Marine Weather Net

Charleston Harbor Marine Forecast




10 - 15





The Marine Weather Forecast In Detail:
AMZ330 Forecast Issued: 605 AM EST Wed Nov 13 2019

Today...N Winds 20 Kt With Gusts To 30 Kt Early, Diminishing To 15 Kt In The Afternoon. Waves 1 To 2 Ft.
Tonight...Ne Winds 10 To 15 Kt.
Thu...N Winds 10 Kt. A Chance Of Showers.
Thu Night...N Winds 10 Kt. A Chance Of Showers In The Evening, Then Showers After Midnight.
Fri...N Winds 10 To 15 Kt With Gusts To 20 Kt. Showers.
Fri Night...N Winds 15 To 20 Kt. Waves 1 To 2 Ft. A Chance Of Showers.
Sat...N Winds 15 To 20 Kt. Waves 1 To 2 Ft. A Chance Of Showers.
Sat Night...N Winds 15 To 20 Kt. Waves 1 To 2 Ft. A Chance Of Showers.
Sun...N Winds 10 To 15 Kt.
Sun Night...N Winds 5 To 10 Kt. Unless Otherwise Noted, Waves 1 Foot Or Less. Charleston Harbor Water Temperature 64 Degrees.
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Area Forecast Discussion
National Weather Service Charleston SC
632am EST Wednesday Nov 13 2019

High pressure will prevail across the region through tonight. A low pressure system will impact the region Thursday night into Saturday before a coastal storm potentially affects the area early next week.

Near Term - Until 6pm This Evening
13/11z observations show the freezing line has reached all the way to the lower South Carolina coast with freezing temperatures oozing into the marshy portions of the Georgia coast. Based on the latest data, it appears the growing season will likely come to an end for much of the area this morning. Marine-based stratocumulus is impacting coastal portions of McIntosh County and have adjusted sky cover grids to reflect this. Otherwise, skies are clear. Wind Chills values have dropped into the upper teens to mid 20s. Overall, the forecast is in good shape and only required minor adjustments.

Today: A modified, continental polar airmass will become further entrenched across the region today as cold air advection persists with the passage of a potent mid-level trough off the U.S. East Coast. H8 temperatures will bottom out in the 1-6C range later this morning before very slowly rising this afternoon with the initiation of weak warm air advection. Despite full insolation, highs will struggle to warm through the day with such cold temperatures occurring aloft and north low- level winds holding firm. Highs look to warm into the upper 40s to lower 50s for most areas by mid-afternoon with mid 40s occurring in the Allendale-Moncks Corner corridor. The record low maximums for all three climate sites will be challenged. Although winds will gradually diminish through the day, speeds look to remain high enough to keep wind chills into the lower- mid 40s except upper 40s across the far southern zones. The extensive stratocumulus field over the warmer Atlantic will largely remain offshore, its far western fringe may approach Sapelo Island by late afternoon and winds veer more to the northeast.

Lake Winds: Winds remain elevated across Lake Moultrie early this morning within a strong cold air advection pattern. Speeds at Pinopolis have been solidly in the 20-25 kt range for much of the night and this will continue through daybreak before slowly diminishing. A Lake Wind Advisory will remain posted for the lake through 1pm EST.

Short Term - 6pm This Evening Through Saturday
Tonight: A wedge of high pressure is forecast to strengthen across the interior tonight as a weak coastal begins to sharpen off the South Carolina and Georgia coasts. Isentropic assent/warm air advection will strengthen atop the inland wedge overnight as the 925-700 hPa begins to veer in response to the kicking out of the upper-level cyclone currently spinning over northern Mexico. The cold/dry airmass coupled with relatively high model condensation pressure deficits suggest it will be hard for any measurable rainfall to occur prior to daybreak Thursday. Some of the wetter CAMs such as the NSSL-WRF and ARW are likely overdeveloping the extensive stratocumulus field over the warmer Atlantic; typical in these types of synoptic patterns. Suspect there will likely be some sort of concentrated shower activity approaching the lower South Carolina coast after 5-6 AM, but most should remain offshore through sunrise. Dry conditions will be maintained tonight except for mid-upper Charleston County where 20% probability of precipitation will be introduced just before sunrise. Lows will range from the lower 30s inland to the lower- mid 40s along the beaches. No p-type issues are expected with shower activity expected to remain offshore and pronounced warm air advection noted just off the surface.

The need for frost/freeze headlines will be assessed later today once morning CO-OP and mesonet observations are received. Headlines may not be needed if enough of the forecast area observes a freeze this morning.

Thursday: High pressure will weaken over land early as a coastal trough forms along the Southeast coast. Temps should start off chilly, especially inland, but will gradually warm into the low/mid 50s inland to upper 50s/around 60 near the coast during the afternoon. Isolated to scattered showers are possible, especially east of the I-95 corridor late in the day when forcing begins to increase with surface low pressure developing south/southwest of the area. Models have been persistent in showing low-level moisture and strong isentropic lift increasing during overnight hours, resulting in scattered to numerous showers spreading across the area from southwest to northeast. Greatest precipitation coverage should occur across southern areas in Southeast Georgia after midnight, where numerous to widespread showers are expected closer to low pressure developing/strengthening over northern Florida and/or just offshore, then should peak closer to coastal locations through daybreak. Low temps will be noticeably warmer than the previous night, ranging in the low/mid 40s inland to low/mid 50s along the coast.

