textproduct: Wakefield

WHAT HAS CHANGED

Heat Advisories have been expanded for Wednesday to include a large portion of the Piedmont. Extreme Heat Watches have been expanded for Thursday and Friday.

KEY MESSAGES

1) A major heat wave begins Wednesday and continues into the weekend with the hottest conditions likely Thursday through Saturday. This has the potential to be the most significant in both magnitude and duration since July 2012 for most of the CWA.

2) Isolated showers or storms are possible late Saturday afternoon into Saturday evening with a better chance for isolated to scattered showers or storms Sunday afternoon and evening.

3) Temperatures gradually trend closer to normal next week, along with a more unsettled pattern.

DISCUSSION

As of 340 PM EDT Tuesday...

KEY MESSAGE 1...A major heat wave begins Wednesday and continues into the weekend with the hottest conditions likely Thursday through Saturday. This has the potential to be the most significant in both magnitude and duration since July 2012 for most of the CWA.

Latest analysis depicted a strong ridge stretching from the Gulf into the Great Lakes this afternoon. At the surface, high pressure remains over the region. This has allowed for one more day of pleasant temps with temps as of 250 PM ranging from the mid-upper 80s with a few locations around 90F. Meanwhile, dew points were in the upper 50s to mid 60s for most.

Model guidance continues to remain in strong agreement on an anomalously strong upper level ridge building across the eastern half of the United States through Saturday breaking down during the weekend. As such, confidence continues to remain high that this will lead to a significant heat wave for the local area, potentially the most widespread and of longest duration since July 2012.

The heat wave begins Wed with much warmer temps expected across the area. High pressure will be firmly in control at the surface and the upper ridge will continue to strengthen. Highs are expected to range from the upper 90s NW to the upper 80s SE. Dew points are forecasted to mix out across the coast and SE, but will remain steady west of I- 95. This will lead to heat indices (what temps will feel like) up to around 105-106F across the Piedmont and the lower 100s up to the I- 95 corridor and interior portions of the Northern Neck. As such, confidence has increased enough to expand the Heat Advisory for Wed across a large portion of the Piedmont. Will note that confidence in reaching 105F heat indices was too low across the southern Piedmont and the Richmond Metro to include those locations in the advisory. However, it will be quite hot regardless.

Even hotter conditions are likely Thu through Sat with ensembles continuing to show a 594dm (potentially even stronger) upper level ridge and 850 temps of 21-25C. As such, confidence continues to increase that many areas could see temperatures at or above 100F, especially Fri and Sat. In fact, a local tool calculating max temp from thickness depicts up to 102-103F across portions of the FA. This is quite impressive and lends additional confidence to the very high temps from deterministic models and the NBM. Nevertheless, still think the NBM is a bit too high for temps (Fri and Sat). As such, have highs around 100F NW to the low-mid 90s SE Thu and 98- 102F for most Fri and Sat. Will note that a few locations may reach 103F Fri (most likely in the NW Piedmont if it occurs). These temps (if realized) would potentially break daily record highs for up to three days in a row (Thu-Sat). Additionally, if temps reach this high, expect the dew points to mix out inland. This could potentially put a cap on the higher-end heat index scenarios, however, heat indices are likely to be close to Extreme Heat Warning criteria across a large portion of the area Thu-Sat with widespread heat indices of 105-110F+ likely. Along the coastal zones adjacent to the bay and SE, there could be a bit of a seabreeze due to the weak pressure gradient at the surface. This would allow for slightly lower temps but higher dews, and ultimately result in similar heat indices. Will also note that wet bulb globe temps (WBGT) around 90F are possible north of US-460 on Thu and up to 90-91F across most of the area Fri and Sat. The combination of very high temps, heat indices, the duration of the heatwave, and the increase in outdoor activity due to the holiday weekend have all factored in to the decision to expand the Extreme Heat Watch. The Extreme Heat Watch is now in effect beginning Thu generally along and north of US-460 (including the Tri-Cities and the Richmond Metro) and expands south to include most of the local area (excluding Mecklenburg, the VA Eastern Shore, the MD beaches, and NE NC). Additional consideration was given to extending the watch through Sat, however, after coordination with neighboring offices, have decided to hold off for this update and reevaluate tomorrow. Nevertheless, additional heat products are likely on Sat (high confidence) and Sun (moderate confidence). Additional Heat Advisories are likely outside of the watches each day for most (if not all) of the area).

KEY MESSAGE 2...Isolated showers or storms are possible late Saturday afternoon into Saturday evening with a better chance for isolated to scattered showers or storms Sunday afternoon and evening.

