textproduct: Raleigh

WHAT HAS CHANGED

* Nothing significant

KEY MESSAGES

As of 200 AM Sunday...

1) Much drier air works in today and Monday behind a cold frontal passage. A stray shower or storm cannot be ruled out along the Coastal Plain.

2) Diurnally maximized convection returns to central NC Thursday through the weekend.

DISCUSSION

As of 200 AM Sunday...

KEY MESSAGE 1... Much drier air works in today and Monday behind a cold frontal passage. A stray shower or storm cannot be ruled out along the Coastal Plain.

A cold front will be pushing through most of our central NC counties this morning. The front will be slowest to push through the eastern Sandhills and Coastal Plain. Behind the front, northwest downslope flow will aid in dewpoints mixing out and RH levels becoming much more comfortable for late August in the upper 30s to middle 40s percent. It is difficult to tell how low dewpoints may mix out this afternoon, but statistical guidance and HREF suggest perhaps middle 50s in the NW, upper 50s in Raleigh and low 60s in the SE. The one exception may be the southern Coastal Plain, where moisture may hang out with the front slower to edge through. But all in all, a great afternoon to be outside. Lows tonight may bottom out in the low to middle 60s, with a few of our cooler spots dipping into the upper 50s. That lower humidity should continue into Monday, despite highs the next few days in the mid/upper 80s, to near 90 in the south.

With the moisture lingering in our far SE today, cannot rule out a stray isolated shower or storm, especially Sampson County, though overall ensembles keep most storms to our east along the coast. Some of the guidance, particularly the GFS, indicate a weak surface wave forming along the front as it stalls out along central SC. This wave is progged in some guidance to track north Monday and perhaps buckle the front back north. This could initiate isolated or scattered storms Monday morning or afternoon, most favored in the Sandhills to the central Coastal Plain. Confidence in this scenario is low but if trends continue, rain chances and clouds may increase in our south and east Monday.

KEY MESSAGE 2... Diurnally maximized convection returns to central NC Thursday through the weekend.

A closed mid/upper level low over southern Quebec Tues morning will continue to slowly pivot east-northeast as another series of shortwaves parade across Great Lakes and southern Ontario through Fri. Moisture returns in the low lvls as early as Wed, with deeper moisture return on Thurs, although rich tropical moisture appears limited in the mid/upper levels as west-northwest flow persists over the Mid-Atlantic into the Carolinas. Nevertheless, this should support diurnally driven convection as surface dew points in the 70s return and PWAT values rise back to around or slightly-above normal into the weekend. There may be some mixing out of dew points each afternoon, especially over the Piedmont back into the 60s which may limit the moderate instability to the Sandhills and Coastal Plain.

Thurs appears to have the best chance for measurable precipitation with neutral H5 height tendencies and potential influence from any MCV's from upstream convection over the Ohio Valley. Reasonable high- end totals for any given area will be around 1" to as much as +2" based on the 12z LREF. However, these amounts will not occur everywhere, as is the nature of summertime convection, with most locations likely to receive somewhere between trace amounts to 0.5" between 8 AM Thurs to 8 AM Fri. For now, no widespread concern for excessive rainfall is expected through the forecast period.

AVIATION /06Z SUNDAY THROUGH THURSDAY/

As of 200 AM Sunday...

An area of isolated convection tied to an approaching cold front has largely dissipated owing to more stable conditions taking over. While we cannot rule out a stray shower in the first few hours of the TAF period, the overall probability appears low. With both INT and GSO seeing a storm Sat evening, the chance of sub-VFR stratus or visibilities increases for early Sun, especially if winds can go calm before frontal passage. We included a temporary MVFR restriction for this threat. Guidance appears to be in better agreement of sub-VFR restrictions at FAY and secondarily at RWI. Moisture will still be present at FAY through early Sun ahead of the front and this appears more likely based on the atmospheric setup. We continued this trend for the 06z TAF period at FAY/RWI, with greater LIFR/IFR restrictions at FAY. VFR should prevail after 13z at all terminals, with west to northwest winds developing post- frontal. Some gusts to 18 kt are favored in the afternoon. We cannot rule out a storm near FAY in the afternoon but most activity should reside well east of the terminal.

Outlook: Early morning fog/stratus will be possible Mon morning at FAY/RWI. Otherwise dry VFR weather should prevail through Tue, though a brief shower cannot be ruled out Mon at FAY. Moisture and lift increases midweek and the chance of convection returns Wed- Thu.

RAH WATCHES/WARNINGS/ADVISORIES

None.