textproduct: NWS Wilmington

WHAT HAS CHANGED

Aviation discussion updated after the 00Z Taf Issuance.

KEY MESSAGES

1) Summerlike Bermuda high pressure will maintain southeast to south winds and unseasonably warm weather through Sunday with isolated inland showers possible Sat.

2) The next cold front will arrive late Sunday accompanied by a better chance of showers or t-storms. Much cooler air will follow for Monday and Tuesday.

DISCUSSION

1) Summerlike Bermuda high pressure will maintain southerly winds and unseasonably warm weather through Sunday with isolated inland showers possible.

An upper level ridge will hang tough just off the Southeast coast through Saturday, deflecting the jet stream well to the north across the Great Lakes and New England. At the surface, the upper ridge will support Bermuda high pressure centered hundreds off miles offshore. An extension of the Bermuda high pointing westward across the Carolinas will maintain light southerly winds and unseasonably warm temperatures through the period.

Away from the cool nearshore ocean water, inland high temperatures should reach 80-84 degrees each day through Sunday with nighttime lows in the upper 50s to lower 60s. These temperatures are a good 10 degrees above normal and continues an extended period of above-normal temperatures that began in early March.

Shower chances appear very limited through Saturday near the coast as a warm capping inversion aloft and limited instability due to cool onshore flow will help stabilize the atmosphere. Inland, there is a slightly better (20 percent) chance of pop-up showers beginning Thursday due to cooler mid level temperatures west of the upper ridge and warmer daytime surface temperatures generating small positive and uncapped CAPE. Even in a best case scenario, rainfall amounts should remain light and spotty through Saturday.

2) The next cold front will arrive late Sunday accompanied by a better chance of showers or t-storms. Much cooler air will follow for Monday and Tuesday.

An upper trough will whip through the Great Lakes Sunday and off the Mid Atlantic coast Monday. This will knock the ridge down along the Southeast coast and help push a surface cold front down into the eastern Carolinas Sunday night. As the ridge breaks down and the low and mid level flow both veer southwesterly, a ribbon of deeper Gulf moisture should advect across the Carolinas, increasing precipitable water values to near 1.5 inches and helping support rain chances which have been increased to around 80 percent Sunday afternoon into Sunday night. Predicted timing of this frontal passage has been remarkably stable in the models for the past couple of days now.

Unlike with the frontal timing, there remains a good deal of spread among models with how fast the belt of mid-level winds will be as convection chances peak Sunday afternoon/night. 700 mb wind speeds range from 30 knots on the ECMWF to 40-45 knots on the GFS and Canadian. Bulk shear should be strong enough to support multicells, but further details are still needed before confidence on severe weather potential increases.

Much cooler temperatures will build in behind the cold front for Monday through Tuesday with highs only in the 60s and nighttime lows in the 40s.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Upper ridging to affect the Southeast States with sfc ridging extending across the area from Bermuda high pressure centered well offshore from the Carolinas. This has generally been the mainstay the past few days and therefore will lean toward a persistence type forecast. SSW 20-25 kt LLJ winds will be in place overnight but seems has not deterred the development of patchy fog across the local terminals each early morning. At this point will indicate a generally 08Z-12Z window for MVFR reduced vsby from fog with the potential for IFR reduced vsby, especially LBT/FLO terminals along with the potential for Vertical VSBY issues. Daytime cu to develop again later Thu morning into the aftn with the sea breeze clearing out the Cu in its wake as it progresses inland. Sfc ridge axis inches slightly northward this period with wind directions generally SSW to SSE, becoming SE with occasional gusts to 15 to 20 kt in the wake of the sea breeze as it pushes inland.

Extended Forecast... Mainly VFR conditions are expected, although the potential exists for early morning fog/stratus Fri/Sat. Sea fog may become an issue beginning for the coastal terminals toward the end of the week and up until the CFP late Sun.

MARINE

Through Thursday...Generally a persistence forecast due to the unmoving Bermuda High. Light SWrly flow expected through the period. With wind speeds capped at 10 knots even all the way out to 41013 wind waves will be less of the spectrum than the easterly swell, which will also be weak, the two totaling up to about a 3 ft dominant wave forecast.

Thursday night through Monday...Summerlike Bermuda high pressure will maintain a light southerly wind at 10 kt or less across the area through Saturday. Afternoon seabreezes could increase this by a few knots nearshore, but marine weather conditions should remain benign for the next several days. A southeasterly swell at 8 seconds period will dominate the sea state through Saturday.

A cold front approaching from the west should reach the beaches Sunday night. In the 12-18 hours ahead of this front, winds will veer southwesterly and increase to 15-20 kt. Chances of showers and maybe even a thunderstorm will increase as well. Once the front has cleared the coastal waters late Sunday night, colder air will build in on northeasterly winds that could exceed 20 kt at times. Small Craft Advisory conditions may develop Monday.

ILM WATCHES/WARNINGS/ADVISORIES

NC...None. SC...None. MARINE...None.