textproduct: Charleston

WHAT HAS CHANGED

The aviation section has been updated to reflect the 12Z TAFs. The Small Craft Advisory for the nearshore waters has been extended until 9 AM this morning.

KEY MESSAGES

- 1) Unseasonably cold weather will occur through early next week.

- 2) Developing low pressure offshore could bring winter weather to the region this weekend.

DISCUSSION

KEY MESSAGE 1: Unseasonably cold weather will occur through early next week.

Strong cold advection will continue through daybreak as Arctic high pressure expands into the region from the west. Morning lows are expected to dip into the upper teens far inland to lower 20s coastal. Surface winds around 10 mph will produce wind chills of 10-20F through 9am, therefore a Cold Weather Advisory is in effect for all areas.

Slightly warmer overnight lows and lower wind speeds should preclude the need for any Cold Weather Advisories Tuesday night through Friday.

An even colder, 1050 mb Arctic high will slide into the Southeast Friday night and persist into Tuesday. Based on forecast wind chills, we'll likely need Cold Weather Advisories most nights, potentially extending into the daytime hours. The lowest temps are currently forecast for Saturday night where mid to upper teens are expected in most areas. If the 10-15 mph surface winds occur, we'll need Extreme Cold Warnings for most if not all of the area. High temps Saturday and Sunday are not expected to get out of the 30s.

KEY MESSAGE 2: Developing low pressure offshore could bring winter weather to the region this weekend.

Deterministic and ensemble models are in good agreement regarding the synoptic set up for this weekend. A longwave trough will be located over the eastern CONUS late week as a potent shortwave digs across the large scale trough. WPC Cluster Analysis is in very good agreement with this feature, as shown through the 24-hour Mean 500-hPa Heights and Anomalies plots. Additionally, a 250 hPa jet streak will be located just offshore of the southeast coast. Surface cyclogenesis is expected off the southeast coast this weekend. However, this is where the exact details start to become obscure. The placement, strength, and timing of the low formation could have significant implications to the amount and type of precipitation across the SC Lowcountry and SE Georgia. What we do know- cold air will be in place, as outlined in Key Message 1, and the synoptic set up favor a low forming off the southeast coast. What we do not know- where/when/how much wintry precipitation could potentially impact the region.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

VFR conditions will prevail through the 12Z TAF period.

Extended Aviation Outlook: VFR for much of the extended period. Risk for impacts from low pressure developing off the Southeast U.S. will increase Saturday.

MARINE

Gusty NW winds should gradually settle down through daybreak as the Arctic high builds more fully into the area. Small Craft Advisories will expire by mid-morning for all waters.

Friday night through Sunday could be a significant marine wind event if the guidance trends continue. Strong low pressure could develop along the SC coast while strong, cold high pressure builds in from the west. At a minimum Small Craft Advisories would be needed for all zones, however there are increasing chances for Gales late Saturday into Sunday morning.

CLIMATE

Record Low Temperatures:

January 31: KCHS: 15/1966 KCXM: 19/1966 KSAV: 16/1966

February 1: KCHS: 21/1977 KCXM: 23/1900 KSAV: 23/1977

February 2: KCHS: 19/1980 KCXM: 17/1917 KSAV: 18/1917

Record Low Maximum Temperatures:

January 31: KCHS: 36/1948 KCXM: 34/1936 KSAV: 37/1909

February 1: KCHS: 38/1980 KCXM: 36/1900 KSAV: 38/1900

February 2: KCHS: 38/1980 KCXM: 38/1898 KSAV: 38/1951

Record Snowfall:

January 31: KCHS: 0.6/1977 KSAV: 1.3/1977

February 1: KCHS: no record established KSAV: no record established

EQUIPMENT

The KCLX radar remains out of service. Critical parts are on order and are now scheduled to arrive today. Users should use adjacent WSR-88D sites, including KCAE, KLTX, KJAX, KVAX and KJGX.

CHS WATCHES/WARNINGS/ADVISORIES

GA...Cold Weather Advisory until 9 AM EST this morning for GAZ087- 088-099>101-114>119-137>141. SC...Cold Weather Advisory until 9 AM EST this morning for SCZ040- 042>045-047>052. MARINE...Small Craft Advisory until 9 AM EST this morning for AMZ350- 352-354. Small Craft Advisory until 10 AM EST this morning for AMZ374.