Hot and humid conditions continue through mid week, with isolated to scattered thunderstorms. A cold front brings more widespread precipitation late this week, with cooler and more pleasant conditions for the weekend, though it will remain unsettled.
Today As of 200 AM Wednesday,
Key Messages
- Lower coverage of thunderstorms expected today
- Dangerous heat continues south of HWY 70 today
Early this morning, a weak baroclinic zone resides across the Southeast U.S., roughly from Georgia east through South Carolina and then out into the southwestern Atlantic. Areas of convection are ongoing within this zone, all of which is mostly south and southwest of ENC, associated with at least a couple of MCVs and associated weak areas of low pressure. North of the baroclinic zone, a layer of dry low-mid level air is evident on satellite and recent objective RAP analysis.
The steering flow is very weak thanks to ridging aloft, and guidance is mixed regarding the evolution of the above-mentioned MCVs and surface lows. The general consensus, though, is for these features to move off to the E or ENE as the ridge aloft begins to break down some, and as an upper level wave begins to encroach on the region late in the day.
Based on all of the above, the most likely scenario is for any MCVs/SFC lows to trek east just south of ENC, keeping the strongest low-level forcing, and greatest coverage of thunderstorms, to our south. However, the southern half of ENC will be right on the gradient between the better lift and moisture to the south, and the drier, more stable airmass, to the north. Therefore, should any low or MCV pass closer to ENC than currently forecast, the risk of showers and thunderstorms would consequently end up higher, especially south of HWY 70. As mentioned above, the flow aloft is very weak, which will not be supportive of organized convection, keeping the risk of severe thunderstorms very low.
The above-mentioned drier air should help to keep dewpoints lower across the northeastern half of ENC, consequently lowering the risk of heat impacts. Further south, dewpoints are forecast to remain high enough to support heat index values approaching 105 degrees. The nearby drier air and potential for dewpoints to be lower than forecast makes the heat risk a bit more marginal for headlines. It's close enough, though, and today marks a continuation of a longer duration heatwave. In light of this, we'll keep the Heat Advisory going for now, especially to highlight the cumulative effect of the heat, dating back to last week.
Tonight As of 200 AM Wednesday,
Increasing low-mid level moisture is likely this evening and tonight as the flow aloft begins to increase some out of the south/southwest. Within this flow, it's possible an MCV will emerge out of South Carolina, and shift NE across southeastern NC tonight. Mcv development and evolution can be tricky at times, especially with weak flow aloft. However, there appears to be a decent signal for the potential of isolated to scattered nocturnal convection to develop across parts of the area associated with the above-mentioned MCV. The lack of stronger flow aloft should keep the risk of severe thunderstorms low. However, with increased moisture and slow storm motions, there will be a risk of heavy rain and minor flooding.
Thursday through Tuesday As of 1 AM Wednesday,
Key Messages:
- Cold front will bring heavy rain and relief from the heat late week into the start of next week
- Flooding concerns Thursday and Friday
Broad troughing aloft will extend an area of lower pressure across the eastern US late week. At the surface, a potent cold front will work its way across the Appalachians with pre-frontal troughing developing across the Carolinas. The cold front will take its sweet time crossing the FA on Friday, likely not moving offshore until Saturday morning. Once offshore, the front will stall through the weekend and support the development of a series of lows that will move northeasterly away from our coast. This stalled boundary will then slowly lift north as a warm front on Monday and Tuesday.
Good news: This FROPA will cause an air mass change, bringing an end to the oppressive heat and humidity that has plagued ENC for the past week. Bad news: the combination of the aforementioned synoptic and meso setup within a moisture loaded atmosphere is a recipe for multiple days of rain and flooding concerns.
Impressive PWATs on the order of 2.25-2.75"+ will overspread the area on Thursday, gradually decreasing from north to south through Saturday as the front settles offshore, then surging again from south to north at the start of next week as the front lifts north. Moisture of this magnitude will support heavy rainfall from any cell that forms, and the slow progression of the front will increase concern for training cells. Instability will be greatest on Thursday (2000-3000 J/kg), allowing for some storms to become strong to severe. On Friday, the combination of lower CAPE, greater PWATs, and better forcing will create a greater flooding concern. Wpc currently has all of ENC outlined in marginal (level 1 4) and slight (level 2 ) risks for flash flooding Thursday-Saturday. The coast and areas along and south of Highway 264 are expected to see the most precip through Tuesday (2-4") with lower amounts to the north (1-2"). Locally higher amounts are possible wherever stronger and/or training cells occur.
Heat advisories may still be needed for portions of the area Thursday and Friday with heat indices forecast to reach around 105. Friday's FROPA will be the swan song for this oppressive heat and humidity with highs on Saturday and Sunday staying in the low- to mid-80s and dewpoints ranging from the upper-60s to low-70s. Compared to this past weekend, some places across the coastal plain will see a nearly 20 degree high temperature difference. Temps will gradually rebound at the start of next week (mid- to upper-80s).
11z Wednesday through Sunday Through 12z Thursday As of 700 AM Wednesday,
Key Messages
- Lingering BR/FG risk this morning
- Lower TSRA risk today
Recent surface obs show VIS fluctuating between LIFR and MVFR due to BR/FG. However, area webcams suggest the reduced VIS is more due to shallow fog. Because of this, VIS should quickly improve by 12-13z. Vfr conditions are then expected to prevail as we move into the afternoon and evening hours. Today's airmass is somewhat drier and not quite as unstable as the past few days. Because of this, the coverage of TSRA is expected to be lower, and mainly confined to southern sections of ENC. In light of this, I'll continue with a PROB30 for KOAJ, but keep TSRA out of the rest of the TAFs. Moving into tonight, a slow-moving upper level wave is forecast to move through ENC, and this may lead to an overnight TSRA risk, especially from KOAJ to KEWN. Where TSRA occur, there will be an increased risk of sub-VFR conditions.
Thursday through Sunday As of 2:50 AM Wednesday,
There will be several chances for sub-VFR CIGs and VIS through the long term, especially Thursday through the weekend when a cold front will bring heavy rainfall to the area.
Through tonight As of 3 AM Wednesday,
Great boating conditions will persist through the day. Variable 5-10 kt winds will become southerly by this evening. Seas will be 1-3 ft at 8 seconds.
Thursday through Sunday As of 3:10 AM Wednesday,
The period will start with southwesterly winds at 5-10 kt, increasing to 10-15 kt Thursday. A strong cold front will cross the waters late Friday, which will increase winds to 15-20 kt as they veer to the north. A northeasterly surge behind the front will increase winds to 20-30 kt on Saturday. Gales are possible for the coastal waters north of Cape Hatteras, the northern Pamlico Sound, and the northern rivers and sounds. On Sunday, northeasterly winds will gradually decrease to 15-20 kt with gusts to 25 kt.
1-3 ft seas at the start of the period will build to 2-4 ft by early Friday. Prolonged northeasterly fetch will build seas from north to south Friday night into Sunday with peak heights expected Sunday afternoon. 5-10 ft seas are possible across the central waters with 4-7 ft seas across the northern and southern waters.
Highest PoPs will be Thursday-Saturday with heavy rain, gusty winds, and frequent lightning possible.
Nc, heat advisory from 11 am this morning to 8 pm EDT this evening for ncz044-079-080-090>092-094-193>196-198-199. Marine, none.
