Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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635 FXUS62 KRAH 261801 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 200 PM EDT Thu Apr 26 2018 .SYNOPSIS... A warm front will retreat northward across the central Carolinas through this evening, immediately preceding an area of low pressure that will track across central NC and into southern VA late tonight. A trailing trough will linger over the southeastern U.S. Friday and Friday night. && .NEAR TERM /THROUGH TONIGHT/... As of 1100 AM Thursday... Just a slight adjustment made to the hourly temperatures this morning to account for warmer than projected temps. Otherwise, near term forecast on track. 12Z upper air analysis and water vapor imagery depict a well-defined mid/upper level low pressure system crossing the Mid-South. The strongest mid level winds are rounding the base of the low this morning. Once these winds rotate through, the system should begin to slowly open up and take a east-ne direction. On this trajectory, the system will traverse along the spine of the southern Appalachians. Meso-analysis depicts moisture beginning to pool along a 925-850mb boundary situated west-to-east in proximity of the SC/NC border. As the moisture gradually deepens and heating destabilizes the atmosphere, expect to see a few showers develop in vicinity of this boundary by mid afternoon. The approach of the mid/upper level low will induce a low level sly flow over the Carolinas, aiding to push this boundary into our southern Piedmont and Sandhills by late afternoon. Thus, the idea of slight-small chance PoPs for showers across our southern counties later today warranted. While skies are partly cloudy/partly sunny across the region late this morning, moisture advection aloft will lead to increasing/thickening cloud coverage from the west-sw this afternoon. Expect skies to become overcast across the Piedmont by mid afternoon, and across the remainder of central NC prior to early evening. Appears that enough insolation will occur across the southeast half for temperatures to warm into the mid-upper 70s. Across the northwest, increasing cloud cover may inhibit insolation to keep temperatures near 70/lower 70s. If clouds are slow to arrive/thicken, temperatures in this region will be solidly in the lower 70s. ~WSS Tonight: The probability of rain will rapidly increase across the srn and wrn Piedmont after sunset, as the aforementioned lead frontal wave lifts newd from SC. Weak instability may support a few rumbles of thunder during the evening there, though with most of that rain likely to hold west of Highway 1. A secondary band of convection will then likely accompany the parent wave of low pressure, beneath the focused forcing for ascent accompanying the upr wave, as they track across the remainder of cntl NC after midnight. Focused forcing for ascent and cooling temperatures aloft accompanying the upr wave may provide for a better chance of thunder embedded within that convective band, including some surface-based owing to theta-e advection/mixing and resultant moist neutral low level thermal profiles per bufr forecast soundings. Strong wind gusts may accompany the convective band, but a lack of more appreciable boundary layer moisture (ie. surface dewpoints only in the mid-upr 50s), and the aforementioned weakening of the height/wind fields aloft --and bulk shear values to around 35-45 kt-- as the upr wave deamplifies, suggests any severe threat will be low. Lows in the 50s. ~MWS && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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As of 350 AM Thursday... The deamplifying short wave lifts north, with its associated surface low passing across the Delmarva peninsula early Friday afternoon. A few lingering showers will be possible in the morning, with shower coverage increasing along with a chance for a few thunderstorms in the northeast during the afternoon as a weakening cold front edges slowly east across the area. Some sun ahead of the front will allow highs to reach the low to mid 70s. Cool air advection will be weak behind the front with predominantly westerly flow and scattered cloudiness overnight. Mins will range from around 50 northwest to mid 50s in the southeast. A reinforcing dry cold front will move across the area Saturday night. So, despite dry conditions with plentiful sunshine this weekend, temperatures will be slightly cooler than normal through Monday, with highs mostly 70 to 75 each day after morning mins mostly in the mid and upper 40s.
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As of 200 PM Thursday... Long range forecast continues to be dry with a warming trend. An upper level trough will pass across the area Sunday and Sunday night. High pressure building in early next week will allow for the airmass to begin warming concurrent with height rises behind the upper trough passage. Conditions will be dry with mostly clear skies to accompany a warming trend Tuesday through late week. Highs Monday will be in the low to mid 70s, near 80 on Tuesday, and in the low to mid 80s Wednesday and Thursday. Morning lows will follow a similar trend, from around 50 Tuesday morning to around 60 Thursday morning.
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&& .AVIATION /18Z THURSDAY THROUGH TUESDAY/... As of 125 PM Thursday... An approaching low pressure system will cause aviation conditions to deteriorate from the west southwest this evening and persist until early Friday morning. Ceilings will thicken and lower with widespread MVFR ceilings expected later this evening, starting in the west between 00Z-03Z, and elsewhere after 03Z. In addition numerous showers and a few thunderstorms will overspread central NC from the west, beginning around 00Z in the west, reaching the Coastal Plain and the I-95 corridor after 05Z. The bulk of the convection will depart our eastern-northeast counties around daybreak. In vicinity of the stronger storms, sfc wind gusts around 35kts possible along with torrential downpours and some hail. Aviation conditions will gradually improve Friday morning with VFR parameters anticipated by mid day, persisting into the afternoon. The exception will be isolated-scattered showers that will develop along a slow moving cold front drifting east across central NC. In proximity of the showers, expect a brief period of MVFR ceilings and MVFR/IFR visibility in heavy showers. VFR conditions expected Friday night through Tuesday as central NC will have a period of tranquil weather. A sfc cold front will glide southeast across the region Saturday night. At this time, the atmosphere appears too dry and stable to support anything more than a band of clouds and possibly a shower or two near the Virginia border. && .RAH WATCHES/WARNINGS/ADVISORIES... NC...None. && $$ SYNOPSIS...MWS NEAR TERM...WSS/MWS SHORT TERM...mlm LONG TERM...mlm/Franklin AVIATION...WSS is the U.S. government's official web portal to all federal, state and local government web resources and services.