Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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951 FXUS62 KRAH 171353 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 853 AM EST Tue Jan 17 2017 .SYNOPSIS...
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A cold front will approach from the northwest this evening, then track southeast through central North Carolina Wednesday morning. In the wake of the front, high pressure will build into the region from the northwest Wednesday night and Thursday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 830 AM Tuesday... ...Dense Fog Advisory expanded to include portions of the Triangle and Sandhills through 10 AM EST this morning... Expect dense fog this morning to lift/scatter out by or shortly after 15Z this morning as the lingering CAD wedge over central NC starts to experience top-down erosion as southwesterly low-level flow begins to strengthen in advance of a shortwave approaching the Mid-Atlantic from the W/NW. Expect overcast skies to become broken this afternoon, perhaps scattering out entirely by mid to late afternoon. 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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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 330 AM Tuesday... The lingering frontal system to the northwest will finally be pushed across the area as an upper level low develops moves southeastward out of the great lakes. This should push precipitation through the area by late Wednesday afternoon and maybe some drying after that. Until then, expect periods of rainfall and fairly warm temperatures as max temps rise into the mid 60s to low 70 with highest temps across the southwest. After precipitation moves out of the area to the east, a surface high moving in from the NW will take over the weather pattern drying things out but also cooling temperatures. Lows Wednesday night in the low 40s. && .LONG TERM /Thursday through Monday/... As of 330 AM Monday... This time frame will feature above normal temps and alternating wet and dry periods. Polar air will hold well to our north, affecting only northern and eastern Canada into 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. Thu/Thu night: A brief dry period is expected as the front settles just to our south and a weak continental high builds over the area from the west, beneath a prominent mid level ridge in the wake of Wednesday`s potent shortwave trough swinging out over the Atlantic. Expect fair to partly cloudy skies Thu, with increasing clouds late Thu into Thu night as the next shortwave trough (now over Baja California) pushes east then lifts NE, approaching NC from the SW as it takes on a negative tilt. As this trough moves in, falling mid level heights and a preceding low level jet nosing into central NC will foster deepening of moisture and an increasing chance of rain overnight, affecting the western CWA first. Highs 55-60 and lows in the mid-upper 40s. Fri/Fri night: Rain is likely early Fri morning, particularly over the northern and western forecast area, as the combination of upper divergence, mid level DPVA and height falls, and low level moisture transport appears to peak around 12z Fri. As the negatively tilted and deamplifying shortwave trough shift to our NNE, the front to our south should shift back northward as a warm front, as another round of shortwave ridging follows, persisting through Fri night. Expect rain chances to decrease SW to NE Fri afternoon as drying aloft punches in from the WSW, with dry weather but low clouds likely Fri night. Expect highs Fri from the mid 50s north to mid 60s south, where the northward-moving warm front will first arrive. Lows 45-50. Sat into Mon: Expect fair and warm weather Sat as the mid level ridge shifts overhead and over the East Coast. Thicknesses are projected to be well above normal, perhaps by as much as 40 m, although shallow mixing may mean that the thickness values could be overestimating the warming realized at the surface. Expect highs of 60-67. By Sun, attention turns to quickly deepening low pressure over the southern Plains, within the active and progressive southern stream. As this low shifts through the Mid-South and NNE into the Ohio Valley, a strong negatively tilted trough will approach our area from the W and SW. The GFS and ECMWF remain in remarkably good agreement on timing and evolution of this feature as well as with the corresponding surface frontal configuration, with a primary low tracking into the Ohio Valley, an occluded low moving into the western Carolinas, and a trailing front shifting E then NE through GA and the Carolinas Sun night. There remains the threat for a few strong storms late Sun into Sun night in our area, with this risk supported by a highly energetic and strengthening system featuring vigorous upper divergence, intense DPVA, strong kinematics with a sweeping curved hodograph, and abundant moisture with PW over 1.5". Will mention isolated thunder, with minimal CAPE values and subdued lapse rates limiting the coverage. Will trend the high pops down from SW to NE Sun night into Mon morning as the dry slot arrives, but will keep scattered showers late Mon as the trough axis shifts through the area. Highs in the upper 50s NW to mid 60s SE Sun, then around 60-65 Mon. -GIH && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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AS OF 900 AM Tuesday... 24 Hour TAF period: LIFR/IFR ceilings and visbys are expected to improve to MVFR this afternoon, possibly scattering out to VFR by late afternoon (esp RDU/FAY/RWI). Any improvement in conditions this aft/eve will be short-lived, however, as conditions are expected to deteriorate from N/NW to S/SE (earliest at Triad and latest at FAY) tonight/Wed morning as an upper level disturbance tracks through the central Appalachians into the Mid-Atlantic and an attendant cold front /low-level trough/ progresses east of the mountains through VA/NC. Expect the best potential for rain and low ceilings between 03-15Z Wed as the slow moving front progresses SE through central NC. Looking Ahead: 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...
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Dense Fog Advisory until 10 AM EST this morning for NCZ039>042- 073>077-083>086-088.
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&& $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Ellis LONG TERM...Hartfield AVIATION...Vincent

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