370 FXUS62 KRAH 132002 AFDRAH AREA FORECAST DISCUSSION National Weather Service Raleigh NC 400 PM EDT Mon Sep 13 2021 .SYNOPSIS... High pressure centered just off the North Carolina coast will drift slowly eastward and further offshore through early this week, while continuing to extend westward into the Carolinas. && .NEAR TERM /TODAY AND TONIGHT/... As of 330 PM Monday... A strong 593 dam mid-level ridge is centered over NC today, resulting in another day of sunny skies and dry weather. At the surface, Bermuda high pressure will continue to slowly move east, but still extend west to the NC coast, with a lee trough continuing to set up across VA/NC. S/SW low-level return flow around the high along with the mid-level ridge is helping temperatures to rise even warmer than yesterday, with highs generally in the upper-80s across the far northern Piedmont to lower-90s elsewhere. This is about 7-10 degrees above normal but not enough to threaten any record highs. Furthermore, dew points in the 60s mean the heat indices are relatively close to the actual temperatures. As the ridge weakens and moves offshore tonight, the flow aloft will shift to a moist southeasterly direction. This could result in the development of some scattered low and mid level clouds by the early morning particularly in the southeast. Slightly higher thicknesses along with the clouds will help keep lows tonight a few degrees warmer than last night, in the mid-to-upper-60s. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 355 PM Monday... As a longwave trough moves east across the Northern Plains and Great Lakes on Tuesday and Tuesday night, the offshore ridge of high pressure both aloft and at the surface will be pushed further east, causing some weak height falls of around 10-20 dam over central NC. This will also change the deep-layer flow to a more moist south- southeasterly direction, increasing PW values to around 1.25-1.50" on Tuesday night. Thus while it will be too dry during the day for any precipitation and mostly sunny skies are expected, by tomorrow night clouds will be on the increase especially in the southeast. Low-level thicknesses around 5-10 m lower than today will support highs on Tuesday maybe a degree or two lower than today, in the upper-80s to near 90. Lows Tuesday night will again be in the mid-to- upper-60s. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... As of 330 PM Monday... The long term begins with upper-level ridging near Bermuda, and an upper-level trough stretching NE from the mid-MS Valley to the eastern Great Lakes Region. The ridge will then build SE towards FL through Saturday as the trough lifts NE, then upper-level high pressure builds quickly from the Southwest to the mid-Atlantic by early next week. At the surface, high pressure off the coast will continue southerly flow across the region Wednesday, then low pressure moving north near the coast and high pressure across the Appalachians will switch flow to easterly Thu/Fri, then the high along the Appalachians will build north and linger through early next week, maintaining south to southeasterly flow through the period. Lowering heights and increased cloud cover will help drop high temperatures closer to normal on Wednesday. However, rising dewpoints into the upper 60s to low 70s will make it feel more muggy, with heat index values ranging from the upper 80s NW to mid- 90s SE. Increasing moisture and instability will allow for diurnal isolated to scattered showers and thunderstorms to return to the forecast on Wednesday, however storms are not expected to be severe at this time. We're still keeping a close eye on the potential tropical cyclone development from the upper-low to our SE. NHC currently has the area of concern under a 10 percent chance of tropical cyclone development in the next 2 days and a 50 percent chance of development in the next 5 days. Most models and their ensembles keep the low offshore and to our east, however moisture throughout the column will remain elevated and PWs could increase to near 2 inches for the Coastal Plain on Thu/Fri. Diurnal convection will continue through the weekend, with highs rising closer to 90 thanks to the building ridge. Upper heights will only be around 1 standard dev above normal for our area from the ridge, but with dewpoints near 70, heat index values will remain summer-like and in the low to mid-90s for early next week. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... As of 140 PM Monday... 24-hour TAF period: Confidence is high that VFR conditions will prevail through this evening, with clear skies and light south/southwest winds. As the ridge of high pressure aloft moves offshore, southeast flow will bring increased moisture, which could result in some scattered low-level clouds late tonight and early tomorrow morning, especially in the far southeast. There is also a chance for some sub-VFR ceilings/visibilities from mist/low stratus around sunrise in the far southeast, including FAY, though it can't be entirely ruled out at RWI either. Looking beyond 18Z Tuesday: VFR conditions and dry weather will prevail on Tuesday. Increasing moisture and low pressure off the NC coast may then result in isolated to scattered showers and storms each afternoon/evening from Wednesday through Saturday, along with possible fog/low stratus each morning. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...KC/Hartfield NEAR TERM...Danco SHORT TERM...Danco LONG TERM...JJT AVIATION...Danco