textproduct: Raleigh

SYNOPSIS

An in-situ cold air damming ridge will extend across the Carolinas and Virginia today, while coastal low pressure will rapidly strengthen while tracking along the East Coast. Cold high pressure will follow and migrate across the Southeast, while modifying, through Thursday.

NEAR TERM /THROUGH TONIGHT/

As of 400 AM Tuesday...

* A cold, soaking rain early today will yield to west to east drying and clearing from late afternoon through evening.

A positively-tilted shortwave trough stretching this morning through a couple of perturbations over wrn MO and the srn High Plains will lift across and offshore the Middle Atlantic and Carolinas through this evening, then offshore overnight. Downstream of that trough, intense low through mid-level WAA now centered squarely over the Carolinas will both provide strong ascent and transport of a plume of 1.5" and ~200 % of normal PWs across and offshore the Carolinas and srn Middle Atlantic through this afternoon.

At the surface, the center of a weakening, 1027 mb, Arctic high now centered over ME will progress quickly ewd and offshore. An in-situ cold damming ridge will be left behind the transitory and weakening high and across the favored cold air damming region across the Carolinas and neighboring VA and GA today. Meanwhile, a pair of deepening lows now centered at 1008 mb over the nern Gulf and at 1011 mb just off the cntl SC coast, respectively, will consolidate and rapidly deepen while tracking along and just offshore the Atlantic coast, to around 985 mb near the srn Nova Scotia coast by 12Z Wed. Through the same time, continental Polar high pressure now centered at 1022 mb and with unseasonably cold temperatures over the srn Plains, will progress ewd and into the OH and TN Valleys, with associated cold and dry air advection that will spread east of the Appalachians and across cntl NC from late this afternoon through tonight.

A large, mainly stratiform precipitation shield accompanying the aforementioned, intense WAA now overspreading cntl NC will serve to lock in an in-situ cold air damming airmass, when temperatures throughout the morning will be near steady in the mid 30s to lwr 40s. As the WAA regime and deep moist axis depart by early to mid afternoon, so too will the rain shield, with following downslope flow and CAA in the stable in-situ CAD layer. As such, west to east erosion of the CAD airmass should result during the afternoon and evening, which should allow for some temperature recovery into the 40s, most strongly over the srn Piedmont. Skies will further clear overnight, with light nwly stirring becoming calm in many areas by sunrise, and with low temperatures in the mid 20s to lwr 30s.

SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/

As of 330 AM Tuesday...

* Clear or mainly so, and unseasonably cold

Strengthening, quasi-zonal flow will prevail across the Southeast and Carolinas this period, downstream of an elongated, positive tilt trough that will extend from a strongly-amplifying shortwave over ON and the upr Great Lakes wswwd to another major shortwave over the srn Rockies and Southwest. Within that regime, strongly rising heights and strong and deep subsidence over cntl NC early Wed will tend toward weakly falling ones by Thu morning, with the latter supportive of the maintenance of both altocumulus and cirrostratus ceilings into cntl NC just beyond this period (ie. through the day Thu).

At the surface, continental Polar high pressure, now centered at 1022 mb and with unseasonably cold temperatures over the srn Plains, will progress ewd and across the Southeast through early Thu.

The sensible weather over cntl NC related to the pattern described above will feature a sunny or mostly so Wed, with ~10 F below average high temperatures mostly in the mid-upr 40s, except lwr 50s across srn counties. Wed night should be equally as clear, or mostly so, and cold, with low temperatures mostly in the mid-upr 20s, except around 30 F in urban areas.

LONG TERM /THURSDAY THROUGH MONDAY/

As of 230 AM Tuesday...

* Highest chances for precipitation still Friday and Friday night, with lower confidence in chances Saturday through Monday.

Aloft, a s/w will track ewd from the Four Corners, across the srn Plains and lwr/mid MS Valley on Thu/Thu night, then continue ewd across the srn Appalachians and Carolinas on Fri. Meanwhile, the longwave trough will remain over the Plains/Intermountain West Thu/Thu night, as yet another s/w drops sewd from sw Canada to the cntl Plains. This s/w may finally help the longwave trough progress ewd across the cntl and ern CONUS Fri night through Sat night. Central NC should be under the influence of wswly to swly flow through at least Sat. A trailing s/w may move across the region Sun or Mon, but model variability increases over the weekend into early next week. At the surface, a dry cold front will move southward across the area on Thu, with Arctic high pressure ridging swd into the area as it moves ewd from the Midwest across the OH Valley and into the Northeast US Thu night. Meanwhile, an area of low pressure will develop over the NW Gulf Thu night, then eject newd across the Southeast US and off the Carolina coast Fri/Fri night. The biggest difference between the operational runs of the GFS and EC is the strength and track of the Arctic high, which could impact temperatures and perhaps p-types across the NW Piedmont. The low should continue to move away from the area and out over the Atlantic Sat/Sat night, with high pressure moving across the region in its wake. The next low pressure system should develop over the cntl Plains/mid-MS Valley Sat or Sat night, tracking across the region Sun or Mon, though timing varies amongst the models.

Precipitation: Thu should generally be dry, with precipitation expected to spread enewd across the area Thu night/Fri morning, lingering through Fri night. While the operational EC and GFS both generally dry out by Sat night (GFS earlier than EC), there is still enough spread in the ensembles to hold on to slight chance through Sat night/Sun morning. Precipitation should largely be rain, however there is a chance for some wintry precipitation to mix in at the beginning and possibly the end of the event. For now, confidence and impacts remain low. Additional precipitation is possible with the trailing s/w either Sun or Mon, but given the significant difference in timing, will keep chances below slight for now.

Temperatures: Thu should be the warmest day of the extended period, with highs ranging from around 50 degrees across the north to mid 50s south/SE. Low confidence in temperatures Thu night through Fri night, as they will depend on the strength and position of the Arctic high, track and strength of the low, and the associated precipitation. Highs will remain below normal Fri-Mon, lowest on Fri. Lows should generally remain near to slightly below normal, generally ranging from mid/upper 20s to low/mid 30s.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

As of 650 AM Tuesday...

A large shield of stratiform rain, moderate to heavy at times, and mostly LIFR-IFR ceilings and IFR-MVFR visibility restrictions, will taper off/move east and out of cntl NC this afternoon. Ceilings may be slow to lift after the rain departs, amid a rain-moistened, cold air damming airmass, at least until drier air and stronger nwly flow overspreads cntl NC this evening. That nwly flow may also result in a short period of gustiness, especially at INT and GSO. Skies will then become clear overnight, as cold and dry high pressure builds in from the west.

Outlook: Another storm system will bring a risk of flight restrictions and rain, the latter of which may begin as a short period of snow over the Piedmont, Fri-Sat.

RAH WATCHES/WARNINGS/ADVISORIES

None.