Area Forecast Discussion

WHAT HAS CHANGED

* Updated Aviation discussion through Monday evening.

* An isolated severe thunderstorm is possible within a larger area of a chance of showers and thunderstorms into the overnight period, especially in the northeast Piedmont, northern Coastal Plain, into the central Coastal Plain.

* A slight chance of severe thunderstorms (level 2 of 5) for Tuesday into Tuesday night. Damaging wind the main threat.

KEY MESSAGES

As of 1235 PM Sunday...

1) An isolated severe thunderstorm is possible within a larger area of a chance of showers and thunderstorms into the overnight period, especially in the northeast Piedmont, northern Coastal Plain, into the central Coastal Plain.

2) A slight chance of severe thunderstorms (level 2 of 5) for Tuesday into Tuesday night. Damaging wind the main threat.

3) A return to a more dry pattern on Wednesday, with rain chances increasing next weekend.

DISCUSSION

As of 1235 PM Sunday...

KEY MESSAGE 1... An isolated severe thunderstorm is possible within a larger area of a chance of showers and thunderstorms into the overnight period, especially in the northeast Piedmont, northern Coastal Plain, into the central Coastal Plain.

The H5 trough continued to remain over the eastern states with the main trough axis offshore of New England and Mid-Atlantic coast. The Flow aloft over NC was from the NW and this can be problematic in the summer. Cold air aloft associated with the trough and periods of lift associated with the leading edge of disturbances within the flow bring unsettled conditions with a chance of showers/storms.

It has been stable across the region today as the residual low stratus associated with the previous days CAD event lingered. Even at early afternoon, only some elevated instability was noted increasing over top of central NC from the NW, with lingering stable stratocumulus over much of the region. Temperatures have struggled to even reach the mid 70s to near 80.

Another shortwave is expected to track from the Great Lakes SE into the Mid-Atlantic region tonight, which is expected to bring another chance of showers and thunderstorms across portions of VA into north-central and NE NC. The hi-res models are still varying in the placement of the higher POP, but the general outlook is for an increase in instability with the approach of the disturbance along with an increase in moisture again tonight. The NW flow aloft is also expected to increase and we will be on the southern end of the stronger winds aloft tonight into Monday. This may support some organized storms overnight which may track into our region from VA. WE will carry 40-60 POP in the northern and eastern Piedmont into the Coastal Plain overnight. This activity should exit SE early Monday, followed by another chance of PM showers/storms later as additional energy from upstream approaches in the increasing NW flow aloft and MLCapes late in the day as highs reach the mid 80s to lower 90s.

KEY MESSAGE 2...

A slight chance of severe thunderstorms (level 2 of 5) for Tuesday into Tuesday night. Damaging wind the main threat.

Yet a stronger NW flow and another strong disturbance aloft will approach later MOnday night and Tuesday. Models agree that we will we unstable and becoming moreso with heating Tuesday into the upper 80s to lower 90s. MLCapes may exceed 1500-2000 j/kg. However, early morning thunderstorm complex(s) may send outflow boundaries into the region Tuesday morning as the storms weaken on late night and morning approach from the central Appalachians. Even so, renewed development is expected Tuesday afternoon along a pre-frontal trough or residual outflow boundaries over the Piedmont, then move into the Coastal Plain and Sandhills. Some of the storms may become severe, with damaging wind the main threat. Although there is currently a slight risk for essentially the entire area for severe storms Tuesday into Tuesday night, this has plenty of potential to change given much of our forecast Tuesday will rely on what happens with the storms upstream early Tuesday and the placement of outflow and pre-frontal boundaries to start the day Tuesday. Stay tuned.

It appears that the best chance of strong to severe storms will be during the afternoon into the evening for our region, as new development should occur by early afternoon on the said boundaries and last well into the night as they spread SE.

KEY MESSAGE 3... A return to a more dry pattern on Wednesday, with rain chances increasing next weekend.

After the frontal passage Tuesday night into Wednesday, high pressure will build in as the front stalls to our south. Each afternoon will have high temperatures in the upper 80s to lower 90s, with lows dipping into the mid 60s to lower 70s. These temperatures are normal for this time of year. The front will also usher in drier air, with PWs around 1.2 in Wednesday through Friday. This will diminish rain chances, however a very isolated shower cannot be ruled out each afternoon. Rain chances look to increase next weekend as the front starts to retrograde back northward and a mid-level disturbance approaches the region from the west.

AVIATION /00Z MONDAY THROUGH FRIDAY/

As of 700 PM Sunday...

VFR conditions are favored to start the TAF period. In the immediate near-term, there is the potential for isolated showers and storms with a disturbance moving south out of VA. Most high-res model solutions indicate the favored time period for any storms is between 03-09z. While the guidance is mixed on coverage and location, clustering from the HREF would suggest the best potential would be at RDU and RWI, with a secondary threat at GSO. Overall confidence remains low, but did include a PROB30 for these terminals. With little change in the airmass over the last 24 hours, the potential for LIFR/IFR stratus and patchy fog is again favored Mon morning. A broad suite of model guidance is mixed on stratus versus fog, but given favorable conditions for crossover temperatures to be met or exceeded in light winds, introduced the potential for IFR visibilities. Any sub-VFR conditions should lift by 14-15z, with WNW to N winds in the afternoon on Mon. Isolated to scattered convection may develop along the sea-breeze and a surface boundary Mon aftn/eve, most favored at FAY/RWI. For now, opted to leave this out of the current TAF given low confidence on coverage.

Outlook: Areas of stratus or fog is again possible Tue morning. A higher threat of scattered to numerous showers and storms are expected Tuesday afternoon and evening ahead of a cold front. Some may be strong to severe. Mainly VFR conditions should prevail Wed through Fri.

RAH WATCHES / WARNINGS / ADVISORIES

None.