Area Forecast Discussion

WHAT HAS CHANGED

Day 2 Slight Risk (Thursday) was moved slightly north with afternoon update.

Heat Advisory has been issued for Thursday for much of SE VA.

KEY MESSAGES

1) Hot and humid Thursday-Friday, along with isolated to scattered, mainly late-day showers and storms.

2) A cold front crosses the area early Saturday, bringing drier, and somewhat cooler temperatures to the region.

3) Hot and humid again Sunday, then trending cooler and somewhat unsettled next week.

DISCUSSION

As of 400 PM EDT Wednesday...

KEY MESSAGE 1...Hot and humid Thursday-Friday, along with isolated to scattered, mainly late-day showers and storms.

High pressure remains centered well off the Southeast coast, with a lee trough in place across the piedmont. A belt of stronger westerly flow will continue across the northern half of the area today, but instability is rather elevated farther south as well (sfc-based CAPE to ~2500 J/Kg and ML CAPE to ~1500 J/Kg. Shear is rather weak (~20 kt), so no widespread SVR storms are expected, but with localized strong to marginally SVR storms possible into the early evening. With minimal shear, expect storms to diminish in coverage fairly rapidly after sunset, but will linger chc PoPs across the east through midnight. Lows only falling into the low 70s for most overnight.

Surface high pressure anchors offshore as an upper ridge builds across the Southeast Thu-Fri. The upper ridge will be centered south of the local area with stronger flow aloft impinging on the Mid- Atlantic, allowing for the potential for upper level disturbances to traverse the region and spark mainly diurnal chances for showers and storms. SPC has backed off a bit on the southern extent of the Day 2 Slight Risk (level 2/5) for strong to severe storms over the region Thursday, most likely in response to lower storm coverage (and weaker shear to the south). Guidance shows a shortwave aloft translating eastward to our north on Thursday. A lee surface trough will also be in place across the region Thursday afternoon. Forecast soundings show decently steep mid level lapse rates Thu aftn/evening for this part of the country, but deeper moisture may be a bit lacking for Thursday. Some robust pulse- type cells with gusty winds are certainly possible given the thermodynamic environment. Somewhat stronger shear is progged across the northern third of the CWA where the potential exists for more organized convective structures. The other issue Thursday will be the increasing heat and humidity. Have issued a Heat Advisory across Hampton Roads and up the W side of much of the Bay where dew pts will struggle to mix below the lower 70s, leading to heat indices ~105. Temps may be slightly higher farther west into central VA (upper 90s), but dew pts have a better chance at falling a few degrees during peak heating. Will allow tonight's shift to determine if the Heat Advisory needs to be expanded.

Additional Heat Advisories may be needed for mainly E-SE portions of the area Friday as well. At this time, Friday has a slightly better chance for seeing dew pts mix down into the 60s across inland areas during peak heating hours. Additional showers and potential for strong storms continues Friday afternoon and evening as upper heights fall ahead of the next cold front approaching from the N. Shear is again not looking particularly impressive, but with additional forcing from the front and very hot temps, this looks like a somewhat higher SVR threat overall.

KEY MESSAGE 2...A cold front crosses the area early Saturday, bringing drier, and somewhat cooler temperatures to the region.

Latest guidance continues to depict the upper level ridge shifting offshore Friday night into the weekend as a strong upper trough/low across northern Ontario very slowly moves to the E-SE. While the airmass in the wake of the front will remain warm, the wind shift to N-NE should lead to cooler conditions Saturday, especially at the coast, along with lower dew pts area-wide. ECMWF ensemble and GEFS show the PWAT anomalies dropping to below normal values.

KEY MESSAGE 3...Hot and humid again Sunday, then trending cooler and somewhat unsettled next week.

Low level southerly flow returns Sunday into early Monday ahead of the next cold front. At this time, most of the model guidance depicts the upper level flow remaining W-SW beyond that, which suggests the front will tend to stall into the middle of next week. It will trend cooler into next week, with highs falling back into the 80s along with at least diurnal showers and storms continuing.

AVIATION /00Z THURSDAY THROUGH MONDAY/

As of 750 PM EDT Wednesday...

Most of the SHRA/TSRA activity has moved offshore, but a brief downpour or two is still possible around SBY over the next hour or so. VFR conditions prevail overnight with a SW wind around 10 kt. VFR continues for most of Thursday, though an additional round of showers/storms is possible in the late afternoon and evening. Confidence is low on placement but could include sea breeze activity and/or storms moving into the Piedmont from the west. Winds Thursday SW 5-10 kt.

Outlook...Mainly VFR conditions Friday into the weekend. However, a greater chance of afternoon/evening storms is expected Friday along/ahead of a cold front. A few strong-severe storms are also possible with strong winds, localized VSBY reductions, and heavy rain the main threat. Lower rain chances Saturday with diurnal showers/storms returning Sunday-Monday.

MARINE

As of 355 PM EDT Wednesday...

Key Messages:

- Small Craft Advisories are in effect for the coastal waters through tonight as southerly flow and seas increase.

- Benign marine conditions Thursday through the majority of the weekend. Another period of elevated southerly winds is possible late Sunday into Sunday night.

High pressure is centered offshore this afternoon with winds currently 10-15 kt with gusts to 20 kt in the Ches. Bay and 15-20 kt with gusts to 25 kt in the coastal waters. Winds over the coastal waters will increase tonight to ~20 kt with gusts up to 30 kt, mostly over the northern coastal waters, and become more SW. Seas will also build to 4-5 ft tonight with the increase in winds. Small Craft Advisories continue for the coastal waters this afternoon into late tonight to account for this. Will note that the conditions are quite marginal for the southern coastal waters and may only see brief gusts to 25 kt. Winds and seas diminish Thu with generally benign marine conditions (outside of any convection) likely from Thu into Sun with mostly SW flow. Another period of elevated S winds is possible from late Sun into Sun night, although this is currently looking marginal.

A moderate risk of rip currents has been sustained for all beaches today. A low risk of rip currents is expected Thu into the weekend.

CLIMATE

Record High Temperatures:

- Date: Thu 6/11 Fri 6/12

- ORF: 98 (1911) 99 (1986) - RIC: 97 (1984) 100 (1914) - SBY: 96 (1914) 98 (1914) - ECG: 99 (1947) 97 (1947)

Record High Min Temperatures:

- Date: Thu 6/11 Fri 6/12

- ORF: 75 (2020) 76 (2016) - RIC: 75 (1914) 74 (1986) - SBY: 73 (2013) 75 (1947) - ECG: 75 (2020) 76 (2016)

AKQ WATCHES / WARNINGS / ADVISORIES

MD...None. NC...None. VA...Heat Advisory from 11 AM to 8 PM EDT Thursday for VAZ078-084- 085-089-090-097-098-520-523>525-528>531. MARINE...Small Craft Advisory until 4 AM EDT Thursday for ANZ650-652- 654-656-658.