textproduct: Wakefield

WHAT HAS CHANGED

Temperatures, dew points, and rain chances have decreased for Tuesday. An unsettled pattern continues through the rest of the week.

KEY MESSAGES

1) Heat and humidity persists today with isolated to scattered showers and storms possible late this afternoon into this evening.

2) An unsettled pattern continues through the remainder of the week. However, uncertainty remains high.

DISCUSSION

As of 255 PM EDT Monday...

KEY MESSAGE 1...Heat and humidity persists today with isolated to scattered showers and storms possible late this afternoon into this evening.

Afternoon weather analysis showed generally zonal flow aloft with a shortwave moving from OH into WV noted by a change to NW flow aloft. At the surface, the Bermuda high continues to remain off the SE coast. As such, hot and humid conditions continue with temps as of 2 PM in the lower 90s and heat indices around 100F. Afternoon highs in the low-mid 90s are expected with heat indices around 100F.

The latest radar indicates a healthy MCS across WV into far S PA. This line of storms is much more robust than CAMs showed. As such, it remains unclear how much this line of storms will hold together as it crosses the mountains of WV/VA. CAMs generally show only isolated convection east of the mountains later this afternoon into this evening apart from the ARW which keeps convection going all the way to the coast. While mesoanalysis shows some lingering MLCIN across SE VA/NE NC, it also shows S winds east of the mountains (presumably due to a lee trough) and 1500-2500 J/kg of MLCAPE. With S winds (as opposed to SW winds that CAMs had) and an unstable environment east of the mountains with favorable low-level instability along and north of I-64, it is entirely possible that CAMs are wrong and this line of storms continues into central VA later this afternoon into this evening. If it does, a severe risk for predominantly damaging winds will exist. Currently SPC has a marginal risk (level 1/5) for severe storms along and north of I-64 with a portion of Dorchester County in a slight risk (level 2/5). However, if the storms do make it across the mountains, this threat may need to be expanded and/or increased. Outside of the severe potential, locally heavy rainfall is possible with any storms. WPC has a marginal ERO across far northern portions of the area to account for this potential. Convection should taper off overnight with remnant cloud cover potentially lingering. Lows tonight in the 70s are expected.

KEY MESSAGE 2...An unsettled pattern continues through the remainder of the week. However, uncertainty remains high.

NW/WNW flow aloft develops Tue through the remainder of the week as a ridge aloft builds across the central CONUS while a trough lingers across New England and Canada. At the surface, the Bermuda high will start to break down. This will allow for an active pattern to persist with a daily potential for isolated to scattered storms each afternoon/evening. CAMs show multiple rounds of MCSs developing in the WNW/NW flow aloft. However, where they track and when they develop will have large implications to the local weather. Most CAMs have an overturned airmass moving into the region in the wake of today's MCS for Tue. As such, HREF (as well as most individual models/CAMs) show dew points in the upper 60s to around 70F Tue afternoon (as opposed to the mid 70s from the NBM) and lower surface temps. Therefore, have blended in lower guidance for dew points but held off (for now) on dropping high temps by more than a degree or two due to uncertainty regarding whether or not partial clearing can occur during the afternoon. This resulted in heat indices remaining below heat advisory criteria. As such, no heat headlines will be issued at this time. Will note that latest guidance keeps temps even cooler than the current forecast. In general, highs in lower 90s are the most likely scenario with locally upper 80s or mid 90s possible Tue. Additionally, as a result of the overturned airmass, widespread cloud cover and mixed dew points could result in very little instability Tue afternoon. HREF mean CAPE only shows around 500 J/kg for most of the area (which for August is very low). As such, confidence in storm development (and especially severe potential) for Tue has decreased substantially. Nevertheless, SPC has maintained a marginal risk (1/5) for severe storms across most of the area with a slight risk (level 2/5) across portions of Piedmont. WPC has also maintained a marginal ERO across the area for Tue.

SPC has maintained a marginal risk (level 1/5) for severe storms across southern portions of the FA Wed. However, confidence continues to remain low given uncertainty in aforementioned MCS timing and impacts. For now, have largely kept NBM PoPs (15-35%) to account for the potential for isolated to scattered storms. By Tue, models should have a better handle on what weather we can expect for Wed. Beyond Wed, the pattern remains similar with only a slight chance (15-20%) for a few isolated showers or storms on Thu with a better chance on Fri (30-50% PoPs). Outside of convection, temps remain near normal with highs in the upper 80s to lower 90s Wed and Thu and mid 80s to lower 90s Fri.

AVIATION /18Z MONDAY THROUGH SATURDAY/

As of 155 PM EDT Monday...

Primarily VFR conditions prevail through the 18z taf period. The stable airmass that has persisted through much of the day should gradually destabilize later this afternoon. As such, expect FEW-SCT CU to develop with CIGs around 5000ft. Isolated to scattered showers and storms may move into northern portions of the area later this afternoon into this evening with the greatest chance north of I-64. However, confidence in the convection holding together as it crosses the mountains is low. As such, added a PROB30 for SBY from 23z-02z to account for the potential. While most CAMs don't show the line of storms reaching RIC, current radar suggests a much more organized line of storms than CAMs showed. As such, there appears to be potential that this line of storms currently moving into WV holds together as it crosses the mountains and impacts RIC. Therefore, have added a PROB30 for RIC from 21z-01z to account for this potential. Cannot rule out this convection reaching the coast (and SE terminals), however, confidence is too low to reflect in the TAFs at this time. Convection should taper off overnight with partly to mostly cloudy skies Tue.

Outlook: Expect predominate VFR conditions prevail Tue through Thu. However, daily low-end chances for isolated to scattered showers and storms exists each day. Along with this comes a chance for early morning stratus/ground fog each late night/early morning Wednesday through Friday AM.

MARINE

As of 225 PM EDT Monday...

Key Message:

- Sub-SCA marine conditions are expected to prevail through most of the week.

Bermuda high pressure remains centered well offshore this afternoon, with weak sfc low pressure across the eastern Great Lakes. A weak surface trough is noted over inland portions of the area. The wind is generally W to SW 5-10 kt. Seas are 1-2ft nearshore, 2-3ft offshore, with ~1ft waves in the Ches Bay (1-2 ft lower Bay). With a weak pressure gradient, expect the winds to shift to the S-SE at ~10 kt later this aftn into this evening. Convective coverage is expected to be isolated to locally scattered this evening with a heavy lean toward the northern Ches Bay and Atlantic zones for better coverage. A few hi-res models bring the convection as far south as the mouth of the Bay and adjacent rivers and coastal zones but those solutions appear to be outliers from the consensus. That said, locally gusty winds are the main threat from any convection that manages to move into the region this evening. A brief wind shift to NW 8-12kt remains possible early Tuesday morning as the weak surface trough tracks across the coast, before becoming light onshore and then southerly by Tuesday evening. Latest CAM guidance has backed off considerably on the potential for scattered to numerous storms on Tuesday. Debris cloudiness from MCS(s) to the W and NW of the area will likely limit instability and subsequent storm coverage and intensity Tuesday afternoon and evening. Greater convective coverage is possible on Wednesday but with low confidence on the details.

A cold front will gradually approach late in the week and may push far enough south to shift the wind to the N-NE by late Friday into next weekend. Models are generally keeping the winds rather light, but if the front actually pushes south of the waters, this would potentially bring SCAs, but uncertainty is high at this range. Seas throughout the week will be ~2ft in the coastal waters, 2-3ft in the offshore waters, and 1ft to occasionally 2ft waves in the Ches Bay.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...None. VA...None. MARINE...None.