Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 130010 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 708 PM EST Fri Jan 12 2018 .SYNOPSIS... A strong cold front will surge through the region this evening, with a secondary cold front to move through early Friday. Much colder and drier air will flow into NC from the NW Saturday through Monday. && .NEAR TERM /THROUGH TONIGHT/... As of 701 PM Friday... The main convective line extended from Greensboro to Wadesboro (western Piedmont) as we near 00z/13 January, or 7 PM local. The main weather hazards will be locally heavy rain, wind gusts to 40 mph, and possibly an isolated damaging wind event. There is essentially no CG lightning associated with the line. Cloud tops are only near 25k feet. Dew points in the mid 60s (ample low level moisture for organized convective lines) were in place over central and eastern NC. However, temperatures were only in the mid to upper 60s - greatly limiting the chance of widespread severe organized storms. The line may become stronger as it moves NE through the area as the dew points in the mid 60s are tapped, but any wind damage occurrences are expected to be isolated. There was a report of isolated wind damage from Catawba County (GSP) area earlier with this line as some trees were downed by convective winds mixing down to the surface. The latest hi-resolution models depict the line moving through the Triangle and Fayetteville areas between 800 and 1100 PM, then through the Interstate 95 corridor between 1100 PM and 200 AM. Wind gusts to 40 mph have been reported at KGSO (Greensboro) at 640 PM. The main issue should be the gusty winds to 40 mph with the line, with only isolated stronger winds expected (mainly near the line segments). Flash flood guidance is very high (it has been very, very dry). Also, the fast movement of the heavy rain elements will limit any areas getting excessive amounts. Therefore, only locally heavy rain of 0.5 in 30 minutes will only be enough for very short term street flooding, covered by special weather statements and/or Urban and Small Stream Flood Advisories. Other than these hazards associated with the main convective line, no other severe weather is expected after the line moves through by the aforementioned times. After the line, the boundary layer will be stabilized and there will still be occasional rain and showers can be expected until the main cold front (analyzed at 00z over far western NC) comes east through the areas between 400 am and 900 am (west to east). && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... As of 335 PM Friday... The negatively tilting but dissipating mid level shortwave trough will be heading well to our NE by Sat morning, but with the main trough axis still to our W, southwesterly steering flow will persist over NC, keeping a steady feed of weak vorticity streaking over the region. We should see some lingering sprinkles or shallow showers extending through Sat morning (and perhaps into the afternoon) over the NE CWA, as one particularly noteworthy vorticity lobe streaks NE through the area along and ahead of the 850 mb frontal zone. Otherwise, skies will be partly to mostly cloudy during the day, with gradual clearing Sat night as the phasing but broad and dampening mid level trough axis approaches from the west. Expect highs just around 40 in the Triad, ranging to lower 50s in the far E where the most pronounced cold air advection will be last to arrive. Expect lows of 20-27 Sat night with diminishing winds. -GIH && .LONG TERM /SUNDAY THROUGH FRIDAY/... As of 225 PM Friday... Other than an adjustment to the forecast in the Tuesday and Wednesday time frame, previous forecast looks on track. A fresh, 1038 mb Arctic high, now extending from Alberta to the nrn Plains, will have built across the MS/OH Valleys and middle Atlantic states by 12Z Sun, with associated much colder nely low level flow directed across cntl NC. The presence of an associated low level thermal trough will yield temperatures in the lwr-mid 30s north to around 40 or so degrees south on Sun, with very cold temperatures mostly in the mid-upr teens, in strong radiational cooling conditions, Sun night. A strong clipper low will meanwhile have migrated to the Great Lakes by Mon morning, where it will occlude through Tue. Subsequent secondary/coastal cyclogenesis is then expected along the middle Atlantic and New England coast through the middle of the week, as the parent upr trough amplifies across the Appalachians and middle Atlantic states. Any coastal cyclogenesis is likely to be initially slow/weak, owing to the presence of fast, strongly meridional flow downstream of the trough, at least until the trough lifts across about 40N, where the presence of a strong/blocking positive height anomaly over the N. Atlantic will provide room for flow amplification. Models are coming into better alignment Tuesday into Wednesday for the H5 trough to develop a closed low anywhere from the Ohio Valley to the Mid Atlantic region. This scenario brings a much better chance for higher QPF over central North Carolina with a sufficiently cold airmass in place. For now, will introduce a chance for snow Tuesday night into Wednesday. The further west the closed low forms, the greater the possibility that precipitation east and south of the Triangle will mix with or be all rain. Temperatures are expected to be in the 40s by Tue, in WAA downstream of the aforementioned clipper low, followed by 30s Wednesday and Thursday. Lows mostly in the teens to 20s, mildest Tue-Wed mornings. Dry weather will continue on Friday as a ridge builds overhead. Temperatures Friday will rise to near seasonal normals. && .AVIATION /00Z Saturday through Wednesday/...
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As of 705 PM Friday... SSE flow at 10-20kt will shift to the W at 20-35kt for a brief time as a convective line moves through the KGSO/KFAY/KRDU and KRWI areas between 00z/13 and 04z/13 from west to east. CIGS and VSBYS will be in the IFR to MVFR range. After the line moves through, MVFR to IFR CIGS will persist through late tonight, with occasional showers with VFR TO MVFR CIGS. The cold front will move through between 09z and 13z from the west ending the showers. CIGS will be VFR, and VSBYS will lift out to VFR. Winds will become NW at 15-20kt Saturday. Looking beyond 18z/Saturday, VFR conditions are expected through Monday as VFR to MVFR CIGS Saturday afternoon improve and clear Saturday night, then remain clear Sunday and Monday. Winds will diminish to light Saturday night and Sunday.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...Badgett SHORT TERM...Hartfield LONG TERM...MWS/Franklin AVIATION...Badgett

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