Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 171136 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 636 AM EST Tue Jan 17 2017 .SYNOPSIS... Cool high pressure over the area will move offshore this morning. A warm front will push northward into the area today, and will be followed by a warm southwest flow late today into early Wednesday. The front will push back southward as a cold front Wednesday afternoon, with high pressure again building in for Wednesday night through Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 330 AM Tuesday... Water vapor imagery this morning showing moisture moving into the area from the southwest and a low pressure system moving through the Ohio Valley with a frontal system extending through the Tennessee Valley and into the deep south. As a result of this moisture increase we are starting to see some pockets of dense fog across the southwest Piedmont. Models are mixed on the progress this fog will make to the northeast but will monitor and issue products as needed. As the front hangs northwest of the area today, the NW Piedmont and northern tier will be the most likely to see any kind of precipitation today as some weak isentropic lift over the deteriorating wedge front remains in place through the afternoon and pre-frontal precipitation begins to creep into the area from the northwest. Indications are that we should begin to scatter or lift out by later in the afternoon and while this may ultimately determine max temperatures, expect highs in the 60s across the area with warmest temps in the southwest. Some wind gusts are possible after the wedge lifts out late in the afternoon but nothing more than 15-20 kts. && .SHORT TERM /TUESDAY AND TUESDAY 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 /12Z TUESDAY THROUGH SATURDAY/... AS OF 635 AM Tuesday... 24 Hour TAF period: Dense fog is occurring in portions of the forecast area but has stayed out of the major TAF sites at this time. Patchy fog should continue through daybreak with KRDU the most likely to see any problems from fog. After sunrise, ceilings are eventually expected to break out although it may take until the afternoon to do so. Some gusty winds are possible up to 20 kts or so this afternoon. Long term: A frontal system will move through the area on Wednesday. High pressure returns on Thursday for a brief stay before the next system moves in Thursday night through Friday night. High pressure then returns once again for the weekend. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Ellis SHORT TERM...Ellis LONG TERM...Hartfield AVIATION...Ellis

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