Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281129 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 729 AM EDT Tue Mar 28 2017 .SYNOPSIS... An upper-level disturbance crossing the region will bring unsettled weather today, followed by quiet conditions tonight and Wednesday as a cool front settles southward into the area. Another storm system moving through the central U.S. Wednesday will approach our area Thursday, bringing another round of stormy weather late Thursday through Friday night. && .NEAR TERM /THROUGH TONIGHT/... As of 400 AM Tuesday... A low pressure system that is very evident on satellite, water vapor, and radar imagery is working its way through the Ohio Valley at this time and helping to push a band of showers and thunderstorms into the western Piedmont at this time. All storms are sub-severe at this time but the line is expected to hold together through the early morning hours as it pushes eastward. This initial line of showers and storms is expected to make it through the CWA by early afternoon and exit to the east. Behind this line, another line is expected to form during the peak heating of the afternoon and strengthen as it moves eastward. Looking at forecast soundings, the most favorable conditions will be along the I-95 corridor where 700- 1000 J/kg of instability, upwards of 40 kts of bulk shear and good low and mid-level lapse rates will set the stage for the possibility of some severe weather. SPC has placed all of central NC in a marginal risk for severe weather. LCLs are very high and hodographs do not indicate much helicity at least in the 0-3 km range, therefore do not expect tornadoes with this system. The most likely severe threat will be damaging winds with some small hail possible as well. This fits in well with the history of this storm system. After this secondary line exits to the east, conditions will gradually begin to clear with VFR conditions returning to the area. Temperatures will be tricky depending upon convective coverage but despite that, another warm day is expected with highs in the mid 70s across the north to lower 80s in the southern counties. Lows in the middle 50s. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 400 AM Tuesday... Quiet weather day on Wednesday as surface high pressure builds in from the north behind the exiting frontal system and an upper level ridge extends northward out of the southern Caribbean. A bit cooler with the airmass change with highs in the low 70s across the northeast to upper 70s in the southwest. Lows are expected to be in the mid 40s across the northeast to middle 50s in the southwest. && .LONG TERM /Thursday through Monday/... As of 345 AM Tuesday... Thu through Sat: The backdoor cold front is expected to settle just south of NC early Thu as cool high pressure noses in from the north. In the mid levels, a shortwave ridge shifts across the SE and Carolinas Thu, while a potent low pushes slowly eastward through the central and southern Plains. Major model differences start to emerge between the GFS and ECMWF Thu, resulting in a low confidence forecast. Both models take the mid level low and trough eastward through the Mid/Lower Miss Valley / Mid South / Gulf States and Carolinas / Southeast through early Sat, however the GFS digs energy into this low much more deeply than what is shown by the ECMWF, and this in part results in notable differences with the push of the front back north through NC, with the more southern-track GFS keeping the front to our south through Thu night (with a cool stable wedge regime in the NC Piedmont) followed by a slow northward push Fri, while the slightly weaker/more northerly ECMWF takes the milder air northward into central NC as early as late Thu. While the high to our northeast is not particularly strong nor is it being significantly reinforced aloft, this air mass should still be dense enough for the cool pool to stay lodged into the NC Piedmont through Thu. Will have highs Thu from the mid-upper 50s NW ranging to near 70 SE, with a slight chance of rain or drizzle in the west with overrunning flow strengthening over W NC as the 850 mb anticyclone shifts off the Carolina coast. As the mid level low/trough crosses the region with a negative tilt, it will be accompanied by a complex occluding surface frontal system, with a more southern track and less potential instability on the GFS (which develops strong forcing for ascent near the E Gulf Coast/FL Panhandle Thu/Thu night) and a more northern track with greater potential instability on the ECMWF. Have generally followed the slightly weaker ECMWF, although both models have been trending stronger with the shortwave trough in recent runs, so confidence remains low. There does appear to be enough moisture (PW of 1.25-1.5") and forcing for ascent, including DPVA, enhanced upper divergence, and low level mass convergence, for a continuation of likely pops, focused on Thu night through Fri evening, tapering down WSW to ENE Fri night into early Sat as the mid level shortwave trough and surface frontal system push to our east with a weak cool front settling southward through the area. Highs from the mid 60s to lower 70s Fri with cloudy skies and numerous showers/storms, and in the low-mid 70s Sat with partial sunshine and rising heights aloft as another mid level ridge axis approaches in the wake of the exiting trough. Sat night-Mon: Expect generally quiet weather Sat night/Sun as weak surface high pressure builds in from the north in tandem with the mid level shortwave ridging. Yet another shortwave trough crosses the S Plains into the lower Miss Valley Sun night into Mon, while the weak frontal zone to our south tracks back northward. Expect fairly seasonable temps Sun, perhaps still a little above normal as the incoming surface high will be cut off from a polar air source. Warmer thicknesses Mon, behind the weak warm front, will be offset with increasing clouds with the trough`s approach, so expect highs from the lower to upper 70s Mon. -GIH && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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As of 730 AM Tuesday... 24 Hour TAF Period: A line of showers extending through the central part of the CWA will continue to slowly move eastward this morning. Not much potential left for thunder with this round of rain. Later in the day, expect a line of showers to develop in the Triad around 18z and push eastward reaching the Triangle by 20Z and pushing eastward after that. KRWI and KFAY will be the most likely locations to experience any thunder this afternoon. Some storms could become severe with damaging winds the most likely threat but coverage of severe, and thunderstorms in general should be fairly limited. After 00z showers and storms will exit to the east and winds will become more northwesterly. Some wind gusts this afternoon of 15-20 knots. Some MVFR ceilings could be possible with heavier showers but otherwise expect mainly VFR conditions today. Long term: A low pressure system will cross the area on Friday through Friday night with the potential for showers and thunderstorms. High pressure with VFR conditions should return for the weekend.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Ellis SHORT TERM...Ellis LONG TERM...Hartfield AVIATION...Ellis

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