textproduct: Raleigh

WHAT HAS CHANGED

* Isolated pockets of heavy rainfall remain possible through this evening, and are possible again Tue.

KEY MESSAGES

As of 205 PM Monday...

1) Numerous showers and isolated to scattered storms both today and Tue may produce pockets of heavy rainfall, although not everyone will see heavy rain.

2) Wetter pattern begins to break down, although most of the extended forecast will still have a chance of showers.

DISCUSSION

As of 205 PM Monday...

KEY MESSAGE 1... Numerous showers and isolated to scattered storms both today and Tue may produce pockets of heavy rainfall, although not everyone will see heavy rain.

As previous shifts have noted, we remain in a high-PW environment near 2", about 175-200% of normal, with a deep feed of moisture from the Atlantic and Gulf from the surface through the mid levels. This is manifesting in spotty areas of decent rain rates, from a tenth to over a half inch per hour within storm clusters from just south of the Triad into the Triangle and down into the S Coastal Plain and E Sandhills. The surface front analyzed from the S Plains across the Mid Miss Valley and Ohio Valley to the E Great Lakes will remain to our N through Tue, keeping us status quo within steady influx of warm moist air amidst broad SBCAPE and shots of dynamic forcing for ascent, including that generated by subtle mid level perturbations and MCVs being drawn N and NNE around the periphery of the offshore- centered mid level anticyclone. RAP-based mesoanalysis shows 1000- 2500 SBCAPE over the area, supporting the current convection despite deep layer bulk shear generally under 20 kts. Hi-res models show the current area of showers and storms persisting over mainly our central and SE, as activity continues to track NNE from SC into early evening. We'll also see convection blossoming over the higher terrain spreading NE and E late afternoon through this evening affecting the N and W Piedmont, with lift boosted in the right entrance region of a jet core to our N, augmented by MCVs rolling up from the Gulf Coast. Will start with highest pops from the Hwy 1 corridor east, followed quickly by a peak on pops from the Triangle to the N and W through this evening. While river and stream levels are very low due to the ongoing drought conditions, any high rain rates could result in rapid runoff and ponding of water on roads and in low and poor drainage areas. The exit of dynamic forcing and nocturnal relative stabilization should result in a trend to a lull in pops after 2 AM tonight.

Looking ahead to Tue, with no significant change in air mass, source region, or forcing mechanisms, persistence should rule. After considerable overnight stratus and patches of fog, another slow lifting of this low deck is expected through the morning, then any bit of insolation and heating will push up CAPE values to support scattered to numerous showers and storms in the still-damp column. While this will mean another threat of storm clusters with locally high rain rates, exactly where this rain might fall is difficult to pinpoint. The latest HREF members show a somewhat similar pattern to today, with the highest afternoon pops in our SE, trending to having the higher pops in the NW by evening as activity rolls off the mountains. Overall, though, pops will be above normal, and isolated street flooding will again be possible.

KEY MESSAGE 2 ... Wetter pattern begins to break down, although most of the extended forecast will still have a chance of showers.

A stationary front that has been anchored across Virginia will slide south through North Carolina Wednesday night into Thursday. While this will still keep a high chance of rain in the forecast, flow out of the west will not contain as much moisture as the southerly flow that has been occurring over the weekend, and overall rain totals should be less. Much of Thursday night and Friday should be dry across the area. However, the front should then become hung up across South Carolina and Georgia through the weekend, and a wave of low pressure will ride along the front. The low should bring some higher chances of rain back into the forecast, primarily to the south of US-64 and the highest on Saturday and Saturday night. The front will then continue to push south, and the chance of rain will decrease. Highs will be in the 80s Wednesday, Thursday, and Friday, with highs dropping into the 70s for Saturday, Sunday, and Monday.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

As of 752 PM Monday...

Scattered to numerous showers/storms have overturned the air mass over most of the region which lowers the chance of additional showers. However, the western and northern Piedmont continued prime for showers/storms for the next few hours through 05z-06z. This is especially evident in the Triad which is near the developing showers/storms near the Blue Ridge at 00z/this evening. It appears most of the showers will begin to weaken and fade away around 06z. Low stratus is then expected to develop at most locations between 05z and 08z (IFR). Some MVFR fog is also possible. This stratus should linger in the IFR category through late Tuesday morning followed by VFR conditions for a while in the early to mid afternoon. Scattered to numerous showers/storms are expected after 18z, but we will try in later forecasts to pin down the most likely areas to have sub-VFR conditions and for how long.

Looking beyond 00z Wed, the cycle of low stratus and patchy fog from late evening through mid morning will persist through Thu, with daily scattered to numerous showers and storms possible. Drier weather is expected Fri behind a cold front, but a few showers and storms may return Sat.

CLIMATE

Record High Minimum Temperatures:

May 25: KGSO: 70/2019 KRDU: 71/2019 KFAY: 71/2019

May 26: KGSO: 70/2019 KRDU: 73/2011 KFAY: 75/2004

May 27: KRDU: 72/1991 KFAY: 72/2006

May 28: KGSO: 70/2012 KRDU: 74/1914

RAH WATCHES/WARNINGS/ADVISORIES

None.