Area Forecast Discussion

WHAT HAS CHANGED

* No significant changes.

KEY MESSAGES

As of 145 AM Friday...

1) Today may be the last 80 degree day for the season at many locations, with well above normal temperatures forecast.

2) Widespread cloud cover and mostly virga expected late Sat night into Mon. Good chance for measurable rain Wed into Fri, but timing and amounts remain highly uncertain.

DISCUSSION

As of 145 AM Friday...

KEY MESSAGE 1... Today may be the last 80 degree day for the season at many locations, with well above normal temperatures forecast.

Some patchy fog may occur again this morning, with the I-95 corridor the favored location today. However, the low clouds and fog should clear by late morning, with just a few passing high clouds this afternoon. While typical conversations revolve around the first and last 90 degree days of the year, today may be a day to talk about the last 80 degree day of the year. This typically occurs on October 21 at Greensboro, October 31 at RDU, and November 11 at Fayetteville. Have added a climate section below in the discussion as this forecast package increased the forecast highs at all three climate sites, although record highs are not forecast to be reached (values ranging from 84 to 87). A dry cold front will push south into North Carolina tonight, dropping high temperatures to a range from the mid 60s to the mid 70s on Saturday.

KEY MESSAGE 2... Widespread cloud cover and mostly virga expected late Sat night into Mon. Good chance for measurable rain Wed into Fri, but timing and amounts remain highly uncertain.

Confidence continues to increase in a dry, no measurable rain, forecast for this weekend into Mon as most model guidance trends towards mostly increasing cloud cover and at best non-measurable very light rain falling from mid-lvl cloud bases. Moisture loosely associated with remnants of TC Vance is still expected to lift into the central Plains tonight into Sat before slowly spreading out across the eastern CONUS into early next week. However, most of this moisture will likely remain in the mid/upper-lvls once reaching the Mid-Atlantic and Carolinas as a reinforcing surge of cooler and drier air will precede the influx of moisture. Lift remains very limited and mostly confined to a sharpening upper trough and any mid- lvl disturbances within the shearing out wave. The deterministic GFS appears to be the final hold out and still brings minor accumulations within a stronger mid-lvl wave, but this solution is an outlier at this point. Near to slightly above normal PWAT values, again confined mostly to the mid/upper levels, will likely still combine with the forcing from the upper trough to support increasing cloud cover and periods of virga, but this chance for measurable rain appears to have dried up.

The better signal for measurable rainfall continues to be sometime within the Wed into Fri night timeframe as a strong mid/upper low shifts from the West Coast on Sun into the Central Plains and MS Valley into the mid-week timeframe. How this feature will develop and evolve is understandably uncertain as the driving features will not phase until this weekend with potentially additional smaller scale waves influencing its evolution into the late week period. Looking closer from a global and AI ensemble guidance hardly paints a picture for significant rain. The wettest ensemble solution is the AIGEFS and its 50th percentile 24 hour QPF ranges from 0.25 to 0.5" across the Carolinas, greatest in the mountains. Whether the warm front is able to lift into or even through our area (to increase instability and rain rates) is highly uncertain and further complicated by a trend within the AIFS ensemble, which is highlighting a surface low development closer to the Carolina coast, which would persist northerly winds across the area and keep central NC within stratiform precipitation and greatly limiting the higher- end rainfall potential.

CLIMATE

Record High Temperatures:

October 30: KGSO: 84/2016 KRDU: 86/1996 KFAY: 87/1950

AVIATION /11Z FRIDAY THROUGH TUESDAY/

As of 655 AM Friday...

TAF period: High confidence in VFR TAFs at INT/GSO, while there is high confidence in LIFR conditions to start the 12Z TAF period at RWI. While RWI has had LIFR visibilities for much of the overnight, rising surface temperatures should allow for ground fog to mix out by mid morning. Models still show the potential for patchy fog at RDU/RWi for a couple of hours, and will leave the TEMPO groups there. By late morning, all terminals should be VFR through the rest of the TAF period. The wind will be around 5 kt out of the northwest today, veering to the northeast after a cold front passes through the area tonight.

Outlook: The weekend continues to trend drier with less moisture, and dry VFR conditions may continue through Tuesday.

RAH WATCHES / WARNINGS / ADVISORIES

None.