Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 120646 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 246 AM EDT Thu Oct 12 2017 .SYNOPSIS... A cold front will drop slowly southward through central NC today. A cooler, less humid, air mass will settle in behind the boundary Friday and Saturday. && .NEAR TERM /THROUGH TONIGHT/... 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 && .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 /SATURDAY THROUGH WEDNESDAY/...
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As of 245 AM Thursday... On Saturday, a wedge will remain in place across the Triad. This will keep conditions very cloudy at least in the NW Piedmont on Saturday with some thinning of the clouds further south and east. No rain is expected outside of a sprinkle or two. Temperatures will climb back up into the upper 70s to low 80s for daytime highs. By Saturday night the wedge will begin to break down as a stronger frontal system begins to move through the the Midwest. Ahead of this system, high pressure will move out to sea and bring winds back to a more southwesterly direction. This will increase warm air advection and put temperatures solidly back into the 80s. Lows Sunday in the 60s. On Monday the front will approach the Carolinas, bringing a chance for showers and thunderstorms for much of the day. There are still some timing differences in the models with the GFS promoting a faster solution that the ECMWF. As a result earliest rain chances would begin on Monday morning and although the GFS has the front through the area by 6z Tuesday, The ECMWF hangs on to precipitation through at least the morning in the eastern areas of the CWA. High temps on Monday will be highly dependent upon the progression of the front with highs in the mid 70s likely across the north with low 80s in the southern Tier. By Tuesday a much colder airmass will make its presence known and highs may not get out of the 60s across the north with lower 70s elsewhere as fall returns with a vengeance. By Tuesday night lows will sink into the upper 40s in most locations. Wednesday and most likely the rest of the week will be dominated by much cooler and drier continental high pressure with highs in the upper 60s to lower 70s which after this past week, we may need to be reminded that these temperatures are indeed normal for this time of year.
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&& .AVIATION /06Z Thursday through Monday/... As of 200 AM Thursday... Aviation conditions will deteriorate through 12Z Thu as areas of fog and low clouds develop across central NC. The widespread IFR/LIFR parameters will likely linger through 14Z, with slow improvement into the MVFR category, due to ceilings, expected. After 16Z, expect scattered showers and isolated t-storms to develop across the southern half of central NC, some of which will be in proximity of KFAY. Northeasterly low level flow will maintain a layer of moisture across central NC through Saturday. This will yield a high probability of adverse aviation ceilings with prolonged periods of IFR/LIFR ceilings along with areas of fog or drizzle Thursday night through late morning Friday, and again Friday night through mid morning Saturday. The early morning LIFR/IFR ceilings will slowly lift into the MVFR range by late morning-early afternoon both days. Probabilities for VFR conditions will increase Sunday into the Monday as the air mass modifies and the low level flow becomes swly ahead of an approaching cold front. && .CLIMATE... Record Highs... GSO RDU FAY Oct 12: 90 in 1904 88 in 2010 90 in 1919 Record High Minimums... Oct 12: 64 in 2002 68 in 1990 68 in 1990 && .RAH WATCHES/WARNINGS/ADVISORIES... None. $$ SYNOPSIS...WSS NEAR TERM...Badgett/Hartfield SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...WSS CLIMATE...MWS

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