Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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822 FXUS62 KRAH 151733 RRA AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1233 PM EST Mon Jan 15 2018 .SYNOPSIS... 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. && .NEAR TERM /THROUGH TUESDAY/...
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As of 1000 AM Monday... Skies have cleared over the vast majority of the CWA with the exception of the extreme northeastern counties as a coastal low continues to move up the coast. While this is presenting some freezing rain issues in the vicinity of the coast, this will have no impact on central NC today as we remain between the coastal low to the east and an approaching upper system over the Midwest. Temperatures in the low 20s across the area will rise above freezing and into the upper 30s to low 40s. Previous discussion follows. -Ellis An upper level jet, producing some decaying high 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. -JJM
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/... As of 345 AM Monday... ...Light Snow Possible Wednesday Morning/Afternoon... The mid/upper level flow will again become amplified across the region during this time, as a positively tilted trough will approach the area from the west, allowing an arctic cold front to move through the area Wednesday morning/afternoon. The precip with this system is expected to generally be along and behind the surface front. With low level thickness values crashing behind the front we`ll likely see precip start as a cold rain or mix of rain/snow, before changing to all snow (though we may see just rain for a majority of the time across the far SE). The latest GFS/NAM (generally a 0.10" or less liquid equivalent) continue to show less precip than the ECMWF (up to 0.20" of liquid equivalent), with the bulk of the precip expected across the northern half of the area on the GFS/NAM. Regardless it`s looking like we may see some light accumulating snowfall across the northern half of the area on Wednesday. Expect we could see up to 1 to 1.5 inches of snow generally near and north of the U.S. highway 64 corridor, with amounts ranging from a trace to near half an inch to the south. Amounts are dependent on the cold air arriving on time, which at times is a tripping point for NWP models for locations east of the mountains, thus the forecast is still a rather low confidence one. Low temps on Wednesday morning are expected to range from the mid to upper 20s NW to the lower 30s elsewhere. Highs on Wednesday will generally be in the 30s, with some locations likely to see temps fall during the afternoon. && .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 /18z MONDAY THROUGH SATURDAY/...
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As of 1230 PM Monday... 24 Hour TAF Period: Quiet forecast over the next 24 hours as VFR conditions are expected to remain in place at all TAF sites. Winds will be somewhat variable this afternoon at 5-10 kts but will consistently feature some portion of a northerly component. Some high clouds in the east could propagate into the KRWI area but for the most part expect clear skies to prevail. No restrictions to visibility are expected overnight. Long term: The main concern will be the threat of winter weather mainly on Wednesday morning with the threat evolving from west to east into Wednesday afternoon. Expect precipitation to being as rain and then transitioning over to snow with a potential period of wintry mix during this transition. The greatest threat will be for northern terminals but it is possible that all terminals could see accumulating snow. During this time both ceilings and visibilities could be hampered. Precipitation is expected to end on early Thursday morning and then a return to VFR conditions as high pressure takes over.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...JJM NEAR TERM...Ellis/JJM SHORT TERM...BSD LONG TERM...BSD AVIATION...Ellis

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