124
FNUS72 KMLB 180755
FWSMLB
SPOT FORECAST FOR GRASSY ISLAND...SFWMD
NATIONAL WEATHER SERVICE MELBOURNE FL
355 AM EDT THU JUN 18 2026
FORECAST IS BASED ON IGNITION TIME OF 0900 EDT ON JUNE 18.
IF CONDITIONS BECOME UNREPRESENTATIVE, CONTACT THE NATIONAL WEATHER
SERVICE.
...HEAT ADVISORY IN EFFECT FROM 11 AM THIS MORNING TO 7 PM EDT
THIS EVENING...
DISCUSSION
SCATTERED SHOWERS (30%) AND LIGHTNING STORMS ARE FORECAST TO DEVELOP
INTO THE AFTERNOON AND EVENING. THE POTENTIAL EXISTS FOR AN
ISOLATED STRONG STORM. SOUTH WINDS AT 5-10MPH WITH GUSTS TO
15-20MPH ARE FORECAST. NO CRITICAL RH CONCERNS ARE EXPECTED.
DISPERSION VALUES WILL BE FAIR TO GENERALLY GOOD. AN AFTERNOON
HIGH OF 96F IS FORECAST WITH A MAXIMUM HEAT INDEX VALUE UP TO
108F. REMEMBER TO TAKE EXTRA PRECAUTIONS TODAY FROM THE HEAT.
REST OF TODAY
SKY/WEATHER.........MOSTLY SUNNY (35-45 PERCENT). SLIGHT CHANCE OF
SHOWERS AND THUNDERSTORMS EARLY IN THE
AFTERNOON. CHANCE OF SHOWERS AND THUNDERSTORMS
LATE IN THE AFTERNOON.
CHANCE OF PCPN......30 PERCENT.
MAX TEMPERATURE.....AROUND 96.
MIN HUMIDITY........49 PERCENT.
WIND (20 FT)........SOUTH WINDS 6 TO 8 MPH. GUSTY AND ERRATIC WINDS
EXPECTED NEAR THUNDERSTORMS LATE IN THE
AFTERNOON.
MIXING HEIGHT.......3900 FT AGL INCREASING TO 4500 FT AGL LATE IN
THE AFTERNOON.
TRANSPORT WINDS.....SOUTH 10 TO 12 MPH.
DISPERSION INDEX....30 INCREASING TO 53.
LVORI...............4 DECREASING TO 1 LATE IN THE MORNING.
TIME (EDT) 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
SKY (%).........30 40 50 48 44 46 44 46 50
WEATHER COV..... SCH SCH CHC CHC
WEATHER TYPE.... RW RW RW RW
TSTM COV........ SCH SCH CHC CHC
CHC OF PCPN (%).0 0 0 10 10 20 20 30 30
TEMP............82 88 90 91 93 94 95 96 94
RH..............85 72 66 62 56 53 51 49 51
20 FT WIND DIR..S S S S S S S S S
20 FT WIND SPD..6 7 8 8 8 8 8 8 8
20 FT WIND GUST.10 13 14 15 15 15 15 15 15
MIX HGT (KFT)...2.0 2.8 3.1 3.4 3.9 4.2 4.4 4.5 4.3
TRANSP WIND DIR.S S S S S S S S S
TRANSP WIND SPD.12 12 12 12 12 10 10 10 10
DISPERSION IDX..30 40 44 48 51 53 53 54 53
LVORI...........4 3 1 1 1 1 1 1 1
TONIGHT
SKY/WEATHER.........PARTLY CLOUDY (40-50 PERCENT) THEN BECOMING
MOSTLY CLOUDY (55-65 PERCENT) THEN BECOMING
PARTLY CLOUDY (35-45 PERCENT). CHANCE OF
SHOWERS AND THUNDERSTORMS EARLY IN THE EVENING,
THEN SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS
LATE IN THE EVENING.
CHANCE OF PCPN......30 PERCENT.
MIN TEMPERATURE.....AROUND 76.
MAX HUMIDITY........97 PERCENT.
