textproduct: Raleigh

WHAT HAS CHANGED

* No significant changes to the forecast.

KEY MESSAGES

As of 225 PM Monday...

1) Marginal fire weather concerns persist for Tuesday, although spring green-up will mitigate the threat.

2) Cold front will bring showers and isolated strong storms primarily Wednesday night and Thursday.

DISCUSSION

As of 225 PM Monday...

KEY MESSAGE 1... Marginal fire weather concerns persist for Tuesday, although spring green-up will mitigate the threat.

Southwest surface flow will ramp up once again Tue morning on the westward side of the Bermuda ridge. Nocturnal low level jetting will be decreasing and exiting by mid morning, but with good heating and deep mixing taking place, we should still be able to easily tap into winds aloft to support sustained speeds of 10-20 mph, with frequent gusts up to around 25 mph. In conjunction with these blustery winds, RH is expected to drop to a minimum of 28-40% in the afternoon, higher than today but still somewhat concerning for fire weather. The NC Forest Service officials in the field report that fuels have greened up sufficiently, reducing the threat for adverse fire conditions, particularly with borderline meteorological conditions, so an Increased Fire Danger is not needed at this time. But we will continue to monitor conditions, and we will revisit as needed.

A reminder: While the burn ban has been lifted in 81 counties in NC by the NCFS, it remains in place for Forsyth, Guilford, Davidson, Randolph, Alamance, Chatham, Stanly, Montgomery, Moore, Anson, Stokes, Rockingham, Davie, Rowan, Iredell, Cabarrus, Gaston, Mecklenburg and Union counties.

KEY MESSAGE 2... Cold front will bring showers and isolated strong storms primarily Wednesday night and Thursday.

The primary driver for precipitation this week will come from a cold front that will slowly move across the region. While showers could arrive in the Triad as early as late Tuesday night, and across the rest of the forecast area on Wednesday, widespread showers are expected Wednesday night and Thursday. The chance of showers will linger Thursday night and possibly even Friday across southern counties.

Precipitation amounts: this appears likely to be a well-needed soaking rain for the entire area. The WPC QPF calls for a general 0.75 to 1.25 inches across the region. In addition, since the rain will not all fall in a six hour time period, but should be spread out over a day or even two days, this should maximize the potential for the ground to absorb all of the water, as opposed to having runoff. However, this rainfall will barely make a dent in the rainfall needed to overcome the drought.

Severe weather potential: the entire forecast area is in the general thunderstorm category for Wednesday, but SPC has not outlined an area with at least a 15% probability (slight risk) for Thursday yet. Thursday does appear to be the most likely day for thunderstorms, particularly Thursday afternoon, although a capping inversion appears likely to limit the instability that will be available for thunderstorms. Effective shear, on the other hand, looks to be at least 30 kt in all locations, if not 40 or 50 kt depending on the location and model. This is likely to be a typical HSLC (high shear, low CAPE) scenario for central North Carolina, which is capable of producing severe weather, but only if enough instability is realized for thunderstorms to develop. This will be closely monitored as we go through the week.

AVIATION /18Z MONDAY THROUGH SATURDAY/

As of 1220 PM Monday...

VFR conditions are likely to hold across central NC terminals through 18z Tue. Periods of high thin clouds moving NW to SE with a few mid clouds are expected, mainly this afternoon through evening, but otherwise fair skies are likely with no vsby restrictions. Surface winds will be generally from the SW or SSW, at 10-15 kts with infrequent gusts to 15-22 kts this afternoon, under 10 kts tonight into early Tue morning, then 12-18 kts with frequent gusts to 18-28 kts (highest INT/GSO) after mid morning Tue.

Looking beyond 18z Tue, gusty winds will persist through Tue afternoon, weaken toward nightfall, then become gusty again Wed. VFR conditions will hold through Wed, then sub-VFR conditions will become likely Wed evening (especially NW) through Wed night and much of Thu, as a cold front brings a high chance for showers and a few thunderstorms with blustery winds. VFR conditions should then return behind the front Wed night, lasting through Sat.

RAH WATCHES/WARNINGS/ADVISORIES

None.