textproduct: Raleigh

WHAT HAS CHANGED

As of 107 PM Friday...

* Nothing appreciable.

KEY MESSAGES

As of 107 PM Friday...

1) Continued light patchy rain through this evening. Overcast with patchy dense fog possible tonight.

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

DISCUSSION

As of 107 PM Friday...

KEY MESSAGE 1... Continued light patchy rain through this evening. Overcast with patchy dense fog possible tonight.

The sfc cold front remains stalled to our south this afternoon while cooler, saturated nely flow remains locked in over central NC. The steadier rain has moved well east of the Coastal Plain at this point following the exit of a lead vorticity perturbation. The strong short-wave/vort max has dug deep into GA/AL this afternoon, largely directing convection to our south into FL. Any lingering light patchy drizzle/rain over the area should dissipate with time through this evening. Otherwise, overcast conditions are expected again tonight for much of central NC with warm overnight lows lower to mid 40s. Similar to this morning, expect reduced visibility largely from elevated fog (lowered stratus) with perhaps some locally dense fog possible in areas. Best signal for dense fog appears to possibly be in the Foothills/Western Piedmont where some thinning of the clouds may result in radiational fog.

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

Developing moist isentropic ascent atop the shallow sloped low/mid- level frontal boundary is expected to support light stratiform rain over the Mid-Atlantic, but timing and southern extent of the precipitation footprint remains uncertain and highly dependent on the evolution of mesoscale features (position and strength of 925- 850mb WAA/FGEN). The EPS has been consistently the northern most solution with precipitation directed over the Virginias, although its AIFS counterpart has shift slightly south compared to model runs from 12z Thurs. The GEPS/GEFS/AIGFS-ensemble remain farther south and paint highest probabilities of > 0.1" across the NC/VA border. Best chances will likely be along and north of the I-85 corridor into the northern Coastal Plain.

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.

Most likely scenario: Minimal amounts of liquid equivalent with most places only achieving trace amounts to 0.05". Light rain and conversational onset of some sleet Mon afternoon/evening ends as a cold light rain with surface temperatures above freezing throughout Mon night into Tues morning. No hazardous weather or impacts to travel expected.

Worst-case scenario (5-10% chance): Onset of pure sleet Mon afternoon/evening results in very light sleet accumulation (abated a bit by warm ground and above freezing surface temps) transitions to light freezing rain after sunset when surface wet-bulb temps drop below freezing. Even in this scenario freezing rain accrual will almost certainly be less efficient than a 1:1 ratio since air temps will likely be > 28 degrees. Minor impacts to travel for Tues morning commute would be possible due to a light/thin glaze on elevated surfaces and bridges.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

As of 710 PM Friday...

Confidence is high in poor aviation conditions dominating at all central NC terminals through at least mid morning Sat. A frontal zone has settled to our S, with cool high pressure nosing into NC from the N and NE. While patchy MVFR cigs have dipped into far north- central NC in the last few hours, the cool flow combined with moist air in the low levels will bring a continued high threat for IFR/LIFR cigs at central NC terminals tonight through mid morning. Vsbys are expected to drop to MVFR prior to 05z and to IFR and perhaps LIFR overnight until returning to mainly MVFR by around 12z- 13z. LIFR/IFR cigs are likely to hold until around 14z-16z N and 16- 19z S, when cigs are expected to rise to MVFR for an hour or two before becoming VFR as clouds scour out from N to S. Confidence is high that VFR conditions will return by 19z at northern terminals (INT/GSO/RDU/RWI) by 21z S (FAY). Surface winds will be light, under 8 kts, and variable or from the NNE and N through Sat.

Looking beyond 00z Sun, VFR conditions should hold through Sat evening, but sub-VFR vsbys in fog are possible late Sat night through Sun mid morning, especially over the S and E (RWI/FAY most likely to be affected). Starting Sun evening, another weather system will bring low gray clouds and a high chance for sub-VFR conditions, lasting into Tue. And cold rain or drizzle, perhaps mixed at times with sleet, is likely Mon/Mon night. Brisk/gusty winds from the NE are possible Sun evening through at least Mon morning.

RAH WATCHES/WARNINGS/ADVISORIES

None.