textproduct: Wakefield

WHAT HAS CHANGED

Heat Advisories have been issued for the far NW counties for Heat Indices around 106 on Wednesday.

Extreme Heat Watch has been issued East central VA including the Northern Neck and the for the MD Eastern Shore (excluding the MD Beaches).

Updated 12z aviation discussion.

KEY MESSAGES

1) Following a brief period with seasonable temperatures Today, a major heat wave is likely beginning Wednesday, peaking Thursday through Saturday, before breaking down by late this weekend. This has the potential to be the most significant in both magnitude and duration since July 2012 for most of the CWA. Shower/thunderstorm chances remain very low through Saturday afternoon.

2) Temperatures gradually trend closer to normal late in the Holiday weekend and beyond, along with a more unsettled pattern.

DISCUSSION

As of 245 PM EDT Monday...

KEY MESSAGE 1...Following a brief period with seasonable temperatures Today, a major heat wave is likely beginning Wednesday, peaking Thursday through Saturday, before breaking down by late this weekend. This has the potential to be the most significant in both magnitude and duration since July 2012 for most of the CWA. Shower/thunderstorm chances remain very low through Saturday afternoon.

The 00z/30 ensemble guidance continues to remain in decent agreement on a anomalously strong upper level ridge building across the eastern half of the United States starting today and then breaking down by the Holiday Weekend. There continues to remain subtle differences in exact location of the location of the ridge, nevertheless, 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.

For today, high pressure continues to build south out of New England this morning. As the high moves south winds will begin to shift out of the SE and allow much warmer and humid air to return to the area. Temperatures today will remain around or slightly above seasonable inland with high temperatures in the upper 80s to low 90s. While along the coast onshore flow will persist allowing temperatures to remain slightly cooler with highs in the middle 80s. By Wednesday, much warmer temperatures are expected across the area. High pressure will be firmly in control at the surface and the upper ridge will continue to strengthen. Temperatures inland are expected to rise in the middle to upper 90s especially along and west of I-95. While closer to the coast and across the SE temperatures will be in the lower 90s. 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 in the triple digits across the west with some areas in Heat Advisory Criteria. With high enough confidence in the forecast A Heat Advisory has been issued for counties in the far NW for Wednesday morning through evening as some portions of those counties will potentially reach Heat Indices of 105+.

Thursday through Saturday Ensembles show a 594dm upper level ridge and 850 temps of 21-24C, confidence increases that some areas could see temperatures at or above 100F, especially Thursday through Saturday. If temperatures 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. Along the coastal zones adjacent to the bay and SE there could likely be seabreeze development due to the weak pressure gradient at the surface. This will allow for slightly lower temps but higher dews. This will still lead to similar Heat Indices. With enough confidence in the forecast and after collaboration with neighbors a Extreme Heat Watch has been issued for East central VA including the Northern Neck and the for the MD Eastern Shore (excluding the MD Beaches) Thursday-Friday. These areas have the highest confidence in Heat Indices potentially reaching 110+. Will note that the best chance of 110+ Heat Indices across the MD Eastern Shore is Friday but with some low confidence in mixing on Thursday decided to add them in the watch. Elsewhere probabilities for Heat Indices reaching 100 are low Thursday, but increase Friday-Sat. Therefore, these area maybe put in a watch later in time. By Saturday the ridge starts to weaken and break down. As this occurs this will likely be the last day where temperatures are likely to be around triple digits. Models continue to show quite a bit of mixing occuring but heat Indices are still likely to be 105+ with isolated areas at or above 110.

The only real opportunity for showers and storms in this pattern would be with seabreeze-initited convection along the coast. 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. PoPs are negligible Wednesday and Friday, with 15-30% PoPs by late Saturday as the ridge starts to break down and seabreeze convection becomes increasingly likely. This will all be better resolved as we get closer.

KEY MESSAGE 2...Temperatures gradually trend closer to normal late in the Holiday weekend and beyond, along with a more unsettled pattern.

The ridge starts to truly break down by Saturday, as multiple shortwaves gradually turn the flow aloft to the W-NW late in the weekend and beyond. It continues to look like a slow process, so temperatures likely stay above normal through Sunday but with higher chances for aftn/evening tstms. With a very favorable thermodynamic environment in place, severe thunderstorms of the pulse variety, plus possibly upstream MCS activity moving this way from the NW, would be on the table..

AVIATION /12Z TUESDAY THROUGH SATURDAY/

As of 700 AM EDT Tuesday... Patchy fog/low stratus across the area, but expect this to rapidly dissipate after 12-13Z. E-NE winds shift to the SE later today, at 5-10 kt. Mostly clear for the rest of the day. Light S-SW winds tonight should keep fog and stratus away from the main terminals.

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 345 AM EDT Tuesday...

Key Messages:

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

- Moderate Rip Risk for VA Beach/Eastern Currituck today, low northern areas.

E-NE winds winds average ~10 kt or less early this morning. Seas are a bit elevated across the southern coastal waters (3-4 ft), with 2-3 ft or less to the north. Winds gradually veer to the E-SE this aftn, and then become southerly tonight, and generally remain that way through the rest of the week. S-SW winds will show some diurnal backing to SSE in the late aftn/evening each day, averaging between 10-15 kt and seas of 2-3 ft nearshore.

Rip Currents: Continued with the moderate rip current risk for VA Beach/Eastern Currituck due to onshore flow and waves around 3 ft, and low north with nearshore waves 2-3 ft or less. By Wednesday, a low rip risk returns for all beaches.

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 VAZ064-075>078-085-517>522. Heat Advisory from 11 AM to 8 PM EDT Wednesday for VAZ048-064- 509>511. MARINE...None.