Sugar Mountain

Forecast Discussion

Summary

SYNOPSIS

... Surface high pressure will allow for dry conditions to continue through Thursday, with rain chances returning Thursday night as developing low pressure brings widespread rainfall to the region through Saturday. Dry conditions return on Sunday and will continue into early next week.

NEAR TERM /THROUGH THURSDAY/... As of 940 PM: Mid and high clouds have briefly thinned across the northern tier of the forecast area this evening, but lower level stratocumulus is already starting to fill back in from the west as indicated in most model time-height sections. Still anticipate the northwest piedmont to be among the cooler areas overnight with the thinnest cloud cover permitting slightly better radiating conditions. A patchy fog mention has been added in this area toward daybreak.

Otherwise, the forecast remains on track with generally quiet weather east of a weak occluded frontal boundary situated over the Ohio River valley and inching eastward toward the central Appalachians. The compact low over Michigan will continue its gradual march eastward and push the boundary into the northern reaches of the area, with little impact other than bringing some low to mid-level stratus to the mtns. Increasing southerly flow ahead of a storm system expected to organize over the southern plains will push this boundary back northward, leading the way to increasing moist southerly flow aloft. The high clouds will act to dampen or diminish diurnal temperature trends, with lows mostly in the 30s (although upper 20s likely in portions of NC Piedmont) overnight with highs in the 40s to low or even mid 50s, warmest southeast of I- 85, on Thurday. An SPS remains in effect for the threat of black ice across much of the area overnight where near to slightly below freezing temperatures will coincide with lingering snowpack, especially across the NC portion of the forecast area.

SHORT TERM /THURSDAY NIGHT THROUGH SUNDAY NIGHT/... As of 210 PM EST Wednesday: A strong ulvl low will cutoff and bring a very moist occluded sfc low to the FA Fri morning which will slowly cross northeast thru early Sun. With a rather stg insitu wedging developing early Fri...llvl isent lift will co-join with deep dynamical forcing and help produce deep saturation thru the column. Modeled profiles show PWATs arnd 300 percent of normal for this time of year as GOM moist flux quickly combines with se/ly Atl flow. The overall modeled qpf responses have remained fairly consistent with previous runs...but the GEFS plumes have risen with better clustering arnd the mean. Also...the latest NAM is very wet as it keeps more cyclonic flow over the area and hence brings in more Atl moisture while the low crosses overhead Fri evening. Didn/t increase the storm total precip too much yet...but like what the NAM is doing across the srn BR and escarpment with higher totals. So...upward adjustments were made in these areas.

A look at the RFC ensemble river fcsts have the South Fork Catawba nearly reaching moderate flood stage and others reaching advisory levels in the area. Will make mention in the HWO of possible hydro issues Fri into Sat for the entire FA as antecedent soil moisture remains elevated from the previous wintry event. There will could be a brief period of -sn or -rasn early Fri morning across the northern mtns...yet any snowfall amts will be negligible.

A cold day on tap Fri with highs mainly in the 40s. As the wedge breaks down Sat and the sfc flow aligns more sw/ly...highs will likely reach near normal levels both Sat and Sun. Mins will remain in the 40s each night except Sun night with as better cooling conds setup and allow temps to drop into the 30s over the fcst area.

LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 240 PM EST Wednesday: An ulvl trof will give way to a deep n/ly flow and strong descending subsidence Mon ahead of a building ulvl ridge. There is some disagreement with the timing of the trialing upper trof as the latest CMC is abt 12 hrs slower than the GFS/ECMWF solns. However...this feature wont affect the sensible wx fcst as profiles will likely remain quite dry during the day outside of some mid to upper level clouds. A rather nice and dry period looks to be in store each day as max temps reach normal levels or above in downslope flow Mon and weak s/ly flow Tue into Wed as a broad sfc high centers across the mid/Atl region.