textproduct: Raleigh

SYNOPSIS

High pressure will extend across the South Atlantic states through Tuesday.

NEAR TERM /THROUGH TONIGHT/

As of 145 PM Sunday...

Quasi-zonal to broadly and weakly anticyclonic flow will prevail across the Southeast through tonight, while a low amplitude shortwave trough now over the Dakotas will progress across the Great Lakes.

At the surface, high pressure will remain over the Middle Atlantic and Carolinas.

After initially clear skies this afternoon, a plume of srn stream cirrus and cirrostratus, now evident in GOES-E satellite data from the sern N. Pacific to the mid through upr MS Valleys, will progress through the aforementioned broadly anticyclonic flow aloft and across cntl NC (especially early) tonight. Meanwhile, moisture and associated IFR-MVFR ceilings, now centered from nrn FL nwwd through the Savannah Basin, will be directed nwd and across the srn and wrn Piedmont of NC Mon morning. Low temperatures will likely display a somewhat larger than average range mainly as a consequence of the arrival and presence of the low cloudiness over wrn zones, where lwr- mid 30s will be likely, ranging to lwr-mid 20s over the nrn Coastal Plain.

SHORT TERM /MONDAY AND MONDAY NIGHT/

As of 215 PM Sunday...

Quasi-zonal flow will continue across the Southeast, around a sub- tropical high that will extend in the mid-levels from cntl and srn MX to the wrn Gulf.

At the surface, high pressure initially centered along the srn Middle Atlantic coast will split, with the main center that will drift to near and north of Bermuda and another that will settle across the South Atlantic coast. A coastal front will strengthen between the two and along and just offshore the Southeast coast.

Stratocumulus ceilings over the srn and wrn Piedmont will linger through the morning, then scatter through the afternoon-evening. While the stratocumulus decrease in coverage, high-level ceilings, probably orographically-enhanced across cntl/srn VA and nrn/ern NC, will develop and prevail by evening and continue at times through the night.

Temperatures Mon will be slow to rise through the 40s during the morning, where the aforementioned stratocumulus ceilings result, while warming through the 50s should result otherwise and elsewhere in cntl NC. Following afternoon high temperatures will likely range from lwr/mid 50s over the nw Piedmont to lwr 60s in the ern Sandhills and srn-cntl Coastal Plain.

Return, sswly flow in the low-levels will promote strengthening moisture advection and favor the development of very low overcast and/or areas of fog Tue morning. Low temperatures will trend milder and into the upr 30s to mid 40s.

LONG TERM /TUESDAY THROUGH SUNDAY/

As of 100 PM Sunday...

* Patchy to areas of fog possible early Tues.

* Unseasonably warm temperatures mid to late week with temperatures 15-25 degrees above normal.

* Considerable forecast uncertainty this weekend.

Moisture advection from the Southeast, with limited thermal advection, early Tues morning is expected to lift into the western Piedmont and gradually ooze eastward into Tues morning. This pattern may support a northward advection of the widespread fog, some dense, across SC and eastern GA this morning. Available hi-res guidance is just now extending into Tues and is very aggressive with showing a similar evolution over central NC Tues morning. Among available guidance, probability of < 1 mile range from 20-50% across mainly the Piedmont Tues morning lingering until after 15z in spots. Have added patchy/areas of fog to the forecast, but not quite convinced in development of dense fog quite yet and have kept mention out of the HWO for now.

A backdoor cold front sagging into the area Wed night into Thurs will briefly interrupt the gradual warming trend before lifting back north as a warm front through the day on Thurs; bringing near record warmth by Fri and perhaps into Sat.

Forecast confidence is considerably low this weekend. This uncertainty stems from the very large timing and amplitude run-to- run variations of a southern stream mid/upper level low forecast to be positions off the CA coast Tues morning. From a 100 member grand- ensemble perspective, the best rain chances will come around a cold frontal passage, which is forecast to occur anytime within a 24 hour window between early Sat morning through Sun morning. Most likely amounts from this ensemble approach suggest 24hr totals range from trace amounts to around 0.33" (25th and 75th percentiles) with reasonable high-end amounts of around 0.50"; greatest totals more probable across the Piedmont with lowest amounts in the Coastal Plain and Sandhills.

AVIATION /00Z MONDAY THROUGH FRIDAY/

As of 630 PM Sunday...

VFR conditions, with light and variable winds around high pressure that will build across and offshore the srn Middle Atlantic, will prevail through tonight. As the high drifts offshore through Mon, moisture and associated IFR-MVFR ceilings now centered from nrn FL, nwwd through the Savannah Basin, will be directed nwd and across the wrn Piedmont of NC Mon morning. 2000-4000 ft ceilings will consequently become likely at INT/GSO around 12Z Mon, then linger through early-mid afternoon. A period of IFR cigs are possible, especially between 12z and 15z/Monday.

Outlook: Areas of fog and stratus are expected to develop Tue and Wed mornings, amid an increasingly moist, return flow regime across the Southeast. Marginal low-level wind shear will also be possible Tue night.

RAH WATCHES/WARNINGS/ADVISORIES

None.