Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 120039 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 830 PM EDT Wed Oct 11 2017 .SYNOPSIS... A weak surface trough will linger over central North Carolina through tonight, keeping our weather warm, humid, and unsettled. A cold front will drop southward through the region Thursday, bringing a cooler and less humid air mass into the area for Friday. && .NEAR TERM /THROUGH TONIGHT/...
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As of 830 PM Wednesday... The thunderstorms have been rather widely scattered late this afternoon and early evening, but the ones that have occurred have dropped very heavy rain. Radar estimated amounts of 1-3 inches were common with the stronger storms that occurred over portions of the Triangle, and near Henderson and Warrenton to near Roanoke Rapids. Officially 1.12 inches fell at the RDU Airport, with nearby totals of 2+ inches in northwest and north parts of Raleigh. PW`s were at record levels for October, 2+ inches and the storms were diurnally driven. With the loss of heating, the storms weakened quickly after sunset, and this trend is expected to continue. Minor small stream and urban flooding was reported over Raleigh and Morrisville. A cold front will be changing our hot, humid, and at times thundery weather as it comes in from the north later tonight. Isolated showers will be possible with the front as it should be entering the northern tier of NC counties late tonight, with only these areas likely to see any substantial influx of slightly cooler and drier air overnight. Likely development of widespread low clouds will also impede the nocturnal temperature fall. Lows tonight should range again in the lower to mid 70s, with some 60s confined to the northern tier. -PWB/GIH
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&& .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 305 PM Wednesday... The cold front will push southward through NC through Thu, with drier and more stable air pouring into northern sections, while the southern and eastern CWA will remain sufficiently moist and potentially unstable to support retention of a scattered shower and isolated storm threat, particularly in the afternoon. Nocturnal cooling and plentiful low level overrunning moisture on a northeasterly low level flow will lead to considerable low clouds with drizzle and fog Thu night. This will be focused along the spine of the encroaching wedge ridge, where moist isentropic upglide will be deepest and most pronounced, and will go with chance pops in the NW CWA with slight chances of measurable precip elsewhere Thu night. With a slower arrival of cooler post-front air, have brought up highs a bit to the upper 70s north to mid 80s south, still above normal with thicknesses running 25-30 m above normal. Lows Thu night 63-68 with skies trending to overcast. -GIH && .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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As of 300 PM Wednesday... Subtropical ridging overhead will trap low level moisture in place into early this weekend as surface high pressure settles down the Atlantic coast in typical CAD fashion. The parent high pressure system will be well removed off to the northeast and progressive, which will result in very weak isentropic lift Friday into Saturday, which will further weaken through the day Saturday as the cool air advection is cut off by veering surface flow. Will keep PoPs in the 20 to 30 percent range graduated higher west. Highs will be coolest on Friday with highs perhaps not reaching 70 in the damming region in the northwest, with upper 70s along the coast. Saturday will be a touch warmer with the damming eroding early with highs from mid to upper 70s. Return flow will produce our warmest day on Sunday, as plentiful sun and southwest warm air advection send high back into the low and mid 80s. A fairly vigorous cold front will be approaching very early next week as it crosses the mountains Sunday night and across central NC during the day. Will have small chance PoPs early, increasing in the afternoon as the frontal passage will be during favorable daytime heating. Low level convergence will be strong in the sharp trof associated with the front, but H85 flow is westerly and only 10-15 knots with no moisture advection of significance. Mid and upper support will be sufficient to support thunder, but do not see any parameters that raise particular concerns. Highs will stall in the mid 70s northwest due to earlier frontal passage, while the southeast could reach mid 80s. Cool and dry high pressure builds in behind the front Tuesday and Wednesday. Significant cool down is anticipated with a 50-60 meter crash in the low level thicknesses indicative of highs mostly in the mid and upper 60s and morning lows cooling into the low to mid 50s Monday night, with mid and upper 40s on Tuesday night.
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&& .AVIATION /00Z Thursday through Monday/... As of 830 PM Wednesday... 24 Hour TAF Period: Isolated storms and showers moving across the NE Piedmont will continue to weaken this evening. Sub-VFR cigs and visbys are again expected to develop across the area during the pre- dawn hours, with the worst conditions (IFR/LIFR) expected at KFAY/KRWI. Cigs may briefly improve to VFR, however, northeasterly low level flow behind a southward sinking cold front on Thursday morning will lead to MVFR cigs returning across the area from NE to SW on Thursday. In addition, isolated to scattered showers and storms will be possible on Thursday afternoon at KFAY. Outlook: IFR conditions are likely to return Thursday evening with areas of light rain or drizzle through Thursday night. This pattern is likely to hold Fri through Sat, with IFR conditions probable from mid evening through mid morning, and MVFR conditions from late morning through early evening, both days. VFR cigs/vsbys should return Sunday into Monday. && .CLIMATE... Record Highs... GSO RDU FAY Oct 11: 90 in 1919 89 in 1912 91 in 1939 Oct 12: 90 in 1904 88 in 2010 90 in 1919 Record High Minimums... Oct 11: 66 in 1999 68 in 1990 68 in 2002 Oct 12: 64 in 2002 68 in 1990 68 in 1990 && .RAH WATCHES/WARNINGS/ADVISORIES... None. $$ SYNOPSIS...Hartfield NEAR TERM...Badgett/Hartfield SHORT TERM...Hartfield LONG TERM...mlm AVIATION...BSD/Hartfield CLIMATE...MWS

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