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Office: CHS

FXUS62 KCHS 211142

Area Forecast Discussion
National Weather Service Charleston SC
642 AM EST Wed Nov 21 2018

High pressure will prevail through Friday, then a low pressure
system will move through on Saturday. A cold front will move
through Sunday night followed by high pressure into the middle
of next week.


Today: Surface high pressure will encompass much of the Southeast
U.S. including the local forecast area. A few patches of stratocu
are expected to linger into perhaps mid morning before stronger
drying occurs below the subsidence inversion. Guidance has settled
on mainly mid 60s for max temps this afternoon with abundant sunshine.
We nudged temps up just a degree or two given this latest low level
thickness values and numerical guidance trends. Light winds are
expected today, mainly from the northeast this morning and north
this afternoon.

Tonight: Dry weather will prevail as high pressure continues to
build north of the region. Temps should decouple early with readings
falling after sunset but likely steady-out late tonight as the low
level gradients tightens. A few colder sheltered spots well inland
could see some patchy frost but it looks like the onset of a light
breeze will negate stronger overnight radiational cooler. Skies
will be mainly clear with a few thin high clouds at times.


Mainly dry conditions are expected Thursday as the southeast remains
under the influence of strong high pressure centered to the north. A
mid/upper level shortwave trough crossing overhead late in the day
will serve mainly to increase cloud cover. Though a few showers
cannot be entirely ruled out, these would be most likely to occur
over marine zones when the shortwave interacts with weak coastal
troughing. Upstream ridging will then follow behind, crossing
through Friday as coastal troughing deepens/expands and surface high
pressure becomes more wedge-like. Precipitation chances will first
expand primarily across coastal waters but then activity likely
shifts towards land zones as the trough axis slides towards the
coast late. Rain chances then greatly increase overnight Friday into
Saturday as low pressure moves in quickly from the west-southwest.
Model inconsistency regarding the track appears to have increased
but a rough consensus indicates the track is probably too south/east
for much warm sectoring locally. Mid-level support looks generally
unimpressive based on the latest guidance and suggests that just a
slight chance of thunder could exist over marine zones mainly
Saturday afternoon.


While a fair bit of uncertainty continues, some improvement in
conditions is looking possible Sunday as the low pulls away from the
area with a drier atmospheric column filling back in over the region
temporarily. An upstream phase-locked low pressure system will then
transit northeast near the Great Lakes region, pulling Gulf moisture
well inland and supporting an additional period of elevated POPs
Sunday night into Monday as a cold front crosses the forecast area.
Drier high pressure is then expected to persist into mid-next-week.


VFR at KCHS/KSAV through 12Z Thursday.

Extended Aviation Outlook: VFR conditions are expected to prevail at
both terminals through late Thursday. Flight restrictions become
increasingly likely Friday through Saturday as low pressure impacts
the area.


Weak cold air advection this morning and only modest surging on tap
for marine locations seaward from the immediate coast with 15 kt
reported pre-dawn. High pressure and a fairly neutral low level
temp advection pattern today should result in a north flow in
the 10 to 15 kt range and seas 2 to 3 ft with some 4 footers out
close to the Gulf Stream.

Tonight: High pressure builds north of the waters and low level
pressure gradients will tend to tighten after midnight, especially
headed toward dawn on Thursday. North flow will become more north
to northeast and speeds should increase close to 20 kt late. Seas
will build to 3-4 ft near shore and 4-5 ft offshore.

A tight surface pressure gradient will lead to building winds and
seas, and Small Craft Advisories will be needed Thursday morning
persisting into late Saturday or very early Sunday. Gusts to near
gale strength look possible overnight Thursday into early Friday.
Another round of Small Craft Advisories will be possible Monday as a
cold front crosses the waters.


Strong northeast winds Wednesday night through Friday combined with
increasing astronomical effects will likely result in minor to
moderate coastal flooding with the Thursday and Friday morning high





