textproduct: Raleigh

SYNOPSIS

Tropical Storm Chantal will drift slowly north northwestward across the coast of South Carolina overnight or early Sunday morning. Its remnant low pressure will then drift slowly north to northeastward through northeastern SC Sunday and central NC Sunday night into Monday.

NEAR TERM /THROUGH TONIGHT/

As of 245 PM Saturday...

* Scattered showers and isolated storms still expected along and east of Hwy 1 through tonight.

Surface high pressure centered just off the Mid Atlantic coast this afternoon will continue to extend SW through the NC Piedmont into early this evening, although this ridge (and its comparatively lower dewpoints as compared to the Coastal Plain) will be steadily overcome and supplanted by the encroaching Tropical Storm Chantal, located about 100 mi SE of CHS this afternoon and drifting slowly to the N. The current bands of tropical convection now pushing westward over our SE are feeding on moderate CAPE, but with poor deep layer shear. The downturn in CAPE after nightfall should result in a relative dip in coverage later this evening. Deeper moisture (as seen on GOES layer WV) and higher PWs (~2.0-2.4") sitting over the NC coastal areas will spread steadily inland through tonight, although pockets of somewhat drier air aloft over our NW should temporarily limit the westward extent of showers through tonight. Skies should trend to partly (W) to mostly (E) cloudy overnight with rising rain chances mainly along and E of Hwy 1, highest in the SE (e.g., CTZ/GSB), and isolated to no pops in the NW. After highs today in the mid 80s to lower 90s, lows tonight should be in the upper 60s to lower 70s.

SHORT TERM /SUNDAY AND SUNDAY NIGHT/

As of 335 PM Saturday...

* Slight risk of excessive rainfall over much of central NC Sun/Sun night, with amounts of 1-4 inches possible.

* Marginal severe storm risk over our southeast areas Sun/Sun night for the threat of an isolated tornado or two.

TS Chantal is expected to make landfall over the central or northern coast of SC early Sun morning before tracking northward then NE, reaching the E Sandhills Sun evening as a depression, then moving roughly along the I-95 corridor through E NC through Sun night. By this time, both the strong/deep Atlantic moisture flux and the surface wind field are likely to have weakened from their current state. However, in this tropical environment, PW is still expected to be well above normal, 2.2-2.5" across the CWA, with a deep LCL-0C layer aoa 4 km, favoring warm rain processes and supporting the risk of heavy rainfall. Many of the recent CAM runs show the heavier rain areas spreading west of the center over the Piedmont Sun, and in particular our far S and SW sections (including some flashy streams like the Rocky River) could see multiple inches of rain through Sun night. There is still too much uncertainty in coverage and amounts for a flood watch at this time, however one may be needed tonight or Sun morning if these CAM trends hold. Regarding the surface winds and severe threat, while the surface wind field will have spread out and decreased, a few stronger gusts remain possible, esp in and near convective cells with substantial vertical growth as higher winds aloft mix groundward. Models do show decent (25-35 kt) low level southeasterly jetting to the E and NE of the storm's center, nosing into our Coastal Plain and E Sandhills counties Sun into Sun evening, and this resultant brief curvature to the hodographs could support a weak spinup or two in our SE, esp if we can achieve any CAPE between tropical rainbands. Expect likely to categorical pops CWA-wide, which is a notable westward push from earlier forecasts. Given the more expansive cloud cover and precip, have nudged highs down a bit to 80-85. Lows around 70 to the mid 70s, with pops trending down and shifting into mainly NE sections as the remnant low center tracks through the E CWA overnight.

LONG TERM /MONDAY THROUGH SATURDAY/

As of 250 PM Saturday...

* Remnants of Tropical Storm Chantal likely to have minimal impacts to the region by Monday. * Afternoon/diurnal shower chances return Tuesday through Saturday.

* Hot and humid conditions expected each day, with the hottest day being Tuesday.

By Monday morning, the remnants of Tropical Storm Chantal should be in the northeast portions of the CWA as a tropical depression. Impacts from the storm are expected to be less on Monday than on Sunday, however there is still a chance for pockets of locally heavy rain. This is especially true in the northeast where convergence with a coastal front is expected. The risk of severe weather and tornadoes associated with the system on Monday still appears to be limited. Otherwise, maximum temperatures on Monday should range from the upper 80s in the northeast to the low 90s in the southwest. Overnight, temperatures should drop into the low to mid 70s.

Tuesday is expected to be the hottest day of the period in wake of the tropical cyclone. Temperatures are expected in the 90s across the region, with heat indices reaching the upper 90s to the low-to- mid 100s. Along with this, scattered showers/storms are possible Tuesday afternoon and evening. Temperatures will also stay warm overnight, only dipping into the low to mid 70s, leaving little relief from the heat. Wednesday through Saturday, we should stay in a pattern of afternoon and evening showers and embedded thunderstorms. The best chance for this will be on Thursday and Friday as a cold front looks to approach the region. Temperatures during this period should be in the upper 80s to low 90s, with lows overnight in the upper 60s to low 70s.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

As of 830 PM Saturday...

Preceding and related to Tropical Storm Chantal, bands of showers/isolated storms, then an area of IFR-MVFR ceilings, will spread inland and across cntl NC tonight-Sun morning. Rain, embedded convection, and flight restrictions will then continue through the 00Z TAF period, and beyond through Sun night-Mon, as low pressure related to the remnants of Chantal tracks very slowly north to northeastward through cntl NC. Nely surface winds will not be particularly strong but will gust at times into the teens to around 20 kts especially with daytime heating Sun.

Outlook: A humid airmass will favor areas of morning stratus and fog and afternoon-evening showers/storms through most of next week.

RAH WATCHES/WARNINGS/ADVISORIES

None.