textproduct: Raleigh

WHAT HAS CHANGED

As of 300 PM Thursday...

* Low probability of wintry mix on Monday and Tuesday.

KEY MESSAGES

As of 300 PM Thursday...

1) Beneficial light to moderate rain will continue through early this evening. Low clouds and drizzle will persist overnight, with steadier rain possible across the far south. Patchy fog will also be possible especially over the far north. Continued drizzle and light rain may continue on Friday, followed by dry and warmer conditions this weekend.

2) Low probability of wintry mix Mon into Tues morning, but predominant precip type, and amounts remain uncertain.

DISCUSSION

As of 300 PM Thursday...

KEY MESSAGE 1... Beneficial light to moderate rain will continue through early this evening. Low clouds and drizzle will persist overnight, with steadier rain possible across the far south. Patchy fog will also be possible especially over the far north. Continued drizzle and light rain may continue on Friday, followed by dry and warmer conditions this weekend.

A cold front is draped from TN into the central Appalachians and central VA, with a weak 1008 mb surface low analyzed along the front over far western NC. A subtle boundary marked by a wind shift and small temperature/dew point gradient from the associated trough is also bisecting central NC from SW to NE. SE of the boundary, SW winds are gusting up to 20-25 kts with much lighter winds behind it. Light to moderate rain will continue this afternoon, with the heaviest and steadiest rain shifting to our SE zones in the late afternoon and evening as the cold front begins to sink south into our region. Instability looks very limited with the 12z HREF depicting 100-250 J/kg of MUCAPE at most in the late afternoon and evening across the south. A heavier convective shower and/or rumble of thunder can't be ruled out, but no severe weather is expected. Not concerned about a flooding threat either given how dry it has been and rain rates being mainly light to moderate. Still, the mean flow being parallel to the front could result in some training, and can't rule out some brief heavier rates. So isolated ponding on roads is possible. On average, additional rainfall through 12z Friday is expected to range from about 0.1-0.3" over the northern Piedmont to 0.3-0.6" over the southern Piedmont, Sandhills, and Coastal Plain. But based on the HREF LPMM along with QPF from individual high-res models like the HRRR and NAMNest, localized stripes of additional 1-1.25" will be possible. Decreased today's forecast highs to mid-50s to lower-60s based on latest trends as all the rain and cloud cover are keeping us on the cooler side of guidance.

As low-level moisture lingers over the region, patchy drizzle may continue overnight especially south and east. Winds will become light, and some clearing could occur behind the cold front this evening over the northern Piedmont. Thus high-res models indicate there may still be enough lingering low-level moisture for some patchy fog there overnight. Another surface wave moving across GA/SC may begin to spread some steadier light rain into our far southern counties overnight as well. Leaned on the warmer side of guidance for tonight's lows with all the cloud cover, ranging from lower-to- mid-40s in the far north to lower-50s in the far south.

Post-frontal nely flow will lock in on Friday across central NC as lingering low-level moisture promotes continued chances for drizzle and light rain through much of the day and night. Best chances for any steadier rain will remain in the east Friday afternoon as a wave of low pressure rides along the front to our southeast. The low will pull offshore through early Saturday, ending rain chances across central NC. Highs Friday afternoon will struggle to eclipse the lower to mid 50s. Guidance is hinting at potential areas of dense fog late Friday night into early Saturday morning as well.

This weekend is shaping up to be dry with a slight warming trend with highs in the mid 60s Saturday and lower 70s Sunday.

KEY MESSAGE 2... Low probability of wintry mix Mon into Tues morning, but predominant precip type, and amounts remain uncertain.

A low amplitude northern stream wave is forecast to drift across the Northeast Sun into Mon and strong confluence in its wake will favor an eastward progression, and strengthening, of a cold Arctic surface high over the Northeast Mon into Tues. The initial surface frontal zone is expected to stall over the Southeast and off the SC coast by Mon morning and set the stage for a classical CAD pattern over at least the Mid-Atlantic.

Developing moist isentropic ascent atop the shallow sloped low/mid- level frontal boundary is expected to develop over the Mid-Atlantic, but timing and southern extent of the precipitation footprint is uncertain. The EPS has been consistently the northern most solution with precipitation directed over the Virginias while the GEPS/GEFS farther south and closer to the NC/VA border into the Triangle. Best chances will likely be along and north of the I-85 corridor.

Using top-down and nomogram techniques for expected p-type, the overwhelming model consensus is that the 850-700mb layer is expected to remain > 155dam over NC and likely will not support anything other than sleet, freezing rain, or cold rain. The surface wet-bulb zero line and strength of the warm nose will likely determine predominant p-type over our area. Unfortunately, predictability in these variables remains low for our area at this time to say much with any degree of certainty. Overall the event appears to be relatively light with low probabilities of even minor impacts, and a very real possibility that even our northern counties only receive trace amounts of cold rain. Expect details to become clearer as we approach the medium and short-range model guidance.

AVIATION /19Z THURSDAY THROUGH TUESDAY/

As of 200 PM Thursday...

24-hour TAF period: Light to moderate rain will continue to spread across central NC this afternoon, with associated MVFR to IFR (even localized LIFR) ceilings. MVFR to IFR visibilities will also be possible in rain. SW winds may continue gusting to 15-25 kts across the south and east for a few more hours before diminishing this evening. While the steady rain will push to our east later this evening, patchy drizzle may continue, with another area of rain potentially reaching our far southern counties overnight. There should be enough lingering low-level moisture to result in widespread LIFR ceilings after about 06z, and a brief period of clearing this evening over the northern Piedmont may result in some patchy fog there overnight as well. Ceilings will be slow to lift tomorrow, eventually reaching IFR by mid to late morning, potentially MVFR around INT and GSO.

Outlook: Generally VFR conditions are expected late Friday into a good part of the weekend behind this system.

Another chance of flight restrictions and rain will result in cold air damming early next week.

RAH WATCHES/WARNINGS/ADVISORIES

None.