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Spot Forecast
Issued by NWS Greer, SC
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000
FNUS72 KGSP 181135
FWSGSP

Spot Forecast for Big Witch...BIA
National Weather Service Greenville-Spartanburg SC
735 AM EDT Thu Apr 18 2024

Forecast is based on ignition time of 0800 EDT on April 18.
If conditions become unrepresentative...contact the National Weather
Service.

.DISCUSSION...
Clear and dry today behind a subtle cold front advancing across the
Carolinas.  There`s a decent swath of dry air aloft that afternoon
mixing should be able to tap into, which allows afternoon RHs to drop
into the lower 30s.  Now, there`s some model variation in how low
dewpoints will fall, so there`s an outside chance the RHs could drop
a bit lower than what`s in the tabular section below...with the lowest
reasonable RH based on the high-resolution models being around 28%.

Winds will be more anemic today.  Despite the cold frontal passage,
it looks like there`s just not much wind to mix down, so even in the
heat of the day when mixing is at its peak, gusts won`t get above
 7-9mph.  Transport winds will be westerly, but similarly slow, which
will somewhat constraint smoke dispersal.

Tonight, conditions will deteriorate as a line of broken showers and
thunder approaches from the west.  Rain will likely continue into the
rest of Friday.

.REST OF TODAY...

Sky/weather.........Sunny (5-15 percent).
Max temperature.....Around 75.
Min humidity........31 percent.
Wind (20 ft)........Light winds becoming west around 5 mph late in
                    the afternoon, then becoming light late in the
                    afternoon.
Mixing height.......7000 ft AGL.
Transport winds.....Northwest 6 to 9 mph shifting to the west 5 to
                    6 mph late in the afternoon.
Smoke dispersal.....Poor (3200 knot-ft) early in the morning
                    increasing to good (34800 knot-ft) in the
                    afternoon.
LVORI...............3.
ADI.................7 early in the morning increasing to 48 in the
                    afternoon.
Stability class.....1.
Pcpn amount.........0.00 inches.
Ceiling (FT)........1300 increasing to 23000 in the late morning
                    and afternoon, then decreasing to 9000 late in
                    the afternoon.
Visibility (SM).....10.
Sfc pressure (in)...26.49.

TIME (EDT)      8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
Sky (%).........21  15  7   2   1   3   4   6   10  7
Weather cov.....
Weather type....
Tstm cov........
Temp............53  58  61  64  67  70  72  74  75  75
Dewpoint........49  48  47  46  45  44  43  43  42  42
RH..............83  70  61  52  45  39  36  33  31  31
20 FT wind dir..N   N   NW  NW  W   W   W   W   W   SW
20 FT wind spd..2   2   2   3   3   3   3   3   5   3
20 FT wind gust.3   3   3       5   6   6   6   6   6
Mix hgt (kft)...0.5 1.1 1.6 2.4 3.0 4.3 5.8 6.4 7.0 5.3
Transp wind dir.NW  NW  NW  NW  N   NW  W   W   W   SW
Transp wind spd.7   8   8   9   7   6   5   5   6   5
LVORI...........4   3   2   2   2   1   1   1   1   1
ADI.............7   11  17  28  27  31  33  36  48  30
VRate kt-ft/10003   8   11  19  18  21  23  26  35  21
Ceiling (hft)...13  240 230 240 250 250 250 240 240 90
Visibility (sm).10  10  10  10  10  10  10  10  10  10
Sfc pres (in)...652 653 653 654 653 652 652 651 650 649

.TONIGHT...

Sky/weather.........Partly cloudy (20-30 percent) then becoming
                    mostly cloudy (60-70 percent). Slight chance of
                    rain showers after 3 am. Slight chance of
                    thunderstorms after 3 am.
Min temperature.....Around 56.
Max humidity........79 percent.
Wind (20 ft)........Southwest winds around 5 mph shifting to the
                    south 5 to 6 mph in the late evening and
                    overnight, then becoming light early in the
                    morning. Gusty and erratic winds expected near
                    thunderstorms after 3 am.
Mixing height.......500 ft AGL.
Transport winds.....Southwest 5 to 6 mph shifting to the south 6 to
                    9 mph early in the evening, then shifting to
                    the southwest 7 to 9 mph overnight.
Smoke dispersal.....Fair (18500 knot-ft) early in the evening
                    decreasing to poor (2400 knot-ft) late in the
                    night.
LVORI...............3.
ADI.................2 to 27.
Stability class.....3.
Pcpn amount.........0.12 inches.
Ceiling (FT)........9000 increasing to 23000 late in the evening,
                    then decreasing to 16000 overnight decreasing
                    to 8000 after 3 am decreasing to 2700.
Visibility (SM).....8.
Sfc pressure (in)...26.45.

