textproduct: Raleigh

WHAT HAS CHANGED

* No major changes

KEY MESSAGES

As of 215 AM Friday...

1) After dry weather today and only a slight chance of showers and storms in the far west on Saturday, moisture and probability of convection will increase on Sunday and continue into at least early next week.

DISCUSSION

As of 215 AM Friday...

KEY MESSAGE 1... After dry weather today and only a slight chance of showers and storms in the far west on Saturday, moisture and probability of convection will increase on Sunday and continue into at least early next week.

There is high confidence that a positively-tilted mid/upper trough will approach from the OH/TN Valleys this weekend. While the trough should still be far enough west to keep much of central NC dry on Saturday outside of the far western Piedmont where POPs are slight chance, it will slowly make its way east on Sunday and Monday, with deep SSW flow ahead of it bringing increasing moisture (PW values of 2-2.5 inches, or 125-150% of normal). Despite widespread cloud cover, high temperatures in the 80s and dew points in the 70s should still allow for weak to moderate instability to develop. And by Monday, embedded upper impulses and possible upper divergence from a jet over the Appalachians may provide some forcing for ascent. All of these ingredients should result in widespread showers and storms from Sunday into Monday night, and ensemble mean QPF is generally in the 0.5-1.5 inch range on average during this time. Locally higher amounts are possible, and WPC includes our region in a marginal (level 1 of 4) risk for excessive rainfall on Monday. This certainly provides an opportunity for more relief from the ongoing drought.

Despite good model agreement on widespread rainfall on Sunday/Monday, there are still major differences between the global models on how the trough evolves. The GFS continues to keep its southern portion stronger and closes off a low over the OH Valley and Central Appalachians by Monday, and the 00z CMC does something similar. This solution would result in stronger mid-level flow and a possible severe storm threat, compared to the ECMWF which does not have a closed low over the OH Valley and thus has weaker flow overall.

The trough will lift NE and deamplify from Tuesday onward, but continued moist SW flow should result in above-normal shower and storm chances through much of the workweek, albeit gradually decreasing each day. This will keep temperatures in check with highs mostly in the 80s.

AVIATION /11Z FRIDAY THROUGH TUESDAY/

As of 620 AM Friday...

FEW/SCT fair weather cu is expected by this afternoon around 5-7 kft before gradually diminishing after sunset. Winds will remain very light to nearly calm and variable through this afternoon before becoming predominantly out of the south into the overnight. Shallow moisture return tonight may result in fleeting sub-VFR stratus, from FAY into the western Piedmont Sat morning, although confidence is too low to include at this time.

Outlook: More substantial moisture return is expected around and especially behind a warm frontal passage on Sun as it lifts northward into VA. The approach of a mid/upper level disturbance and persistent fetch of southwesterly flow into early next week will bring a risk for waves of showers/storms, maximized in the afternoon/evening with an overnight and early morning risk for sub- VFR stratus.

RAH WATCHES/WARNINGS/ADVISORIES

None.