Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 211726 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 126 PM EDT Tue Mar 21 2017 .SYNOPSIS...
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A cold front will track southeast of the mountains into the Carolinas this evening into tonight. A weak surface low will develop within a pre-frontal trough invof the South Carolina border this afternoon. The aforementioned low will shift southeast toward Cape Fear tonight as the aforementioned front progresses through central North Carolina. In the wake of the front, Canadian high pressure will build into the region from the north mid-week, then settle along the Mid-Atlantic coast late week.
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&& .NEAR TERM /Through Tonight/...
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As of 115 PM Tuesday... Overview: In the upper levels, small amplitude disturbances embedded in NW flow aloft are progged to traverse the Carolinas this evening/ tonight. 16Z WV imagery, radar imagery and RAP data show several disturbances upstream over the central MS river valley (IA/MO) this afternoon. The northern disturbance is progged to track through the Mid-Atlantic invof the mason-dixon line late this eve/tonight, while the southern disturbance/MCV is progged to track through TN into GA/SC. A cold front progressing SE into the Appalachians this morning will track slowly S/SE into central NC late this aft/eve. Strong insolation /diurnal pressure falls/ will enhance a pre- frontal trough downstream of the front (east of the mountains) and aid in the development of a weak surface low invof the NC/SC border by ~00Z. The surface low is progged to track ESE toward Cape Fear overnight as the cold front progresses S/SSE through central NC and an upper level disturbance tracks SE through TN to the Southeast coast. Today: Expect dry conditions to prevail through mid to late afternoon given weak forcing, marginal low-level moisture and a strong cap associated with an unmodified elevated mixed layer (H7-H5 lapse rates ~8C/km) advecting over the region from the west. The low- level airmass over central NC has been modified by warm advection during the past 12-18 hrs. This, in combination with skies and unimpeded Spring insolation will result in highs ranging from the mid/upper 70s to lower 80s. Tonight: Strong insolation and low-level moisture advection from TN into northern GA and Upstate SC is expected to erode the cap and result in convective development within the pre-frontal trough over southeast TN and Upstate SC (perhaps as far NE as CLT) by 21-00Z this afternoon. With the best low-level moisture expected to advect into GA/SC this afternoon, airmass destabilization/cap erosion in central NC late this aft/eve may be confined to the SC border counties, primarily in the SW Piedmont/Sandhills. North of Hwy 64, forecast soundings show a capped atmosphere in place the entire day, with little or no destabilization in advance of FROPA. With the above in mind, convection is expected to develop ~00Z in the SW Piedmont, with activity progressing E/ESE invof the NC/SC border overnight. Chances for convection will decrease from W-E after midnight as activity progresses toward Cape Fear and, ultimately, offshore the Carolina coast. Confidence in convective development/ coverage decreases heading north toward the Hwy 64 corridor, and portions of the N/NW Piedmont and NE Coastal Plain may ultimately remain dry during/after FROPA late this evening. Severe Potential: The potential for severe weather late this aft/eve and early tonight appears to have diminished for much of central NC, except invof the NC/SC border where destabilization/cap erosion is still anticipated and environmental conditions remain supportive of organized (multicellular or supercellular) convection with an attendant threat for damaging winds and hail up to the size of quarters. The potential for severe weather will be greatest along the NC/SC border between ~7 pm and ~3 am. -Vincent
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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
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As of 115 PM Tuesday... Expect a clearing trend in the morning as a drier airmass advects into the region from the north, with clear skies during the afternoon and evening. Cold advection is expected to persist for the majority of the diurnal heating cycle on Wed as Canadian high pressure builds into the Mid-Atlantic from the NW. Expect highs much cooler than today, in the mid/upper 50s N/NE to lower 60s S/SW. Lows Wed night may be tempered by increasing mid/upper level cloud cover after midnight. Will indicate lows ranging from the upper 20s (rural and low-lying areas east of I-95) to lower/mid 30s. -Vincent
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... As of 340 AM Tuesday... Thursday through Friday: Cold high pressure located over the Mid- Atlantic will extend south/southwestward into central NC on Thursday, before moving offshore Thursday night into Friday. This should result in dry conditions for the end of the week, with a warming trend commencing on Friday. However, the cold surface high will allow for well below normal temps on Thursday and Thursday night, with perhaps another freeze for portions of the area on Thursday night (especially northeast). Expect high temps on Thursday will be in the lower to mid 50s, with lows temps on Friday morning generally in the lower to mid 30s, with a few locations in the usual cold spots dropping into the upper 20s. High Friday are expected to be around 60 NW to the mid to upper 60s SE. Friday night through Monday: A mild pattern is expected for the weekend into early next week as a mid/upper level low moves east- northeastward from the central/southern Plains into the Ohio Valley and Great Lakes region. Meanwhile, mid/upper level ridging over the region to start the period will shift eastward and offshore. This will allow for increasing warmth and moisture to transport into central NC for the weekend, lingering into early next week as the main frontal zone will remain to the north/northeast of central NC. Expect high temps will be in the 70s during this period, with even a few locations toughing 80 late weekend/early next week, while low temps are generally expected to be around 50/in the 50s. With increasing southwesterly initially and the aforementioned disturbance passing to the north of the region expect we may see periods of showers and some storms from Saturday afternoon onward. && .AVIATION /18Z Tuesday through Sunday/...
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As of 115 PM Tuesday... 24 Hour TAF Period: VFR conditions will prevail through the TAF period at most terminals (INT/GSO/RDU/RWI), the exception being FAY where MVFR ceilings and scattered convection will be possible this evening into tonight, primarily between 00-06Z. Light/variable winds will become Northerly at 10-15 knots in the wake of a backdoor cold frontal passage between sunset and midnight at northern terminals (INT/GSO/RDU/RWI), midnight and sunrise at the FAY terminal. Gusts up to 20-25 knots will be possible between sunrise and noon on Wed. Winds will veer to the NE at ~10 knots by the end of the TAF period early Wed afternoon. Looking Ahead: VFR conditions will prevail through the end of the work week in assoc/w a dry surface ridge as high pressure builds into the Mid-Atlantic and then shifts offshore the DELMARVA. Sub-VFR ceilings will be possible on Friday in assoc/w the development of a southerly return flow as high pressure shifts further offshore. A potential for sub-VFR ceilings assoc/w return flow will persist over the weekend. -Vincent
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Vincent LONG TERM...BSD AVIATION...Vincent

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