textproduct: Raleigh

WHAT HAS CHANGED

Refreshed forecast based on recent guidance. Updated aviation as well.

KEY MESSAGES

1) Strong cold front will bring an increased chance for severe storms on Monday.

DISCUSSION

KEY MESSAGE 1...Strong cold front will bring an increased chance for severe storms on Monday.

On Monday a potent upper longwave trough looks to swing into a negative tilt and sling a strong 50-60 kt LLJ along and ahead of the translated sfc cold front. While the deep layer bulk shear is impressive, the low level shear really stands out as strong with the 0-3 km layer indicating near 50 kts shear and 300 m2/s2 SRH. MUCAPE looks to be on the order of near 1000 J/kg so that would be plenty of instability to raise concern of some intense convective triggering and downdrafts. Given the shear profile storm modes could be some discrete supercells or QLCS with both damaging wind and tornado threats. It is not very often when SPC has a 30 percent risk (essentially Enhanced Risk) for severe weather on Day 4 and this is out for almost the entire CWA. Timing should be more fine tuned as we get closer and the CAM guidance starts to cover possible convection evolution, but it looks like a good chance for a daytime passage, which would more likely involve diurnal destabilization.

Thermal profiles quickly cool on the back edge of this system which could allow for a quick transition to some snow showers from west to east late Monday afternoon into evening.

Please monitor the forecast as more details will be available over the weekend as we get closer.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

VFR conditions expected thru period with dry conditions and mostly clear skies - perhaps FEW/SCT cirrus skirting part of the area at times. Forecast is primarily based on wind trends with initial winds 10-16 kts gusting 22-28 kts out of the south to SW today then gradually decreasing tonight to under 7 kts. LLWS is possible for some of the sites including RDU in the 03-08z time frame. By later Saturday morning winds look to mainly shift out of the NW near 5 kts or less.

Outlook: Increased moisture could lead to sub-VFR conditions returning as early as Sunday evening. Gusty winds are also expected Sunday afternoon into Monday as the next weather system moves across the region. Severe weather is possible Monday.

RAH WATCHES/WARNINGS/ADVISORIES

None.