textproduct: Raleigh

WHAT HAS CHANGED

* No major changes were made with the afternoon forecast package.

KEY MESSAGES

As of 135 PM Sunday...

1) Increased Fire Danger today and again tomorrow, with possible Red Flag criteria being met at times on Monday.

2) Patchy frost will be possible over rural nrn Piedmont locations tonight, then again over most of cntl NC (except perhaps the srn Sandhills and srn Coastal Plain) Tue morning.

3) Chances for measurable rainfall increase this weekend, but no significant amounts are expected.

DISCUSSION

As of 135 PM Sunday...

KEY MESSAGE 1... Increased Fire Danger today and again tomorrow, with possible Red Flag criteria being met at times on Monday.

Post-frontal gusts of 20 to 30 mph persist this afternoon while drier air continues to filter in from the west. After collaborating with the NCFS and surrounding NWS Offices in NC, an Increased Fire Danger statement was issued for today for the western Piedmont and Sandhills of central NC. The combination of very dry to historic dryness within 100-hr fuels, dropping RH values into the 20s and teens, and gusty northwest winds 20 to 30 mph will support a risk rapid spread of any wildfires by this afternoon. Given the lack of rainfall from this morning, fine fuels should recover/dry very quickly by this afternoon and be prime for easy fire ignition.

On Monday, guidance is simulating quite deep mixing potential (as high as 10,000 feet; ~700 mb). As such, went far above the NBM for wind gusts tomorrow, peaking in the 20 to 30 mph range much of the afternoon (infrequent 35 mph gusts may be possible). Humidity will drop into the 15 to 25% range Monday afternoon. The combination of gusts and low RH will surely require at the very least an IFD for Monday. Further coordination with the NCFS is ongoing to assess the potential for Red Flag Warnings for possibly some of NC. An update will likely occur this evening.

KEY MESSAGE 2... Patchy frost will be possible over rural nrn Piedmont locations tonight, then again over most of cntl NC (except perhaps the srn Sandhills and srn Coastal Plain) Tue morning.

Strong radiational cooling of the post-frontal airmass tonight will favor low temperatures in the mid-upr 30s over rural Piedmont locations to lwr-mid 40s elsewhere, supportive of patchy frost in typically cooler, rural locations over the nrn Piedmont.

A strong sfc high is expected to traverse over the Mid-Atlantic Monday into Tuesday. This will lock in nely flow Monday night with low-level thicknesses generally ranging between 1305 to 1325 m. Statistical guidance continues to suggest possible near to just below freezing lows in our traditionally cooler spots along the NC/VA border. There is some uncertainty wrt to how much mixing might persist overnight, but overall looks to be a decent signal for at least frost producing temperatures to be reached Tuesday morning across the northern Piedmont/Coastal Plain.

KEY MESSAGE 3... Chances for measurable rainfall increase this weekend, but no significant amounts are expected.

A mid/upper level ridge axis is expected to build over the Great Lakes and Midwest by Thurs and slowly advect eastward with time through the forecast period, supporting broad high pressure draped over western Atlantic and extending westward over the Southeast and Carolinas. This will greatly limit any precip chances through the workweek with gradually moderating surface temperatures. The pattern becomes marginally more favorable for measurable rainfall this weekend as an occluding surface low over Ontario directs a plume of greater deep-layer moisture over the Southeast and into the Carolinas within perturbed southwesterly flow aloft. Even so, no significant rainfall is expected as LREF grand-ensemble probabilities of >0.5"/24 hours remains incredibly low at 5-10% through the weekend.

AVIATION /00Z MONDAY THROUGH FRIDAY/

As of 750 PM Sunday...

VFR conditions will persist, with high confidence, at central NC terminals over the next 24 hours. High clouds over the eastern half of the area currently are associated with an upper level trough over the East Coast and behind a surface cold front moving off the coast. These high clouds will continue an eastward exit, leaving just fair skies overnight through mid-late Mon morning. Daytime heating will bring sct-bkn clouds based at 6-8 kft AGL late morning through much of Mon afternoon. Surface winds from the WNW or NW will diminish by 02z, then increase again after 14z Mon, 8-15 kts with gusts up to 20- 28 kts through Mon afternoon.

Looking beyond 00z Tue, winds should diminish by mid evening Mon. VFR conditions are likely to hold through the work week.

RAH WATCHES/WARNINGS/ADVISORIES

None.