textproduct: Raleigh

WHAT HAS CHANGED

* In Thursday's drought update, conditions have worsened to an Extreme Drought over much of north-central NC, with Severe Drought elsewhere in central NC.

* Confidence is increasing that a backdoor front early Sun will bring noticeably cooler air especially into our northern areas by Sun afternoon, lasting into Mon.

* Rain chances for late Mon night through Tue are looking less clear.

KEY MESSAGES

As of 155 AM Friday...

1) Much above normal temperatures will persist through Saturday. Cooler air arrives Sun.

2) High chances for measurable rain late Sat through Sun morning, but amounts are unlikely to significantly improve our worsening drought. By Tue, a pattern shift will allow for more typical diurnal scattered showers and storms through the middle and end of next week.

DISCUSSION

As of 155 AM Friday...

KEY MESSAGE 1... Much above normal temperatures will persist through Saturday. Cooler air arrives Sun.

The combination of surface high pressure centered NE of the Bahamas extending over the Southeast coast and an 850 mb anticyclone centered near SAV will continue to bring above-normal low level thicknesses to the Carolinas today through Sat, up to 25-30 m above normal. We'll maintain a weak NW steering flow aloft, and with a lack of moisture influx through the low and mid levels, any clouds will be largely limited to sct to briefly bkn high-base cu this afternoon. This high insolation with elevated thicknesses favors highs around 10-15 degrees above normal today, in the mid 80s to around 90. Given that today will be our third consecutive day of atypically warm temperatures, our Heat Risk is forecast to be a Level 2-of-4/Moderate for portions of central NC, including from the Triangle area and N Sandhills into the Coastal Plain, largely due to the high heat impact levels during the day, from late morning through the afternoon when isolation will be strongest. This Level 2 indicates that this heat may begin to affect anyone without adequate cooling or hydration. Those who must work or exert in direct sunshine at the hottest part of the day should be extra cautious, stay well hydrated, and take cooling breaks in the shade. By Sat, thicknesses will remain around 25 m above normal, but the approaching upper level shortwave trough and corresponding surface low from the NW is likely to bring enough increasing high and mid clouds in the afternoon to help curb the heat impacts. By Sun, a backdoor front expected to drop through the area is expected to bring in a cooler air mass from the north, resulting in highs that will be 10-20 degrees cooler than Sat, coolest N.

KEY MESSAGE 2... High chances for measurable rain late Sat through Sun morning, but amounts are unlikely to significantly improve our worsening drought. By Tue, a pattern shift will allow for more typical diurnal scattered showers and storms through the middle and end of next week.

A weak mid level shortwave trough will eject from the large closed low centered over S Saskatchewan today, crossing the N Great Lakes region through tonight, undercutting an omega block over E Hudson Bay and N Quebec. This wave will then track slowly SE through the central Appalachians Sat and amplify over the Northeast states and Mid Atlantic region Sat night/Sun as it begins to get absorbed into another large gyre over the NW Atlantic. This wave will be accompanied by a surface low tracking along a frontal zone from lower MI across NE OH through tonight, before a new low forms over WV/VA early Sat and shifts over and off the VA Tidewater late Sat into Sat night. Moisture with these features is not terribly deep or plentiful, confined through the mid and lower levels as moisture transport will be modest. But PWs in the 125-150% of normal range and the incoming DPVA and low level mass convergence along and S of the surface low do support a window of high pops, starting mid afternoon Sat in our W then spreading E through Sat night before exiting from our SE Sun afternoon. Confidence is high that everyone should see at least a tenth of an inch, and the 75th percentile total rainfall is right around a half inch, all suggesting that the most likely amounts will be around a quarter to half inch. This rain will be very welcome, but it is not expected to be sufficient to put much of a dent into the ongoing and worsening drought. Regarding thunder chances, forecast MUCAPE values are pretty meager, generally under 250 J/kg, albeit with decent deep layer bulk shear around 30 kts. Expect any storms to be scattered and disorganized, with a low chance of strong storms.

The aforementioned low will shift off the Mid Atlantic coast Sun, allowing the strengthening trailing backdoor cold front to push southward through NC, propelled by increasing NNE flow around the exiting low. The cooler air mass wedging in from the NNE is likely to bring a fairly sharp cooldown by Sun evening, although subtle timing differences remain, resulting in a lower confidence in the specifics of Sun highs. The most likely highs Sun are in the 60s N and 70s S, but with timing differences, highs may still be able to reach the 70s in the N.

Precip chances get murky beyond Mon, as we trend to a faster mid level flow with flat ridging from NW Mexico across the S Plains/Mid South/Southeast by mid week, followed by further flattening to near zonal flow across the southern half of the CONUS. But the greater potential tapping of Gulf moisture in the low levels and faster mid and upper flow does suggest a trend toward more typical spring or early summer weather with nearly daily scattered showers and storms.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

As of 650 AM Friday...

VFR conditions are likely to persist over the next 24 hours, with high confidence. Only sct to briefly bkn high-base cu at 8-10kft AGL are expected, mainly this afternoon, but otherwise skies will remain fair to clear. Surface winds will be light, under 8 kt, except 8-14 kts from the W or SW 13z-23z, with isolated/infrequent gusts up to 18-22 kt, mainly at FAY.

Looking beyond 12z Sat, VFR conditions should dominate through midday Sat. The chance for sub-VFR conditions will increase as showers and a few storms sweep through the area from late Sat afternoon through Sun morning. Another round of showers and sctd storms with possible sub-VFR conditions will occur late Mon night through Tue evening.

RAH WATCHES/WARNINGS/ADVISORIES

None.