Marine Weather and Tides
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|Sunrise 6:57AM||Sunset 7:45PM||Tuesday April 7, 2020 9:20 AM EDT (13:20 UTC)||Moonrise 6:18PM||Moonset 5:48AM||Illumination 100%|
7 Day Forecast for Marine Location Near Isle of Palms, SCHourly EDIT Help
Area Discussion for - Charleston, SC  (on/off)  Help NOTE: mouseover dotted underlined text for definition
FXUS62 KCHS 071015 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 615 AM EDT Tue Apr 7 2020
SYNOPSIS. A series of disturbances will pass overhead through Wednesday. A cold front will move through Thursday, followed by high pressure.
NEAR TERM /THROUGH TONIGHT/. Nudged hourly temperatures up a few degrees as lows are running warmer than expected. Latest RAP/H3R is fairly consistent with previous runs with isolated-scattered showers/tstms forming over the Charleston Tri-County area by mid-afternoon.
A northwest flow regime will remain in place today as subtropical ridging builds across the Gulf of Mexico and into the lower Mississippi Valley ahead of a powerful cyclone digging across California. A shortwave rounding the apex of the upper ridge near the Ozarks early this morning is forecast to slide down the ridge's eastern flanks and propagate across North Carolina into the South Carolina Midlands later this afternoon. This feature is expected to initiate scattered convection across North Carolina into northern/central South Carolina during peak heating as the atmosphere becomes moderately unstable. While the best upper forcing and region of strongest H8 moisture transport look to pass by to the north late with the shortwave, the area along/north of a Walterboro to Charleston line could remain close enough for isolated to perhaps scattered showers/tstms to form, mainly from 3 PM through sunset.
The convective pattern is a bit more uncertain across the remainder of southern South Carolina and Southeast Georgia as surface high pressure centered well offshore of the Florida Space Coast tries to hold its influence on the local forecast area. There is a bit of signal that an H7 shortwave could approach the CSRA and Southeast Georgia very late in the afternoon and produce a secondary area of convection over central Georgia, but this activity will likely be weakening as it approaches interior Southeast Georgia closer to sunset. This trend is noted in most of the CAMs. Pops will range from 20-30% across the Charleston Tri-County area across much of Southeast Georgia with a small area of non-mentionable pops in the Springfield-Hardeeville-Downtown Savannah area. As is typical in northwest flow regimes, even a slight deviation in the timing/placement of the embedded shortwaves could have an unusually large impact on the evolution of convection. Later adjustments will be needed as the day progresses and short term/mesoscale trends become more apparent. Any lingering convection during the evening should dissipate by midnight.
Temperatures will rise quickly after sunrise with highs likely to peak in the mid 80s away from the coast with mid 70s at the beaches. There could even be a few upper 80s along the I-95 corridor if convection can hold off long enough. A robust resultant sea breeze circulation will begin to form along the beaches by early afternoon and make steady progress inland through early evening. Gusty winds will occur across mainly the coastal South Carolina counties as it pushes inland. Gusts could approach 25-30 mph at times in the Beaufort to Charleston corridor. Lows early Wednesday will range from the lower 60s inland, mid 60s at the coast with upper 60s at the beaches, Downtown Charleston, and around the Santee-Cooper lakes. Some low stratus with origins from the northeast Gulf of Mexico could approach the Altamaha River by sunrise Wednesday.
SHORT TERM /WEDNESDAY THROUGH FRIDAY/. Wednesday: Mid-level ridging to our west weakens, which causes heights to lower over us. Though, west northwest flow prevails. A series of weak waves embedded within the flow should move over us through the day and into the night. Weak surface troughing is expected to be along the Southeast coast during the day. At night, a cold front is forecasted to approach from the northwest. Though, it won't reach our area. Deep moisture will be in place during the morning with PWATS ~1.5". Models show this moisture getting pushed to the south with time as drier air moves in from the north. These same models still indicate the best moisture and shower potential is generally south of the Savannah River during the daylight hours. The sea breeze may provide some lift, though it may not make it too far inland. The end result is we continued the chance POPs across most of GA, and slight chance elsewhere. Instability is decent in these southern locations. Showalter values approach -2 with BLCAPEs approaching 1,000 J/kg. Lapse rates are marginal, but 0-6 km bulk shear is ~50 kt. With DCAPEs ~500 J/kg there remains the potential for an isolated strong or maybe even damaging wind gust in these storms. Whatever convection forms will quickly dissipate with the setting sun in the evening, allowing for a dry overnight. High temperatures are expected to be well above normal, cooler at the beaches. The overnight lows are forecasted to be warm enough to put some records in jeopardy.
Thursday: The mid-level ridge to our west will dissipate, causing zonal flow to prevail over the Southeast. At the surface, a cold front approaches our area from the northwest. The front is expected to weaken as it gets closer. Models are in good agreement showing very little lift and moisture ahead of the front. We only have slight chance POPs across mainly our GA counties in the morning followed by dry conditions everywhere for the afternoon. Compression ahead of the front along with partly sunny skies could allow most temperatures to make a run for 90 degrees away from the beaches. The front is expected to cross through during the evening or overnight hours. Aside from maybe some light showers near the Altamaha River, most locations should remain dry. Temperatures finally cool down, most notably late at night.
