High pressure will continue to build over the Carolinas this weekend, as a front remains stalled offshore. A cold front will move through early next week with low pressure developing along it. High pressure will build back over the area mid week. Another low and cold front move in late in the week.
Tonight As of 645 PM Saturday,
Based on the latest guidance, and current temperature trends, the mention of freezing fog was expanded to include more of the coastal plain later this evening into early Sunday morning. The back edge of the cirrus shield has now reached central NC, and guidance suggests it will reach ENC around 10pm this evening. It's after this point that the probability of fog is expected to increase, and short-term guidance continues to show a decent signal for this. We'll continue to closely monitor trends to determine if fog headlines are needed, including the potential for any freezing fog headlines.
PREVIOUS DISCUSSION, Area of isentropically driven -RA cont to sweep eastward through ENC, with most widespread south of Hwy 70 and little to no rain to the north. This band of lift and associated rain will shift eastward and weaken by evening, with a quiet and cool night ensuing. Some patchy to areas of fog again tonight, with the potential for some patches of fzfg acrs the nwrd coastal plain counties. Lows in the low 30s away from the beaches, and in the 30s to near 40 beachfront.
Sunday As of 3 PM Sat, High pres dominates with temps warming back into the 50s, still below climo but closer to where we should be for early Dec. Skies will be partly cloudy to the north, to mostly cloudy south where an active subtropical jet cont to stream mid/high clouds through the region.
Sunday night through Saturday As of 3 PM Sat, Small precip chances Mon, with dry and seasonably cold mid week. Another weather maker possible by week's end.
Monday, The start of next week brings another chc of precip with passage of cold front expected. Aloft, upper low will swing through, and spur offshore cyclogenesis late in the day and evening. Typical cold air chasing moisture scenario, where temps tumble through late afternoon, but moisture is coming to an end. There may be some overlap where rain mixes with and changes over to some snow, but very limited to no impacts expected even if this low end scenario pans out, as daytime highs will be in the 40s and a 'warm' ground would be in place. Mon night lows will be the coldest of the period, with 20-25 on the mainland, and 30-35 on the beaches and immediate coast.
Tuesday through Thursday, Dry conditions across the board return as high pressure builds back in at the surface behind Monday's front and trough axis aloft finally pushes E of the coast. Highs in the 40s Tue warming back into the 50s Wed as winds become Sw. Good radiational cooling will bring lows into the 20s for most of Mainland ENC, with 30s on the beaches and OBX Tue night/Wed morning.
Friday through Saturday, Next chc for appreciable precip arrives by week's end, as next shortwave trough swings through the Ern CONUS in a cont active synoptic pattern. Due to uncertainty this far out in details and timing, pops kept at low chc (30%) or lower for now.
00z Sunday through Thursday As of 645 PM Saturday,
Key Messages
- Moderate to high confidence in FG formation tonight, including a risk of FZFG
Widespread IFR CIGs are ongoing across ENC this evening, including all TAF sites. The IFR conditions are holding on longer than previously forecast, and the TAFs have been updated to reflect this trend. The question, then, is when do low clouds clear out (if at all), and how quickly will BR/FG form after that point. There appears to be 2 possible scenarios.
1) Low CIGS continue to linger longer than expected, then gradually lower through the night with modest reductions to VIS.
2) Low CIGs clear out, and widespread FG develops shortly after with significant reductions to VIS.
The latest guidance appears to be leaning towards scenario #2, and the TAFs will reflect this as well. In either scenario, a mix of IFR and LIFR conditions are expected, and confidence in IFR/LIFR is now high. The biggest difference between the 2 scenarios appears to be whether or not VIS drops to LIFR, and whether or not temperatures fall below freezing, allowing a period of FZFG to develop. At this point, the probability of FZFG is 20-40% for KOAJ, KISO, and KPGV, and <20% for KEWN. Given only modest probabilities, I've opted to keep FZFG out of the TAFs for now, but this potential will be closely monitored. Cigs and VIS should gradually improve Sunday morning, but in this type of pattern, improvement tends to be slower. I expect all sites to be back to VFR by Sunday afternoon.
Outlook: By Monday, pattern becomes wet again return to sub-VFR flight cats likely as the developing low pressure makes it closest point of approach. Vfr conditions are then once again expected Tue into Wed across ENC.
As of 3 PM, Latest obs show light nwrly winds in the 5-15 kt range, and seas of 3-5 ft, highest outer waters. High pressure will build in from the north through the weekend with stalled front offshore. Winds become N-NE tonight and Sunday but remain light. Seas will subside to mainly 2-4 ft tonight, occasionally up to 5 ft across the outer central waters.
Mon, Backdoor front passes through with a sharp ramp up in nrly winds. Solid SCA conditions expected, with the possibility for gales, esp the better mixed Gulf waters offshore south of Cape Hatteras. A gale watch has been issued where probs for gales exceed 80%. Seas will quickly inc to 6-10 ft during the day Mon and remain there through early Tue.
Tue through Thu, Winds and seas relax a bit, though by late Wed winds turn swrly and inc to 15-25 kt for the sounds and nearshore waters, and 20-30 kt with potential gale gusts for the warmer outer waters south of Hatteras.
Nc, none. Marine, gale watch from Monday afternoon through Monday evening for amz152-154-156-158.
