Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 261827 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 227 PM EDT Sun Mar 26 2017 .SYNOPSIS... A weakening upper level disturbance will pivot northeast across our region this afternoon. Bermuda high pressure will otherwise extend west into the southeastern U.S. through Mon. && .NEAR TERM /THROUGH TONIGHT/... As of 1045 AM Sunday... Little change required to the near term forecast. 12Z upper air analysis depicts a deep south-southwest flow over central NC. The mid levels of the atmosphere remain quite dry and will remain so. Meanwhile, the lower levels are marginally moist and expected to change little through early Monday. A weakening mid- upper level trough will lift newd across the region this afternoon. This system may spread or trigger a few showers in vicinity of the NW Piedmont including the Triad region. Showers expected to be spotty due to limited moisture and weakening support. Current forecast of the highest PoPs confined to the western half of the Triad appears on target at this time. Otherwise, expect a mixture of cloud/sun through this afternoon. Any showers that occur along and east of highway 1 will be isolated and too remote to mention in the forecast at this time. The moderating air mass coupled with peeks of sun will boost afternoon temperatures into the low-mid 70s this afternoon. If sun becomes more prominent this afternoon, could see a few upper 70s over the Sandhills and coastal plain. ~WSS While shortwave ridging aloft behind the departing mid level trough will likely yield dry conditions tonight, the mid level moist axis accompanying the trough will be left behind; and this may support a lingering shower or two over the wrn Piedmont tonight. Low temperatures centered in the middle 50s. ~MWS && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... As of 405 AM Sunday... A kicker shortwave trough now over the Four Corners, and a trailing lower amplitude perturbation near the Baja of CA, will both move generally Ewd across the MS Valley on Mon, and into the Carolinas Mon night. Lapse rates aloft will steepen into the 6.5-7 C/km range first Mon by a modified EML plume preceding the troughs, then as the associated cool pool aloft accompanying the troughs moves overhead Mon night, with an associated increase in (still-weak) instability of around 500-1000 J/kg over the Carolinas Mon afternoon and night. The models indicate the perturbation now over the Baja will slightly outpace the main shortwave trough over the Four Corners, such that the associated forcing for ascent accompanying the perturbation will spread E and interact with the weak instability axis over the Carolinas, and consequently result in scattered showers and storms Mon afternoon, particularly along and west of U.S. 1, where diurnal timing of the forcing for ascent will be maximized. The chance of showers and storms will increase overnight, as the parent shortwave trough and preceding forcing for ascent cross the Appalachians. The aforementioned steep lapse rates aloft, and relatively cool thermal profiles/low freezing level around 10 k ft, and 30-35 kts of mid level flow, may support the development of small hail in the storms. Instability would appear to be too limited to support any severe hail threat, however. It will again be warm, in the middle 70s to around 80 degrees, with lows in the middle to upper 50s. && .LONG TERM /Tuesday Night through Sunday/...
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As of 230 PM Sunday... Wed-Wed Night: With a shortwave ridge aloft, expect mostly sunny to partly cloudy skies with above normal highs in the mid/upper 70s. Thu: High pressure is expected to extend southward into the Carolinas Thu morning (in the form of a backdoor cold frontal passage) in association with height/pressure rises in the wake of an upper level low moving offshore New England into the Canadian maritimes. With low-level NE flow emanating from the cool Labrador current in NE portions of the state and an increased likelihood for cloud cover in SW portions of the state, temps Thu afternoon could be as much as 15-20F cooler than Wed afternoon. With the above in mind, have decreased highs to the mid/upper 50s west to lower 60s east. Thu night: Expect an increasing potential for rain from west-east between midnight and sunrise Fri as an upper level low progresses from the central MS river valley to the Ohio valley and low level flow backs/strengthens downstream over the Carolinas and Mid- Atlantic. Lows in the mid 40s to lower 50s, depending on rain /evap cooling/. Fri-Fri Night: Confidence in the evolution of the aforementioned upper level low, attendant sfc cyclone and associated warm/cold fronts at this range is low to begin with, let alone when a CAD wedge may be in place at the beginning of the period. All guidance continues to indicate precipitation, thus have increased precip chances to high likely (60-70%). From a pattern recognition standpoint, a potential for severe weather cannot be ruled out, however, little more can be said at this range in the forecast. The temperature forecast on Fri/Fri night is challenging to say the least. At this time will show the coolest temps in the Triad (highs in the low 60s) and warmest temps in the Sandhills and SE Coastal Plain (lower 70s). Expect clearing skies in the wake of a cold frontal passage Fri night, with lows in the upper 40s to mid 50s. Sat-Sun night: Expect a warming trend with dry conditions Sat in the wake of the aforementioned upper level low progressing offshore the Mid-Atlantic coast. A continued warming trend with dry conditions is expected on Sun as a shortwave ridge aloft tracks into the region from the west. -Vincent
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/... As of 115 PM Sunday... Varying degrees of cloudiness will result in periods of MVFR ceilings across central NC through 00Z Tuesday, primarily in vicinity of the Triad terminals. In addition, pockets of fog may reduce the visibility into the IFR category at KFAy and KRWI early Monday morning. In the near term, a few showers may cross the Triad terminals through 21Z, though the showers are expected to be light with limited adverse affects to aviation aside from slightly lower ceilings. A marginally moist and conditionally unstable air mass will result in periods of MVFR ceilings across the region through Wednesday. The lower ceilings will most likely occur between 10Z and 16Z. There is the possibility of a few showers and thunderstorms Monday afternoon, and again late Monday night through early Tuesday afternoon. Near the heavier showers and storms, expect MVFR ceilings and MVFR/IFR visibilities. A cold front will drop southward through central NC Wednesday, then stall to our south. The approach of an upper level low will increase sly flow a few thousand feet above of the cool stable dome of air at the surface, leading to widespread MVFR/IFR parameters due to low clouds and areas of rain late Thursday into Friday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...WSS/MWS SHORT TERM...MWS LONG TERM...Vincent AVIATION...WSS

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