Friday: The mid-levels consist of zonal flow over our area. At the surface, a cold front will be offshore and moving away in the morning. Meanwhile, high pressure starts to moves in from the distant northwest. Models hint at maybe some light showers along parts of the coast. Since they are behind the front, we opted to only go with slight chance POPs for now. The most noticeable thing should be the cooler temperatures, with highs generally in the low to mid 70s.
LONG TERM /FRIDAY NIGHT THROUGH MONDAY/. The 00Z models finally started to come into some alignment for the long term. High pressure to our northwest should bring dry conditions and cooler temperatures Friday night into Saturday. Saturday night into Sunday a strengthening storm system moves from the Gulf Coast to the Southeastern U.S. Models all seem to key on a large area of heavy rainfall, but they disagree on what part of the Southeast gets it and when. Impacts for our area could range anywhere from some light rain to possibly several inches of rain. Given the wide variation, we went with high end chance POPs with the anticipation more changes will be needed.
AVIATION /10Z TUESDAY THROUGH SATURDAY/. VFR. There will be a risk for showers/tstms this afternoon, but it remains unclear this far out whether direct impacts to either KCHS or KSAV will occur. The best chances for impacts will be a KCHS based on the latest high resolution guidance. Will include VCTS from 20-00z.
Extended Aviation Outlook: Gusty winds are possible each afternoon through Thursday. Showers could bring brief flight restrictions to KSAV each afternoon.
MARINE. Today: Southwest winds this morning will back to the south this afternoon as a robust resultant sea breeze circulation pushes inland. Speeds will average 15-20 kt along the Charleston County waters with 10-15 kt elsewhere. The depth of the mixed layer along the sea breeze should be enough to support 15-20 kt with gusts to 25 kt in the Charleston Harbor mid-late afternoon, so a Small Craft Advisory will be issued beginning at 2 PM. The gust potential looks a bit more limited over the cooler Charleston County waters, so will hold off on the issuance of a Small Craft Advisory there. Seas will average 1-3 ft from Edisto Beach south to Altamaha Sound out 20 NM with 2-4 ft across the Charleston County and Georgia offshore waters.
Tonight: The potential for frequent gusts to 25 kt should end in the Charleston Harbor by 8 PM as the sun sets. Otherwise, winds will veer more uniformly southwest as the sea breeze dissipates. Winds will average 10-15 kt, except 15-20 kt over the Charleston County waters. Seas will average 1-3 ft from Edisto Beach to Altamaha Sound out 20 NM to 2-4 ft over the Charleston County and Georgia offshore legs.
Thursday through Saturday: High pressure offshore and a surface trough along the coast will enhance SW winds through Thursday. Wind gusts could approach 25 kt for a short time Thursday afternoon for the Charleston Harbor and the Charleston County coastal waters. But it should be for a brief enough time period and a small enough area for us to not need any Small Craft Advisories. Elsewhere, winds should top out at 15-20 kt. A cold front will cross through the waters Thursday night, causing winds to veer to the NW. No advisories are expected with the front.
Rip Currents: Swell periods are forecast to drop from 12 seconds this morning to about 10 seconds this afternoon as a robust sea breeze develops along the coast. Despite the lowering periods, the combination of gusty wind and lingering astronomical influences will continue to support an elevated risk for rip currents. Winds of 15-20 kt along the lower South Carolina coast will push the rip current risk into the high category, while slightly lower speeds along the Georgia coast will yield a solid moderate risk.
TIDES/COASTAL FLOODING. Tide levels in the Charleston Habor are expected to reach 6.9-7.0 ft MLLW with high tide this morning. While there is a chance the level will just reach or barely exceed the 7.0 ft MLLW minor flood threshold, the duration should be less than an hour. For this reason, a Coastal Flood Advisory will not be issued. No major impacts are expected, but a portion of Hagood Avenue adjacent to Gadsden Creek will likely flood as well as the Hagood Avenue/Fishburne Street intersection in Downtown Charleston. Trends will be monitored in a case departures trend higher as low tide approaches. Levels should remain shy of the 9.2 ft MLLW minor flood thresholds at Fort Pulaski this morning.
There will be higher probability for beaching minor flood thresholds in the Charleston Harbor and Fort Pulaski with the evening high tide. A Coastal Flood Advisory could be needed.
Higher than normal tides are expected most of this week due to astronomical influences from the upcoming full moon and perigee. Additionally, winds are forecast to be onshore at times with ocean swell, which would further elevate the tides. As a result, minor to perhaps moderate coastal flooding is expected with each high tide through Thursday. Coastal Flood Advisories will be needed. By Friday, offshore winds should lessen the chance of coastal flooding.
CHS WATCHES/WARNINGS/ADVISORIES. GA . None. SC . High Rip Current Risk through this evening for SCZ048>051. MARINE . Small Craft Advisory from 2 PM this afternoon to 8 PM EDT this evening for AMZ330.
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|Charleston Executive Airport, SC||171 mi||26 min||SW 6 G 12||9.00 mi||Fair||70°F||62°F||78%||1018.3 hPa|
Link to 5 minute data for KJZI
Wind History from JZI (wind in knots)
|1 day ago||E||E||E||E||E|
|2 days ago||N||NE||N||NE||NE|
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Wind Forecast for Charleston, SC (9,2,3,4)(on/off)  Help
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