textproduct: Raleigh

WHAT HAS CHANGED

* A low-end severe weather risk is more apparent across the Sandhills and southern Coastal Plain into the afternoon hours.

* Precipitation chances have increased for Sunday through Monday night.

KEY MESSAGES

As of 325 AM Thursday...

1) Waves of showers and embedded thunderstorms will move across the area today, shifting southeast during the afternoon and ending this evening providing some much needed rainfall.

2) Scattered showers midday Saturday will give way to a brief period of dry weather before a more unsettled pattern brings increased rain chances Sunday afternoon through Monday night.

DISCUSSION

As of 325 AM Thursday...

KEY MESSAGE 1...Waves of showers and embedded thunderstorms will move across the area today, shifting southeast during the afternoon and ending this evening providing some much needed rainfall.

A batch of showers and a few embedded thunderstorms that spread east across central NC during the late evening and overnight hours has moved into coastal NC as of early this morning. Another more widespread area of showers and perhaps a few embedded storms has developed across the Foothills and western Piedmont during the past few hours.

This developing area of precipitation is simulated well by many of the convection allowing models as the best forcing for ascent spreads across the region in an anomalously moist airmass with PW values in excess of 1.5 inches which is nearly 200% of normal. The airmass is generally marginally unstable and lapse rates are not remarkable but there should be enough forcing for some decent rain rates. This precipitation should persist with rather extensive coverage through the mid to late morning hours and then shift eastward. A southeastward advancing cold front will move across the Piedmont during the late morning and especially the early afternoon hours stabilizing the boundary layer as the best forcing for ascent shifts east and the precipitation transitions into a lighter and more showery nature. The front will take longer to move across the Sandhills and southern Coastal Plain proving a potential window for enough destablization to combine with 50 to 60 kts of deep-layer shear. This will result in a low end severe weather risk and the SPC has expanded the marginal risk of severe storms into the Fayetteville and Goldsboro areas with the greatest risk from a damaging wind gust from 12 to 6pm. A few lingering showers will continue across southern areas during the early evening with all of the precipitation over by mid evening.

This event should provide some much needed rain to the area. Given the multiple rounds of precipitation, convective enhancement and varied rain durations, precipitation amounts will vary a good deal. Most of the guidance indicates that rainfall totals will range from a half inch to an inch, with higher end amounts of one and a half inches. The most recent HREF shows the highest rainfall totals extended from Charlotte across the Triangle area toward Roanoke Rapids with pockets of rain in excess of 1.5 inches.

KEY MESSAGE 2...Scattered showers midday Saturday will give way to a brief period of dry weather before a more unsettled pattern brings increased rain chances Sunday afternoon through Monday night.

Surface high pressure will be transient through the first half of the weekend, sliding east as a weak shortwave ripples across the north as well as the Deep South. With increased moisture returning to the region on Saturday, scattered showers are expected to develop, mainly across the southern and eastern counties where moisture profiles are deepest. High temperatures will remain at or just below average, with afternoon highs ranging from the mid 70s to near 80. The primary forcing and moisture axis will shift toward the coast later Saturday and Saturday night, focusing the precipitation along and east of the Coastal Plain and allowing for a brief period of clearing ahead of the next frontal passage.

The pattern becomes unsettled again Sunday into Monday as a frontal boundary lingering across the Southeast begins to lift northward. This feature is expected to merge with a cold front tracking east across the Ohio and Tennessee Valleys and into the Mid-Atlantic region late Sunday night. While model guidance continues to show inconsistencies regarding the exact timing of showers and storms, expect precipitation to begin as early as Sunday morning in the south and the afternoon to the north. Isolated strong storms could develop across the region Monday afternoon as the front sweeps across the area. Models are showing PWs surging to nearly 1.25 (well above the daily mean), resulting in the possibility of enhanced rainfall. This unsettled pattern will continue through Monday night as the cold front gradually exits the region.

AVIATION /12Z THURSDAY THROUGH MONDAY/

As of 635 AM Wednesday...

Through 12Z Friday: Multiple rounds of showers and possibly a thunderstorm along with the passage of a cold front will result in poor aviation conditions today.

Widespread MVFR to IFR conditions with VSBY and CIG restrictions have developed almost all of central NC early this morning. A widespread area of showers and perhaps an embedded storm continue to move across central NC early this morning with the greatest coverage from Rocky Mount, Raleigh and Fayetteville south and east. Other patches of rain will spread across the area through the mid morning hours. CIGs will continue to lower into the IFR to MVFR range today and become the primary restriction with areas of rain and some fog reducing VSBYS at times. A southeast advancing cold front will produce a wind shift to northerly winds during the late morning and midday hours. The front wont move across the Sandhills and Coastal Plain until the early afternoon hours allowing these locations to remain in the warm sector resulting in a greater risk of thunderstorms along with with wind gusts up to 20 kts along with a possible thunderstorm and thunderstorm wind gust up to 35 kts.

As drier air moves into the Triad late in the afternoon and evening, sky conditions will improve during the evening hours resulting in VFR conditions. The moisture will be more stubborn across the rest of the area where MVFR CIGs will persist during the evening and into the overnight. If clearing occurs in these areas, some MVFR fog is apt to develop late tonight. There is also the potential for some marginal LLWS during the predawn hours on Friday.

Outlook: After lingering stratus and possibly some fog clears on Friday morning, a period of mainly fair weather is expected into early Saturday. There will be also be another chance of showers and storms with adverse aviation conditions as another cold front moves across the region on Sunday into Monday.

RAH WATCHES/WARNINGS/ADVISORIES

None.