textproduct: Raleigh

WHAT HAS CHANGED

As of 550 AM Wednesday...

* Dense Fog Advisory until 9 AM EST this morning for Edgecombe, Wayne, Wilson, Sampson Co. * Areas of dense fog likely again Thu morning across the Coastal Plain, Sandhills, and srn Piedmont

KEY MESSAGES

As of 300 AM Wednesday...

1) Areas of dense fog likely in the Coastal Plain this morning, then again Thu morning across the Coastal Plain, Sandhills, and srn Piedmont

2) Still expect an extended period of much above normal temperatures, including potential near-record warmth, starting Thu and stretching through at least Tue. Rain chances should be highest Sun/Mon

DISCUSSION

As of 300 AM Wednesday...

KEY MESSAGE 1... Areas of dense fog likely in the Coastal Plain this morning, then again Thu morning across the Coastal Plain, Sandhills, and srn Piedmont

Areas of fog continue to develop and expand as forecast over the ern Carolinas this morning, including into the RAH Coastal Plain, where Tue afternoon-evening clearing was most pronounced and favored maximized radiational cooling of richest low-level moisture characterized by afternoon surface dewpoints (and crossover temperatures) in the upr 40s to mid 50s F. A Dense Fog Advisory will probably be needed for the Coastal Plain within the next hour or so, provided observational trends continue. Meanwhile to the west and throughout the rest of cntl NC, radiation fog and mist should be patchier in coverage and not as dense, owing to greater cloud coverage from both scattered to broken stratocumulus, residual to and trapped by the stability/temperature inversion related to previous days' cold air damming, and also high-level ceilings. Daytime heating today should cause fog to disperse/dissipate by ~14Z, with following unseasonably warm temperatures mostly in the mid 70s this afternoon.

Areas of fog and very low overcast are likely to redevelop late tonight-Thu morning over a larger portion of cntl NC, including much of the Sandhills and srn Piedmont, in addition to the Coastal Plain.

KEY MESSAGE 2... Still expect an extended period of much above normal temperatures, including potential near-record warmth, starting Thu and stretching through at least Tue. Rain chances should be highest Sun/Mon

Strong mid level ridging building over and just off the Southeast U.S coast late this week through early next week, topping a strong surface ridge extending westward across the Southeast coast, will ensure above normal temps for several days, at least into the middle of next week. The latest model output continues to favor anomalously high daily low level thicknesses, around 50 m above normal Thu and at least 55-60 m above normal Fri through Tue (and likely beyond). This suggests highs around 20 deg F above normal, given decent insolation, while daily lows will be quite warm as well, in the mid 50s to lower 60s, which are actually close to the normal highs for this time of year. Fri, Sat, and Tue appear likely to be the warmest days, and both highs and lows through this stretch will be very close to records at GSO, RDU, and FAY.

This mid level ridging will be countered by a deep phased mid level trough over western NOAM, from Alberta and Manitoba southward to the Desert Southwest, and the movement of the northern stream portion of this trough will help drive our peak rain chances starting over the weekend. Initially, the warm and subsiding mid levels over NC, along with the surface ridge initially helping to limit Gulf- and Atlantic- source moisture flux into our area, will keep us mostly dry into Sat, although isolated showers can't be ruled out. While the southern portion of the trough will close off a low and retrograde back over and just W of NW Mexico, energy kicking out of the trough Fri, from the Four Corners NNE through the Dakotas, will get absorbed into the northern portion of the trough as it crosses central Canada and the Great Lakes into eastern Canada and the St Lawrence Valley over the weekend, although model spread with the amplitude and speed of this feature becomes pretty large by Sun. This broad northern stream trough will help flatten the ridge over the Mid Atlantic region and push a surface cold front southward toward NC, although models still favor keeping this front just to our N. Nevertheless, a prefrontal increase in both clouds and PW should lead to increasing shower chances, highest Sun through Mon, with perhaps a storm or two as well. Despite the clouds and precip potential, thicknesses will remain anomalously high Sun/Mon, keep temps (especially lows) well above normal into early next week. The northern and southern streams are likely to stay unphased into mid week, and as the NW Mexico low shifts eastward, it will build renewed ridging over the Gulf and Southeast, thus keeping our heights aloft and surface temps well above normal. Pops should drop back to near climatology for Tue.

AVIATION /11Z WEDNESDAY THROUGH SUNDAY/

As of 550 AM Wednesday...

Residual moisture, from widespread IFR-MVFR ceilings in cold air damming over the Piedmont on Tue, will continue to pool at the base of an associated, lingering temperature inversion based in MVFR range and manifest as MVFR stratocumulus ceilings across the NC Piedmont and RWI this morning. These ceilings will likely scatter/clear from west to east through ~14Z, as the flow in the cloud layer veers from swly to a drier wswly one.

Meanwhile to the east, LIFR fog and stratus has mostly remained in the ern Coastal Plain and just 10 or so miles to the east of FAY and RWI. While it may yet develop a little farther west and into the FAY vicinity through 13Z, the aforementioned MVFR stratocumulus ceilings over the Piedmont and at RWI will likely inhibit any appreciable wwd expansion of the LIFR restrictions to RWI. Daytime heating should cause any fog and very low overcast that develop this morning to disperse to VFR by ~14Z, with a swly surface wind that will strengthen to between 6-12 kts and which may gust briefly and occasionally into the mid teens kts from late this morning through early this afternoon.

An area of LIFR fog and stratus will likely redevelop late tonight into Thu morning, most likely in cntl NC at FAY, RWI, and perhaps as far northwest as RDU.

Outlook: While areas of stratus and/or fog will be possible each morning through the rest of the week, probability of occurrence will be highest at ern sites (ie. FAY and RWI), where low-level moisture will be richest and deepest.

RAH WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 9 AM EST this morning for NCZ028-043-078- 089.