textproduct: Raleigh

WHAT HAS CHANGED

* Lowered POPs for this morning.

KEY MESSAGES

As of 302 AM Wednesday...

1) Marginal Risk (level 1 of 5) for isolated severe storms this afternoon/evening.

2) Extended period of near to below normal temperatures expected, with an additional round of stratiform rain for much of the region likely on Saturday.

DISCUSSION

As of 302 AM Wednesday..

1) Marginal Risk (level 1 of 5) for isolated severe storms this afternoon/evening.

A strong short-wave continues to generate convection over the Deep South this morning. A bit further north, a weaker short-wave is generating shallow convection over IL/IN/OH. Based on latest observational trends and high-res guidance, think that these two areas of convection will largely split central NC with highest QPE remaining to our north and south this morning. Pockets of light rain are still likely to move across areas of central NC starting near sunrise and through early afternoon, but again think it may be fairly limited. Regardless, residual convective debris clouds will persist through late morning limiting destablization for a bit.

As we enter the early to mid afternoon, suspect that we'll see some clearing of the cloud base, and with dew points expected to rise into the mid to upper 60s, weak instability is likely to develop. By late afternoon/early evening, increasing shear associated with an approaching mid-level jet streak will promote wind profiles conducive for possible supercells. Latest RREFS and HREF helicity output favor left-moving supercells (highest probabilities along the NC/VA border). As such, any isolated stronger updraft could produce damaging hail and wind gusts. A secondary area to watch may be in the Charlotte to Fayetteville vicinity where high-res guidance is bullish on the development of a differential heating boundary which could trigger stronger convection. However, given convective initiation is likely to occur closer to sundown, not entirely sure strong updrafts capable of generating large hail will be realized. Lastly, while hail and wind are the primary concerns in isolated stronger storms, 0-1 km SRH will push >150 m2s2 possibly supportive of a brief tornado.

Any linger convection should push east of central NC by ~03 to 06Z.

2) Extended period of near to below normal temperatures expected, with an additional round of stratiform rain for much of the region likely on Saturday.

Surface high pressure centered over the central US, along with general troughing over the eastern US will allow for near to below normal temperatures to prevail for much of the extended forecast. The coolest day will be Saturday, as stratiform rain and cloudy conditions should only allow temperatures to rise into the low-to- mid 60s, with lows dropping into the upper 30s to low/mid 40s Saturday night. This is around 10-15 degrees below normal for this time of year.

On Saturday, a low pressure system will form off of a stalled front off the coast of Florida and strengthen as it moves up the NC coast, bringing the next best chance of widespread rain. Instability will be very low with only a few J/kg of MUCAPE being shown by the mean of the LREF along with the global models. Thus, a cool stratiform rain is expected beginning late Friday night. 50th percentiles of the ensembles are still showing a decent spread with rainfall totals, with the GEFS now showing lower totals than the European ensemble which is opposite of what was being depicted earlier. In a 24 hour period ending late Saturday night, the GEFS is suggesting a range from about 0.05 inches north and west to around 0.4 inches in the southeast, while the European ensemble has a range around 0.1- 0.8 inches during the same time. This is a decrease in QPF from this time yesterday. Additionally, the probability of at least measurable rain (0.01 inch) from the LREF for the CWA ranges from 60% in the northwest to 80% in the southeast. Any rain should move out of the area late Saturday night, with high pressure returning to the region.

AVIATION /10Z WEDNESDAY THROUGH SUNDAY/

As of 623 AM Wednesday...

MVFR ceilings are finally spreading across central NC this morning, with KINT/KGSO and KFAY all having dropped to MVFR. Expect this to expand eastward with time this morning before the cloud deck scatters out some this afternoon. Timing of rain this morning and potential storms this afternoon and evening discussed below remain valid at this update. Additionally, added in a re-surgence of MVFR ceilings at KRWI late tonight.

Previous discussion:

VFR conditions persist early this morning. Still expecting sites to sock back in to MVFR/IFR in the next few hours as a low-level moisture and associated pockets of rain move across central NC. Some clearing of the morning cloud debris is likely this afternoon, as some sites may return to VFR. There is some uncertainty still, but it appears there is still a signal for showers and storms to generate late this afternoon and evening along an advancing cold front. Brief sub-VFR conditions and gusty winds may occur at any terminal that's impacted by this isolated afternoon convection. Any lingering convection should move east of central NC by ~03 to 05Z.

Outlook: Another chance of flight restrictions and rain will accompany an area of low pressure forecast to track across or just south of the Carolinas late Fri night-Sat.

RAH WATCHES/WARNINGS/ADVISORIES

None.