Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 150816 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 315 AM EST Mon Jan 15 2018 .SYNOPSIS...
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Arctic high pressure will retreat northeast on Monday as an area of low pressure begins to organize over the Great Lakes region. This will allow for a brief warmup to near normal conditions by Tuesday afternoon, just ahead of a cold front set to introduce a wintry mix to the area overnight Tuesday into Wednesday.
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&& .NEAR TERM /THROUGH TUESDAY/...
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As of 300 AM Monday... An upper level jet, producing some decaying upper level cloud cover across the region, will transition north and east off of the US Coast by sunrise. This will ultimately aid in the strengthening of a surface low off of the DELMARVA Peninsula by mid afternoon Monday, which will eject north, helping to force the controlling high pressure a bit further north and east into Tuesday. Locally, skies continue to clear, with the exception of the coastal plain counties in the east which are seeing an encroaching low to mid level cloud deck loosely associated with the aforementioned low off the Atlantic Coastline. Some significant model differences remain with the eventual behavior of this feature. Thus far, the more aggressive NAM seems to be closer to observations, while the synoptic models like the GFS have been struggling with saturating the 1-3kft cloud layer. We should eventually see these clouds push north/east of the forecast area around lunchtime Monday, but certainly could see some impact on the overnight low temps and possibly high temps if it can retain a BKN/SCT intensity. Otherwise, a warming trend will continue Monday afternoon with near normal conditions returning by Tuesday as westerly to southwesterly winds briefly return ahead of the frontal boundary passage. In general, expect upper 30s/lower 40s on Monday afternoon with 40s/50s prevalent on Tuesday. Temperatures will once again fall into the lower 20s overnight into early Tuesday morning. Near zero precipitation chances through Tuesday evening, with POPs slowly rising into the overnight hours as the front approaches from the north and west.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... As of 245 PM Sunday... The initial inland sfc low associated with the high amplitude positive-tilted trough over the NE-central US will fill over the Eastern Great Lakes/NE US late Tuesday-Tuesday night, eventually giving way to a coastal low development well off the Mid-Atlantic Coast Wednesday-Thursday as the potent upper trough assumes a neutral tilt as it pivots east across the region. There continues to be a large model spread WRT to the timing and strength/amplification of the trough and it`s associated ana-frontal precip band, driven by strong shortwave dynamics and f-gen that`s progged to move west-east across central NC late Tuesday night and into the day on Wednesday. Operational versions of the GFS continue to be drier while the Euro maintains up to 0.20" liquid equivalent. With afternoon temps on Tuesday expected to moderate into the 45 to 50 degree range ahead of the attendant sfc cold front, current timing and thermal profiles, still supports precip starting as rain or a rain-snow mix at onset Tuesday night with a west to east change- over to snow early Wednesday morning and into the afternoon(east) as the expansive Arctic High builds in from the west. As previous forecast discussions have noted, one model pitfall and potential forecast concern is that NWP models tend to advect low-level cold air east of the mountains too quickly, which in itself can be a self limiting process as considerable dry sub-cloud layers develop. Given continued high uncertainty, will make only minor changes to current forecast. Current best guess for snowfall amounts are an inch or two from the Triangle north and west into the Triad region, with less than an inch south and east of the Triangle. There may not be any snow accumulation in the sandhills. These amounts are low confidence at this time and will likely change as model guidance continues to evolve. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... As of 1 AM Monday... Mid level heights are expected to increase in the wake of the departing system, with surface high pressure slowly sliding eastward across the Southeast U.S. This will result in a warming trend through the remainder of the week, into the weekend. Dry weather is generally expected. However, we can`t completely rule out a weak disturbance moving across the area by the weekend, possibly yielding a small chance for some showers. Expect high temps will warm from the upper 30s to lower 40s on Thursday to the 50s and 60s by the weekend. Lows will follow a similar trend, from the teens on Thursday morning to 30s by Sunday morning. && .AVIATION /00z MONDAY THROUGH SATURDAY/... As of 622 PM Sunday... 24-Hour TAF Period: High confidence VFR conditions will persist at KINT/KGSO through this period as high pressure continues to build into the area. There is a chance some low MVFR clouds around in the 1-2 KFT range could develop over KRDU, KFAY, and KRWI between 06Z and 09Z, lingering until 18Z or so. Ceilings have been measured lowering east of the forecast area at this hour, but confidence on just how far west this will make it before daybreak remains low. Have withheld mention at RDU, but left a SCT layer in at FAY and a BKN layer in at RWI where there is a bit more confidence. Winds will remain relatively light through the period, highest in the east and lowest in the northwest. Looking ahead: High pressure will extend into the region through Mon afternoon before retreating to the NE Mon night, although VFR conditions will persist. Next chance for sub-VFR conditions will arrive late Tue through Wed as a potent upper level trough slowly crosses the region. VFR conditions will return for Thu/Fri as mild high pressure builds in from the west. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...JJM NEAR TERM...JJM SHORT TERM...CBL/Franklin LONG TERM...BSD AVIATION...JJM/KC

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