textproduct: Wakefield

WHAT HAS CHANGED

Updated aviation discussion for 18z TAFs

Slight (level 2/4) excessive rainfall outlook added for Monday

KEY MESSAGES

1) While not as hot as the past two days, heat indices peak around 105 degrees this afternoon. A Heat Advisory is in effect for most of the area.

2) Strong to severe thunderstorms are again possible today and Monday. Damaging winds remain the primary threat from storms. There is also an increased risk for flash flooding Monday.

3) Temperatures gradually trend closer to normal by early next week, with unsettled weather continuing into the midweek period.

DISCUSSION

As of 255 AM EDT Sunday...

KEY MESSAGE 1...While not as hot as the past two days, heat indices peak around 105 degrees this afternoon. A Heat Advisory is in effect for most of the area.

Early convective activity and outflow has cooled temps into the 70s with dew points in many spots in the 60s (!). This feels quite comfortable compared to the last few nights where temps and dew points respectively remained in the 80s and 70s through most of the overnight/early morning hours.

We continue to expect the upper-level ridge, which has been the primary driver of the prolonged heat wave, to break down further today. A weak trough will also slowly inch eastward in the OH Valley region. Despite these changes, another hot and humid day is on the way, though peat heat indices will be 5-10 degrees cooler than experienced Friday and Saturday. A Heat Advisory remains in effect for all of central and eastern VA, the lower MD Eastern Shore, and NE NC, minus the VA Eastern Shore and the NC/MD beaches. Additional showers/storms could also provide relief by the evening. A few degrees cooler again on Monday with highs "only" in the lower 90s. While a few locations near the Albemarle Sound may flirt with 105 F heat indices, do not currently anticipate additional heat headlines at this time. Furthermore, convective coverage and cloud cover is expected to be higher.

KEY MESSAGE 2...Strong to severe thunderstorms are again possible today and Monday. Damaging winds remain the primary threat from storms. There is also an increased risk for flash flooding Monday.

Additional thunderstorms are likely to develop this afternoon. As with the previous days, there remains relatively low confidence on the exact evolution of these storms, including where they would initiate. The consensus is for higher coverage just to our W and NW but a few of the CAMs (such as the 00z HRRR) are more enthusiastic about higher coverage in our CWA, particularly along the I-95 corridor. Will also need to keep an eye on any residual mesoscale boundaries from yesterday's convection as potential areas of initiation and higher coverage. The influence from the decaying ridge will tend to keep far SE VA and NE NC dry, but cannot rule out a pop up storm given the hot and humid air mass. On that note, any storms that develop today could also pose of risk of damaging winds given the very favorable thermodynamic profiles. Very frequent lightning and heavy rain would also be expected. SPC has maintained a slight risk (level 2/5) for the northern tier of our forecast area, with a marginal risk to the S.

The weak trough axis aloft will be a little closer to the area Monday. Most models are in agreement that widespread thunderstorm development will commence by the early afternoon as surface troughing sharpens. Again, the specific details remain unclear but the RRFS/REFS suite depicts storms initially forming inland and moving toward the coast by the evening. Strong wind gusts, lightning, and heavy rain would again be the main risks from storms. Deep-layer will be weak but will need to watch for locally enhanced shear along any boundaries. While SPC currently has a marginal risk for the area, would not be surprised if a slight risk was eventually required to address the risk of water-loaded downdrafts. In addition to any severe threat, Monday also looks like the most favorable day for any flooding potential. PWATs are expected to peak around 2.2- 2.3" in the afternoon/evening timeframe with deeply saturated profiles seen in forecast soundings. Both the REFS and HREF show the potential for localized totals in excess of 3-4" and these amounts could easily lead to flash flooding in urban and flood-prone areas. After collaboration with WPC, a slight ERO (level 2/5) has been introduced and includes much of central and eastern VA. A Flood Watch could be required in future forecast updates.

KEY MESSAGE 3...Temperatures gradually trend closer to normal by early next week, with unsettled weather continuing into the midweek period.

