textproduct: Raleigh

WHAT HAS CHANGED

As of 245 AM Sunday...

* Increased Fire Danger today, and possibly again Mon and Tue. Regardless, a state-wide fire ban, issued Sat by the NC Forest Service, prohibits all open outdoor burning until further notice.

KEY MESSAGES

As of 245 AM Sunday...

1) Widespread freezing conditions this morning, with a hard freeze (ie. <28F) probable in typically colder, rural locations.

2) Increased Fire Danger today, and possibly again Mon and Tue. Regardless, a state-wide fire ban, issued Sat by the NC Forest Service, prohibits all open outdoor burning until further notice.

3) Unseasonably mild-warm, and mainly dry, as a frontal system wavers mainly north and west of cntl NC through the weekend.

DISCUSSION

As of 245 AM Sunday...

KEY MESSAGE 1... Widespread freezing conditions this morning, with a hard freeze (ie. <28F) probable in typically colder, rural locations.

A 1035 mb, cP surface high now centered over the Delmarva will extend swwd across NC while progressing offshore today. With clear skies and associated calm, to light sely stirring in urban areas, optimal radiational cooling conditions of the cP airmass will result this morning. 06Z hourly temperatures were already at or below even the latest National Blend of Models (NBM) low temperature forecast at several observing sites and appear well on their way to widespread freezing conditions mostly between 26 and 32F, except for perhaps a degree or two above in the urban Triad and Triangle.

KEY MESSAGE 2... Increased Fire Danger today, and possibly again Mon and Tue. Regardless, a state-wide fire ban, issued Sat by the NC Forest Service, prohibits all open outdoor burning until further notice.

Dry fuels will further dry today, as relative humidity values decrease to minimums between 15-25% over all but the srn Sandhills to srn and cntl Coastal Plain, where 25-35% values will be more likely. After coordination with NCFS on Sat, they requested an Increased Fire Danger Statement anywhere RH was expected to be 35% or less, regardless of wind. Regarding winds, they are expected to veer through sely/sly and increase to 6-10 kts, and be accompanied by occasional afternoon gusts into the teens kts over the Piedmont, in the clockwise/anticyclonic flow around the aforementioned, offshore high.

Surface winds will further veer to swly and strengthen into the 8-14 kt range, with stronger and more frequent gusts into the teens to low 20s kts Mon and Tue afternoons. And while return flow moisture will cause the antecedent, continental airmass to gradually modify, it will do so more slowly and less aggressively than the moist- biased NBM. Gridded forecast dewpoints were consequently derived from the driest NWP guidance, including the 00Z/29th HRRR through the end of its run time Mon evening, which yields min RH on Mon of 35-40%, with mostly 40-45% values derived from the driest MOS guidance on Tue. Given that all NWP guidance are notoriously too quick and aggressive with early stages of moisture return in such regimes, it would not be surprising if RH values each afternoon are observed 5-10% lower than currently forecast. As such, the NCFS- requested 35% RH values for additional Increased Fire Danger Statements may be achieved again Mon-Tue.

KEY MESSAGE 3... Unseasonably mild-warm, and mainly dry, as a frontal system wavers mainly north and west of cntl NC through the weekend.

Anomalous mid-level ridging over the central US will shift east and amplify across the east coast through late week. Flow aloft will largely remain wnwly through Tuesday promoting dry conditions but warming temperatures into the upper 70s/lower 80s.

For Wednesday and beyond, there is some differences amongst ensembles/deterministic models in simulating the strength and evolution of a few short-waves over the central US. Regardless, guidance is in good agreement with simulating generally swly flow aloft and a period of lingering anomalous PWAT across central NC through next weekend. This pattern should favor generally diurnal convection from Wednesday onward, with highest chances likely across the west and central Piedmont via orographic convection rolling off the mountains and/or along sfc troughing.

AVIATION /11Z SUNDAY THROUGH THURSDAY/

As of 640 AM Sunday...

Canadian high pressure and associated very dry air will favor VFR conditions through tonight. A band of VFR stratocumulus may develop from the coast to the Piedmont this afternoon through tonight, coincident with an area of lift and moistening centered around 850 mb/~5000 ft AGL. Otherwise, initially calm to light ely/sely surface winds this morning will modestly strengthen and veer to sly through this afternoon, with some mid-late afternoon gustiness into the teens kts possible mainly over the wrn Piedmont (INT/GSO).

Outlook: Return flow moisture, around what will be a persistent, Bermuda high regime through the upcoming week, will favor a chance of sub-VFR ceilings especially over the wrn Piedmont by mid-week. Lift and rain chances will otherwise be low.

RAH WATCHES/WARNINGS/ADVISORIES

None.