textproduct: Raleigh

WHAT HAS CHANGED

* No major changes with the afternoon forecast update.

KEY MESSAGES

As of 200 PM Wednesday...

1) Seasonably warm conditions develop and persist through Saturday.

2) Measurable precipitation chances and frequency of events increase starting this weekend through the end of April, although no significant rainfall is expected.

DISCUSSION

As of 200 PM Wednesday...

KEY MESSAGE 1... Seasonably warm conditions develop and persist through Saturday.

A high-latitude omega blocking pattern is expected to develop over Canada as early as Thurs and persist into the weekend. This will allow for weak southwesterly surface flow to persist over the area and steadily raise low-level thicknesses by 2-5m each day. These thicknesses and deep, boundary-layer mixing will likely support unseasonably warm temperatures --10-15 degrees above normal-- beginning this afternoon through Sat. A weak area of low pressure is expected to track along a stalled boundary over the Mid-Atlantic late Sat into Sat night and push a weak cold front through our area by Sun morning; effectively settling daytime temperatures back to near normal.

Based on these temperatures, Heat Risk is highlighting Minor to Moderate levels (Level 1 and Level 2 respectively) through Sat. This level of heat will primarily affect those individuals who are especially sensitive to heat and without access to adequate cooling and/or hydration. One positive is that the air mass will remain very dry with 30-40 degree dew point depressions during peak heating, and result in minimum RH values in the 20-30s.

KEY MESSAGE 2... Measurable precipitation chances and frequency of events increase starting this weekend through the end of April, although no significant rainfall is expected.

The forecast pattern slowly evolves underneath the high- latitude omega blocking pattern with troughing over the northern/central Plains and riding over the Great Lakes. A gradual eastward progression is expected into mid-week next week as a series of shortwaves gradually break down the ridge. There is a signal in the guidance for two main chances for measurable rainfall through the forecast period; late Saturday into Sun and Tuesday.

Late Saturday into Sun: A convectively modified shortwave ejecting over the Ohio Valley Sat afternoon is expected to shift across the Mid-Atlantic Sat evening into Sun morning. This feature, along with eastward advection of seasonably anomalous deep-layer moisture, will help direct convectively perturbed westerly flow over the Carolinas. Forcing for ascent will be overall quite weak and localized along the track of MCV's from upstream convection so significant precipitation is not expect. Expect primarily trace amounts to around 0.3".

Tuesday: A more significant trough is forecast to pivot from the Four Corners Region to the Great Lakes from Sun to early Tues around the parent closed-low over Saskatchewan/Manitoba. Once again, the Carolinas will only see glancing influence from the trough and mainly directs another plume of seasonably anomalous deep-layer moisture and perturbed westerly flow. This band of moisture is surprisingly well modeled in available guidance to bring briefly light stratiform rain to the region Tues morning. Then, in its wake, lingering low level moisture and warm boundary layer temperatures, may continue to support scattered afternoon/evening showers and storms. Predictability of storm intensity is too low at this time.

AVIATION /00Z THURSDAY THROUGH MONDAY/

As of 649 PM Thursday...

VFR conditions persist this evening while light radar echoes move across the northern Coastal Plain. A few light rain drops may reach KRWI the next few hours, but overall expect this precipitation to be non impactful. Residual gusts should subside here with loss of heating. Light to calm winds will otherwise persist through the rest of the 24 hour TAF period under VFR skies.

Outlook: Dry weather and VFR conditions are generally expected to persist through the work week. The next best chance for more widespread light rain and associated restrictions returns Saturday as a cold front moves through the region.

RAH WATCHES/WARNINGS/ADVISORIES

None.