textproduct: Raleigh

WHAT HAS CHANGED

* No significant changes from the previous forecast.

KEY MESSAGES

As of 255 PM Wednesday...

1) Convective coverage through this evening should be less than previous days overall, but still expect scattered to numerous showers and storms across the SE Coastal Plain and in the north and west including the Triad and Triangle. A few strong wind gusts are possible across the north.

2) Mainly dry conditions are expected on Friday before rain chances increase again in the south on Saturday, though overall coverage and amounts should be less than in recent days.

3) A drier and cooler period will follow from Sunday into Wednesday with mainly isolated diurnal convection. The one exception is Monday when shower/storm coverage looks greater.

DISCUSSION

As of 255 PM Wednesday...

KEY MESSAGE 1... Convective coverage through this evening should be less than previous days overall, but still expect scattered to numerous showers and storms across the SE Coastal Plain and in the north and west including the Triad and Triangle. A few strong wind gusts are possible across the north.

We remain in a moist SW flow regime, on the western periphery of offshore-centered ridging and in the warm sector S of a weak front to our N over the Ohio Valley and Mason Dixon line. Our PW remains well above normal but slightly lower than yesterday, as shortwave troughing dipping into the N Mid Atlantic and Northeast has tamped down the mid level ridging, causing our mid level flow to veer to more westerly. But we're still seeing moderate SBCAPE in the 2000- 3000 J/kg range, with decent heating having started with the lifting of the morning multi-layer stratus, and our deep layer bulk shear is around 30 kts, a bit higher than previous days. Regional radar trends are fitting fairly well with earlier CAM output showing sct- numerous showers and storms over central and NE SC across SE NC, with another band of convection over the NC and SW VA mountains and adjacent foothills. These two areas should culminate in peaks of shower/storms coverage across the N Piedmont/far N Coastal Plain as well as the E Sandhills across the SE Coastal Plain, through the mid evening hours. With the improved bulk shear fostering better cell organization and higher DCAPE than previous days, there's a risk for strong to isolated severe wind gusts across the N Piedmont into the N Coastal Plain. Isolated minor flooding remains possible where cells can train, with the highest chance in the urban Piedmont areas like the Triad area cities and towns which saw 1-3" yesterday. Convective activity should dwindle and exit out of the central and SE Coastal Plain shortly after midnight, with fair to partly cloudy skies late tonight and patchy fog possible in the S and E.

As the front to our north settles S into NC Thu with a weakening trend, pops will be largely shifted across our southern half, mainly along and S of Hwy 64, as slightly lower dewpoints settle into our northern areas. Isolated downpours are possible Thu afternoon in the far SE, but the overall threat for heavy rain and any strong storms looks quite low.

KEY MESSAGE 2... Mainly dry conditions are expected on Friday before rain chances increase again in the south on Saturday, though overall coverage and amounts should be less than in recent days.

The quasi-stationary boundary looks to be well to our south on Friday according to recent deterministic guidance and the vast majority of GFS/ECMWF/CMC ensembles. Thus Friday should be partly to mostly sunny and largely free of precipitation, with fairly good confidence. The next chance for showers and storms comes from late Friday night/early Saturday morning into Saturday afternoon (first in the SW) as the stalled boundary to our south tries to lift back north and a weak wave of low pressure associated with an upper disturbance currently over the TX and OK panhandles rides east along the front. The main chance for convection would be across our southern zones, but given only slightly above normal PW values, overall coverage and rainfall amounts do not appear high. Still, this will depend on exactly how far north the low and boundary are able to get, which is uncertain. Conditions will turn more comfortable on Friday and Saturday as highs reach the upper-70s to lower-80s (near normal) and dew points drop into the 50s. Forecast lows Friday night are in the upper-50s to lower-60s.

KEY MESSAGE 3... A drier and cooler period will follow from Sunday into Wednesday with mainly isolated diurnal convection. The one exception is Monday when shower/storm coverage looks greater.

Another low pressure system tracking across and offshore New England will drop a backdoor cold front south through central NC on Saturday. This will mostly put an end to our rain chances by Saturday evening, with drier weather from Sunday into the middle of next week under the influence of NW flow aloft as we remain on the backside of longwave troughing over the North Atlantic. Still can't rule out isolated showers or storms each day with disturbances rotating around the trough and marginal daytime instability. The best chance for this looks to be on Monday as a stronger shortwave moves SE through the Northeast US and Mid-Atlantic. Still, ensemble mean rainfall amounts are less than half an inch as PW values are not overly impressive. Temperatures will turn cooler than normal from Sunday through Wednesday with highs in the mid-70s to lower-80s and lows in the 50s.

AVIATION /00Z THURSDAY THROUGH MONDAY/

As of 738 PM Wednesday...

Scattered thunderstorms may affect areas around KRDU and KRWI through around 03Z; otherwise, a return to VFR conditions is expected at all sites after 06z Thursday. A weak cold front will move south through the region late tonight. Thus, the SW surface winds this evening into the overnight hours will become more westerly by daybreak, then northerly between mid morning and noon.

Looking beyond 18z Thursday, conditions will be mostly VFR through Friday night into early Saturday. Then, as a disturbance aloft tracks west to east over SC Saturday brief showers and MVFR conditions are possible in the south. A cold front will move south through NC late Saturday, and VFR conditions should prevail for Sun/Mon.

CLIMATE

Record High Minimum Temperatures:

May 27: KGSO: 72/1991 KRDU: 72/1991 KFAY: 72/2006 May 28: KGSO: 70/2012 KRDU: 74/1914

RAH WATCHES/WARNINGS/ADVISORIES

None.