The only real opportunity for showers and storms in this pattern would be with seabreeze-initited convection along the coast or convection firing off the lee trough. These large heat domes also bring a risk of "ring of fire" type convective complexes, i.e., thunderstorm clusters riding the northern periphery of the ridge. However, with the heat ridge centered over western VA/eastern KY, this does not appear very likely. As such, rain chances are negligible through Fri. However, a few isolated showers or storms are possible (15-40% PoPs) by late Saturday afternoon into Sat evening as the ridge starts to break down. A better chance for isolated showers or storms arrives Sun (35-50% PoPs) as the ridge continues to break down. Any convection on either day could affect temps/dew points for subsequent days. As such, confidence in temps and heat indices is lower on Sun given uncertainty regarding convection on Sat.

KEY MESSAGE 3...Temperatures gradually trend closer to normal next week, along with a more unsettled pattern.

The ridge continues to break down next week across the Eastern CONUS as a new ridge strengthens across the central CONUS. This should place the local area in NW flow which should lead to near normal temps and an unsettled pattern. For now, have 50-60% PoPs Mon and 35-55% PoPs Tue.

AVIATION /19Z TUESDAY THROUGH SUNDAY/

As of 145 PM EDT Tuesday... VFR conditions will prevail through the TAF period at all terminals, with mostly clear skies expected. Generally light winds at RIC and SBY have already shifted to the southeast, while the southern terminals are still seeing northeasterly winds. Winds will continue to shift to the south at all terminals overnight, becoming S-SW by tomorrow morning. A few gusts to 15-20 kts are possible at SBY by mid-morning tomorrow.

Outlook: VFR conditions will continue through most of this week as high pressure builds S across the area and then settles offshore. Other than isolated showers/storms, mostly dry conditions are expected through the upcoming week.

MARINE

As of 330 PM EDT Tuesday...

Key Messages:

- Sub-SCA marine conditions are expected to prevail through the week, with winds becoming southerly starting tonight.

High pressure remains the dominant feature across the Eastern Seaboard this afternoon. Winds have gradually been transitioning from northeast/east to southeast/south as the high in the North Atlantic gradually slides south. This regime of southerly winds will continue through the rest of the week and into the weekend, with generally sub-SCA conditions prevailing. S-SW winds will show some diurnal backing to SSE in the late afternoon/evening each day. With the southerly winds, there may be some channeling effects within the Bay and across the nearshore coastal waters, increasing winds to 10- 15 kts during the afternoon. While a few gusts may reach 18-20 kts, have opted not to issue any SCAs for the Bay because it is so marginal and short-duration. Waves in the Bay will remain between 1- 2 ft, and seas across the nearshore coastal waters will be 2-3 ft for the duration of the week after decreasing this evening from 2-4 ft.

Rip Currents: Continued with the moderate rip current risk for VA Beach/Eastern Currituck due to onshore flow and waves around 3 ft for the remainder of today, and low north with nearshore waves 2-3 ft or less. Have decided to go with a moderate rip risk for tomorrow for the southern beaches, though it will be more marginal than today as seas start to lower and flow becomes parallel to the shore. By Thursday, a low rip risk returns for all beaches and continues through the end of the week.

CLIMATE

Record Highs later this week:

- Site: Wed 7/1 Thu 7/2 Fri 7/3 Sat 7/4

- RIC: 102/1945 100/1953 100/1954 100/2002 - ORF: 100/1901 100/1901 99/1954 98/1997 - SBY: 98/2012 99/2014 98/1954 100/1919 - ECG: 101/2012 97/1953 98/1954 100/1997

Record High Mins later this week:

- Site: Thu 7/2 Fri 7/3 Sat 7/4

- RIC: 76/2014 77/2014 77/1900 - ORF: 78/2018 78/2014 79/2012 - SBY: 77/1968 76/2014 78/2012 - ECG: 76/2014 78/2014 78/2012

AKQ WATCHES/WARNINGS/ADVISORIES

MD...Extreme Heat Watch from Thursday morning through Friday evening for MDZ021>024. NC...None. VA...Extreme Heat Watch from Thursday morning through Friday evening for VAZ048-061-062-064-068-069-075>078-081>086- 090-509>523. Heat Advisory from 11 AM to 8 PM EDT Wednesday for VAZ048- 060>062-064-067>069-509>511. Extreme Heat Watch from Friday morning through Friday evening for VAZ060-066-067-079-080-087>089-092-097-098-524-525- 528>531. MARINE...None.