TIME (EDT)      6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM
Sky (%).........7   7   6   14  19  28  38  47  55  63  71  79
Weather cov.....                                    SCH CHC CHC
Weather type....                                    RW  RW  RW
Tstm cov........                                    SCH SCH SCH
Temp............73  71  66  64  63  62  61  60  60  59  58  58
Dewpoint........43  44  45  45  45  45  45  45  45  46  47  48
RH..............34  39  47  50  52  55  56  58  59  62  65  69
20 FT wind dir..SW  SW  S   S   SE  S   S   S   S   S   S   SW
20 FT wind spd..5   5   5   6   6   6   6   5   5   5   5   3
20 FT wind gust.7   6   7   7   7   7   7   6   6       6   5
Mix hgt (kft)...3.7 2.1 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
Transp wind dir.SW  W   SE  S   S   S   S   S   SW  SW  SW  SW
Transp wind spd.6   5   6   9   9   9   9   8   9   7   9   8
LVORI...........2   2   2   2   2   3   3   3   3   3   3   3
ADI.............27  2   3   4   4   4   4   5   6   5   6   5
VRate kt-ft/100019  8   2   4   4   4   4   4   4   3   4   4
Ceiling (hft)...90  90  90  250 250 230 230 190 190 160 80  27
Visibility (sm).10  10  10  10  10  10  10  10  10  10  9   8
Sfc pres (in)...649 649 650 649 649 648 648 647 647 646 646 645

.FRIDAY...

Sky/weather.........Partly sunny (65-75 percent). Rain showers and
                    chance of thunderstorms.
Max temperature.....Around 68.
Min humidity........60 percent.
Wind (20 ft)........Light winds becoming southwest 5 to 8 mph.
                    Gusty and erratic winds expected near
                    thunderstorms in the morning and early
afternoon.
Mixing height.......3600 ft AGL.
Transport winds.....West 7 to 14 mph.
Smoke dispersal.....Poor (2900 knot-ft) early in the morning
                    increasing to good (43700 knot-ft) in the
                    afternoon.
LVORI...............3.
ADI.................5 early in the morning increasing to 49 in the
                    afternoon.
Stability class.....4.
Pcpn amount.........0.25 inches.
Ceiling (FT)........1900 increasing to 6000 early in the morning.
Visibility (SM).....7 in the morning and early afternoon.
Sfc pressure (in)...26.43.

TIME (EDT)      6AM 7AM 8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
Sky (%).........81  82  84  81  73  57  51  54  57  57  57  57
Weather cov.....CHC CHC LKY LKY LKY DEF DEF DEF DEF DEF DEF LKY
Weather type....RW  RW  RW  RW  RW  RW  RW  RW  RW  RW  RW  RW
Tstm cov........SCH SCH SCH CHC CHC CHC CHC CHC CHC CHC CHC CHC
Temp............56  57  57  58  60  61  63  65  66  67  67  67
Dewpoint........48  49  50  51  53  54  54  54  54  53  53  53
RH..............74  75  76  79  78  76  72  69  64  62  61  60
20 FT wind dir..S   SW  SW  SW  SW  W   SW  W   W   W   W   W
20 FT wind spd..3   5   5   5   5   7   7   7   7   8   8   8
20 FT wind gust.5       6   6   7   9   10  10  12  12  12  12
Mix hgt (kft)...0.5 0.5 0.6 0.8 1.1 1.8 2.8 3.2 3.6 3.3 3.2 3.0
Transp wind dir.SW  S   SW  W   SW  W   W   W   W   W   W   W
Transp wind spd.7   7   7   8   9   9   13  14  14  12  12  12
LVORI...........3   4   4   4   4   3   3   1   1   1   1   1
ADI.............5   5   5   6   12  21  39  46  49  39  38  37
VRate kt-ft/10003   3   4   6   9   14  31  39  44  33  32  31
Ceiling (hft)...19  19  60  60  60  60  60  60  60  60  60  60
Visibility (sm).8   7   7   8   8   9   9   9
Sfc pres (in)...645 645 645 646 647 648 647 645 644 644 643 643

$$
Forecaster...Mike Rehnberg
Requested by...Dave Collins
Type of request...PRESCRIBED
.TAG 2410923.2/GSP
.DELDT 04/18/24
.FormatterVersion 2.0.0
National Weather Service Weather Forecast Office
