Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/08/20
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1021 PM EDT Thu May 7 2020
.SYNOPSIS...
Cool and dry air will remain over the region, before a frontal
system brings showers on Friday. Colder Canadian air will arrive
over the weekend, which will maintain below normal temperatures and
could create frost and freeze conditions across the region.
Temperatures will rebound early next week.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 1020 pm EDT: The forecast remains on track, with deep-layer
northwest flow stretching from the central Plains to the Southern
Appalachians late this evening. Mid and high-level cloudiness
continues to approach forecast area well east of a prominent trough
digging southward from the northern Plains. With modest height rises
over the southeast, and surface high pressure in place across the
area, good radiational cooling conditions are expected through the
early overnight hours. This should permit temps to fall quickly back
into the upper 30s to lower 40s across most of the area. However,
the encroaching mid/high clouds late in the night should halt the
radiational cooling, hopefully just short of any significant frost
and freeze issues. Will continue to feature patchy frost in the
mountains and across the NC foothills in the forecast and the HWO.
The upstream trough will sweep quickly southeast toward the southern
Appalachians by late in the day on Friday. A robust southwesterly
flow of moisture will spread into the area through the day ahead of
this wave, with very gusty high elevation winds in the southern NC
mountains, and increasing rain/shower coverage through the day.
Still anticipate the best dynamics passing mainly to the north of
the area, while any hint of instability will be shunted well to the
south. This should make the mainly afternoon rainfall event a fairly
low impact one, with any isolated 1 to 2 inch rainfall amounts
confined to the Smokies and nearby mountain upslope areas. Winds
will approach Advisory criteria, gusts above 45 mph, mainly along
only the highest ridges of the southern NC mountains, so no wind
hazard headlines will be posted at this time. The passing cold front
should be squarely in the heart of the forecast area by late day,
with colder air poised to fill in from the northwest. Despite the
warm advection and rebounding thicknesses, clouds and increasing
precipitation should cause temperatures to struggle into the 50s
mountains and 60s east through the day.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 145 PM EDT Thursday: The overall synoptic pattern has not
changed much from the previous fcst. A cold front will be exiting
the FA to the east Fri night, while an anomalous 1025 mb high builds
south across the MS Valley. With temps quickly dropping behind the
front expect a period of continued precip switching over the -snsh
or a rain snow mix across the NC mtns. This precip wont last too
long however as very dry air mixes in from the northwest. Snowfall
amts will be light with generally an inch or less mainly across the
Smokies and ridges of the TN/NC line.
With the new cP airmass mixing in...mins will drop below freezing
across the mtns shortly aft midnight and remain sub-freezing thru
daybreak before a slowly warming takes place. The higher elevs abv
3.5 Kft shud see a hard freeze with temps remaining below 28 F for at
least 4 hrs. Thus, the freeze watch still looks good for the NC mtns
and NE GA. Winds will be quite gusty early morning Sat, but subdue
fairly quickly during the day as the p/grad loosens sigfnt/ly. A
high elevation wind adv may be needed for the morning hrs, however.
With the very good mixing and drier Canadian air building in...min
RH values will drop to 25% or less outside the mtns. There likely
wont be much of an overlap of low RH with stronger winds for a high
fire spread concern, however, a fire danger statement will likely be
needed Sat afternoon aft conferring with surrounding offices and
forestry officials.
With the sfc high settling over the FA Sat night, very good rad
cooling conds will set up, and mins will drop into the mid to upper
30s over most locales, thus a frost adv will likely be issued on
Sat. Max temps will be held a good 20+ degrees below normal Sat and
about 8-10 degrees below normal Sun as the high center shifts
offshore and relatively warm sw/ly flow modifies the airmass. Mins
will be quite cold Fri night, with daily records possibly broken at
KAVL and KCLT by a couple degrees.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As fo 220 PM EDT Thursday: A quick moving h5 s/w will swing across
the OH Valley Sun night and an associated cold front may have just
enuf moisture to work with to generate -shra/snsh across the nrn NC
mtns...yet any sn accums would be minimal. This front will cross the
rest of the FA dry as another stg cP high builds in from the
northwest. This airmass wont be as cold as the previous cP air on
Sat, however, it will help lower mins to frost levels across the NC
mtns both Sun and Mon night.
The airmass will be slow to modify as the high remains quite broad
while it crosses the FA and keeps winds n/ly then weak sw/ly late in
the period. So, will anticipate good insol each day Mon/Tue with
highs remaining below normal by a few degrees. With drier sfc td/s
persisting on Mon, the non/mtns could see RH values drop to the
25-30% range and create fire wx concerns. Wed and Thu look like nice
days as temps finally rise back to normal and sfc td/s remain in the
40-50 F range. The only chance noted for precip during this time
looks to be weak and isol upslope showers ahead of a developing wrn
storm system Wed afternoon into Thu.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
At KCLT and Elsewhere: Anticipate VFR conditions through most of the
current TAF period, as mainly mid to high level moisture arrives
from the west late tonight through Friday morning. The deeper
moisture will arrive quickly through the afternoon hours ahead of
the approaching shortwave and associated surface cold front, with
occasional MVFR cigs or visibility possible under any better rain
showers. Light winds tonight will quickly become gusty from the S to
SW with mixing late Friday morning. Peak gusts into the 20 to 30 kt
range are expected during the afternoon hours. Thunderstorms are not
expected within the fairly stable airmass.
Outlook: A cold front will move east of the terminal forecast area
Friday night, with brief northwest flow moisture near KAVL. Dry high
pressure returns from the west over the weekend. Frost on aircraft
could become an issue over the weekend, especially Sunday morning.
Otherwise, dry conditions will likely persist into early next week.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 96%
KAVL High 100% High 100% High 100% High 91%
KHKY High 100% High 100% High 100% High 91%
KGMU High 100% High 100% High 100% High 98%
KAND High 100% High 100% High 100% High 94%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Freeze Watch from late Friday night through Saturday morning
for GAZ010.
NC...Freeze Watch from late Friday night through Saturday morning
for NCZ033-048>053-058-059-062>065-501-503-505-507-509.
SC...None.
&&
$$
SYNOPSIS...17
NEAR TERM...HG
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...HG