A weak flow pattern very typical for the middle of summer with daily chances for showers and storms takes shape midweek. A rather high coverage of showers/storms is again expected Tuesday (PoPs ~70%) with generally chc PoPs (30-50%) Wednesday-Friday. Temperatures will also trend back toward seasonal norms for most of next week, ranging from the upper 80s to lower 90s.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

As of 145 PM EDT Sunday... VFR conditions prevail for the majority of the 18z TAF period. SCT CU clouds have developed inland with S winds around 10 kt, possibly around 15 kt at ORF, this afternoon/evening. There is a risk for some afternoon/evening storms across the northern terminals, including RIC/SBY. PROB30s continue to cover this with localized reduced VSBY and gusty winds. Behind the convection, patchy fog is possible overnight in areas that received rainfall. With this, SBY could see MVFR CIGs and VSBY after 06z/06.

Outlook: Outside of continuing chances for showers/storms and localized flight restrictions, mainly VFR conditions prevail this week.

MARINE

As of 255 AM EDT Sunday...

Key Messages:

- Sub-SCA marine conditions are expected to prevail through the remainder of the weekend into early this week, with mainly south- southwesterly winds.

- Elevated wind gusts from strong thunderstorms are possible during afternoon and evening hours today and Monday.

High pressure continues to extend from the Southeast to off the Mid- Atlantic coast early this morning. The wind had shifted to N/NE behind a convective outflow, but is now shifting back to S/SE 5- 10kt. Seas are ~2ft with ~1ft waves in the Ches. Bay. High pressure remains in vicinity of the Southeast coast through at least early this week allowing for continued, mainly light, southerly flow. Some diurnal wind speed and direction variability is likely to prevail today and Monday (mainly S-SW overnight into the morning, becoming S- SE in the late aftn/evening), and there will likely be a few hour period late this aftn and evening where a SSE wind increases to 10- 15kt with gusts to ~20kt. Isolated showers/tstms later this aftn and early evening mainly for the Ches. Bay and rivers, with potentially better coverage of showers/tstms Monday aftn and evening. Strong wind gusts are possible in any tstms. Any stronger wind gusts will be handled with SMWs. Seas will be ~2ft through the remainder of the weekend into early next week, with 1ft to occasionally 1-2ft waves in the Ches. Bay, although seas/waves may build to 2-3ft late this aftn/evening with the increased SSE flow. A very weak cold front may settle into the Carolinas by the middle of next week, but sub-SCA conditions are expected to continue with 2-3ft seas and 1-2ft waves in the Ches. Bay.

CLIMATE

Record Highs: Richmond, VA (RIC) tied the record for today (7/4) at 100, last set in 2002.

Salisbury, MD (SBY) set a new record high today (7/4) of 102, breaking the old record of 100 from 1919.

Norfolk, VA (ORF) set a new record high today (7/4) of 100, breaking the old record of 98 degrees set in 1879.

- Site: Fri 7/3 Sat 7/4 Sun 7/5

- RIC: 100/1954 100/2002 102/2012 - ORF: 99/1954 98/1997 98/2012 - SBY: 98/1954 100/1919 102/2012 - ECG: 98/1954 100/1997 100/2012

Record High Mins:

- Site: Fri 7/3 Sat 7/4 Sun 7/5

- RIC: 77/2014 77/1900 79/2012 - ORF: 78/2014 79/2012 80/1999 - SBY: 76/2014 78/2012 81/2012 - ECG: 78/2014 78/2012 77/2024

EQUIPMENT

KAKQ radar is down due to mechanical issues without an estimated time of return.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...Heat Advisory until 8 PM EDT this evening for MDZ021>024. NC...Heat Advisory until 8 PM EDT this evening for NCZ012>017- 030>032. VA...Heat Advisory until 8 PM EDT this evening for VAZ048-060>062- 064>069-075>090-092-097-098-509>525-528>531. MARINE...None.