textproduct: Raleigh

WHAT HAS CHANGED

As of 245 PM Friday...

* Marginal risk for isolated severe hail and gusty winds has been added across our southern Piedmont for Saturday afternoon/evening.

KEY MESSAGES

As of 241 PM Friday...

1) There is a low-end threat of some showers tonight in our northeast. There is a marginal threat for severe weather from isolated storms Saturday afternoon and evening in our southwest. There is a non-zero threat of storms Monday in our southeast.

2) The combination of unseasonably high temperatures, low humidity, and a passing cold front creates an "increased fire danger" window for the Piedmont region.

3) A continental Polar high and airmass over the Middle Atlantic will be supportive of frost/light freezing conditions next Tue-Tue night, but wnwly flow aloft will yield periods of high-level cloudiness that may inhibit optimal radiational cooling.

DISCUSSION

As of 241 PM Friday...

KEY MESSAGE 1... There is a low-end threat of some showers tonight in our northeast. There is a marginal threat for severe weather from isolated storms Saturday afternoon and evening in our southwest. There is a non-zero threat of storms Monday in our southeast.

Satellite imagery this afternoon depicted a weak short-wave moving over and generating showers over the OH/PA/NY/WV vicinity. At the sfc, a weak front will settle south into VA tonight before reaching somewhere near the southern Piedmont. Decaying showers associated with the upstream short-wave will possibly reach our far northeastern counties tonight. A few gusts could occur (~20 mph or so), but overall expect just trace to a few hundreds of an inch of rain with these showers.

As the front settles south into our southern Piedmont or NC/SC border tomorrow, a solid theta-e (and associated instability) gradient will set up in this vicinity. Aloft, a weak short-wave will move across the Mississippi Valley Saturday afternoon/evening. Weak forcing from this feature along with weak sfc convergence along the theta-e gradient will likely trigger isolated convection somewhere near Charlotte before expanding eastward along the NC/SC border. There is generally good agreement amongst the CAMs in CI over this general vicinity, although a few keep the convection further south (e.g. ARW/NSSL). Hodographs in this vicinity do elongate with time (but remain straight), with most guidance suggesting upwards of 25 to 35 kts of shear possible during the afternoon/evening. While boundary layer moisture will be modest, mid-level lapse rates will peak upwards of 7 C/km and with PWAT expected to be sub 1 inch limiting water loading, isolated large to severe hail may be possible with any stronger storm. Additionally, forecast soundings indicate inverted-V shapes, supportive of a stronger gust in isolated stronger storms. Any lingering convection should subside Saturday evening. There is a low-end threat of some showers tonight and also Saturday afternoon and evening. There is a non-zero threat of storms Monday in our southeast.

A much stronger cold front is expected to cross the region on Monday, though considerable model spread remains regarding the exact timing of the frontal passage. Deterministic and AI guidance have continued to trend slower, mainly favoring the afternoon and evening hours over the eastern half of NC. This delay may allow for a little bit of instability to develop with peak heating ahead of the boundary. AI models suggest a small severe threat over eastern areas of central NC, where dewpoints are expected to get up to the low 60s, a few hundred J/kg of CAPE and deep shear near 40 kts, again mainly across the east and in the afternoon. With that, confidence remains low due to a lack of significant moisture with the frontal passage, and any showers or storms are expected to be very isolated.

KEY MESSAGE 2... The combination of unseasonably high temperatures, low humidity, and a passing cold front creates an "increased fire danger" window for the Piedmont region.

Fire danger concerns remain heightened for central NC following Monday's cold frontal passage. While Sunday features near-record highs in the mid-to-upper 80s under moist southwest flow (dewpoints in the 50-60s), a sharp airmass change on Monday afternoon will see RH values plummet below 35%, particularly across the western Piedmont. Given the SPC's 40% fire weather probability and the SACC's high-risk designation for the Piedmont, we will continue to monitor the threat and coordinate with NCFS as needed.

KEY MESSAGE 3... A continental Polar high and airmass over the Middle Atlantic will be supportive of frost/light freezing conditions next Tue-Tue night, but wnwly flow aloft will yield periods of high-level cloudiness that may inhibit optimal radiational cooling.

Wnwly flow aloft will prevail across the mid-latitudes of the CONUS next week, around a sub-tropical high forecast to become re- established over the Southwest - though not to record-breaking levels of recent days. Within that fast and progressive regime, a lead shortwave trough will be in the process of progressing across and offshore the Northeast Mon night-Tue, with following rising heights and subsidence that will favor the progression of an underlying cP high from the Great Lakes to the Middle Atlantic on Tue. Although the associated airmass over the Middle Atlantic will be supportive of frost/light freezing conditions Tue morning and night, the aforementioned wnwly flow will favor periods of high- level cloudiness that the models suggest may maximize with the modest amplification of a shortwave trough across and offshore the South Atlantic states Tue night-early Wed. That cloudiness may consequently inhibit optimal radiational cooling Tue night.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

As of 154 PM Friday...

VFR conditions persist this afternoon with sswly gusts of 15 to 20 kts starting to develop at several terminals. Flow should generally weaken after sunset tonight. However, decaying showers from VA may stream across KRWI late tonight which may include a few gusty downdrafts (~20 kts or so). While some stirring of the sfc flow is likely, a strong low-level jet (45 to 50 kts) is expected to develop over the region. As such, LLWS will be possible late tonight into Saturday morning.

Outlook: A strong cold front will clear across the area Monday, with a slight chance of showers and storms mainly at KFAY in the early afternoon. Post-frontal nwly gusts of 25 to 30 kts will be possible into Monday evening.

CLIMATE

Record High Temperatures:

March 22: KGSO: 85/1948 KRDU: 89/1907 KFAY: 88/1948

March 23: KFAY: 86/1948

Record High Minimum Temperatures:

March 22: KFAY: 63/1948

RAH WATCHES/WARNINGS/ADVISORIES

None.