493
FXUS62 KKEY 170733
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
333 AM EDT THU JUL 17 2025
..NEW DISCUSSION, MARINE, AVIATION
DISCUSSION
ISSUED AT 330 AM EDT THU JUL 17 2025
COMPOSITE INFRARED SATELLITE AND DERIVED VORTICITY ANALYSIS
PLACES A LOW-LEVEL CYCLONIC FEATURE CENTERED SOMEWHERE IN THE
VICINITY OF THE NORTHERN GULF COAST BETWEEN LOUISIANA AND THE
FLORIDA PANHANDLE. AN EXPANSIVE LOW-LEVEL ANTICYLONIC FEATURE
DOMINATES THE NORTH ATLANTIC, SUPPORTING THE MEAN EAST TO
SOUTHEASTERLIES ACROSS THE FLORIDA KEYS AND THE ADJACENT NEARSHORE
AND OFFSHORE COASTAL WATERS AT THIS EARLY THURSDAY MORNING HOUR.
FINALLY, A WELL-DEFINED TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT)
CELL CONTINUES TO SPIN JUST OFF THE FLORIDA EAST COAST, SLOWLY
MIGRATING WESTWARD. KBYX DOPPLER RADAR HAS BEEN RELATIVELY ACTIVE
OVERNIGHT, SUPPORTED BY THE AFOREMENTIONED CYCLONIC FEATURES IN
CLOSE PROXIMITY TO THE KEYS. HOWEVER, A WEDGE OF DRY AIR SAMPLED
IN THE 850-500 MB ISOBARIC LAYER IN THE 00Z EVENING SOUNDING AT
KEY HAS LARGELY LIMITED THE DEPTH OF THIS SHOWER ACTIVITY, WITH
VERY FEW LIGHTNING STRIKES DETECTED IN THE OVERNIGHT PERIOD.
TEMPERATURES ARE GENERALLY IN THE LOWER 80S ACROSS THE ISLAND
CHAIN, WITH DEW POINTS IN THE SEASONABLY MUGGY MID TO UPPER 70S.
TODAY WILL LIKELY MARK THE FINAL BEST CHANCES FOR MEASURABLE
RAINFALL FOR THE NEXT SEVERAL DAYS, AS THE AFOREMENTIONED HIGH
STRENGTHENS IN THE NORTH ATLANTIC. GLOBAL MODEL FORECAST SOUNDINGS
HIGHLIGHT FORMIDABLE MID-LEVEL DRY AIR ADVECTING TOWARDS THE KEYS
IN THE FRESHENING EAST TO SOUTHEASTERLIES, AND THUS ELECTED TO
NUDGE RAIN AND THUNDER CHANCES DOWN TO SLIGHT LEVELS FOR TONIGHT
THROUGH SUNDAY NIGHT. AS A SECONDARY, WEAK HIGH PRESSURE FORMS IN
THE EASTERN GULF, BREEZES WILL GRADUALLY SLACKEN BY LATE IN THE
WEEKEND INTO EARLY NEXT WEEK, WHEN MORE STAGNANT JULY CONDITIONS
CAN BE ANTICIPATED.
THE FORECAST BECOMES INCREASINGLY COMPLICATED FOR THE EARLY TO
MIDDLE OF NEXT WEEK. THERE IS AT LEAST SOME NUMERICAL WEATHER
PREDICTION ENSEMBLE MEMBER AND MEAN SUPPORT FOR A FRONTAL
BOUNDARY STALLING IN THE VICINITY OF THE SOUTHEAST, WITH POSSIBLE
WEAK CYCLOGENESIS OCCURRING SOMEWHERE ALONG THIS FEATURE.
MEANWHILE, YET ANOTHER TUTT CELL IS PROGGED TO RETROGRADE FROM THE
WESTERN NORTH ATLANTIC SOUTHWESTWARD INTO THE GULF. THE
COMBINATION OF THESE FEATURES MAY LEAD TO YET ANOTHER ABOVE NORMAL
RAINY AND THUNDERY PERIOD FOR MONDAY THROUGH MID-WEEK IN THE
VICINITY OF THE KEYS, AND WE WILL CONTINUE TO MONITOR THIS
POSSIBLE SYNOPTIC PATTERN ENFOLDING.
MARINE
ISSUED AT 330 AM EDT THU JUL 17 2025
A STRONG AREA OF HIGH PRESSURE WILL BUILD WESTWARD ACROSS THE
NORTH ATLANTIC TOWARDS THE FLORIDA PENINSULA, SUPPORTING
FRESHENING EAST TO SOUTHEAST BREEZES OVER THE NEXT SEVERAL DAYS.
SMALL CRAFT SHOULD EXERCISE CAUTION HEADLINES WILL LIKELY NEED TO
BE POSTED FOR PORTIONS OF THE FLORIDA KEYS COASTAL WATERS
BEGINNING AS EARLY AS THIS EVENING, POSSIBLY LASTING THROUGH
FRIDAY.
AS A SECOND, WEAK AREA OF HIGH PRESSURE BUILDS OVER THE
EASTERN GULF FOR THE SECOND HALF OF THE WEEKEND THROUGH EARLY NEXT
WEEK, EAST TO SOUTHEAST BREEZES WILL SLACKEN, BECOMING LIGHT TO
GENTLE.
AVIATION
(06Z TAFS)
ISSUED AT 330 AM EDT THU JUL 17 2025
VFR CONDITIONS WILL PREVAIL AT EYW AND MTH FOR THE 06Z TAF
PERIOD. EARLY MORNING SHOWERS ARE LIKELY TO PRODUCE BRIEF PERIODS
OF MVFR CIGS AND VIS, BUT ARE NOT SUFFICIENT TO WARRANT TEMPO
GROUPS AT THIS TIME. WINDS WILL INCREASE TONIGHT AS SHOWER
COVERAGE DECREASES, AND GUSTS ARE EXPECTED AFTER SUNSET.
PRELIMINARY POINT TEMPS/POPS
KEY WEST 90 83 90 83 / 40 20 20 30
MARATHON 90 83 90 83 / 30 20 20 20
KEY WATCHES/WARNINGS/ADVISORIES
FL...NONE.
GM...NONE.
PUBLIC/MARINE/FIRE...BT
AVIATION/NOWCASTS....AJP
DATA ACQUISITION.....BT/AJP
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