FXUS62 KCHS 261941 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 341 PM EDT Sun May 26 2019 .SYNOPSIS... High pressure and unseasonably hot conditions will persist most of this week. Some relief from the oppressive heat is expected by next weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Note: The highs so far today at KCHS and KSAV have been 100 degrees and 101 degrees respectively which break the previous daily records. See Climate section below for details. Another unseasonably warm night on tap with the summer-like pattern remaining in place. Stayed above MOS guidance for low temperatures based on what happened last night and the unusual pattern which yields mostly lower to mid 70s inland and closer to 80 at the coast. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... Memorial Day through Wednesday: Record heat will continue as the region sits underneath an anomalous mid and upper anticyclone across the Gulf of Mexico and Florida. At the surface we find an elongated ridge of high pressure from the Atlantic across Florida, while a thermal trough is situated over or near the local region. H5 heights are as high as 5890-5900 meters Monday, then fall about 10 meters Tuesday and Wednesday. Even so, all these heights are close to record levels for late May. Combined with H85 temps that are also near record May levels at 20-22C and utilizing the low level thickness forecast scheme, we are still forecasting 100F or greater across the vast majority of the region all three afternoons. There will be a sea breeze each day, but it's inland progression will be a struggle on Monday with it not reaching maybe the US-17 corridor by late. Because of the onshore circulations, this will at least hold shoreline temps down to the upper 80s and lower 90s. Night time lows will struggle to get down to the lower and middle 70s, with even upper 70s along some coastal locations and in downtown Charleston. Regarding the potential for Heat Advisories, which we will issue when the heat index reaches 105F this early in the year, is a possibility all three afternoons. But with a deep offshore flow, dew points inland will mix out similar to the past few days. It's over the coastal counties where our concern is the greatest, as the pooling of higher dew points in the lower and middle 70s behind the sea breeze will develop. Since it is still a marginal event for Monday afternoon, limited in both time and space, we will defer any advisory to the midnight set of meteorologists. Unfortunately there is still little or no chance of any much needed rainfall. There might be a stray short-lived shower on the sea breeze each afternoon, but PoP is no greater than 5 or 10%. Thus we will add to our ongoing two week stretch where most places have not received any precipitation during this time. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... The mid-level ridge will remain in place Wednesday night, then finally flatten out Thursday night followed by zonal flow Friday and Saturday. Surface high pressure will continue to dominate our weather pattern through Thursday. The models still show a cold front approaching our area Friday or Saturday. They have trended wetter, which seems a little suspicious considering the front will be running into our very dry airmass. We opted to only introduce slight chance POPs Friday and Saturday. But early indications are rainfall amounts won't put much of a dent in our drought. Temperatures will trend downwards each day. However, they are still forecasted to remain above normal. && .AVIATION /19Z SUNDAY THROUGH FRIDAY/... VFR at KCHS/KSAV through 18Z Monday. Extended Aviation Outlook: VFR. && .MARINE... Tonight: South to southwest winds will prevail, mainly 15 kt or less with some gusts to 20 kt. Seas will average 2-3 ft, highest to the east. Monday through Friday: A huge area of high pressure that covers a large chunk of the Atlantic, with its ridge axis near or just south of 30 degrees north latitude will dominate the area. This will produce a general SW flow at or below 15 kt through mid week, although sea breeze influences will give a little boost to speeds in Charleston Harbor and on the AMZ350 waters each afternoon and early evening. Seas on average will be 2-3 ft through Wednesday or Thursday. Later in the week there is a little stronger pinching of the gradient around the ridge and an inland trough, so winds and seas do increase a notch, but nothing high enough for an advisory. && .CLIMATE... The ongoing heat wave will challenge or break many of these records: EARLIEST 100 DEGREE TEMPERATURES: KCHS: May 26, 2019 (previously June 2, 1985). KSAV: May 25, 2019 and 1953. KCXM: June 1, 1985. MONTHLY RECORD HIGHS FOR MAY: KCHS: 100 set May 26, 2019 (previously 99 set May 21, 1938). KSAV: 101 set May 30, 1898 and May 31, 1945. KCXM: 99 set May 21, 1938 and May 26, 1953. RECORDS FOR SUN 05/26... Station Record High Year(s) ------- ----------- ------- KCHS 98 1953 KSAV 100 1953 Station Record High Min Year(s) ------- --------------- ------- KCHS 75 1998 KCXM 79 1998 RECORDS FOR MON 05/27... Station Record High Year(s) ------- ----------- ------- KCHS 98 1989 KSAV 98 1989, 1962 KCXM 95 1962, 1926 Station Record High Min Year(s) ------- --------------- ------- KCHS 76 1991 KSAV 77 1878 KCXM 78 1991 RECORDS FOR TUE 05/28... Station Record High Year(s) ------- ----------- ------- KCHS 97 1967, 1964 KSAV 96 1964, 1898 KCXM 93 2000 Station Record High Min Year(s) ------- --------------- ------- KCHS 76 2000 KSAV 76 1885 KCXM 80 2000 RECORDS FOR WED 05/29... Station Record High Year(s) ------- ----------- ------- KCHS 95 1945 KSAV 98 1945, 1898 Station Record High Min Year(s) ------- --------------- ------- KCHS 76 2018 KSAV 75 1885 KCXM 77 1998 RECORDS FOR THU 05/30... Station Record High Year(s) ------- ----------- ------- KCHS 95 2004 KSAV 101 1898 Station Record High Min Year(s) ------- --------------- ------- KCHS 75 1982 KSAV 75 1924 KCXM 78 1998 RECORDS FOR FRI 05/31... Station Record High Year(s) ------- ----------- ------- KCHS 98 1953 Station Record High Min Year(s) ------- --------------- ------- KCHS 77 2004 KSAV 75 2004 RECORDS FOR SAT 06/01... Station Record High Min Year(s) ------- --------------- ------- KCHS 77 1974 KSAV 76 1880 && .EQUIPMENT... The Downtown Charleston (KCXM) observation will be unavailable until further notice. The cause of the outage is unknown. Technicians will address the outage on Tuesday. WFO Charleston will only conduct upper-air soundings at 12Z until further notice due to a shortage of helium. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Heat Advisory until 8 PM EDT this evening for GAZ099>101- 114>119-137-138-140. SC...Heat Advisory until 8 PM EDT this evening for SCZ042>045- 047>052. MARINE...None. && $$ NEAR TERM...RJB SHORT TERM...33 LONG TERM... AVIATION...33/RJB MARINE...33/RJB CLIMATE... EQUIPMENT...