Area Forecast Discussion

WHAT HAS CHANGED

Heat Advisory has been expanded northward into the Northern Neck through 8 PM this evening.

KEY MESSAGES

1) Hot and humid today-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 330 AM EDT Thursday...

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

High pressure remains centered well off the Southeast coast early this morning. Aloft, ridging will persist across the Gulf Coast eastward into the SE CONUS. Stronger flow aloft will likely stay mostly N of the local area today as heights aloft hold steady or rise slightly. It will be hot over the region today high temperatures rising well into the mid and upper 90s. Forecast highs are near record values for the date, see Climate section below for further details on specific records at the main climate observation sites. The warmest temperatures are expected away from the immediate coast/Eastern Shore. Forecast soundings continue to show some drier air aloft which will likely allow afternoon dew points to mix out by a few degrees. This is most prevalent over the western half of the area with dew points mixing into the upper 60s during peak heating. Farther east, moisture appears to be a bit deeper with less potential for dews to mix into the 60s during the afternoon. Accordingly, max heat index values are highest along and just west of the Ches Bay this afternoon, mainly in the 103-105 degree range. Have expanded the Heat Advisory northward into the Northern Neck in coordination with the Sterling, VA WFO. The Heat Advisory remains in effect from 11 AM through 8 PM this evening. The heat headlines may need to be extended southward into NE NC as well pending greater clarity on low level moisture profiles and potential for drier air mixing to the surface this afternoon. Regardless of the finer details, it will be quite hot across the area today and people should take precautions to mitigate heat related impacts this afternoon.

The other weather concern today is the potential for isolated to scattered late afternoon/evening thunderstorms. Forecast soundings continue to show decently steep mid level and very steep low level lapse rates this afternoon into the evening. MLCAPE progs are on the order of 2000-3000 J/kg but deep layer wind shear will be lacking. Most guidance keeps shear in the 15-25 kt range (highest N). Some robust pulse-type cells with gusty winds are certainly possible given the thermodynamic environment in place with DCAPE values above 1000 J/kg. SPC has maintained basically the same outlines of Slight and Marginal Risk areas with mainly the NW half of the area in the Slight Risk. With a bit more shear across the far northern counties, potential exists for more organized convective structures and associated strong straight line wind potential. Convection is expected to linger through the evening but should come to an end by midnight or so.

Hot conditions will continue Friday with widespread high temperatures again in the mid to upper 90s. Records will again be in jeopardy with specifics in the Climate section below. Additional Heat Advisories may be needed for mainly E-SE portions of the area. 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 especially Friday evening as upper heights fall ahead of the next cold front approaching from the N. Shear is again not looking particularly impressive, but flow aloft strengthens modestly during the evening, especially across the northern third of the area, with additional forcing from the front and very hot temps, this looks like a somewhat higher SVR threat overall. SPC has maintained the Slight Risk for areas along and north of the VA/NC border with a Marginal Risk to the south. A 30% wind contour has been expanded southward and now includes areas north of a line from Farmville NE into Dorchester County, MD.

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 /09Z THURSDAY THROUGH MONDAY/

As of 545 AM EDT Thursday...

VFR conditions prevail early this morning with a SW wind 5-10 kt. VFR continues for most of today, though an additional round of showers/storms is possible in the late afternoon and evening. Confidence is low on placement and timing. Included PROB30 groups at all but ECG from very late afternoon into the evening hours. Winds remain SW 5-10 kt outside of any convective influences.

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 200 AM EDT Thursday...

Key Messages:

- A period of elevated southwesterly flow gradually tapers off this morning. Small Craft Advisories have been cancelled.

- Another period of elevated southerly winds is possible late Sunday into Sunday night.

Latest surface analysis depicted high pressure well offshore. Winds were SW 10-15 kt with gusts up to 20 kt for most. Winds and seas have dropped below SCA criteria. As such, have cancelled SCAs across the coastal waters. Winds and seas continue to diminish today with generally benign marine conditions (outside of any convection) likely to continue from this morning into early Sun. Another period of elevated S winds is possible from late Sun into Sun night. SCAs are possible with this surge, but confidence is low at this time. Additionally, there is chance for isolated to scattered storms today and scattered storms on Fri. Gusty winds are possible with any convection.

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 this morning to 8 PM EDT this evening for VAZ075>078-084>086-089-090-097-098-520-522>525- 528>531. MARINE...None.