textproduct: Wakefield

WHAT HAS CHANGED

WPC has expanded the Day 2 Slight Risk for Excessive Rainfall for areas along I-95 Saturday-Saturday Night to now include the NW piedmont.

KEY MESSAGES

1) Unsettled and humid through Sunday as a frontal boundary lingers near the region, bringing scattered to numerous showers, thunderstorms, and localized heavy rain.

2) Dry with seasonable temperatures early next week, with temperatures warming above normal by midweek as an upper ridge builds back into the region.

DISCUSSION

As of 200 PM EDT Friday...

KEY MESSAGE 1...Unsettled and humid through Sunday as a frontal boundary lingers near the region, bringing scattered to numerous showers, thunderstorms, and localized heavy rain.

A cold front has slowly dropped southward across the forecast area today, and extends across southern VA and is slightly buckled across NE NC. Satellite imagery is highlighting increasing cloud cover across the northern half of the area and partly cloudy to mostly clear skies across southern VA and NE NC. There is a relatively sharp temperature gradient today due to the aforementioned cloud cover. Current highs are in the lower 90 to spotty mid 90s (NE NC) across the south, with northern areas measuring temperatures in the upper 70s (mainly Eastern Shore) to the low-mid 80s.

SPC has maintained the Marginal Risk (level 1/5) for areas along and south of I-64 (excluding the coast) as the boundary slowly moves southward across the area this evening into tonight. The front will be the focal point of the convection, and local radar is already detecting some development across south-central VA, which are now right on the cusp of Lunenburg and Mecklenburg counties. SPC mesoanalysis is depicting good instability from generally the Tri- Cities area and south, which is the best environment for any severe is depicted by the Marginal Risk. Shear is not overly impressive, but with steep low level lapse rates, isolated wet microbursts cannot be ruled out this afternoon and this evening. The front continues to sink south tonight, with most of the showers/storms ending overnight. There continues to be a good signal for low stratus and possible some fog across the piedmont overnight. Have maintained mention of fog in these areas, though exactly how far east this potential fog creeps is still somewhat uncertain. Humid with lows in the upper 60s to lower 70s south, with somewhat drier air to the north where lows drop into the mid 60s.

Widespread precipitation chances peak Saturday afternoon/night, as the stalled boundary lifts back north as a warm front, along with a more pronounced mid-level shortwave disturbances push across the area. Forecast soundings show high precipitable water values, modest instability (skinny CAPE profile), and weak steering flow, which should yield efficient warm rainfall processes and additional localized hydro concerns (supported by an area-wide WPC ERO Marginal Risk and a localized upgrade to Slight for portions of the I-95 corridor, including metro RIC. Despite the increasing confidence that localized flooding is possible somewhere in our forecast area, these still remains uncertainty in the exact locations, so have decided to not go with a Flood Watch for Saturday/Saturday night at this time. The HREF, which typically provides a good signal for areas where the heaviest rainfall/highest amounts, is not honing in on any specific area at this time, but will likely start to once we get closer to the event on Saturday evening/night. Considerable cloud cover will keep a lid on Saturday highs to the low to mid 80s N, but highs reach into the upper 80s SE. There may even be some weak CAD, potentially keeping far NW zones even cooler (but still very humid). The boundary washes out Sunday, leading to noticeably lower convective coverage for the NW 1/2 of the area, but PoPs remain high chc to likely for the SE.

KEY MESSAGE 2...Dry with seasonable temperatures early next week, with temperatures warming above normal by midweek as an upper ridge builds back into the region.

The upper level flow becomes NW on Monday as a strong upper level trough dives SE from the Great Lakes and pushes off the NE and mid- Atlantic coast Monday night, with an upper level ridge slowly expanding NE from the lower MS Valley. This looks strong enough to drive the sfc cold front south of the CWA Monday, and bring significantly lower dew pts more typical of September. As high pressure builds in behind the front, we are forecasting mostly sunny skies with highs in the 80s Monday. A pleasant night Monday night/Tue AM is on tap, with lows mostly in the low-mid 60s and some 50s possible across the piedmont and interior MD eastern shore due to possible radiational cooling. Diurnal shower and thunderstorm chances gradually tick back up mid-to-late week as heat and moisture start to return as the upper level ridge expands E-NE to the TN Valley and central/southern Appalachians. Temperatures are also forecast to climb back to slightly above normal for mid-September, with highs generally in the mid-upper 80s and lows mid-late week. Overnight lows will be more reflective of the time of year, dropping into the 60s each night.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

As of 130 PM EDT Friday...

A front has dropped across SBY and just south of RIC, and intermittent to prolonged periods of MVFR CIGs have been prevailing at these two terminals. Otherwise, VFR conditions prevail at PHF, ORF, and ECG, with partly cloudy skies and lighter northerly winds prevailing. Isolated to scattered showers are possible this afternoon, with the highest confidence at RIC and ECG. Have updated the PROB30 at these terminals to a TEMPO, while TEMPOs have also been added for PHF and ORF. After any convection trends downward overnight, areas north of the front (mainly in the piedmont) will likely see IFR to LIFR CIGs and possibly some fog. Have decided to put a prevailing line at RIC to reflect this increasing confidence in this scenario. MVFR CIGs are possible at ORF and PHF as well. While Saturday morning looks to be mostly dry, shower and thunderstorms will start to develop by midday to early afternoon and become widespread through tomorrow night. Winds will generally be between 5-10 kts of the north-northeast today, becoming easterly tonight and tomorrow in the wake of the front.

The frontal boundary gradually lifts back north later Saturday- Saturday night/early Sunday. A high chance for showers/storms is currently forecast from late Saturday afternoon into Saturday night. Periodic IFR-LIFR VSBY restrictions in heavy rain will be possible during this timeframe. Remaining unsettled Sunday, with the highest shower/storm coverage across SE VA/NE NC. Becoming dry and mainly VFR by Monday with NE winds.

MARINE

As of 230 PM EDT Friday...

Key Messages:

- A period of generally benign marine conditions is favored from this weekend through Monday morning.

- Low-end SCAs are possible with NE winds behind a front late Monday- Monday night.

A weak cold front has pushed through the area and is located just south of local waters this afternoon. Winds have turned to the NNE and latest obs show breezy conditions near 15kt sustained and a few gusts close to 20kt. Seas are around 2ft and waves in the bay/rivers are 1-2ft.

The flow becomes E then SE tonight into Saturday, with winds generally 10-15 kt (highest north) through Saturday night as the front moves back north as a warm front. Onshore flow should be able to help seas build to 3ft tomorrow and perhaps even close to 4ft off the MD coast. Winds become S-SW at ~10 kt on Sunday. Sub-SCA marine conditions are favored through early Monday. Another front is expected to cross the marine area on Monday, with a wind shift to the NE following the passage. This front appears to be a bit stronger, with some of the 12z models showing the potential for low- end SCA conditions behind the front late Monday. Winds subside and shift to the east Tue. Local wind probs for sustained 18 kt winds have increased again and show widespread ~50% probs Monday afternoon through late Monday night and even a period of close to 90% near the Mouth of the Bay. SCA level seas are possible (mainly south) by late Monday-Monday night as winds become NE.

The rip current risk will remain low today, with the northern beaches bumping up to moderate on Saturday as flow becomes onshore. A low rip current risk returns to all beaches on Sunday.

AKQ WATCHES/WARNINGS/ADVISORIES

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