Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 161804 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 104 PM EST Mon Jan 16 2017 .SYNOPSIS...
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High pressure along the Mid-Atlantic coast will gradually shift offshore tonight and Tuesday, in advance of a cold front approaching the mountains from the west. The cold front will progress east of the mountains Tuesday night, track southeast through North Carolina Wednesday morning, then southward offshore the Carolina coast Wednesday afternoon as an associated upper level disturbance tracks offshore the Mid-Atlantic coast.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 1245 PM Monday... Expect little change in sensible wx conditions this afternoon into tonight. High pressure centered along the Mid-Atlantic coast will gradually shift offshore (though continue extending SW into central NC) late tonight as a shortwave ridge progresses through the Mid- Atlantic. Weak southwesterly warm advection atop the cool/shallow airmass extending into the region from the NE will help maintain the CAD wedge in place for the remainder of this afternoon. Weak nocturnal cooling of the shallow moist layer in place over central NC should result in lowering ceilings and perhaps fog /lowering visbys/ tonight. Expect only several degrees of diurnal variation between highs this afternoon and lows tonight. -Vincent
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&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
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As of 105 PM Monday... The lingering CAD wedge is expected to undergo top-down erosion during the day Tuesday as southwesterly low-level flow strengthens in advance of a shortwave approaching the Mid-Atlantic from the W/NW. Initially overcast skies should become broken by early afternoon, perhaps scattering out entirely from the Triangle southward and eastward. Broken to overcast cloud cover is most likely to persist the longest across the N/NW Piedmont where occasional sprinkles cannot be ruled out. Challenging temperature forecast. Expect highs in the upper 50s (N/NW) to mid 60s (S/SE) Tuesday afternoon. Expect rather mild lows Tuesday night as the MSLP gradient tightens in advance of the approaching cold front and a southwest breeze persists much of the night. Expect lows in the mid to upper 50s, possibly a few degrees cooler in the Northern Piedmont/NE Coastal Plain where precipitation assoc/w the front is most likely to occur prior to sunrise Wed. It should be noted that a large amount of uncertainty persists with regard to the precise coverage/timing of precip assoc/w the upcoming cold frontal passage early Wed. -Vincent
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&& .LONG TERM /Wednesday through Sunday/... As of 310 AM Monday... This period will feature warm temps and alternating wet and dry days. Polar air will remain bottled up well to our north, affecting only eastern Canada and Maine, leaving NC in a mild pattern with low level thicknesses staying well above seasonal normals. A very wavy and progressive flow across the southern CONUS will bring bouts of unsettled weather reminiscent more of early spring than of the heart of winter. Wed/Wed night: Areas of rain should be ongoing Wed morning, ahead of a small but potent shortwave trough that moves from the Ohio Valley ESE across VA/NC Wed/Wed night. An occluded frontal system ahead of this wave will shift over and off the mid-Atlantic coast, dragging a cold front slowly SSE through the state late in the day. Mild WSW flow ahead of this front should equate to highs in the mid 60s to near 70 despite abundant cloud cover. Expect good chance to likely pops, weighted early in the day, exiting to the east in the afternoon. Cooler lows are likely Wed night with fair skies post- front, although lows will still be above normal, in the lower to mid 40s. Thu/Thu night: A brief dry period is expected as the front settles to our south and a weak continental high builds over the area from the west, beneath a prominent mid level ridge sitting between the aforementioned exiting wave and ahead of another strong low/wave shifting through the central and southern Plains Thu. Fair skies Thu with increasing clouds late Thu into Thu night. Highs in the upper 50s to lower 60s. Lows in the lower to mid 40s. Fri/Fri night: High coverage of rain appears likely to return by Fri morning, as the Plains low/trough tracks ENE, deamplifying but taking on a negative tilt as it crosses the Mid-South then Ohio Valley/mid-Atlantic region. Passage of this wave should draw the surface front back northward as a warm front, with another short period of shortwave ridging following for Fri night. Highs in the upper 50s to mid 60s and lows in the mid-upper 40s. Sat into Sun: The mid level ridging holds over the Southeast on Sat, along with a light SW low level flow into NC. Models hint at a potential secondary frontal zone along the Gulf Coast that would, if it occurs, provide a focus for convection, effectively shutting off any moisture influx into NC. As such, Sat should be a generally dry day, with temps once again above normal, peaking in the upper 50s to lower 60s. By Sun, however, the active southern stream culminates in a deepening low over the Southern Plains, Gulf States and Mid- South/W Ohio Valley, with a strong negatively tilted trough approaching our area from the W and SW. The op GFS and ECMWF differ a bit with timing but both indicate this general pattern, with a strong surface low over the mid Miss Valley, a possible occlusion moving into the western Carolinas, and warm frontogenesis across the Carolinas. This has the potential to bring a threat of strong storms late Sun into Sun night. Of course, at this far range, the details cannot be pinned down, and there is still plenty of uncertainty. But the op models do have support from the CFS, and the GFS and ECMWF are fairly close in solution at this range, very surprising considering that the pertinent features of this pattern are still well out over the western Pacific and SE Asia and should not, by all accounts, be very well sampled. Temps should remain above normal through the weekend. -GIH && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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AS OF 1230 PM Monday... 24 Hour TAF period: MVFR ceilings are likely to persist this afternoon into tonight, falling to IFR and perhaps LIFR occasionally during the overnight hours in assoc/w a lingering CAD wedge. Southwesterly low-level flow should gradually erode the wedge from top-down during the day Tue, with MVFR ceilings possibly scattering out to VFR by late afternoon. Looking Ahead: Any improvement in conditions Tue aft/eve will be short-lived, as conditions are likely to deteriorate from N/NW to S/SE (earliest at Triad and latest at FAY) Tue night/Wed morning as an upper level disturbance tracks through the central Appalachians into the Mid-Atlantic and an attendant cold front /SFC-925 trough/ progresses east of the mountains into VA/NC. Expect the best potential for rain and low ceilings to occur between midnight and noon Wed as the slow moving front progresses SE through central NC. Expect a clearing trend in the wake of the front with a brief return to VFR conditions Wed night/Thu. A pattern similar to the one affecting the region today is progged to develop over the region again late this week. With this in mind, expect ceilings to begin deteriorating Thu night/Friday. -Vincent
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Vincent LONG TERM...Hartfield AVIATION...Vincent

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