textproduct: Raleigh

WHAT HAS CHANGED

* No major changes

KEY MESSAGES

As of 240 PM Saturday...

1) A warm and humid day today, with afternoon showers and another round of showers/thunderstorms later tonight.

2) Limited chances of a shower or storm Sunday afternoon and Sunday night, with the greatest chances during the afternoon across the Coastal Plain.

3) A northeast flow will result in near average temperatures and lower humidity on Tuesday and Wednesday that will feel cooler than recent days.

4) The low and mid level flow will become more east and southeasterly late in the work week and weekend resulting in warming temperatures, an increase in humidity, and an uptick in rain chances.

DISCUSSION

As of 240 PM Saturday...

KEY MESSAGE 1... A warm and humid day today, with afternoon showers and another round of showers/thunderstorms later tonight.

Last night into this morning, a boundary set up over central NC, bisecting the region in half. Shower activity started developing along this boundary as it started lifting north over Wake county just after noon. PWs over the region are very high (around 2-2.3 in) which will allow showers to be efficient rain producers this afternoon. This will combine with slow cell motions to create an isolated flooding threat, especially if a shower moves over an urban or poor drainage area. The area of any showers/thunderstorms should increase over the next few hours as the boundary continues north and outflows from previous showers/storms provides additional areas of lift.

Later this evening into tonight, an additional area of shower/thunderstorm development may be possible as a pre-frontal trough moves through central NC from the west. Any rain that develops due to this should move faster than this afternoon's rain, leading to a lower flooding threat.

In terms of the strength of the cells today, severe weather is not currently expected. CAPE values this afternoon look to maximize around 1500-2000 J/kg, with low shear values. This should allow for a few cells to get tall enough to produce lightning, but keep any winds with them below severe strength. However, a few water-loaded downdrafts could produce brief periods of strong gusty winds this afternoon.

KEY MESSAGE 2... Limited chances of a shower or storm Sunday afternoon and Sunday night, with the greatest chances during the afternoon across the Coastal Plain.

A mid level short wave trough across TN and AL at midday today will be located just east of the Blue Ridge on Sunday morning and then move offshore by Sunday evening. The best forcing for ascent will be east of this feature and should be exiting our eastern areas during the afternoon. Deep layer moisture will be above average areawide on Sunday but greatest across the east. Expect Sunday to be less convectively active than today with the greatest threat of a shower or storm across the east during the afternoon. However, a cold front will trail behind the short wave trough and move across the area late Sunday night and there is a limited chance or a shower or storm in the lingering moisture ahead of the front on Sunday night. Highs should range in the upper 80s to lower 90s with lows near 70.

KEY MESSAGE 3... A northeast flow will result in near average temperatures and lower humidity on Tuesday and Wednesday that will feel cooler than recent days.

An anomalously strong mid-level ridge centered in the TN Valley on Tuesday and Wednesday will result in a northerly flow at mid levels across VA and the Carolinas while a 1030 mb surface high pressure system centered over New England will produce a northeast low level flow across the area. The result will be near to slightly above seasonal temperatures that will feel notably cooler than recent weeks. Highs should range in the lower to mid 80s both days and nighttime lows in the lower to mid 60s with some upper 50s (maybe mid 50s) possible in the typically cooler locations. Dry weather with partly cloudy skies and a noticeable northeast breeze at times are expected during the period.

KEY MESSAGE 4... The low and mid level flow will become more east and southeasterly late in the work week and weekend resulting in warming temperatures, an increase in humidity, and an uptick in rain chances.

The upper-level ridge at mid levels weakens late in the week and becomes more west to east oriented as a mid level weakness/upper low organizes near the Bahamas and shifts west into the northern Gulf. Meanwhile the narrow surface ridge extending southwest into VA and the Carolinas weakens late in the work week as a weak coastal front tries to develop off the Carolina coast. The result for our area will be an increase in temperatures, moisture and clouds and depending on the track and evolution of the upper low and coastal font, an uptick in rain chances over the weekend that could increase further early next week.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

As of 710 PM Saturday...

24 hour TAF period: Scattered showers and a few storms will be possible through this evening and into tonight as a weak surface low lifts across the area ahead of an approaching cold front. Some reduced vsbys and breezy conditions will be possible with the showers/storms. Due to increased boundary layer moisture, there could be a period of IFR to perhaps LIFR ceilings and/or sub-VFR visibilities late tonight/early Sunday morning. Confidence on how far east and until when the convection will last is low, and thus so is the timing and development of sub-VFR cigs/vsbys east of the convection. Restrictions may remain in place until the front moves through central NC Sunday afternoon. There will be a limited risk of shower/storm development along the frontal passage Sunday afternoon into the evening.

Outlook: There will be a non-zero chance of low stratus and/or fog development again on Monday morning. VFR conditions are then generally expected to prevail.

RAH WATCHES/WARNINGS/ADVISORIES

None.