textproduct: Raleigh

WHAT HAS CHANGED

As of 220 PM Tuesday...

* No significant changes to the forecast. Confidence remains low as to how quickly the rain will exit our SE on Fri.

KEY MESSAGES

As of 220 PM Tuesday...

1) Wind gusts as high as 20 to 30 mph remain possible Wed.

2) High rain chances late Wed night into early Fri as low pressure tracks along a frontal zone through NC. Thunder chances remain low.

DISCUSSION

As of 220 PM Tuesday...

KEY MESSAGE 1... Wind gusts as high as 20 to 30 mph remain possible Wed.

Surface high pressure will push eastward off the FL coast tonight, setting up WAA and a blustery SW flow over central NC for Wed as a warm front lifts northward into the area. Gusts in our area are most likely to top out at 20-30 mph, particularly in the early to mid morning as daytime mixing taps into the exiting low level jet, and late in the day with the strengthening of SW winds through the BL. The NBM 90th percentile does reach 30 mph over much of the CWA, and the HREF probabilities of a 30+ mph gust is over 40% most areas, so the official forecast will skew toward higher gust potential. Such gusts would not be particularly hazardous overall, but may cause outdoor objects to be blown around and may present difficulties for those drying high-profile vehicles. Regarding fire behavior, while these winds are somewhat concerning, the surface dewpoints are expected to rebound sufficiently to keep min RH levels under critical thresholds, mainly 30-45%. That said, will monitor this expected RH recovery and surface fuel conditions to see if any fire weather statements might be needed.

KEY MESSAGE 2... High rain chances late Wed night into early Fri as low pressure tracks along a frontal zone through NC. Thunder chances remain low.

A warm frontal zone lifting into the area Wed is expected to settle across NC or S VA as surface low pressure tracks from OK/N TX eastward along the front. As this low approaches, southwesterly low level flow will increasingly draw Gulf-source moisture into NC starting Wed night, with increasing and deepening moist isentropic upglide. Aloft, a broad northern stream shortwave trough will sweep through the Great Lakes/St Lawrence/Quebec Wed/Thu, followed by a southern stream shortwave trough moving through the S Plains into the Southeast Thu/Fri. The incoming mid level DPVA (most robust Thu into early Fri) and upper divergence combined with the low level moist upglide and high PWs (up to 200%-250% of normal) support a period of likely to categorical pops. Light rain is expected to spread into the CWA (mainly N half) Wed evening, then increase in coverage and becoming more steady, with chances peaking Thu into Thu evening. As the northern stream wave exits and waits for the slightly stronger southern stream shortwave to arrive, the cold front is expected to briefly hang up across SE NC with a persistent stream of high PW (nearing 300% of normal), so have held onto high chance pops S and E of the Triangle through Thu night and Fri. Overall storm total rain should still be around 0.75-1.25", although training bands of more moderate rain may lead to isolated higher totals. Temps Thu-Fri will be generally mild, especially lows, with clouds yielding a smaller-than-usual diurnal range. Behind this system, there will be no Arctic air available, thus daily average temps will continue above normal through the weekend, with the warmest readings Sat/Sun when highs will be in the 60s and 70s.

A strong backdoor front is expected to drop southward into the Mid Atlantic region Mon or Tue, which would knock temps back down to near or below normal, but model spread with the location of this front is large, reducing confidence in temps Mon-Tue.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

As of 1245 PM Tuesday...

VFR conditions are expected to prevail with plenty of high clouds through the TAF period. A 40-50kt southwesterly low level jet is expecting to develop and move over the region late tonight, bringing a threat for LLWS across all of central NC between 04z-12Z, developing first across the Triad then spreading eastward overnight. W to NW sfc winds 10-15kt with higher gusts attm will back to SW by later this afternoon and remain around 10kt through the period, although gusts may increase up to 20kt again after sunrise Wednesday.

Outlook: Flight restrictions are expected to return Wednesday night though early Friday as a frontal zone moves through the region, bringing restrictions from rain and potentially low ceilings.

RAH WATCHES/WARNINGS/ADVISORIES

None.