803 FXUS62 KRAH 100718 AFDRAH AREA FORECAST DISCUSSION National Weather Service Raleigh NC 320 AM EDT Mon Jun 10 2019 .SYNOPSIS... A cold front will approach central NC from the northwest today, and cross the region late tonight. A drier, more stable, air mass will overspread the region Tuesday. An area of low pressure will approach from the south Wednesday, and lift northward across the eastern Carolinas Wednesday night. && .NEAR TERM /THROUGH TONIGHT/... As of 315 AM Monday... An abundantly moist air mass remains in place across central NC with precipitable water values hovering around two inches. A shear axis lies immediately to our way, the remnants of the former upper level low over the lower OH/TN Valleys. The shear axis is projected to gradually weaken as it lifts east-northeast into the Mid Atlantic today. At the surface, a weak warm front lies across southeast NC early this morning. This boundary projected to become diffuse later today. With the lack of a discernible focus at the surface and weakening support aloft, appears the bulk of the showers and thunderstorms later today will be based on heating. Thus, convective development will be random in nature with coverage averaging 30-40 percent, though possibly higher along our northern and western fringes. While do not currently think a flash flood watch is needed today, the showers and storms will still be efficient at producing locally heavy/excessive rainfall so do expect a few urban and small stream flood advisories for locations that experience showers/storms repeating over the same location. Highs today should be warmer than Sunday, ranging from the upper 70s/around 80 NW to the mid 80s SE. Tonight, a s/w exiting the Great Lakes into southern New England will drive a sfc cold front through central NC overnight. Ahead of the front, expect broken bands of showers and possibly a thunderstorm or two. The coverage expected to be highest over the Piedmont counties during the evening hours, and along the I-95 corridor during the late evening into the first half of the overnight. Again, expect locally excessive rainfall in a few spots but not enough to warrant a flash flood watch at this time. The sfc front should exit our far southeast shortly after daybreak Tuesday. NW flow behind the boundary will usher a notably less humid air mass into the Piedmont toward daybreak. Overnight temperatures expected to vary from the mid 60s NW to around 70 SE. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 315 AM Monday... Discussion will be out shortly. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... As of 320 AM Monday... One more wet period to deal with on Wednesday with consistently drier and eventually warming conditions prevailing as we progress into next weekend. The upper-trough will reach its peak amplitude on Wednesday before becoming increasingly negatively tilted through the end of the workweek. At the surface, high pressure will extend southwestward along the lee side of the Appalachians before transitioning further off the New England coastline. A stalled surface front will attempt to migrate northwestward across the Carolinas Wednesday afternoon, with a weak disturbance progged to propel to the northeast along it, igniting another round of widespread showers and possibly an isolated thunderstorm across central NC. Timing and location of this boundary and associated weak disturbance will be key going forward, with a more easterly track (looking more favorable with each model run) likely to keep the best instability, PWATs, and thus shower/storm coverage east of the region. At this point, have kept categorical POPs across the entire area on Wednesday, however, the best convective shower coverage should remain from the Triangle eastward. Further northwest, the rain reinforced CAD type conditions will keep things cool and moist, but accumulations should remain relatively light in comparison. Have kept thunder chances low at this time, and primarily along and east of the Interstate 95 corridor during diurnally favored periods. Afternoon temperatures will remain 10 to 15 degrees below normal thanks to abundant cloud cover and rainfall. Overnight lows should remain near normal, settling in the 60s. A reinforcing cold front will be propelled east through the area on Thursday coinciding with the exit of the upper-trough, allowing slightly modified Canadian high pressure to filter into the Carolinas. This will allow for dry weather to persist into the weekend, with a gradual warming trend expected to commence on Friday (Highs in the upper-70s to low 80s) with a peak likely on Sunday (Upper-80s to low-90s) ahead of the next weather disturbance which should introduce showers and storms back to the forecast as early as Sunday afternoon, with POPs persisting into early next week. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... As of 150 AM Monday... A very moist and unstable atmosphere will maintain widespread sub VFR ceilings with IFR/LIFR ceilings highly probable through 15Z Monday across central NC. Through 18Z Monday, isolated showers will be possible almost anywhere across the region. After 18Z, as the atmosphere becomes more unstable, scattered showers and thunderstorms will be possible. By early afternoon, ceilings may lift to the MVFR and potentially low end VFR categories. Sfc winds will become sly later this morning, slowly veering to a southwest direction late in the day. A sfc front will approach from the NW late today and traverse our region overnight. Ahead of the boundary, expect broken bands of showers and isolated thunderstorms with MVFR/IFR conditions due to both ceilings and visibilities. The sfc boundary should cross the Triad region between midnight and 3 AM, and exit the the KFAY and KRWI vicinities prior to 8 AM Tuesday. Behind the front, northwest winds will usher a drier more stable air mass leading to improving aviation conditions with VFR parameters anticipated for most of Tuesday. The improvement will be brief as the sfc boundary will stall to our south late Tuesday. An area of low pressure will form on the front Wednesday, then lift nwd across the eastern Carolinas Wednesday night into early Thursday. This low pressure system will spread moisture back into central NC, result in in sub VFR ceilings mainly in proximity of KRDU, KFAY, and KRWI Wednesday through Wednesday night. As the low pulls away Thursday, expect improving aviation parameters across central NC. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...JJM AVIATION...WSS