WIND (20 FT)........SOUTH WINDS 5 TO 8 MPH EARLY IN THE EVENING
BECOMING LIGHT. GUSTY AND ERRATIC WINDS
EXPECTED NEAR THUNDERSTORMS IN THE EVENING.
MIXING HEIGHT.......1900 FT AGL DECREASING TO 400 FT AGL EARLY IN
THE EVENING.
TRANSPORT WINDS.....SOUTH 6 TO 10 MPH.
DISPERSION INDEX....44 DECREASING TO 5.
LVORI...............2 INCREASING TO 6.
TIME (EDT) 6 PM 8 PM 10 PM MIDNGT 2 AM 4 AM
SKY (%).........43 62 65 67 57 43
WEATHER COV.....CHANCE CHANCE S CHC
WEATHER TYPE....RNSHWR RNSHWR RNSHWR NONE NONE NONE
TSTM COV........CHANCE CHANCE S CHC
CHC OF PCPN (%).30 30 20 10 0 0
TEMP............93 86 82 81 80 78
RH..............54 70 79 82 85 91
20 FT WIND......S 8 S 5 S 2 S 2 S 2 S 2
20 FT WIND GUST.14 13 8 7 7 7
MIX HGT (FT)....3400 600 500 500 500 400
TRANSPORT WIND..S 10 S 9 S 6 S 7 S 7 S 7
DISPERSION IDX..44 6 3 3 3 3
LVORI...........1 3 4 5 5 6
JUNETEENTH
SKY/WEATHER.........MOSTLY SUNNY (35-45 PERCENT). SLIGHT CHANCE OF
SHOWERS AND THUNDERSTORMS EARLY IN THE
AFTERNOON. CHANCE OF SHOWERS AND THUNDERSTORMS
LATE IN THE AFTERNOON, THEN SHOWERS AND
THUNDERSTORMS LIKELY LATE IN THE AFTERNOON.
CHANCE OF PCPN......60 PERCENT.
MAX TEMPERATURE.....AROUND 94.
MIN HUMIDITY........53 PERCENT.
WIND (20 FT)........LIGHT WINDS BECOMING SOUTH 5 TO 7 MPH EARLY IN
THE MORNING. GUSTY AND ERRATIC WINDS EXPECTED
NEAR THUNDERSTORMS LATE IN THE AFTERNOON.
MIXING HEIGHT.......1200 FT AGL INCREASING TO 4000 FT AGL LATE IN
THE MORNING, THEN INCREASING TO 5000 FT AGL
LATE IN THE AFTERNOON DECREASING TO 3000 FT AGL
LATE IN THE AFTERNOON.
TRANSPORT WINDS.....SOUTH 7 TO 10 MPH SHIFTING TO THE SOUTHWEST 9
TO 10 MPH LATE IN THE AFTERNOON.
DISPERSION INDEX....3 INCREASING TO 15 EARLY IN THE MORNING, THEN
INCREASING TO 36 LATE IN THE MORNING INCREASING
TO 45 LATE IN THE MORNING INCREASING TO 57
DECREASING TO 37 LATE IN THE AFTERNOON.
LVORI...............6 INCREASING TO 8 EARLY IN THE MORNING, THEN
DECREASING TO 5 EARLY IN THE MORNING DECREASING
TO 3 LATE IN THE MORNING DECREASING TO 1.
TIME (EDT) 6 AM 9 AM NOON 3 PM
SKY (%).........36 34 30 39
WEATHER COV..... CHANCE
WEATHER TYPE....NONE NONE NONE RNSHWR
TSTM COV........ CHANCE
CHC OF PCPN (%).0 0 0 30
TEMP............77 83 91 94
RH..............94 82 62 53
20 FT WIND......S 3G8 S 6G10 S 7G13 S 6G13
MIX HGT (FT)....400 2400 4000 4800
TRANSPORT WIND..S 8 S 10 S 9 SW 9
DISPERSION IDX..3 32 45 57
LVORI...........6 3 1 1
FORECASTER...FEHLING
REQUESTED BY...KYLE THAYER
TYPE OF REQUEST...PRESCRIBED
.TAG 2615729.0/MLB
.DELDT 06/18/26
.FORMATTERVERSION 2.0.0
.EMAIL KTHAYER@SFWMD.GOV
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