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Office: CHS

FXUS62 KCHS 191211
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
711 AM EST Mon Feb 19 2018

.SYNOPSIS...
A warm front is expected to lift across the region today. A
large area of high pressure will then prevail for much of the
week. A cold front should approach the area early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Upper ridging across the southeast Atlantic is forecast
to build northwest over the southeastern United States. The
surface coastal trough will weaken as boundary layer flow
becomes more uniform and veers southerly. low level thickness
values will be much warmer today and once we see the morning low
clouds and fog disperse, we will see more sunshine this
afternoon and temps will respond with highs reaching the upper
70s to around 80 degrees inland from the beaches and barrier
islands. Dry weather should prevail with only slight chances for
a light morning shower or sprinkle across parts of Charleston
and Berkeley counties as the coastal trough lifts north.

Tonight: Models suggest that conditions will be favorable for a
more substantial stratus build-down scenario given higher low
level dew points and sustained Atlantic moisture flux below the
subsidence inversion. Low clouds should expand inland during the
evening hours and fog may be dense in some areas across the
region overnight. Low temps will be very mild once again with
readings in the upper 50s to lower 60s from inland to coast.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
A large ridge of high pressure centered over the western Atlantic
will extend across the Southeast United States, setting up
unseasonably warm temps through mid week. 1000-850mb thickness
values support high temps some 15-20 degrees above normal, peaking
in the upper 70s to lower 80s each afternoon. These temps could
potentially break record-setting highs Tuesday and Wednesday noted
in the climate section below. The expansive ridge will also be
responsible for producing a strong inversion over the area each day,
helping maintain precip-free conditions for much of the week. Other
than warm temps, the main issue should come during late night/early
morning hours when a light southeast wind drives moisture onshore
and leads to stratus that potentially builds down near the sfc.
Given the setup, bouts of fog will be possible as overnight lows dip
into the lower 60s. Patchy fog remains in the forecast Tuesday night
and Wednesday night.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
A large ridge of high pressure centered over the western Atlantic
will be the primary contributor to the weather over the Southeast
United States, allowing warm conditions to persist through the
weekend. In general, temps will be well above normal, peaking into
the upper 70s/lower 80s Friday, Saturday and Sunday. Overnight lows
will be mild, ranging in the upper 50s to lower 60s. The next chance
for more substantial shower chances should arrive late Sunday or
Monday as a mid/upper trough passes to the north with a southward
extending cold front that shifts through the Southeast. Once fropa
occurs, temps should be slightly cooler, peaking in the mid/upper
70s on Monday.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Widespread stratus (IFR/LIFR cigs) blanket the coastal corridor
nearing sunrise. Vsbys were good at KCHS but thanks to effects
from the Savannah River, cigs were barely above the surface and
vsbys were poor at KSAV. Both sites should see improvements by
the late morning with VFR likely this afternoon. After sunset,
models show advection stratus and fog rushing onshore and inland
this evening and we expect IFR or lower conditions to prevail
from mid to late evening through 12Z on Tuesday. Build-down
stratus may produce areas of dense fog overnight.

Extended Aviation Outlook: Flight restrictions are possible Tuesday
night and Wednesday night, mainly due to low stratus and/or fog.
Otherwise, VFR conditions should prevail under high pressure.

&&

.MARINE...
Stratus was noted over the waters on satellite and we suspect
there will be reports of visibility restrictions over the
waters this morning, perhaps lingering over GA waters this
afternoon. Given the fog in the Savannah River Entrance and
low vsbys reports from the St. Simons and Hilton Head areas, we
opted for a Dense Fog Advisory in AMZ352 and AMZ354 through the
morning hours. Tonight, there will likely be foggy conditions
developing on/near the land/sea interface impacting the harbors
and sounds as well as the Savannah River Entrance once again.
Marine dense fog advisories are possible.

A coastal trough will weaken through tonight with very stable
and cool shelf waters reluctant to respond to the developing
south to southeast return synoptic flow. Over the coolest near
shore waters, the flow will likely remain from the east will
speeds less than 15 kt. Over our outer GA waters, there should
be a bit more of a southeast component by tonight. Seas will
average 2 ft or so near shore and 3-4 ft well offshore closer to
the Gulf Stream.

Tuesday through Saturday: High pressure will dominate over the
coastal waters through late week. The pattern suggests fairly quiet
conditions in regards to winds/seas. However, lower 60 dewpts will
spread across the coastal waters as a light southeasterly wind
develops by midweek. The setup could potentially lead to some sea
fog over slightly cooler nearshore waters Tuesday through Thursday.
In general, southeast winds should remain at or below 10-15 kt under
the influence of strong high pressure. Seas will range between 2-4
ft in nearshore waters and peak near 4-5 ft in offshore Georgia
waters.

&&

.CLIMATE...
Record Highs

Tuesday   2/20 CHS   82 1991
               SAV   84 1991
               CXM   78 1918

Wednesday 2/21 CHS   82 1991
               SAV   83 1991
               CXM   80 2001

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Dense Fog Advisory until noon EST today for AMZ352-354.

