Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 161134 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 634 AM EST Mon Jan 16 2017 .SYNOPSIS... High pressure to the northeast will set up cold air damming over central NC through Monday before a low pressure system approaches the area midweek. && .NEAR TERM /THROUGH TONIGHT/... As of 317 AM Monday... Light rain is ongoing across the US-70 corridor early this morning being caused by some low level isentropic lift as surface high pressure over the northeast will move southward into an in-situ damming scenario. This will keep low ceilings locked in for much of, if not all of the day today and well into the evening. Southern and eastern locales have the best chance of seeing a return to VFR conditions today but otherwise expect at least MVFR ceilings to persist throughout the day. High resolution models keep precipitation sporadic throughout the day with perhaps the best chances occurring in the northeast. Expect periods of drizzle and light rain on and off throughout the day. Temperatures will be dependent upon the strength of the damming but as is usually the case with CAD scenarios, we will under cut guidance temperatures quite a bit. Expect upper 40s to low 50s for highs with lows Tuesday morning in the low to mid 40s. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... As of 317 AM Monday... On Tuesday the in-situ CAD will break down and attention will turn to the west where a low pressure system will track through the Ohio Valley and into the great lakes region. This will put central NC in the warm sector ahead of a cold front stretching through Tennessee and into the lower Mississippi Valley. While a moist airmass will be in place, there wont be a lot of dynamics to force any real precipitation threat so expect a slight chance of light showers but nothing more as main precipitation associated with the approaching front will remain northwest of the forecast area. High temperatures will increase considerably into the low to middle 60s from north to south with lows Wednesday morning only dropping into the low to mid 50s. && .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 /12Z MONDAY THROUGH FRIDAY/...
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AS OF 634 AM Monday... 24 Hour TAF period: MVFR ceilings prevailing at this hour as in-situ cold air damming begins to set in across the NW Piedmont. These should either hold at MVFR or descend further to IFR later this morning Expect light winds out of the northeast or east through the period. Ceilings are not expected to lift beyond MVFR levels in most locations on Monday with the exception of KRWI and possibly KFAY late in the day. Otherwise will maintain MVFR conditions through the end of the TAF period. Some light rain will also be possible. Long term: An active pattern will see several systems cross the area next week. While no winter precipitation is expected, adverse aviation conditions due to low ceilings and visibilities are expected.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Ellis NEAR TERM...Ellis SHORT TERM...Ellis LONG TERM...Hartfield AVIATION...Ellis

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