textproduct: Wakefield

WHAT HAS CHANGED

Added low end rain chances and increased clouds to the forecast Monday.

KEY MESSAGES

1) Unsettled and humid through Sunday as a frontal boundary lifts north later today, followed by a cold frontal passage late Sunday. Numerous showers, thunderstorms, and localized heavy rain today-tonight, with scattered showers/storms Sunday.

2) Mainly dry with seasonable temperatures and significantly lower humidity Monday-Wednesday. Temperatures warm back above normal late in the week an upper ridge builds back into the region.

DISCUSSION

As of 355 AM EDT Saturday...

KEY MESSAGE 1...Unsettled and humid through Sunday as a frontal boundary lifts north later today, followed by a cold frontal passage late Sunday. Numerous showers, thunderstorms, and localized heavy rain today-tonight, with scattered showers/storms Sunday.

The latest WX analysis indicates a frontal boundary nearly stationary across northern NC. A strong upper level trough is noted on WV satellite imagery across the lower MS Valley, and this trough will slowly translate eastward towards the local area through tonight. SW flow aloft strengthens today, and should help lift the frontal boundary back to north as a warm front this aftn into this evening. A few spotty showers prevail in the moist humid airmass early this morning, but most areas will remain dry through midday. The recent CAMs are somewhat split on shower/storm development later today, and taking a blend generally develops low chc PoPs by late morning/early aftn, with PoPs increasing to likely for most of the area after ~20-21Z (though with lower PoPs for the eastern shore). Widespread precipitation chances peak after this and persist into the evening, as the stalled boundary lifts back north as a warm front, along with a more pronounced mid- level shortwave disturbances push across the area. The latest models show the best height falls aloft late-gnerally after midnight through sunrise Sunday, so even after the best instability wanes, this additional cold air pool aloft should be sufficient to keep high chc to likely PoPs continuing overnight. Forecast soundings continue to 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 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, there still remains uncertainty in the exact locations, so have decided to not go with a Flood Watch for later today into tonight. The 00Z/12 HREF, which often provides a good signal for areas where the highest rainfall amounts, is not honing in on any specific area at this time with the 3"/3hr PMM peaked at only 10%. Considerable cloud cover will keep a lid on today's highs- the low 80s NW to the upper 80s SE. 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 and some late day storms are still possible in the NW as well.

KEY MESSAGE 2...Mainly dry with seasonable temperatures and significantly lower humidity Monday-Wednesday. Temperatures warm back above normal late in the week 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 well south of the CWA Monday, and bring significantly lower dew pts more typical of September. The models have trended a little farther south and slower with the shortwave on Monday, so do expect to see a 3-6 hr window where clouds increase and even a few isolated showers develop on Monday before the much drier air surges in from the NNW during the afternoon (with PoPs lingering through the aftn across the southern areas). As high pressure builds in behind the front Monday night, a pleasant night is expected Monday night/Tue AM with lows mostly in the upper 50s to lower 60s (low-mid 50s are likely in many locations to the NW of Richmond). The models have trended a bit slower with the return flow of moisture so that now dew pts look to remain comfortable through at least Wednesday as strong sfc high pressure (nearly 1030 mb), sets up from off the New England coast SW into the Carolina coastal plain through midweek. Highs will stay mostly in the low-mid 80s through Wed with lows in the 50s to lower 60s (locally warmer at the immediate coast). The upper level ridge is forecast to expand E-NE to the TN Valley and central Appalachians Thu-Fri. Temperatures climb back to above normal for mid- September, with highs generally in the mid-upper 80s. Low end diurnal rain chances return Thu-Fri (but have trended drier/lower form the previous forecast cycle).

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

As of 730 AM EDT Saturday...

Mainly dry early this morning, with IFR-LIFR flight restrictions mostly confined to southern VA and NE NC away from the immediate coast, though expect some of this to affect RIC/PHF/ORF/ECG through ~15Z so have TEMPO groups given the uncertainty an variable nature of the CIGs bouncing around. Expect to see the low clouds lift and potentially scatter out as the front lifts to the north later today. At SBY, VFR to start, with CIGs potentially dropping to MVFR after 15Z. While most of the morning into early aftn looks to be dry, showers/tstms will start to develop by early- mid aftn and become widespread from late aftn or early evening, lingering through at least the first part of tonight. The highest PoPs are at RIC/PHF, and lowest at ECG. Periodic IFR- LIFR VSBY restrictions in heavy rain will be possible during this timeframe. Winds will be E-NE, before shifting to the SE later in the day and eventually to the SSW overnight. The widespread SHRA/TSRA gradually diminish overnight, but low CIGs likely redevelop between 06-12Z, especially inland.

Outlook: Remaining unsettled Sunday, though with a lower coverage of showers/storms than Saturday, with the highest probs across SE VA/NE NC. Becoming dry and mainly VFR by Monday with NE winds, then staying dry Tue-Wed with light winds expect locally breezy SE VA and NE NC along the coast.

MARINE

As of 230 AM EDT Saturday...

Key Messages:

- Generally benign marine conditions are favored this weekend through Monday morning.

- Low-end Small Craft Advisories are possible with increased NE winds behind a front Monday-Monday night.

A near stationary front is located just south of the coastal waters early this morning, allowing E winds around 5-10 kt. E-SE winds will continue throughout the day at 10-15 kt. Onshore flow should be able to help seas build to 3 ft and perhaps even close to 4 ft off the MD coast. The front will slowly push north towards the area later today as a warm front. This will shift the winds out of the S/SW by late this evening. Winds will generally be 10-15 kt, not increasing much as the front is rather weak. Sub-SCA conditions are favored through the weekend.

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 00z/12 models showing the potential for low-end SCA conditions behind the front late Monday. Local wind probs show a 50-80% chc of sustained 18 kt winds in the Ches. Bay and ~30% chc of 25 kt gusts in the coastal waters Monday into Monday night. With the NE flow, 5 ft seas are possible for the southern coastal waters during this timeframe as well. 5 ft seas could linger in the 20-60 nm zones from Monday night into potentially mid-week.

There is a moderate rip current risk for the northern beaches today as onshore flow increases. A low risk of rip currents is expected for the southern beaches today and all beaches Sunday.

AKQ WATCHES/WARNINGS/ADVISORIES

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