textproduct: Raleigh

WHAT HAS CHANGED

As of 130 AM Friday...

* Other than a very slight slowing trend and a slight uptick in storm total rainfall, no significant changes to the weekend storm system, with a high chance for moderate rain areawide.

KEY MESSAGES

As of 130 AM Friday...

1) Confidence remains high in widespread and mostly beneficial rainfall this weekend, mainly Sun into early Mon morning, although isolated street flooding is possible.

2) Above normal temperatures expected Tue-Thu with very low to no rain chances.

DISCUSSION

As of 130 AM Friday...

KEY MESSAGE 1... Confidence remains high in widespread and mostly beneficial rainfall this weekend, mainly Sun into early Mon morning, although isolated street flooding is possible.

Synoptic overview: Models and ensemble system continue to favor taking the deep mid level low and amplified shortwave trough currently noted on GOES imagery spinning off Baja and taking it E across OK/TX through Sat, into the Mid South and Deep South through Sun, and off the Southeast coast Mon. At the surface, the high centered to our NNW over the Ohio Valley today will drift to over the Carolinas through early Sat, depositing cool/dry air in our area before it shifts SE off the Carolina coast Sat night, setting the stage for in situ cold-air damming. Lift and moisture flux with the approaching mid level shortwave trough is likely to culminate in a deep primary surface low moving from AR to AL/GS Sat night to Sun night, as a secondary low forms and deepens along the CAD/wedge front over the eastern Carolinas.

Rainfall: Agreement is quite good among the deterministic models and ensemble members in a solid area of rain spreading in from the W, with forcing for ascent fueled in part by mid level height falls, vigorous upper divergence, and strong/deep moist upglide at 285K- 310K. Moisture should be deep and plentiful, with PW likely to be 200-250% of normal and a plume of high integrated vapor transport spreading from the Gulf into NC. The timing of the rain is perhaps a bit slower to arrive than previously expected, with rain moving into the western forecast area very late Sat night, then picking up and becoming steady areawide through much of Sun, peaking in the afternoon and evening before a W-to-E departure late Sun night into early Mon, with the early Mon rain chances mainly confined to our E half. Storm total rainfall has gone up slightly since yesterday, still generally 1-2 inches. But chances for amounts over 1" remain 50%-60% over much of the Piedmont, and this is where the peak moist upglide should occur as the nose of a projected 35-45 kt SSW low level jet focuses along the sloping wedge front and enhances lift. In addition, as dewpoints in the warm sector (SE of the wedge front) are poised to rise into the 50s, we may see pockets of weak surface- based convection that could boost rainfall rates locally across the SE CWA. Given our current severe to extreme drought conditions and paucity of rainfall across the area lately, this rain will be largely welcome and beneficial. But brief heavier rain rates over more urban or poor drainage areas could still lead to isolated areas of street flooding.

Where this forecast could deviate: If the mid level low remains very strong and tracks well to our S with a preceding band of convection tracking across the Deep South into S GA and FL and off the GA/FL coast, this has the potential to rob NC of the greatest moisture transport and could reduce these expected rainfall amounts somewhat. While this probability is low, we've seen this scenario before, so it will be worth watching for.

Temps: With confidence increasing that we'll be in an in situ CAD event, Sun highs have been nudged downward slightly in the NW CWA and upward slightly in the SE CWA. Expect a range from the upper 40s in the NW and near the VA border, to the low 60s SE, with a tight gradient somewhere in between. Further adjustments and refinements to Sun max temps are likely as we get closer to the event, and we ultimately could see highs in the Triad trending even cooler while readings trend warmer in the SE CWA. -GIH

KEY MESSAGE 2... Above normal temperatures expected Tue-Thu with very low to no rain chances.

Cooler air and a gusty NE winds will continue into Mon, however flat but strong mid level ridging will build over the Gulf, Deep South and Southeast states through mid week, within modifying surface high pressure. Temperatures will be above normal Tue-Thu, with the mildest readings expected to be Thu when low level thicknesses could be as much as 50 m above normal. This translates to highs around 15 deg F above normal, in the 70-75 range over all but the far N CWA. Some model solutions favor a backdoor cold front dipping into our N and NE areas Thu, which could hold temps down into the 60s there. An isolated passing shower or two may occur during this period, esp in the N CWA, but overall dry weather will prevail. -GIH

AVIATION /12Z FRIDAY THROUGH TUESDAY/

As of 600 AM Friday...

VFR conditions will prevail across central NC through the next 24 hrs, with high confidence. Areas of sct-bkn mid clouds will persist until mid morning, mainly east, then expect just a few high clouds at most through today and tonight. Surface winds will be light, mostly under 10 kts, from the NW or N.

Outlook beyond 12z Sat: VFR conditions will dominate through Sat, then a trend to sub-VFR conditions is likely early Sun morning, with sub-VFR conditions holding with periods of rain through Sun night, lasting into Mon morning in the E. Sub-VFR cigs and gusty conditions should hold through Mon morning with gusty NE winds, but VFR conditions should return for late Mon through Tue. -GIH

RAH WATCHES/WARNINGS/ADVISORIES

None.