&&

$$
NEAR TERM...
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...
MARINE...
CLIMATE...



Office: CAE FXUS62 KCAE 191333 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 833 AM EST Mon Feb 19 2018 .SYNOPSIS... A frontal boundary south of the forecast area will lift north as a warm front this afternoon. Bermuda high pressure will be in control tonight through Thursday bringing well above normal temperatures. Another frontal boundary is forecast to stall just north of the forecast area Friday. && .NEAR TERM /THROUGH TONIGHT/... A frontal boundary was stalled south of the CSRA early this morning. High pressure off the Mid Atlantic Coast was ridging into the Midlands producing wedge-like conditions. An onshore flow was producing widespread low cloudiness across the region. Models show the frontal boundary to our south slowly lifting north this afternoon with clouds decreasing in the wake of the front from south to north. Temperatures will range from the mid 60s over the northern Midlands to the upper 70s in the CSRA. Low-level moisture will remain across the area tonight and with a developing inversion and light winds aloft expect fog and low clouds will develop. A dense fog advisory may be needed. Overnight lows will be in the middle to upper 50s. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... An upper level ridge off the southeast coast will strengthen Tuesday. Surface high pressure over the western Atlantic will continue ridging into the southeastern states. Mostly cloudy skies Tuesday morning will be slow to clear. We should see decreasing clouds during the afternoon. Went with guidance consensus for afternoon highs in the upper 70s to lower 80s. A weak upper level disturbance will move northward from the Gulf of Mexico through central GA and into Upstate SC Tuesday night. Although this short wave should remain west of the forecast area...there is a potential for some showers mainly across the Northern Savannah River Area and western Midlands Tuesday night. Mild temperatures will continue with lows in the low 60s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... No significant changes were made to the long term forecast. Previous Discussion: Models continue in good agreement with high pressure off the coast of the Carolinas and an upper level ridge dominating the region. A cold front will move toward the region Wednesday night and Thursday then stall just west of the forecast area as the high pressure and upper level ridge push the system northward. The front will move northward Thursday night through early Saturday with the next front approaching Saturday night and Sunday. Have taken a cautious approach for Saturday night and Sunday as the GFS remains more progressive while the ECMWF again keeps the front just to the northwest of the area. Temperatures through the long term will be well above normal. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... Frontal boundary remains draped across southern Georgia this morning, but is expected to move north through the forecast area this afternoon. Much of the area had IFR ceilings this morning. Expect improvement as the warm front lifts north of the area this afternoon. Leaned toward the GFS LAMP for the timing. Light winds combined with abundant low-level moisture and drying aloft because of upper ridging will likely result in LIFR fog tonight into Tuesday morning. The GFS and NAM MOS plus SREF guidance were in good agreement indicating significant fog. EXTENDED AVIATION OUTLOOK...Widespread IFR stratus and fog may occur during the early morning hours associated with high low- level moisture in an onshore flow. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$ SYNOPSIS...99 NEAR TERM...99 SHORT TERM...99 LONG TERM...99 AVIATION...99
Office: GSP FXUS62 KGSP 191153 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 653 AM EST Mon Feb 19 2018 .SYNOPSIS... High pressure off the East Coast will provide a southerly flow of air going into mid week with temperatures climbing well above normal. Another cold front arrives from Tennessee by Thursday. This front will stall out and linger just north of our area next weekend. Chances for rain remain in the forecast each day. && .NEAR TERM /THROUGH TONIGHT/... As of 650 AM: No significant changes needed with this update. Radar is still showing decent coverage of -ra and dz, which seems to line up well with the current forecast. Most other elements are near steady state, so no changes needed. As of 300 AM: The upper level flow across the CONUS continues to amplify, with a deep trough over the west and a ridge building over the East Coast. At the surface, high pressure will slowly drift off the Mid-Atlantic coast, while an area of low pressure organizes over the Central Plains. The flow between the high and low atop the CWFA is bringing moisture and upglide, producing areas of light rain and drizzle. The precip is falling into some dry air, causing an in situ CAD wedge to develop over the CWFA. Guidance still shows this wedge holding on thru the day, at least near the Blue Ridge escarpment. Temps will be held down under the wedge, but some erosion around the fringes is expected as precip coverage decreases, which may allow temps to warm into the 60s. In any case, it should be cloudy today with near normal temps in the wedge and above normal elsewhere. Tonight, whatever wedge still in place will likely persist into tonight. Guidance shows a slight uptick in moisture and areas of fog looks likely. Confidence on dense fog is still low, but there may be patches of it out there late tonight. Temps will drop little overnight staying well above normal lows thru daybreak Tuesday. