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 /06Z SUNDAY THROUGH THURSDAY/

As of 140 AM Sunday...

Central NC terminals are mostly VFR at this hour despite widespread showers over much of the area, falling out of VFR cigs. But confidence is high that adverse aviation conditions will overspread central NC through 10z, lasting through at least early afternoon. The rain over the last 18 hours has been due to a surface low now over VA with a trailing cold front through the W Piedmont of NC. As this system pushes east, the rain will exit, soon after 11z at RDU, 13z at RWI, and 15z at FAY. Meanwhile, with the departing surface low strengthening off the VA coast, a backdoor cold front will drop S into NC, starting in the N 07z-09z and progressing S through 19z- 21z. Low clouds will spread in from the N behind the front, low-end MVFR cigs and vsbys much of the time but with periods of IFR cigs. Gradual improvement to VFR is possible from mid afternoon through early evening as cigs climb above 3000 ft AGL, however confidence in this occurrence and timing is low, and central NC terminals may see periodic bkn MVFR cigs lasting through 06z, with bkn clouds varying between 3000 ft and 3500 ft AGL. Surface winds will be light and variable until backdoor front passage, when winds from the NNE or NE at 12-16 kts with frequent gusts to 20-28 kts are expected, lasting from the predawn hours through early this evening, when gusts will die down but sustained winds will hold at 8-12 kts from the NNE.

Looking beyond 06z Mon, MVFR cigs will remain possible through tonight and into Mon morning, with a NNE breeze persisting. VFR conditions should then dominate through mid week, although as a couple of upper level disturbances cross the region, a few showers will be possible mainly NW (INT/GSO) Tue, with a better chance Wed/Wed evening areawide as a stronger low and front moves through, bringing gusty winds late Wed into Thu.

RAH WATCHES/WARNINGS/ADVISORIES

None.