Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 191030 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 700 AM EDT Thu May 19 2016 .SYNOPSIS...An upper level disturbance will push across the region today. A weak and cool surface high pressure will continue to extend into central North Carolina through Friday. A much stronger storm system is expected to move into the region late Friday into early Saturday. && .NEAR TERM /through tonight/... As of 122 AM Thursday... The main issues to deal with today will be the rain chances associated with the upper disturbance, and the expected persistent chilly NE low level supply of cool stable air and overcast associated with the hybrid CAD, resulting in temperatures again 20- 25 degrees below normal for highs. The predominate NE flow continued along the Appalachians and east coast states this morning, courtesy of the low pressure exiting into the western Atlantic and the surface high pressure located over the lower Great Lakes states. This flow is one that continues to advect cool and some marginally drier air into the state from central VA. The NE-E flow extended all the way into central SC and northeast GA where a weak low pressure was noted. Some drier air was trying to work down the coast from the north with some partial clearing of the low clouds noted east of I-95. There was a weakness in the pressure pattern noted over the Appalachians associated with the current weak hybrid CAD high pressure over NC/VA and the stronger high located over the lower Great Lakes states. Radar indicated scattered showers and thunderstorms developing over upstate SC spreading NE into western NC to near Hickory and Statesville. This is area was associated with the approaching upper level disturbance and the mass convergence near the surface wave and front stalled over upstate SC. For the chances of rain today, the latest Hi-Res convection allowing models support the current radar trends in bringing an area of showers and general rain (north in the cool stable air) across the Piedmont this morning. This occurs as the low level flow remains NE bringing a continuous supply of cool stable air into the Piedmont Damming region. This scenario above is favored by the conventional GFS/NAM as well. MOS guidance finally caught up with the much cooler stable temperatures yesterday associated with the NE flow and damming; therefore, we will not have to adjust guidance down as much today as we did yesterday. Bottom line today, expect a good chance of showers in the SE Coastal Plain with occasional rain over the Piedmont. Most of the rain should be light with QPF of around 0.25 expected in the Piedmont, lesser amounts over the Coastal Plain. Temperatures should only go up 3-5 degrees or so as the low overcast develops/persists through the day. Highs only in the 50s NW and N Piedmont ranging into the upper 60s SE. Significant rain chances lower tonight in the rear of the upper disturbance departing to the NE. However, the low overcast conditions should continue tonight enhanced by the low level NNE flow. In fact, the main chilly surface high pressure is forecast to move east to PA later tonight. The high is of sufficient strength and in a proper position to deliver additional cool stable air into the region to allow for the persistence of the CAD, then enhancement of the CAD Friday into Friday night as the next storm approaches from the SW (see discussion below). Lows tonight 50s except lower 60s SE. && .SHORT TERM /Friday through Saturday/... As of 258 aM Thursday... ...Hybrid CAD and Miller B storm system to affect the region into early Saturday... Issues ahead for Friday through Saturday will be mainly with the rainfall forecasts and the continued very cool temperatures for daily highs through at least Saturday. Any severe threat associated with the approaching storm system late Friday and Friday night have essentially been erased by the agreement of the models with hybrid CAD over our region and by the forecast of the storm track to be up along or east of I-95 late Friday night and early Saturday. This storm track is more of a Miller B with one low lifting NE through the TN and OH valley as another develops along the SC/NC coastal area late Friday night, then tracks up the coast Saturday. This pattern has a cool stable and almost "wintry" look to it. To begin Friday, a very cool surface high pressure is forecast to be centered over PA. The strength is expected to be around 1025 MB. The location and strength are both sufficient to deliver additional cool stable air into central NC from the north Friday. This occurs as the initial low pressure is forecast to track NE into the TN valley region by late Friday. All of our region is expected to be dominated by the cool stable low level high to the north. As such, temperatures Friday will be hard pressed to get out of the 60s anywhere in the region. Some upper 50s may again linger around the Triad to Roxboro in the continued hybrid CAD resume. The CAD will be strengthen as the day goes on as a cool stable NE flow pumps into the damming region of the Piedmont. Models suggest that some areas of light rain may develop/overspread portions of the Piedmont during the afternoon before widespread rain arrives Friday night. Even though the parent surface high will move offshore of New England Friday, the cool stable dome will have already been enhanced and firmly established. The coastal front is forecast to be pinned at the immediate coast. As one storm lifts NE toward the central Appalachians, another one will develop and take over near the boundary along the SC coast Friday night. This low will then lift NE along the coast early Saturday. There will be very little chance in this scenario of the coastal front being pulled inland, thus eliminating the severe risk over our region. However, a few elevated thunderstorms are expected to be embedded in the large rain area that overspreads the region Friday night, then ends from the southwest Saturday morning. The storm will then lift away from the region Saturday afternoon with dramatically lowering POP. However... the northerly flow behind the system along with lingering moisture in the low levels should keep any partial clearing confined to the SW Piedmont Saturday afternoon. Highs will be held down again by the residual CAD and then the persistent northerly flow as the storm pulls away. Expect readings to be warmest where any breaks occur in the SW Piedmont (possibly near 70). Most areas will stay in the lower to mid 60s (which is a good 20 degrees below normal). QPF will continue to be a tough call given the complexity of the evolving storm and the hybrid CAD over inland areas. Not to mention the deep south/Gulf coast convection potential. Even though models continue to be generous with 1 to locally 1.5 inches, this may be overdone in some areas. Flash flooding is not anticipated with the lack of strong convection and with the FFG values running rather high in the 3+ inch range in 6 hours. This is not expected to be threatened. But 1 to 1.5 inches in 6 hours may result in some minor flooding in urban and flood prone areas. && .LONG TERM /Saturday night through Wednesday/... As of 3 AM Thursday... Additional energy is expected to dive southward out of Canada helping to close off into a mid/upper level low along the mid atlantic coast late weekend into early next week, which will result in continue chances for showers and possibly some storms depending on the placement of the mid/upper low for Sunday and Monday (chance of convection everywhere for Sunday and limited to just eastern portions of the area my Monday). However, the best chance for precip will be during the afternoon into the evening/more diurnally driven convection. Highs Sunday and Monday are expected to remaining below normal in the 70s. Highs Tuesday and Wednesday will return to more seasonable values as the mid/upper low is expected to lift off to the northeast and surface high pressure is expected to shift offshore finally. Lows temps are expected to be near to slightly below normal for the medium range. && .AVIATION /12Z Thursday through Monday/...
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As of 700 AM Thursday... Low ceilings and occasionally low visibilities as well will persist today and tonight. Occasional rain and drizzle can be expected in the region along with persistent MVFR becoming IFR CIGS at or below 1K feet today. Abundant moisture will continue the low ceilings through tonight and into Friday. However, surface visibilities should improve somewhat Friday before falling again to IFR with rain and fog late Friday into Saturday morning. This occurs as a low level NE flow strengthens out ahead of an approaching storm system from the SW Friday night. This storm is expected to lift N of the region Saturday afternoon. The outlook for Saturday late through Sunday is for improving aviation conditions as the widespread rain/fog move north of the region between 12z-18z Saturday. VFR conditions are expected Sunday into early next week.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...Badgett SHORT TERM...Badgett/BSD LONG TERM...BSD AVIATION...Badgett

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