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 315 AM Monday: Upper pattern dominated by a strong high just off the Southeast coast and a deep trough over the western CONUS. These features remain in place through the period keeping southwest flow over our area. A few weak short waves move through the flow and near our area. A weak upper jet max moves near the area by the end of the period as well. The combination does bring some weak synoptic scale forcing into the area by the end of the period. At the surface, high pressure centered over the Atlantic remains ridged into the through the period. A weakening cold front approaches from the west by Wednesday night. This keep deep southwesterly flow over the area through the period. Moisture slowly increases as well. The main forcing for precip Tuesday will be mechanical upslope flow into the southern Blue Ridge. Expect mainly a slight chance of showers with scattered showers possible over the upslope areas along the NC/SC/GA border area. Weak instability develops Wednesday to go along with the weak synoptic scale forcing. This will increase precip chances into the likely range along and near the southern Blue Ridge into the southwestern NC mountains, with chance PoP elsewhere. Isolated thunderstorms cannot be ruled out over NE GA, the western Upstate and along and west of the French Broad Valley. With this pattern in place, very warm temps are expected during the day and at night. In response, have trended toward the higher range of guidance. This puts record highs at CLT and GSP in jeopardy both days. AVL will be a few degrees below record but still nearly 20 degrees above normal. Lows will be 15 to 20 degrees above normal which is above the normal highs. This also puts record warm lows in jeopardy both days as well. As previous shifts noted, with a saturated low-level inversion and support from MOS guidance, areas of fog are a reasonably good bet early Wednesday morning. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 120 AM EST Monday: The medium range forecast period starts Thursday morning with the 500mb pattern having the center of high pressure near Bermuda and a broad trough over the western two thirds of the nation. The cold front over Tennessee will stall and result in highest rain chances over the mountains on Thursday. The average of instability between the GFS and ECMWF is 500 to 600 CAPE along and south of I-85 late Thursday. The high is expected to be strong enough to push the band of rain associated with the front further west over Tennessee going into Friday. The pattern will be stuck into the weekend with waves of low pressure passing along the front from Louisiana to Kentucky until Sunday night. A strong northern flow shortwave passing across the Great Lakes will take the stalled out surface front eastward. Rain chances will increase over the mountains Sunday night. Frontal rain fades on Monday as it crosses the piedmont which being after the end of the current forecast period. Instability each day is rather low in the current models from Friday through Sunday. Temperatures over ten degrees above normal through the period. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... At KCLT and elsewhere: Patches of -ra and dz continue to develop and ripple across the area early this morning, helping reinforce a weak wedge. The areas of ra and dz should decrease in coverage as dry air works in from the west atop the low cloud deck. Guidance generally holds onto the wedge thru the day, with some erosion from the south and east into the lower piedmont, approaching the Upstate and KCLT sites by late aftn. If enough breaks in the clouds can form, this could allow cigs to briefly improve to MVFR by the end of the daylight hours. For now, I only have small improvement in cigs, with the most improvement at KCLT. KAVL is the usual exception, which should be MVFR for most of the day, and possibly even VFR at times with a downslope, cross-valley flow. Sfc winds will be light, generally ENE, except SE at KAVL and KCLT. Tonight, guidance shows some increase in moisture allowing a return of at least a slight CHC of rain and drizzle. The main concern that guidance is trending toward is widespread fog across the piedmont developing late evening thru the overnight, possibly dense in spots. Confidence Table... 12-18Z 18-24Z 00-06Z 06-12Z KCLT High 83% Med 64% High 83% High 84% KGSP High 80% Med 66% Med 62% High 93% KAVL Med 72% Med 77% High 84% Med 63% KHKY Low 48% Low 50% Low 57% Med 79% KGMU Med 67% Med 62% Low 57% Med 76% KAND Med 61% High 81% High 82% Med 74% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: www.weather.gov/gsp/aviation && .CLIMATE... RECORDS FOR 02-20 MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 75 1939 26 1908 50 1951 4 2015 1939 KCLT 77 2014 31 2015 59 1939 7 2015 1890 KGSP 75 2014 33 2015 57 1939 9 2015 1986 RECORDS FOR 02-21 MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 77 1986 12 1896 54 1997 8 1896 KCLT 75 2011 32 1896 56 1997 6 1896 1986 KGSP 75 1917 35 1978 55 1997 9 1896 1902 RECORDS FOR 02-22 MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 72 1897 27 1939 54 1897 2 1963 KCLT 74 1990 33 1963 62 1897 12 1963 1897 KGSP 76 2011 35 1969 55 1980 10 1963 1963 RECORDS FOR 02-23 MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 76 1982 29 1989 54 1922 10 1939 KCLT 76 2012 29 1901 56 1944 19 2009 1980 1978 1962 1963 KGSP 76 2012 36 1966 57 1922 15 1963 1996 1939 1980 RECORDS FOR 02-24 MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 77 1930 26 1947 50 1985 6 1967 1979 KCLT 80 1982 26 1889 56 1992 16 1967 1930 KGSP 79 1982 33 1901 57 1909 15 1967 1901 RECORDS FOR 02-25 MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 78 1930 17 1967 51 1985 -2 1967 KCLT 82 1930 27 1967 58 1890 7 1967 1914 KGSP 79 1930 30 1967 57 1985 8 1967 && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...ARK SHORT TERM...RWH LONG TERM...DEO AVIATION...ARK CLIMATE...