textproduct: Raleigh

WHAT HAS CHANGED

As of 1255 PM Monday...

* Possible low-end fire concerns during the day on Wednesday.

* High confidence in at least a period of light to moderate rain between Saturday evening into Sunday.

KEY MESSAGES

As of 1255 PM Monday...

1) Much warmer Tue into Wed ahead of a cold front. The front is largely dry and could warrant some low-end fire danger concerns.

2) Widespread light to moderate rain is becoming increasingly likely late Sat night through Sun. Forecast details, such as amounts and areal coverage, remain highly uncertain.

DISCUSSION

As of 1255 PM Monday...

KEY MESSAGE 1... Much warmer Tue into Wed ahead of a cold front. The front is largely dry and could warrant some low-end fire danger concerns

A warming trend, albeit short, is set to take hold tomorrow and into Wed ahead of a cold front set to move through the region midweek. High pressure is currently out over eastern NC. Tonight, while the high shifts toward and off the coast, return flow will set in across the region. However, that will not fully set in until tomorrow. As such, lows tonight will still be cold but just not as cold as we have been. Most areas in central NC will hover in the mid to upper 20s.

A welcomed warmup sets up Tue as the high shifts offshore and return flow set in across the southeast. The airmass building east with flat ridging spreading in support highs generally into the 60s tomorrow, which should put us at about 10 to 15 degrees above normal. Some places in the southern Piedmont may briefly touch 70. For reference, the last time we were 60 or above was Jan 11 for Greensboro and Raleigh, where highs were 64 and 68, respectively. For Fayetteville, it was Jan 22, where the high was 63 degrees. As such, these highs will feel great from the cold we have experienced.

A cold front is slated to move through during the day on Wed. Much of the guidance brings it through during the late morning or afternoon, but the cold air does not fully build south until Wed night. Guidance has continued to trend drier with rain chances, with little if any measurable QPF, with the best chance across the south Wed morning. Highs should still manage to get into the upper 50s NW to mid 60s SE. Depending on how fast dewpoints lower behind the front, there could be some low-end fire danger concerns Wed afternoon with a combination of mild temps, low RH, and brief gusts of 20-25 mph.

KEY MESSAGE 2... Widespread light to moderate rain is becoming increasingly likely late Sat night through Sun. Forecast details, such as amounts and areal coverage, remain highly uncertain.

A mid/upper level trough is forecast to meander off the CA coast through midweek before kicking eastward on Fri. This wave is forecast to shift across the southern Plains and lower MS Valley as a southern stream perturbation on Sat, then into the Southeast, OH Valley, and Carolinas on Sun. The surface cyclogenesis pattern seems to be settling in to a Miller-B type configuration based on the 06- 12z ensemble guidance. This results in an initially primary surface low over the southern Plains that shifts into the Ohio Valley before secondary cyclogenesis develops long the common CAD/maritime boundary east of the Appalachians on Sun. Partial thicknesses suggest an onset of mixed p-type can not be ruled out, but given the strong horizontal-thermal advection (HTA) pattern, this is becoming increasingly unlikely and would be more typical of weak HTA patterns.

A quasi-stationary boundary draped across the Southeast on Sat will provide a focus for favorable ascent on its poleward side as strengthening WAA and moist-isentropic ascent develop over the Carolinas, deepest and strongest over the NC Piedmont. This will likely result in widespread light to moderate rainfall as early as Sat evening, but more likely Sat night into Sun. The evolution of mesoscale details is fairly uncertain at this time range and results in a wide range in potential rainfall amounts (as much as 1" differences within the most likely range between the 25th-75th percentiles). This results in a low confidence rainfall forecast. At the very least, a period of beneficial rainfall appears likely for the Piedmont to help relieve some of the worsening drought conditions.

Alternate scenario: There is a signal in the deterministic guidance that the steady rain may lift northward into VA by Sun afternoon and result in a lull in the light/moderate rain before a line of decaying moderate, to perhaps heavy, band of rain and elevated convection shifts across the area ahead of the cold front. This scenario would cut into the period of beneficial soaking rain and severely cut into rainfall amounts with just isolated pockets of > 1 inch, and dependent on the track of the southern stream trough, perhaps only occurring northwest and south of central NC.

AVIATION /18Z MONDAY THROUGH SATURDAY/

As of 1230 PM Monday...

VFR conditions are likely over the 24 hour TAF period. This morning's deck of VFR clouds will continue to thin and move east across the region at around 8-10kft. Otherwise, light winds should continue to shift to southerly over the next few hours. Tonight, an area of fog remains possible in the west and south, however confidence is still too low to include in the TAFs.

Outlook: Wednesday morning, LLWS is expected ahead of a cold frontal passage. Rain chances and gusty winds will be possible with the front Wednesday. Additional rain chances will return Friday, with more widespread chances and the potential for flight restrictions over the weekend.

RAH WATCHES/WARNINGS/ADVISORIES

None.