Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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271 FXUS62 KRAH 281806 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 206 PM EDT Wed Jun 28 2017 .SYNOPSIS... Canadian high pressure will drift offshore the Mid-Atlantic coast tonight. High pressure will extend into the region from the east on Thursday. An increasingly moist southerly return flow will prevail Friday through the weekend. && .NEAR TERM /Today and Tonight/... As of 135 PM EDT Wednesday... 1024 mb Canadian high pressure centered over WV/VA this morning will shift offshore the DELMARVA late this afternoon/evening as an upper level trough progresses further offshore the Mid-Atlantic coast. High pressure will extend into the Carolinas from the east overnight. With the above in mind, expect below normal temperatures (albeit slightly warmer than yesterday) and dry/stable conditions to persist through tonight, with highs 82-87F (coolest NW, warmest S/SE) and lows ranging from the mid/upper 50s to lower 60s, coolest in the typical rural/low-lying areas. -Vincent && .SHORT TERM /Thursday and Thursday night/... As of 135 PM EDT Wednesday... A relatively dry airmass associated with modified Canadian high pressure extending westward (from the Atlantic) into the Carolinas will persist on Thu, albeit with a gradual increase in moisture from the S/SW during the aft/eve as the surface high moves further offshore, the ridge weakens, and a light return flow commences. Upper level moisture will also increase on Thu as a deamplifying upper level low progresses NE from the TX/LA Gulf coast into the Deep South. With the above in mind, expect dry conditions and increasing cloud cover on Thu with highs in the mid to upper 80s, warmest E/SE. The deamplifying upper level low is progged to make little progress Thu night, progressing NE into northern AL/northwest GA. Strengthening southerly return flow /moisture advection/ is expected to result in the development of stratus from S/SW to N/NE overnight. As a result, expect much warmer lows than observed in previous days, in the mid to upper 60s, except in the far NE Coastal Plain where lower 60s cannot be ruled out. Will introduce a slight chance of showers after midnight in the far S/SW, though the best potential for showers should remain upstream in upstate SC, southwest NC and northern GA where richer low-level moisture will be juxtaposed with DPVA attendant the upper level low. -Vincent && .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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As of 205 PM EDT Wednesday... Increasingly hot and more humid, with scattered diurnal convection, through the weekend. Continued hot, but less humid and with a reduced risk of diurnal convection, over the wrn half of the forecast area by early to mid next week. The models remain consistent in their depiction of an amplifying trough aloft from west-central Canada to the upper MS Valley by Fri, and across the Great Lakes on Sat. Between this trough and a sub- tropical ridge initially over the swrn N. Atlantic, perturbed swly flow aloft will result from the lower MS Valley to the middle Atlantic states; and the most notable (synoptic-scale and predictable) of these disturbances will be a mid level trough now over the nwrn GOM that the models indicate will lift newd across the Carolinas on Fri. The sub-tropical ridge is forecast to expand wwd into the GOM through the weekend, then bulge nwd across the srn U.S. through early to mid next week, while a weakness in the ridge, in the form of a weak shear/trough axis, lingers along the East Coast. At the surface, expansive high pressure will remain over the central N. Atlantic and extend wwd to the sern U.S. coast through the end of the forecast period, while an Appalachian-lee trough sharpens over VA and the Carolinas. Return flow around the high will yield gradually increasing temperatures and humidity levels, marked most abruptly by the passage of a warm front on Fri. Despite mid level warmth associated with the sub-tropical ridge, with resultant weak mid level lapse rates of less than 6 C/km, the aforementioned warming and moistening low levels should prove sufficient for at least scattered diurnal convection throughout central NC Fri-Sat, and probably aided by the aforementioned mid level trough on Fri. Thereafter, the sharpening of the lee trough and mixing out of surface dewpoints (into the lower to middle 60s) to the west will probably shift the focus for convection into the Coastal Plain Sun-Wed. Temperatures will trend from the middle 80s to around 90 degrees on Fri to lower to middle 90s by early next week. Heat indices may near or minimally exceed 100 degrees over the Sandhills, ern piedmont and srn-central Coastal Plain Sun onward.
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&& .AVIATION /18Z Wednesday through Monday/... As of 135 PM EDT Wednesday... 24 Hour TAF Period: VFR (clear/mostly clear) skies and light/ variable winds will prevail through the TAF period in association with Canadian high pressure extending into the region from the north (today) and east (tonight). Looking Ahead: VFR conditions and a light S/SE wind will prevail on Thu in association with a surface ridge extending into the region from the east. MVFR/IFR ceilings (INT/GSO/RDU) and fog (RWI/FAY) may develop between midnight and sunrise Friday morning. Conditions should improve to VFR by noon, though MVFR ceilings could persist into the afternoon at the FAY terminal. Isolated to scattered showers/storms are expected to develop late Friday afternoon, potentially affecting all terminals, with the overall best chance at the FAY/INT terminals. Diurnal convection and early morning stratus/fog are expected to affect all terminals over the weekend and possibly through early next week, as well. -Vincent && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Vincent LONG TERM...MWS AVIATION...Vincent

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