textproduct: Charleston

SYNOPSIS

High pressure will extend across the region through Saturday. A cold front will push offshore Sunday morning followed by another area of high pressure. Another cold front could impact the area by the middle of next week.

NEAR TERM /THROUGH TONIGHT/

The region remains in the southwest sector of a surface high pressure that is shifting eastwards into the Atlantic, with a cold front approaching from the west. Some drier air in the mid-levels has helped to mix out the fog earlier this morning, which is allowing for a rapid increase in temperatures away from the coast. Inland highs are expected to reach up into the mid 70s to lower 80s, warmest across portions of southeast Georgia, and is within reach of the daily record highs. Areas along the coast will see southeasterly to southerly winds advect cooler temperatures off the nearshore waters, which will limit heating potential to the upper 60s to lower 70s.

As the cold front remains well off to our east, no rain is yet expected keeping fog as the main concern heading into the overnight period. Vast majority of guidance shows a bank of sea fog lingering throughout the day just off the southeast Georgia coast which is then advected onto land as temperatures cool. However, if that bank of sea fog is fully eroded, with erosion currently being observed on satellite early this afternoon, that raises uncertainty in the fog forecast. Given relatively weak surface flow and abundant moisture in the boundary layer, radiation fog may still form across land areas. So, while the exact process for how we may get fog is not clear, it is looking like fog will again overspread portions of the area this evening and overnight, especially for areas generally along and east of I-95.

SHORT TERM /SATURDAY THROUGH MONDAY/

Saturday: Fog, some dense, could linger over land into the mid to late morning hours with at least a risk for patchy fog impacting the beaches into the afternoon. The region will still be fully embedded within the warm sector of an approaching cold front as a strong storm system moves across the Great Lakes region. An isolated shower or two from off the Atlantic could brush the coastal areas, but guidance is not overly keen on this scenario, especially as low- level wind fields veer with time. No mentionable pops were included given the overall low chance for anything measurable. Rain chances will increase Saturday evening as the rain band associated with the front approaches from the west. The overall model trends have not changed too much and still favor the better rain chances occurring across the far interior as the decaying frontal rain band marches east. Guidance has been fairly consistent in showing the corridor of greatest forcing associated with both the right entrance region of the polar jet and DPVA ahead of the Great Lakes upper trough passing by well to the north and northwest, but a bit more forcing is noted in 09/12z model cross sections. This may translate into the line holding together a bit more as it exits the South Carolina Midlands, CSRA and central Georgia even though the line will likely be in a steady weakening phase as it moves into the Lowcountry and Southeast Georgia. How much of the line will dissipate before reaching the coast is still uncertain. The pop gradient was tightened a bit based on the latest trends, ranging 40-70% well inland to 20-40% coast, but higher pops may eventually be needed for some areas once this period enters into the temporal window of some of the higher resolution CAMs. Another day of near record warmth is expected with highs ranging from the lower 80s west of I-95 to the mid 60s at the beaches. See the climate section below for specific records. Lows Saturday night will range from the lower 50s in the Allendale- Reidsville corridor to the mid-upper 50s elsewhere.

Sunday and Monday: The cold front will clear the coast by mid- morning with the risk for isolated to scattered showers lingering until FROPA. Otherwise, dry and cooler conditions will prevail as a modified Canadian airmass settles into the Southeast States even as the upper flow aloft remains somewhat cyclonic. It could be a bit breezy Sunday afternoon with the onset of modest cold air advection and winds on Lake Moultrie could get close to Lake Wind Advisory criteria (40% NBM probability for frequent gusts to 25 kt). Highs Sunday will occur early in the day, peak in the upper 50s inland to the mid 60s at the coast, with temperatures either leveling out or even falling a bit in the afternoon as temperatures aloft cool. Lows Sunday night will drop back closer to climatological normals, ranging from the upper 20s well inland to the upper 30s at the beaches. Monday will offer considerably cooler highs with temperatures maxing out in the lower-mid 50s.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Rain chances will begin to increase mid-late week as another cold front pushes offshore and a deep upper trough initiates strong cyclogenesis off the Eastern Seaboard. More seasonable temperatures can be expected for much of the week with temperatures averaging near to slightly below normal for mid-January.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

VFR conditions expected to prevail for the rest of the afternoon hours, though another round of fog is expected this evening and into the overnight hours. Fog looks to form along the southeast Georgia coast, which then expands northeastwards especially for areas generally along and east of the I-95 corridor. While dense fog is possible, confidence is not high enough to include one quarter-mile visibility, so have capped visibility at one half-mile for this set of TAFs. Fog will erode Saturday morning.

Extended Aviation Outlook: A band of showers with a cold front may bring reduced vsbys Saturday night into early Sunday morning. Gusty northwest winds are possible Sunday afternoon.

MARINE

Today through tonight: A narrow corridor of fog remains trapped in the marine layer along the southeast Georgia and southeast South Carolina coast, while the nearshore waters from South Santee to Edisto are clear. It's unclear if this will linger or not, but given an unchanged atmosphere the trend would support this bank of fog to remain throughout the afternoon and into the overnight hours. For now, have extended the Dense Fog Advisory for the waters from Edisto, SC to Altamaha Sound, GA through 8 PM, though it will likely need to be further extended/expanded this evening. As south-southeasterly flow strengthens this evening, the fog is expected to expand in areal coverage across all nearshore waters, though the increased wind speed may limit the thickness of the fog...thus not extending the advisory into the overnight period.

Saturday through Tuesday: There are two main concerns for the period. Some degree of fog, possibly dense with vsby 1 NM or less, could linger across the coastal waters Saturday as warm, moist airmass holds in place over the cool Atlantic shelf waters. The risk for reduced vsbys should end by Saturday night as a low-level wind fields veer and increase ahead of an approaching cold front.

There is a risk for both winds and seas reaching Small Craft Advisory criteria Sunday afternoon through early Monday morning as cold air advection spread east across the waters in the wake of a cold front. The probability for winds reaching frequent gusts to 25 kt is averaging about 40-60% across the nearshore waters and 70-90% over the Georgia offshore waters.

CLIMATE

Record High Temperatures: January 9: KCHS: 78/2012 KSAV: 77/2008

January 10: KCHS: 79/2008 KSAV: 81/1972

Record High Minimum Temperatures: January 10: KCHS: 60/1974 KCXM: 62/1974 KSAV: 63/1937

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Dense Fog Advisory until 8 PM EST this evening for AMZ352-354.