textproduct: Raleigh

WHAT HAS CHANGED

* Slight downward trend in overall rainfall totals through Sunday morning.

* Rain chances continue to increase for Wednesday.

KEY MESSAGES

As of 215 PM Saturday...

1) Much above normal temps persist today. Fairly low RH and ongoing dry fuels will lead to an Increased Fire Danger across south-central NC today.

2) High chances for measurable rain persist for later through Sun morning. Expected amounts have decreased a bit from this morning.

3) Active period of increased frequency of rain events continues into early May.

DISCUSSION

As of 215 PM Saturday...

KEY MESSAGE 1... Much above normal temps persist today. Fairly low RH and ongoing dry fuels will lead to an Increased Fire Danger across south- central NC today.

Warm and deep high pressure will hold over the Southeast coast today, yielding low level thicknesses that remain around 25 m above normal. This will again favor highs in the mid 80s to near 90, although increasing afternoon clouds in the W CWA will lower insolation a bit there during the peak heating of the day. Despite this early season heat, our records should not be threatened (record highs today are 93 at RDU and 94 at FAY, both set in 1925). Heat Risk tied to these high temps remains a Level 2-of-4/Moderate today.

Due to the low level ridging spanning to our S, we'll continue to lack a tap of high low-level moisture into the area today, resulting in min dewpoints in the mid 40s to around 50 over much of the area. These values, along with the warm temps, will result in min RH values in the 25-35% range across the S, and in combination with very dry fine fuels and infrequent gusts up to 15-20 mph today will support an Increased Fire Danger over our southern sections today. A statewide burn ban remains in effect until further notice.

KEY MESSAGE 2... High chances for measurable rain persist for later through Sun morning, though amounts have decreased a bit from this morning.

Aloft, some s/w energy associated with a mid-level s/w tracking across the Great Lakes/Northeast will move ewd across the area this evening, helping further suppress the ridge southward. Another s/w is expected to move quickly across the TN Valley this evening and across the region tonight/early Sunday. At the surface, as of 17Z, the low was located over NW PA, with a cold front draped sswwd across the TN Valley and into the ARKLATEX, and a quasi-stationary front draped ssewd across the mid- Atlantic to off the NC coast. A remnant MCV over nrn GA lifting nwd along the Appalachians and interacting with the s/w aloft has already started producing showers and isolated storms over the mtns east of the cold front. Chances and coverage of showers should increase as the wave moves ewd across central NC and the surface low drops sewd along the quasi-stationary boundary. However, thunder chances remain somewhat limited, with forecast (NAM) MUCAPE of less than 300 J/Kg and 6-Km bulk shear of 20-30 kts. The cold front will remain north and west of the area tonight as the low tracks across SE VA/NE NC and offshore, then finally begin to move into the area Sun morn as the low lifts newd along the mid-Atlantic coast.

The hi-res guidance suggests some renewed convective development along the front as the aforementioned s/w aloft tracks across the area mid-day Sun, but it is all a matter of the timing and location of both features where that convection will occur. The highest chance for any showers/storms Sun will generally be across the srn Piedmont and Sandhills of NC over a limited window of time. Temperatures will also depend on these features, with potential for a large spread in highs from NE to SW. In the wake of the front, the ridge will build into and strengthen over the area through Sun night before slowly shifting ewd and weakening Mon/Mon night. For now, have highs ranging from low/mid 60s NE to low 80s SW on Sun, with lows generally in the 40s. Near to slightly below normal temperatures expected Mon and Tue.

Total rainfall amounts are expected to be generally half an inch or less, though a couple spots could see a little more. Not a drought- busting rain event by any means, but any rain is welcome.

KEY MESSAGE 3... Active period of increased frequency of rain events continues into early May.

Precipitation chances continue to trend down for Tues as models are trending stronger with the ridge axis in place ahead of perturbed flow and narrow mid-level moisture axis that spreads into the Mid- Atlantic on Tues. This initial wave does however work to begin breaking down the ridge into a quasi-zonal flow regime and near- normal PWAT values.

The forecast for Wed is shaping up to be our next chance for widespread light rain. A convectively modified low-amplitude shortwave over the central/southern Plains Tues evening negatively tilts as it moves through the TN Valley and into the Mid-Atlantic Wed morning. This wave along with forcing along the nose of strengthening upper-lvl jet streak will supply deep lift within a plume of richer PWAT of 1 to 1.5 inches. Reasonable low-end amounts show at least measurable across all of central NC with higher amounts around 0.5". In the wake of the mid/upper-lvl moisture band, continued moist and warming boundary layer may support additional showers/storms during the afternoon/evening hours; although this scenario is highly conditional and dependent on several conditions to be met.

There may be some hope for a more appreciable precipitation event just beyond the forecast period into early May. There is a signal within ensemble guidance for a stalling frontal boundary over the Mid-Atlantic/Southeast and weak low pressure spreading more steady rainfall along and north of its track. Member MSLP tracks range from the through the Southeast to over the Carolinas, so forecast confidence in occurrence remains low at this time.

AVIATION /18Z SATURDAY THROUGH WEDNESDAY/

As of 220 PM Saturday...

Through 18Z Sunday: The primary weather feature during the 24 hour TAF period will be a cold front progged to move across central NC. With this front, there will be a period of light rain and low-MVFR cigs (and perhaps some localized IFR cigs). The light rain will initially be possible as early as 22Z across the Triad and 00Z across the rest of central NC. Any rain through at least 07Z should be fairly light and occur with VFR or high-MVFR cigs. After 09Z, we'll begin to see the cold front, in backdoor fashion, move from north to south across central NC. Right up against and in the wake of the front cigs may further drop to low-MVFR or high-IFR and linger through 12-15Z Sunday as cooler air moves in behind the front. In addition to the rain chances, wind will turn to the north in the wake of the front and increase to 15-20kt with higher gusts after 14Z as some BL mixing increases with daytime heating. It's worth noting the many of the NWP sources suggest that the low-MVFR cigs may persist into the afternoon from RDU to FAY eastward.

After 18Z Sunday: behind the backdoor front, sub-VFR cigs will dominate much of late Sun and Sun night, with the lowest cigs at RWI and RDU. VFR conditions should return briefly for Mon, but another round of low cigs is possible Mon night into Tue. Rain chances and potential sub-VFR conditions will return Wed associated with the next front. VFR conditions should return for Thu.

RAH WATCHES/WARNINGS/ADVISORIES

None.