textproduct: Raleigh

WHAT HAS CHANGED

* Precipitation chances and overall rainfall amounts continue to trend down for Wednesday night into early Thursday morning.

KEY MESSAGES

As of 140 PM Tuesday...

1) A broken line of decaying showers are expected to shift across the southern Mid-Atlantic Wednesday evening into the early overnight period.

2) A typical summertime pattern develops this weekend into next week, with warm to hot temperatures.

DISCUSSION

As of 140 PM Tuesday...

KEY MESSAGE 1... A broken line of decaying showers are expected to shift across the southern Mid-Atlantic Wednesday evening into the early overnight period.

Central NC will be situated between a northern and southern- stream shortwave troughs Wed morning, with the former positioned over the Great Lakes and the latter shifting over the western Atlantic. Underneath the core of the northern-stream wave, an occluding surface low over southern Ontario will force a cold front through the Ohio Valley Wed afternoon and through the southern Mid-Atlantic late Wed evening into the early overnight hours.

Low-lvl moisture return will be significantly delayed by an area of low pressure developing over the western Atlantic, in association with the southern-stream wave becoming absorbed into the sharpening northern shortwave. This will likely keep the preceding air mass over the Carolinas considerably more stable than previous forecasts and lead to a weakening/decaying trend within the broken line of deeper convection along and ahead of the front. Some global models suggest weak negative theta-e mid- level lapse rates, which suggests conditional instability may be released behind the front, but with primary DPVA expected north of the area and moisture transport weakening substantially east of the mountains, maintenance of of deep convection appears unlikely.

Latest HREF/REFS LPMM total precipitation fields reflect this trend in the guidance and suggest most locations will now receive only trace amounts to less than 0.1". Some locally higher totals may be possible across the NC/VA Foothills into the western Piedmont, where deeper convection may still exist before rapid weakening takes place and better mid/upper level forcing will overlap the band of mid-lvl moisture.

KEY MESSAGE 2... A typical summertime pattern develops this weekend into next week.

After Wednesday's frontal passage, surface high pressure will build into the region through the end of the week and then shift offshore on Saturday. At the same time, a mid-level ridge will move over the region. Once the high shifts off the southeast coast and the ridge is centered over the region, southerly flow will prevail at the surface, allowing for increasing temperatures. Temperatures will really increase starting Saturday when central NC will have maximum temperatures in the mid-to-upper 80s, increasing to the upper 80s to low 90s on Sunday, Monday, and Tuesday. This pattern is expected to continue into at least mid-week, leading to an extended period of warm to hot temperatures. Also during this time, a few waves of weak energy will move over the top of the ridge. This may allow a few showers and storms to develop each afternoon, especially in the northwest Piedmont. However, weak forcing should keep the region mostly dry.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

As of 745 PM Tuesday...

VFR conditions are expected, with high confidence, over central NC terminals for the next 24 hours, as high pressure centered off the Mid Atlantic coast continues to extend westward over NC. A cold front will approach the region from the northwest late Wed, leading to an increase in VFR clouds based around 6kft AGL after 18z, mainly at NW terminals (INT/GSO). No vsby restrictions are expected through Wed. Sfc winds will be light from the SE or S through morning, shifting to SSW or SW 8-13 kts by midday Wed.

Looking beyond 00z Thu, bkn clouds will dominate Wed evening and night, and a few showers are possible mainly at INT/GSO/RDU as the front passes through, but VFR conditions should dominate. Otherwise, VFR conditions and mostly fair skies will prevail Thu through Sun, although gusty NW winds are expected much of Thu, and the risk for patchy daybreak sub-VFR fog will increase by Sun morning.

CLIMATE

Record High Temperatures:

May 16: KGSO: 92/1941 KRDU: 94/1941 KFAY: 96/1933

May 17: KGSO: 94/1915 KRDU: 92/1947 KFAY: 97/1941

May 18: KGSO: 95/1911 KRDU: 95/1906 KFAY: 96/1911

Record High Minimum Temperatures:

May 17: KGSO: 69/1991 KRDU: 71/2025

May 18: KGSO: 70/2015 KRDU: 72/1896 KFAY: 71/2018

RAH WATCHES/WARNINGS/ADVISORIES

None.