textproduct: Raleigh

WHAT HAS CHANGED

As of 150 AM Saturday...

* Introduced a 20-percent chance of widely isolated showers or storms over the Piedmont late today and this evening.

KEY MESSAGES

As of 150 AM Saturday...

1) A backdoor cold front moves in tonight. We cannot rule out a low- end threat of a few widely isolated storms between 4 and 10 pm.

2) Dry weather and near-record heat will maintain fire weather concerns through much of next week.

3) Near record temperatures possible Tuesday through Thursday.

DISCUSSION

As of 150 AM Saturday...

KEY MESSAGE 1... A backdoor cold front moves in tonight. We cannot rule out a low- end threat of a few widely isolated storms between 4 and 10 pm.

A cold front draped over the lower OH valley and Mid-Atlantic states will push through in backdoor fashion tonight into early Sun. Cool high pressure of around 1032 mb over the Great Lakes will slide into New England by Sun morning, aiding the front to push south and west from SE VA and NE NC tonight and overnight.

Ahead of the front, a pre-frontal trough will pass through during the day, with winds being out of the north most of the afternoon. The airmass will continue to warm from Fri, with low-level thicknesses around 1390m, supportive of low/mid 80s for most of central NC. This is about 10-15 degrees above normal.

A weak area low pressure appears to develop this afternoon near the Charlotte area ahead of the backdoor front. As that happens, it may aid some pooling/convergence of moisture across the Piedmont, Triad, and Triangle for areas along/south of I-40/I-85 and US-64. In this region is where several HREF members are indicating some weak instability on the order of 500 J/kg, in an environment of 20-25 kt of northwesterly deep shear. Moisture is limited with PW's near normal and there appears to be a capping inversion in place. Nevertheless, several CAM solutions do indicate a few widely isolated showers or storms developing initially along the Triad and progressing south and east between 4 and 10 pm, before dissipating over the southern Piedmont and Sandhills. Confidence on this developing given sub-optimal conditions is low. However, cannot fully rule it out with fairly steep 0-3 km lapse rates. If a shower or storm can manage to form, it could feed on some modest DCAPE and inverted-V profiles seen in forecast soundings for some brief 20-30 kt gustiness with their outflow. We opted to introduce 20-percent shower/storm chances in the aforementioned area given the setup. As the front moves through, we could see some gusts from the east of 15- 18 kt within the tighter pressure gradient and cold advection.

KEY MESSAGE 2... Dry weather and near-record heat will maintain fire weather concerns through much of next week.

Dry conditions will persist across the region as minimum RH values drop into the 2530% range this weekend and throughout next week, particularly from Tuesday through Thursday. While the pressure gradient remains relatively relaxedlimiting peak wind gusts to the 1520 mph rangethe lack of significant moisture recovery is notable. Although the forecast combination of humidity and wind is expected to remain just below official "Increased Fire Danger" or "Red Flag Warning" criteria, elevated concerns will persist until a wetting rain occurs. With no meaningful precipitation on the horizon, the statewide burn ban for North Carolina remains in effect.

KEY MESSAGE 3... Near record temperatures possible Tuesday through Thursday.

As the Bermuda high offshore continues to influence the Mid-Atlantic region with warm south/southwesterly flow through the week expect temperatures to climb into the low 90s by Wednesday. Expect temperatures to continue to be 20 degrees above normal through late week with near to record breaking temperatures in the low 90s expected at all 3 climate sites (GSO/RDU/FAY) each day mid to late week.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

As of 600 AM Saturday...

There is high confidence in VFR conditions to start the TAF period. A backdoor cold front will move in later today and tonight as cool high pressure settles across the Mid-Atlantic states. Ahead of the front, several CAM solutions are indicating a low-end threat of some showers and a widely isolated storm or two. Instability is weak, but cannot fully rule out this threat given some moisture pooling along the westward moving frontal zone. The best chance based on the HREF ensemble would be at GSO, INT, and RDU in the hours of 20-24z. For now, given low confidence, kept PROB30 groups. As the front moves through, winds from the north will shift out of the east late tonight into Sunday morning, with some brief gusts of 15-18 kt upon passage. Moisture pooling along the front and weak upslope will favor the chance of MVFR stratus at GSO/INT early Sun morning. Stratus cannot be ruled out at RDU/FAY but confidence is too low to include at these terminals.

Outlook: Morning stratus is possible Mon in a return flow regime, most favored at GSO/INT and RDU. VFR should otherwise prevail through midweek.

CLIMATE

Record High Temperatures:

April 11: KFAY: 90/2001

April 13: KGSO: 88/1930 KRDU: 89/1922

April 14: KGSO: 90/1922 KRDU: 91/1941 KFAY: 93/1922

April 15: KGSO: 90/2006 KRDU: 92/1941 KFAY: 95/2006

April 16: KGSO: 88/2002 KRDU: 92/1941 KFAY: 94/2006

April 17: KGSO: 90/1967 KRDU: 93/1896 KFAY: 92/1941

Record High Minimum Temperatures:

April 13: KGSO: 61/2019 KRDU: 66/1930

April 15: KGSO: 65/2006 KRDU: 64/1993

April 16: KGSO: 66/2006 KRDU: 64/1912 KFAY: 69/1934

April 17: KGSO: 63/2002 KRDU: 67/1896 KFAY: 66/1921

RAH WATCHES/WARNINGS/ADVISORIES

None.