Office: CAE FXUS62 KCAE 210752 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 252 AM EST Wed Nov 21 2018 .SYNOPSIS... Dry high pressure remains over the region. Skies will be mostly clear. These conditions will prevail through Thanksgiving. Temperatures will be below normal with highs in the mid 50s to low 60s. It will be near to below freezing for most areas Thursday night, with lows in the upper 20s to low 30s. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The dry pressure ridge will dominate through tonight. Skies will be clear. The pressure gradient will be weak with light north winds. The guidance consensus supports high temperatures near 60 this afternoon. The consensus indicates lows in the middle 30s north and upper 30s south tonight. Expect scattered frost. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... Canadian high pressure will move across the Great Lakes and into the Northeast U.S. during this time period. High pressure will also extend into the Southeast. Therefore, expect mostly clear skies and dry conditions through Thanksgiving. Temperatures will be below normal with highs in the mid 50s to low 60s. It will be near to below freezing Thursday night with lows in the upper 20s to low 30s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... By Friday, another front will be pushing towards the region, but through the day the surface ridge should remain strong enough to keep conditions dry across much of the cwa. There may be enough moisture moving in from the southeast ahead of the front late in the day Friday to bring a few light showers to the CSRA. Showers may be able to then spread into more of the area by late Friday night/early Saturday morning. Best chance for rainfall for most of the cwa will occur through the day Saturday, then the system moves out of the area by Saturday night. Weak high pressure and a drier conditions return for Sunday. However, another fast-moving frontal system is forecast to arrive Sunday night with another chance of showers expected. This front should move out by Monday afternoon, and drier conditions will follow by Monday night. It will be very cool on Friday, but then temperatures through the long term will be near to slightly below normal. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... Expect VFR conditions through the 24-hour TAF period. High pressure will be in the region. The dry air mass should inhibit fog formation. Skies will be clear. The pressure gradient will be weak with light north winds. EXTENDED AVIATION OUTLOOK...No significant impacts to aviation expected through Thursday. Restrictions may develop Friday and continue into Saturday associated with a low pressure system crossing the region. && .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 211143 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 643 AM EST Wed Nov 21 2018 .SYNOPSIS... High pressure will remain across the region through Thanksgiving and maintain dry and cool conditions. Widespread precipitation is likely late Friday through Saturday as a low pressure system tracks northeast from the Gulf of Mexico. Another wet frontal system will likely arrive early next week. && .NEAR TERM /THROUGH TONIGHT/... As of 630 AM EST: Morning satellite imagery reveals low clouds and patchy fog/freezing fog in the central and southwest mountain river valleys. This will be thickest in the Little Tennessee Valley until around 9 AM, but confined to the immediate vicinity of the river. Otherwise, surface high pressure will weaken as it noses across the southern Appalachians from the west today. Cool thicknesses remain in place, but good insolation and some downsloping will allow maximum temperatures to recover to within a category of climatology. Meanwhile, a backdoor cold front will mass across the Virginias to the north tonight, but generally stay north to northeast of the region through daybreak Thursday. Very shallow northwest flow moisture may bring a few clouds back into the northern mountains late tonight, but with no hint of any precipitation in the subfreezing air. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... As of 205 AM EST Wednesday: Dry and cool hipres will remain in control to begin the short term. A colder backdoor cold front will wedge in from the northeast Thu afternoon with little fanfare outside of CAA and drier sfc td/s. There was some possibility of -fzdz across the BR Thu night on a previous fcst...but the moisture looks to be much more limited by the time the colder air works in. So...a dry fcst is in place until a moist frontal system pushes in from the southwest. Model dprog/dt solns over the past few runs have become drier and a bit warmer. In fact...precip is now not expected to reach the srn FA until late Fri afternoon. Once the precip gets here will quickly spread as it lifts over a dome of very cold hipres thru the overnight and into Sat. With the parent high shifting quickly offshore Fri night...the degree of stg CAA will be limited before a non/diurnal transition takes place arnd 06z due to llvl WAA from the advancing low system. Still expect some -fzra across the nrn BR and not much else besides rain as nomograms and soundings continue to indicate either ice or rain. Raw model sfc temps generally do good with wedge a consensus of raw output was blended into the hr/ly temps which gave a bit warmer conds over the nrn mtns and for a shorter period. Thus...the -fzra shud be rather limited in scope with less than 0.1 inch fcst/d...which will transition to rain before daybreak. Ensem probs for ice indicate arnd a 50 prob for less than 0.1 inch of ice...only a 25 prob for 0.1 inches and zero prob for 0.25 inches. This agrees well with the current fcst thinking of advisory level a mention will be made in the morning HWO. The overall precip amts thru the period have come down a bit with perhaps 1.5 inches over the srn BR over 18 hrs. So...a sigfnt hydro threat is not very likely. The system shud take most of Sat to track northeast of the area and expect improving conds by Sat evening. Max temps will be pretty cold Fri with highs only in the 40s. Sat will see a slight rebound across the srn zones to the l50s...but the NW piedmont and nrn fthills will likely remain in the u40s. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... As of 235 AM EST Wednesday: Little change was made to the ext range fcst. The latest op models agree well with the large scale pattern which features another h5 s/w tracking east across the srn Midwest supporting a moist and vigorous sfc low. A cold front associated with the low looks to cross the FA Sun night with little chance of wintry precip outside of some back-side upslope -snsh or a -ra/sn mix across the wrn NC mtns. Precip amts will be on low-end due to the quickness of the system and a dry slot is progged to push in from the southwest early Mon. Winds will be fairly stg and gusty with this system...esp across the higher terrain where advisory levels may be reached by Mon afternoon into the evening. The low becomes occluded over New Eng thru the period and a secondary low may form across the Glakes which could bring a couple rounds of light diurnal NW flow -snsh both Mon and Tue nights. Max temps on Sun will be near normal...but back to below normal Mon/Tue as another Canadian sfc high builds in from the northwest. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... At KCLT and elsewhere: VFR conditions will continue through the period. Morning river valley fog is thus far staying away from the KAVL airfield and this will have to be closely monitored through 9 AM. Otherwise, the main forecast question will center around the potential for lee troughing to permit some WSW or SW surface winds at times east of the mountains. This looks most likely at the foothill sites toward 18Z, but will keep KCLT winds more WNW for this afternoon. Anticipate very light northerly winds tonight along with continued clear to mostly clear skies. Outlook: High pressure will remain over the region into Thanksgiving Day, with light winds and VFR conditions, except for the potential for patchy overnight fog in the southwest mountain river valleys. Rain will return Friday into Saturday, with associated restrictions possible across the region. Confidence Table... 11-17Z 17-23Z 23-05Z 05-06Z KCLT High 100% High 100% High 100% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 100% High 100% High 100% High 100% KHKY High 100% High 100% High 100% High 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 100% 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: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...SBK NEAR TERM...HG SHORT TERM...SBK LONG TERM...SBK AVIATION...HG