textproduct: Raleigh

SYNOPSIS

A quasi-stationary front over central VA today will move south and across central NC tonight. Low pressure will track across and offshore the Southeast Saturday and Saturday night.

NEAR TERM /THROUGH TONIGHT/

As of 300 PM Friday...

A couple of low amplitude and sheared shortwave perturbations, evident in GOES-E WV satellite data over the TN and lwr MS Valleys and with a mean 700-500 mb trough sampled and centered in 12Z upr air data over the ArkLaTex, will progress across the srn Appalachians and Carolinas through early Sat. The trough will be accompanied by a mid-level frontal zone and band of WAA, now strongly-supporting a shield of rain from nern AR to n-cntl AL, which the models indicate will weaken with time and ewd extent as it progresses into cntl NC by 12Z Sat. Upstream, the models indicate a somewhat stronger shortwave perturbation, evident in satellite data along the NM/CO border but unfortunately not sampled by the 12Z RAOB network, will amplify while digging across the srn Plains and into the lwr MS Valley through the same time.

At the surface, a quasi-stationary front over cntl VA this afternoon, where westbound lanes of I-64 are in the 40s and eastbound lanes near 60 F (probably not really, but maybe or nearly so), will be drawn swd across cntl NC overnight. It will do so between the ern expanse of a ~1018-1020 mb, cP high that will build from the upr MS to OH Valleys and elongated low pressure that will stretch through a couple of weak and weakening frontal waves that will progress across the Deep South.

Considerable, orographically-enhanced high clouds this afternoon will thicken and lower and be accompanied by virga tonight. While some of that precipitation aloft/light rain may begin to reach the ground by 12Z, the aforementioned forecast of weakening of the supporting mid-level Fgen and WAA regime suggest any measurable amounts through that time should be very light and just a few hundredths of an inch maximized over the srn Piedmont. Low temperatures tonight will be regulated mostly by the aforementioned cloud cover, with a signal for modest low-level CAA over the nrn Coastal Plain and nrn Piedmont late, and range from lwr-mid 30s ne to lwr-mid 40s sw.

SHORT TERM /SATURDAY AND SATURDAY NIGHT/

As of 400 PM Friday...

* Hybrid CAD (cool and wet)

A positively-tilted shortwave trough, one that will span a lead perturbation now over the mid-South and an upstream one that will dig across the lwr MS Valley, will progress ewd and across the Southeast Sat and offshore Sat night. A mid-level, 700-600 mb-centered, frontal zone over cntl NC Sat morning will progress newd and off the Middle Atlantic coast through Sat afternoon. Meanwhile, a lwr-level frontal zone, one centered around 850 mb, will progress across SC and sern NC Sat, then across ern NC and offshore Sat night. The models indicate two 925 mb fronts may develop and strengthen, one related to the deeper layer frontal zone over SC and another along the backdoor frontal segment forecast to settle across cntl NC Sat morning.

At the surface, initially elongated low pressure over the Deep South on Sat will consolidate and strengthen as it moves off the SC coast, and newd and well offshore, Sat night. Meanwhile, ~1018 mb, cP high pressure will extend across the OH Valley and srn Middle Atlantic, and in cold air damming fashion over the Carolinas, VA, and GA. A feed of cold and dry air advection at the surface will result over cntl NC.

It will be cool, cloudy, and wet on average throughout cntl NC on Sat, with heaviest rainfall amounts of around a third of an inch over srn zones, nearest the deepest lift and frontal zone over SC. Rainfall and amounts across the rest of cntl NC will rely on both the departing mid-level frontal zone early in the day, which probably will not amount to more than a few hundredths of an inch in any given location, and the secondary 925 mb front that would provide for a tenth to quarter inch elsewhere.

Temperatures will be nearly steady in the 40s amid CAA and diabatic cooling Sat, followed by lows in the 30s by Sun morning. Although rain will taper off generally from west to east through Saturday evening, low overcast from lingering CAD will probably linger into Sunday morning.

LONG TERM /SUNDAY THROUGH FRIDAY/

As of 100 PM Friday...

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

A broad shortwave trough will be working its way off the Southeast coast and pivoting across the Northeast with deep uniformly northwest to northerly flow across the Carolinas to begin the period. Lingering low clouds may remain across portions of the Piedmont, Sandhills, Coastal Plain early Sunday as the in-situ wedge erodes through the early morning hours. By the afternoon, surface high pressure building across the Ohio Valley combined with downsloping northerly winds will likely usher in drier air with minimum RH values of 25-45%. Winds should remain low enough to not cause any widespread fire weather concerns.

Surface high pressure will shift offshore Mon evening and begin a pattern of unseasonably warm temperatures, but dry, through the mid- week period. Greater cloud coverage and a backdoor cold front perhaps drifting into northeastern NC may keep temperatures slightly cooler on Thurs. This front is expected to rapidly lift northward back into VA as a warm front and likely bring highs greater than 20 degrees above normal on Fri. A plume of anomalous moisture leaking across the southern Appalachians into the Mid-Atlanic Fri may be lifted through weak WAA and bring locally thicker clouds and perhaps some light rain, primarily to the Piedmont, on Fri. This may cut into temperatures a bit (5 to 10 degrees cooler) compared to the latest forecast.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

As of 645 PM Friday...

After VFR conditions, with thickening and lowering mid-level clouds tonight, light rain and flight restrictions will result across cntl NC by mid day Saturday, when low pressure will track across and offshore the Southeast. Although rain will taper off generally from west to east through Saturday evening, IFR-MVFR ceilings will linger into Sunday morning.

Outlook: After lingering areas of stratus and/or fog Sunday morning, VFR conditions are expected through much of next week.

RAH WATCHES/WARNINGS/ADVISORIES

None.