Friday: Deep moisture will likely remain across the area early, highest near the coast while surface low pressure deepens offshore. Numerous to widespread showers will likely be ongoing into late morning hours, greatest coverage along the coast. The bulk of precipitation should then shift offshore during afternoon into early evening hours as the main low pressure center shifts to the north/northeast and away from the region. However, scattered showers will be possible through overnight hours as a trailing mid/upper level low begins to shift over the area late. Another issue could be breezy northerly winds that develop near the coast overnight due an enhanced pressure gradient between the departing low and high pressure building in from the north. However, strongest winds should remain over coastal waters. High temps should peak in the upper 50s to lower 60s, warmest at the coast. Low temps should dip into the low/mid 40s inland to upper 40s/around 50 at the coast.

Saturday: A mid/upper level low will shift over the area early before departing off the Southeast coast late. At the sfc, high pressure will prevail with a slightly cooler northerly wind in place throughout the day. The pattern suggests scattered showers over much of the area into afternoon hours before activity begins to diminish from west to east as the mid/upper low begins to shift offshore. High temps will remain cooler, peaking only in the lower 50s across the Tri-County area to mid/upper 50s for areas south (warmest in Southeast Georgia).

Long Term - Saturday Through Tuesday
High pressure should prevail across the area Sunday, favoring mainly dry conditions. Forecast uncertainty is much greater early next week with a large spread in model solutions in regards to the development and track of another low pressure system along and/or off the Southeast coast. However, the general consensus is that a period of weak ridging will occur across the area Sunday through Monday, resulting in slightly warmer temps ahead of a large mid/upper level trough of low pressure approaching the area Tuesday into Wednesday. Temps should be a few degrees warmer during mid week (mid 60s) with isolated to potentially scattered showers developing across the area. Overnight lows should dip into the mid 30s/lower 40s Saturday night, then will be slightly warmer next week, low/mid 40s inland to upper 40s/around 50 at the coast.

Today: Winds have likely peaked early this morning with frequent gusts to gales noted earlier this morning. Gale Warnings will remain posted through late morning. After that, winds will weaken enough to downgrade the warnings to Small Craft Advisories. Speeds should average 15-20 kt with gusts to 25 kt by afternoon. Seas of 5-8 ft nearshore, 8-11 ft offshore this morning will subside to 4-6 ft nearshore, 7-9 ft offshore this afternoon.

Tonight: Winds will remain elevated as the pressure gradient begins to pinch between inland high pressure and a weak coastal trough offshore. Northeast winds will average 15-20 kt with gusts 25 kt, but could be locally higher where the gradient pinches the most. Seas will average 4-6 ft nearshore and 5-7 ft offshore.

Thursday through Sunday: Small Craft Advisory level conditions could linger across offshore Georgia waters through Thursday morning, mainly due to elevated seas. Northerly winds should then remain at or below 10-15 kt with seas no higher than 3-5 ft as a coastal trough takes form and persists into early Thursday night. A fairly strong area of low pressure should then arrive early Friday, causing winds/seas to deteriorate through much of the weekend. A strong pressure gradient between low pressure over coastal waters and high pressure building from the north over land will likely support Small Craft Advisories across most waters Friday afternoon into early Sunday. A portion of the waters could even see gale force wind gusts on Saturday when the pressure gradient and cold air advection is strongest. Conditions should then improve across all waters through the day on Sunday, but lingering 5-7 ft seas could support Small Craft Advisories for offshore Georgia waters into Sunday night.

Tides / Coastal Flooding
Northerly winds are starting to have a negative impact on tidal departures. Positive depatures are diminishing, but it still appears levels will breach advisory thresholds at both tide gauges, although levels may end up more in the minor versus moderate category.

Tide levels will remain higher than normal through at least Saturday due to strong north/northeast winds persisting along low pressure tracking near the Southeast coast. Coastal Flood Advisories could be needed during the morning high tides mid to late week along the entire coast. Deepening low pressure offshore this weekend could also support moderate levels of coastal flooding, especially if rains are ongoing during the time of high tide.

Record Lows for 13 November: KCHS 29/1941 KCXM 34/1968 KSAV 29/1968

Record Low Maximums for 13 November: KCHS 51/2013 KCXM 49/1920 and previous KSAV 50/1920 and previous

NOAA Charleston SC Office: Watches - Warnings - Advisories
GA...Freeze Warning until 10am EST this morning for GAZ087-088- 099>101-114>119-137>141. Coastal Flood Advisory until 11am EST this morning for GAZ117- 119-139-141. SC...Freeze Warning until 10am EST this morning for SCZ040-042>045- 047>052. Coastal Flood Advisory until 11am EST this morning for SCZ048>051. Lake Wind Advisory until 1pm EST this afternoon for SCZ045.
Gale Warning until 11am EST this morning for AMZ350-352-354- 374. Small Craft Advisory until 1pm EST this afternoon for AMZ330.