textproduct: Raleigh

WHAT HAS CHANGED

As of 305 PM Monday...

* Today's severe storm threat has been limited somewhat by the detrimental effects of the early-morning convection on instability, but a risk of isolated tornadoes persists in our far east, plus a second threat of strong straight line winds will accompany the frontal passage late afternoon through mid evening.

* Increased confidence in much below normal temperatures from late tonight through Wed night, although readings should not reach record cold values.

KEY MESSAGES

As of 305 PM Monday...

1) Despite the stabilizing and overturning effects of this morning's convection, the risk of isolated tornadoes persists in our Coastal Plain this afternoon, and a secondary peak risk of strong straight line winds will arrive with frontal passage late this afternoon through mid evening.

2) Much below normal temperatures are expected late tonight through mid week, with the coldest temperatures Wed morning. Readings will be as low as 12-18 degrees below normal, including highs only in the mid 40s to low 50s Tue and Wed, with a morning frost or freeze likely.

3) Dry weather is likely to hold through early next week, but we're watching the potential for a few showers and storms with a front moving in from the north late Sun into Mon.

DISCUSSION

As of 305 PM Monday...

KEY MESSAGE 1... Despite the stabilizing and overturning effects of this morning's convection, the risk of isolated tornadoes persists in our Coastal Plain this afternoon, and a secondary peak risk of strong straight line winds will arrive with frontal passage late this afternoon through mid evening.

The anomalously deep mid level trough extending from MI south through the Mid South will continue to swing E through tonight, with one vort max pivoting ENE through W NC by early evening. Today's wind field from the surface up through the mid/upper levels has unfolded much as expected, with high low level SRH in the prefrontal warm sector followed by a broken QLCS moving through the area, but the numerous convective elements late last night through this morning have greatly hindered the potential instability. While we've seen a few weak circulations ahead of the line, much of this has been E of our CWA thus far where the CINH has yielded to weak-mdt CAPE with modest heating and low level theta-e advection. We had numerous trees downed with the QLCS along with several bowing segments, but none generated more than weak circulations, and surface observations recorded generally sub-severe gusts. That said, we continue to see wavy lines in our far E, within sufficiently high deep layer bulk shear and 0-1 km SRH over 100 m2/s2. And we expect a second thin convective line with fropa from late this afternoon through the mid evening which will bring another round of strong to possibly severe straight line gusts. Even outside of any convection, sustained winds 15-20 mph and gusts to 25-35 mph will be common. All activity should push east of the CWA by 04z, with clearing skies overnight. Winds will shift to westerly and northwesterly and decrease gradually through the night, although gustiness will persist.

KEY MESSAGE 2... Much below normal temperatures are expected late tonight through mid week, with the coldest temperatures Wed morning. Readings will be as low as 12-18 degrees below normal, including highs only in the mid 40s to low 50s Tue and Wed, with a morning frost or freeze likely.

The mean trough axis will swing through the Eastern Seaboard Tue, as chilly Canadian-source high pressure builds in from the W and NW. Low level thicknesses are projected to be 50-65 m below normal both Tue and Wed morning. Winds will stay up a bit tonight into Tue morning, tempering the potential for radiational cooling, although clearing skies will aid cooling. The opposite should be true Wed morning, with increasing and thickening mid and high cloudiness overnight, but with the surface ridge stretching across the CWA resulting in light winds. Lows tonight are expected to be in the mid 20s W to mid 30s E, and solidly in the 20s Tue night/Wed morning, resulting in a frost/freeze threat for those early budding plants.

KEY MESSAGE 3... Dry weather is likely to hold through early next week, but we're watching the potential for a few showers and storms with a front moving in from the north late Sun into Mon.

While not hazardous, there is high model disagreement on the potential for showers and storms late Sun into Mon as a front moves in from the N. The westerly mid level trajectory and the E-to-W surface ridge to our south (limiting Gulf moisture influx) would tend to favor continued dry weather, and we're going this route in the official forecast, but be aware that pops may be needed in this period in later forecasts.

AVIATION /00Z TUESDAY THROUGH FRIDAY/

As of 800 PM Monday...

24 hour TAF period: Widespread restrictions in showers through the early to mid evening in east. Othwise, a gradual improvement to VFR conditions are expected by late evening. Surface winds will continue to be 15-25kt with gusts to 30kt through 10z. Winds will be around 10kt Tue morning, increasing to again with mixing to 10-20kt with gusts to 22k-25kt. Outlook: VFR conditions are forecast through the period (Tuesday through Friday).

RAH WATCHES/WARNINGS/ADVISORIES

None.