Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 261744 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 145 PM EDT Tue Sep 26 2017 .SYNOPSIS... A narrow ridge of high pressure will remain centered over the Appalachians through Wed, while Hurricane Maria tracks northward, offshore the coast of the Carolinas. Meanwhile, a dry cold front will approach from the northwest, then cross NC late Thu and Thu night. && .NEAR TERM /THROUGH TONIGHT/... As of 1030 AM Tuesday... 12Z upper air analysis depicts a stout ne flow in the 925-850mb layer into eastern NC. This flow advecting Atlantic moisture into the region, resulting/maintaining a deck of stratus that has advanced as far west as Asheboro and the eastern edge of the Triad. Still cannot rule out a few showers along the eastern periphery of our forecast area, especially east of a Roanoke Rapids-Wilson line, where low level convergence is maximized. Deck of stratus through early this afternoon will play a role in high temperatures. Expect the western edge of the stratus to erode by mid day, with some breaks in the overcast expected in the Triangle region by early afternoon. This display of sun should aid to boost temperatures into the low-mod 80s. East-northeast of the Triangle, the stratus will likely persist well into the afternoon, inhibiting insolation and resulting in afternoon temperatures in the 70s. Pressure gradient between Maria well offshore of the Outer Banks and an area of high pressure stretching south-to-north along the spine of the Appalachians will result in steady/breezy northeast sfc winds through early evening. Gusts 20-25 mph probable east of highway 1. Partial clearing expected areawide early this evening before the stratus expected to fill back in by late evening, primarily east of highway 1. Overnight temperatures in the 65-70 degree range expected. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 355 AM Tuesday... Based on the official NHC forecast track, by-then Tropical Storm Maria will be ~150 nm east of HSE by 12Z Wed, after which time a turn to the east and an increase in forward speed will occur. The low level flow will consequently back to a (drier) nwly to nnwly direction and result in partly to mostly sunny conditions on Wed. Projected low level thickness values around 1425 meters at GSO will favor well above average temperatures in the upper 80s to lower 90s. Lows in the 60s. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 325 AM Tuesday... Thursday will be our final unseasonably warm day as Maria accelerates eastward and a dry cold front pushes south down the Atlantic coast. Highs Thursday will reach the mid and upper 80s, with some lower 90s possible along the southern tier of central NC. Strong cold air advection will be getting underway Thursday night as high pressure builds east across the Mid Atlantic. This high pressure will then surge south down the Atlantic seaboard over the weekend, with highs falling to mostly upper 70s on Friday, and even further to mostly the mid to upper 70s though Monday. Mins will similarly fall from 60 to 65 Friday morning to the low and mid 50s Saturday through Monday. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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As of 145 PM Tuesday... The circulation around an area of high pressure along the spine of the Appalachians and tropical cyclone Maria offshore of the Outer Banks will maintain a long ne fetch off the Atlantic into central NC. This flow will maintain a stratus deck across much of the northeast Piedmont and coastal plain while a gradual erosion of the stratus deck will occur elsewhere. Thus, expect VFR parameters in vicinity of the Triad this afternoon through Wednesday. In proximity of KFAY and KRDU, MVFR ceilings will persist until mid-late afternoon when ceilings will either diminish or lift into the low end VFR range. In vicinity of KRWI, MVFR ceilings will persist through the afternoon into the evening. The rather tight pressure gradient between the ridge and Maria will result in a steady ne sfc wind, sustained around 10kts in the western Piedmont, and 10-14kts with gusts 20-23kts in the east. Tonight, the stratus deck will gradually expand back to the west, encompassing KRDU and KFAY around or after midnight. Unlike today, though, ceilings are expected to lift/dissipate at both sites shortly after daybreak as the low level flow veers to a north- northwest direction, advecting in a drier air mass. Currently not expecting the stratus to advance as far west as the Triad. For Wednesday, expect improving aviation parameters as Maria begins to pull away to the east-ne and high pressure builds into our region. This will lead to a gradual subsiding the sfc winds and lifting/dissipation of the stratus deck over the northeast Piedmont and coastal plain. VFR parameters expected late in the week through early next week. A surface cold front will advance and progress sewd through central NC late Thu-Thu night. Moisture is limited so currently expect nothing more than a few mid level clouds with the frontal passage. Another sfc front will sweep through the region Saturday, again accompanied by nothing more than a few mid level clouds. These successive fronts will usher in a dry and seasonably cool air mass, resulting in the extended period of VFR parameters.
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&& .CLIMATE... Record high temperatures across central NC for September 27 and 28. RECORD MAX (9/27) RECORD MAX (9/28) RDU 94 / 1998 95 / 1998 GSO 90 / 2007 92 / 1939 FAY 94 / 1986 95 / 1933 && .RAH WATCHES/WARNINGS/ADVISORIES... None. $$ SYNOPSIS...MWS NEAR TERM...WSS SHORT TERM...MWS LONG TERM...mlm AVIATION...WSS CLIMATE...RAH

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