Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 170737 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 235 AM EST Wed Jan 17 2018 .SYNOPSIS... A strong upper level disturbance and associated arctic cold front will move through our region today. This will be followed bitter cold arctic high pressure tonight into Friday morning. A warm-up will begin Friday and extend into the weekend. && .NEAR TERM /TODAY AND TONIGHT/...
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As of 235 AM Wednesday... ...Winter Storm Warning for most of Central NC through 900 PM tonight... ...Winter Weather Advisory for the SE Coastal Plain (Wayne and Sampson through 900 PM... Changes to the forecast... We will have the Winter Storm Warnings and Winter Weather Advisories run through 900 PM this evening and raise snowfall forecast amounts in the Warning area to between 3-6 inches. Forecast trends continue to advertise a deepening/stronger and more cut off mid-level circulation/trough that is forecast to track east across NC this afternoon and evening. This in turn results in a slower system which allows more QPF. Partial thicknesses support snow as the main P- Type over the Piedmont into the Northern Coastal Plain, arriving between 09z and 12z in the western Piedmont, spreading east into the Triangle area by mid morning. To the southeast of the Triangle area, the precipitation is expected to be delayed a few hours, especially along the Interstate 95 corridor, arriving late morning or early afternoon. The delayed system down east means that the precipitation is expected to begin as rain, then transition to snow as the cold air wins out mid to late afternoon. Current data indicated the arctic front had reached through the Mountains and extended NE across central VA. Bitterly cold temperatures behind the front ranged from near zero over TN and in the 20s into Mountains of NC and over northern VA. Temperatures were mainly in the 30s over central NC, with dew points in the 20s. The partial thicknesses and wet bulb temperatures were already supportive of snow over most of the Piedmont, and that is before the arctic air begins to be pulled into the region after 12z. In addition, a low pressure was developing along the arctic front over north Georgia. A light southerly flow into the low pressure has aided in the increase of boundary layer moisture (dew points in the 30s along the Savannah River in GA/SC and nosing up into northern SC. This moisture will be transported into the system as the mid/upper trough sharpens and cuts off through the day and the low pressure tracks along the front. The strengthening upper feature is responsible for the introduction of more lift/moisture transport/QPF. This QPF is expected to be maximized over central NC late morning into the afternoon with moderate to heavy snow. Snowfall details... As for the snowfall forecasts, it appears that a QPF of 0.30 to 0.50 liquid equivalent is most likely across central NC. This uses a blend of the models. Using the 10:1 becoming 15-18:1 snow to liquid ratios would give most of the Winter Storm Warning area between 3-5 inches in the northwest, 3-6 inches from SW to NE through the center of the Piedmont into the Northern Coastal Plain, and lesser 1-3 totals in the SE Coastal Plain (which occurs at the end of the event). The least totals should be in the Clinton to Goldsboro areas where 1-2 inches is expected. Snowfall rates of 0.5 to nearly 1 inch an hour will be possible for 4-6 hours given the latest guidance through the Piedmont and Northern Coastal Plain. Temperatures, precipitation timing, and P-Type details... Snow is expected to develop over the Triad and Yadkin Valley region by 12z, with the heaviest snow between 12z and 18z, gradually tapering to flurries mid to late afternoon. Temperatures will fall into the lower to mid 20s. Snow is expected to spread into the Triangle and western Sandhills region this morning, with the heaviest snow expected between 10 am and 4 pm. Temperatures will fall into the mid to upper 20s this afternoon. The snow will likely begin as a period of rain in the Central and Southern Coastal Plain late morning, then gradually transition to snow from NW to SE as the cold air works in. Dynamical cooling associated with heavier precipitation rates will also aid in the change-over to snow from Fayetteville to Goldsboro mid to late afternoon. Temperatures in the mid to upper 30s will fall quickly by mid to late afternoon into the lower 30s in the Advisory Area. The temperatures will drop quickly today as the arctic air surges in from the north as the precipitation reaches maximum intensity. Expect the snow to taper off from the west late this afternoon and evening. Clearing skies will lead to bitterly cold conditions tonight. Lows 8-18.
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&& .SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
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As of 230 AM Wednesday... Continued very cold with mostly clear skies. Highs only in the upper 30s to lower 40s Thursday. Lows Thursday night in the teens to lower 20s.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/...
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As of 230 AM Wednesday... The extended forecast will feature a warming trend as the upper level pattern transitions to more ridging in the SE and a trough out west. A moderation in temperatures will be slowed by melting snow Friday and Saturday when highs will be in the 40s Friday and upper 40s and 50s Saturday. Lows in the 20s. By Sunday, it should be much milder with highs 55-65. The mild conditions will persist into early next week as the flow in the mid-upper levels remain zonal. An upper level disturbance will be lifting well to our nw Monday. This system`s attendant cold front will approach and cross our region Monday and Monday night, increasing the chance of showers.
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&& .AVIATION /06z TODAY THROUGH MONDAY/... As of 1245 AM Wednesday... 24-Hour TAF Period: Snow will develop and spread into the KINT/KGSO and KRDU areas through 15z. CIGS and VSBYS will lower into the IFR to LIFR categories at times between 12z and 18z in the west, and between 15z and 21Z at KRDU. The snow will gradually taper off and end from the west between 21z and 00z/this evening. In the KFAY and KRWI areas, precipitation is expected to start as rain between 13z and 15z, then change to snow with MVFR CIGS/VSBYS forecast to lower to IFR between 19z and 23z. The snow will end by around 00z, with CIGS and VSBYS forecast to become VFR by 06z/Thurs. Outlook 06z/Thursday through Monday... Generally VFR conditions expected. && .RAH WATCHES/WARNINGS/ADVISORIES...
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Winter Weather Advisory through 9 PM EST Wednesday for NCZ078-089. Winter Storm Warning through 9 PM EST Wednesday for NCZ007-021>025- 038>040-073>076-083-084. Winter Storm Warning through 9 PM EST Wednesday for NCZ008>011-026>028- 041>043-077-085-086-088.
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&& $$ SYNOPSIS...Badgett NEAR TERM...Badgett/BSD SHORT TERM...Badgett/BSD LONG TERM...Badgett/BSD AVIATION...Badgett

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