Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 301138 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 738 AM EDT Thu Mar 30 2017 .SYNOPSIS... Weak high pressure will extend across eastern NC through Thursday. An area of low pressure will bring unsettled weather to the area Thursday night and Friday. && .NEAR TERM /THROUGH TODAY/... As of 425 AM Thursday... The southern edge of a surface high extending down into the area from the north is bringing easterly flow to the area but southeasterly flow along the Appalachians and as a result a growing area of MVFR stratus is starting to build in across the northwest Piedmont. This feature will be influential on today`s weather when it comes to sky cover, precipitation and ultimately temperatures. Later this morning drizzle or even light rain will be possible across the northwest Piedmont as more moisture flows into the area. Depending upon how thick the stratus becomes, and model soundings show a significant cloud deck about 8 kft thick, high temperatures under the stratus could be overdone. As a result have slashed temperatures across the north to below guidance with upper 50s in the Triad but a fairly tight gradient with lower 70s across the southern counties. The triangle will be a major gamble today with anything from lower to upper 60s possible. For now have chosen to go on the lower end but a safe bet will be the middle 60s. && .SHORT TERM /THURSDAY NIGHT AND FRIDAY/... As of 420 AM Thursday... Attention will turn to the southwest on Thursday night as a warm front surges in and temperatures should actually begin to rise overnight at most locations. Good isentropic lift in the west will begin to encourage precipitation over the western portion of the CWA between 0-6Z Friday. Model forecast soundings are virtually saturated throughout the column with PW values near 1.3 inches. The low level jet structure is fairly unorganized early Friday morning and there are several small disturbances in the flow so expect several smaller waves of precipitation which could be scattered in nature at times. As the precipitation pushes eastward it could become a bit more organized into more multicellular or broken lines but shear will be decreasing at this time particularly in the lower levels as winds become southwesterly and more unidirectional with height. Instability will increase slightly with peak heating and a dynamic push from the left exit region of a 500 mb jet could cause a storm or two to become severe. SPC has the eastern half of the area in a marginal risk for severe wx with damaging winds the most likely threat. With decent moisture in this system expect rainfall totals anywhere from a half of an inch on the low end to about an inch on the high end. Temperatures will be tricky on Friday given the convection but with central NC in the warm sector for much of the day expect highs in the low to mid 70s in most locations. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... As of 405 AM Thursday... An energetic Pacific jet will send a series of significant shortwave perturbations into the west-central U.S., where the models indicate they will amplify toward the Four Corners/Srn Plains region and interact with an equally energetic southern stream. That interaction will ultimately shear the perturbations ENEwd into the Middle Atlantic states, with associated episodes of precipitation/convection, about every 72 hours in central NC. This a relatively persistent pattern from recent days, which included the round of convection from this past Mon night, and which will likely result in another one later tonight (highlighted in the short term discussion above). Fri night: The models are now in good agreement with the progression of the upper low initially over the Central Plains, to the nrn Middle Atlantic coast by late Fri night. An accompanying surface trough axis/secondary front will cross the ne Piedmont/nrn Coastal Plain with a lingering chance of showers and a storm or two Fri evening. Otherwise, clearing and cooling will occur, with lows in the lower to middle 50s. Sat-Sun: Beneath longwave ridging bulging Nwd from the Caribbean to central Canada, the weekend is expected to be dry, and mild, with a reinforcing dry frontal passage (the leading edge of a Pacific high) Sat night. Periods of stratocumulus may bubble beneath a strong, 5 k ft subsidence inversion, but not with enough coverage to significantly impact temperatures through the period. Highs in the upper 60s to 70s, warmest ahead of the reinforcing front on Sat. Lows, coolest Sun morning in the 40s, and about a category higher in return SEly flow and increasing deep moisture by Mon morning. The next couple of strong shortwave perturbations will follow on schedule and cross central NC late Mon-Mon night and again just beyond this forecast period (Thu). The result will be another likely probability of showers and storms late Mon-Mon night, preceded by possible weak in-situ CAD during the day Mon. It will otherwise be mild through the period, with temperatures mostly in the 70s and 50s for highs and lows, respectively. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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As of 740 AM Thursday... 24 Hour TAF Period: MVFR ceilings now covering much of the forecast area this morning. Over the NW Piedmont these ceilings should stay locked in all day whereas locations in the south and east may scatter out with daytime heating. Some drizzle may occur over the next few hours at KINT or KGSO. Expect southeasterly winds today with gusts up to 15 kts or so. By Friday morning, more significant precipitation is expected to move in with a warm front that will cross the area from southwest to northeast. This will bring a line of rain into the western Piedmont by 9z or so and into the Triangle area and KFAY by 12z and exiting to the east thereafter. Long term: After the warm front rolls through the area at the end of the TAF period, a cold front will follow on its heels on Friday sparking another round of convection. This will clear out on Friday night and give way to quiet conditions until Monday when another strong low pressure system is progged to cross central NC causing potentially adverse aviation conditions.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...Ellis SHORT TERM...Ellis LONG TERM...MWS AVIATION...Ellis

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