textproduct: Wakefield

WHAT HAS CHANGED

- Slight Risk Excessive Rainfall Outlook area has been expanded to include all but far southeast Virginia and northeast North Carolina on Sunday. Increasing chances for showers and storms presenting both a severe and flood risk for Sunday afternoon and evening

- Probabilities for Heat headlines have increased slightly over southern tier of counties, from Hampton Roads into Northeast NC.

KEY MESSAGES

1) Seasonable this afternoon into tonight with the potential for isolated to widely scattered showers or storms.

2) Severe weather is possible on Sunday with SPC highlighting much of the area in a Slight (2 out of 5) risk. Damaging wind gusts are the main threat, but an isolated tornado also cannot be ruled out. In addition, there is a heavy rain and flooding threat with WPC highlighting much of the area in a Slight ERO.

3) Hot and humid on Monday ahead of a cold front.

DISCUSSION

As of 300 PM EDT Saturday...

KEY MESSAGE 1...Seasonable this afternoon into tonight with the potential for isolated to widely scattered showers or storms.

This afternoon, high pressure located over the eastern Great Lakes continues to ridge southward, holding a weak frontal boundary south of the VA/NC border. Isolated to widely scattered showers or storms remain possible throughout this afternoon into this evening. The best thunderstorm potential is general along and south of the US-460 corridor. Instability is much less impressive compared to yesterday, with only ~1000-1500 J/kg of MLCAPE across southern portions of the forecast area. In addition, an onshore, NE wind (combined with cloud cover) has kept temperatures cooler today with readings in the mid to upper 80s.

Any convection tapers off after sunset. Overnight, remnant decaying showers from the Ohio Valley may try to drift towards far northern/western areas, but any measurable precipitation likely holds off until the daylight hours of Sunday. Otherwise, lows will range from the upper 60s to low 70s under a partly cloudy sky.

KEY MESSAGE 2...Severe storms are possible on Sunday with SPC highlighting much of the area in a Slight (2 out of 5) risk. Damaging wind gusts are the main threat, but an isolated tornado also cannot be ruled out. In addition, there is a heavy rain and flooding threat with WPC highlighting much of the area in a Slight ERO.

An unsettled to potentially active day is expected for Sunday. The expansive upper ridge over the southern tier of the country begins to breakdown as another shortwave trough digs across the Ohio Valley. The surface boundary pushes back north as a warm front, opening the door for deep tropical moisture transport (PWATs climbing to 2.3"+). Recent 12z high-res guidance (specifically the 3km NAM and RRFS) have hinted at a slower northward progression of the warm front, potentially keeping northeastern portions of the area in a bit of a wedge. In addition, morning showers and clouds may limit instability, at least initially. Still, SW of the front a very unstable airmass is expected with MLCAPE values climbing to potentially 2000+ J/kg.

Widespread shower and thunderstorm development is expected later Sunday afternoon through Sunday evening. Deep layer shear of ~25 to 30 knots will support multi-cells and bowing segments capable of producing damaging wind gusts of 50 to 60+ mph and even some isolated hail (despite poor mid-level lapse rates). In addition, E- SE winds along the warm front and 0-1 km SRH values of 150 to 200 will allow for potential rotation and an isolated tornado threat. SPC has most of our Virginia counties highlighted in a Slight Risk for severe storms, with a Marginal Risk for our Maryland and North Carolina counties.

Heavy rainfall is also expected to be a threat on Sunday. Slow moving or back building convection will produce torrential rainfall rates. WPC has expanded the Slight Risk ERO to cover a majority of the area. Scattered instances of flash flooding will be possible, especially across urban and poor drainage areas. Convection gradually weakens Sunday night.

KEY MESSAGE 3...Hot and humid with afternoon storms Monday ahead of the next cold front.

The hot, humid conditions look to peak on Monday ahead of an approaching cold front. Highs will reach the low to mid 90s. The hot temperatures combined with dewpoints in the mid to upper 70s will allow for heat indices of 105+ across southern/southeastern portions of the area and 100-105 elsewhere. Heat Advisories will likely be needed for at least our North Carolina and southeast Virginia counties. Scattered showers and storms are also expected Monday afternoon/evening along the frontal boundary. Drier and slightly cooler conditions arrive Tuesday into midweek.

AVIATION /19Z SATURDAY THROUGH THURSDAY/

As of 140 PM EDT Saturday...

Predominantly VFR is expected through the forecast period at all sites. A front is stalled south of the local area, serving as a focus for showers and possibly a few thunderstorms this afternoon into this evening. The highest potential for a shower or storm to cause any flight restrictions will be at ECG where a PROB30 remains in the forecast. Remnant showers may try to approach far northern/western portions of the area late tonight into Sunday morning, but confidence in any direct impacts at the TAF sites is low. Light and variable to light easterly winds are expected overnight, some patchy ground fog cannot be ruled out, but confidence is too low to include in the forecast. More widespread showers and storms develop Sunday afternoon.

Outlook: Widespread showers and storms Sunday afternoon into Sunday night will bring the potential for localized sub-VFR conditions as well as the potential for strong to damaging wind gusts. Unsettled conditions continue on Monday afternoon and evening ahead of an approaching cold front. Mainly dry/VFR conditions return through midweek as high pressure returns.

MARINE

As of 300 PM EDT Saturday...

Key Messages:

- Small Craft Advisories have been issued for the Chesapeake Bay and coastal waters N of Cape Charles Sunday afternoon into Sunday night for increasing southerly winds and building seas.

- Showers and storms are also expected Sunday, some of which could be strong to severe.

Sub-SCA conditions are expected to prevail through early Sunday. Winds this afternoon are E-NE 10-15 kt with high pressure N of the area. Seas are in the 2-3 ft range. Winds shift to the SE/ESE tonight and then S later Sunday. The pressure gradient is expected to tighten some as a weak front approaches and Small Craft Advisory conditions are expected to develop in the Chesapeake Bay early Sunday afternoon and the ocean by the late afternoon/evening hours. Sustained winds will generally be 15-20 kt with gusts up to 25-30 kt (highest N of Cape Charles on the ocean). Seas briefly build to 3-5 ft and will again be highest N of Cape Charles. Showers/storms could also bring locally higher winds. Winds and seas subside by mid- morning Monday. Thereafter, light flow and benign conditions are favored into the middle and end of next week.

Rip Currents: Despite the onshore flow, a low rip current risk continues today. Will continue with a moderate risk for the northern beaches of Chincoteague and Ocean City Sunday as southerly winds increase and seas build.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 1 PM Sunday to 7 AM EDT Monday for ANZ630-631. Small Craft Advisory from 4 PM Sunday to 7 AM EDT Monday for ANZ632-634. Small Craft Advisory from 7 PM Sunday to 7 AM EDT Monday for ANZ650-652-654.