that result in as far as cloud cover for the eclipse viewing. Partly cloudy skies look likely but there should be enough breaks in the clouds to get a decent view of the moon passing between us and our closest star situated some 93,000,000 miles away. While temperatures are expected to rise into the lower 90s there will be a break in the heat from roughly 1:30 to 3:30 PM. A scattered shower or thunderstorm cant be ruled out, especially in the southern tier of the area. Rest of the week: Relative dry but warm weather continues through Tuesday before the next frontal system passes through the area on Wednesday in association with a low pressure system moving across southern Canada. High rain chances Wednesday will continue through Thursday in the east and possibly into Friday as the front begins to stall near the coast. Temperatures in the low 90s Tuesday and Wednesday will fall back into the mid 80s for Thursday and maybe into the low 80s by Friday. With that, some dewpoints in the lower 60s should make for some very comfortable weather heading into the weekend. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 244 PM Friday... Monday: As continental high pressure begins to merge with an offshore surface high the question for Monday will be how much moisture is in the weak southerly return flow and what will that result in as far as cloud cover for the eclipse viewing. Partly cloudy skies look likely but there should be enough breaks in the clouds to get a decent view of the moon passing between us and our closest star situated some 93,000,000 miles away. While temperatures are expected to rise into the lower 90s there will be a break in the heat from roughly 1:30 to 3:30 PM. A scattered shower or thunderstorm cant be ruled out, especially in the southern tier of the area. Rest of the week: Relative dry but warm weather continues through Tuesday before the next frontal system passes through the area on Wednesday in association with a low pressure system moving across southern Canada. High rain chances Wednesday will continue through Thursday in the east and possibly into Friday as the front begins to stall near the coast. Temperatures in the low 90s Tuesday and Wednesday will fall back into the mid 80s for Thursday and maybe into the low 80s by Friday. With that, some dewpoints in the lower 60s should make for some very comfortable weather heading into the weekend. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... As of 105 PM Saturday... Other than widely scattered showers across the southern Coastal Plain and Sandhills potentially impacting the KFAY terminal, widespread VFR conditions are expected through the 24 hour TAF period. The greatest threat of a local restriction of cigs or vsbys near the KFAY terminal will be from 18 to 22Z with greater coverage to the south and east. Otherwise...skies will be mostly clear through the period with scattered cumulus at around 5kft this afternoon with a mix of scattered fair weather cumulus and cirrus clouds expected on Sunday. Light mainly northwest to northerly winds at less than 7kts are expected this afternoon with light and variable winds expected tonight. Mainly northeast winds less than 6kts on Sunday will veer to east and southeasterly during the afternoon. Looking beyond the 24 hour TAF period... Generally fair weather with VFR conditions are expected on Sunday. The threat of mainly afternoon and evening showers or thunderstorms and late night/early morning fog/stratus increases a bit on Monday and Tuesday. A strong cold front approaches on Wednesday and reaches the coast on Thursdays bringing a greater chance of adverse aviation conditions in showers and thunderstorms. -Blaes && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...BLAES NEAR TERM...BLAES SHORT TERM...CBL LONG TERM...RE AVIATION...BLAES

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