869  
FXUS62 KKEY 170931  
AFDKEY  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE KEY WEST FL  
431 AM EST WED JAN 17 2018  
 
COOLEST WEATHER OF THIS EARLY WINTER SEASON TONIGHT AND THURSDAY  
WINDY CONDITIONS TO OVERSPREAD OUR ENTIRE COUNTY WARNING AREA  
TONIGHT  
   
DISCUSSION
 
   
CURRENTLY
 
 
UNDER PARTLY CLOUDY SKIES AND NORTHEAST WINDS OF 10 TO 15 MPH,  
TEMPERATURES ARE AVERAGING IN THE MID 60S ALONG THE FLORIDA KEYS.  
MEANWHILE, LOCAL RADARS ARE VOID OF ANY SIGNIFICANT PRECIPITATION  
ECHOES. SURFACE WISE, A STRONG, ARCTIC REGION OF HIGH PRESSURE  
(1043 MB) IS CENTERED OVER EASTERN OKLAHOMA, WITH A LOOSENING  
PRESSURE GRADIENT EVIDENT OVER MOST OF THE SUNSHINE STATE. ON OUR  
MARINE DISTRICT, WINDS ARE NORTH TO NORTHEAST NEAR 15 KNOTS.  
 

 
   
SHORT TERM
 
(TODAY THROUGH FRIDAY NIGHT)  
A MASSIVE, ALBEIT WEAKENING ARCTIC REGION OF HIGH PRESSURE  
CENTERED OVER THE SOUTHERN GREAT PLAINS WILL BUILD SOUTHEASTWARD  
AND DOWN THE SPINE OF THE SUNSHINE STATE, RESULTING IN NO  
PRECIPITATION, "WELL BELOW NORMAL" TEMPERATURES AND WINDY  
CONDITIONS TONIGHT INTO THURSDAY. THEREAFTER, THE PROGRESSIVE AND  
ERODING WESTERN ATLANTIC RIDGE WILL ALLOW MODIFYING TEMPERATURES  
AS WINDS TURN PREDOMINATELY FROM THE NORTHEAST BY THE END OF THIS  
WEEK. UNTIL THEN, A NORTHERLY TRAJECTORY PROVIDING MODERATE COLD  
AIR ADVECTION COMBINED WITH COOL NEARSHORE GULF WATERS AND FLORIDA  
BAY WILL LIKELY RESULT IN THE COOLEST WEATHER ALONG THE ISLAND  
CHAIN THIS EARLY WINTER SEASON. (LOW TEMPERATURES SHOULD DROP IN  
THE UPPER 40S IN THE EXTREME UPPER KEYS AND THE LOWER TO MID 50S  
IN THE LOWER KEYS ARE LIKELY)  
 

 
   
LONG TERM
 
(SATURDAY THROUGH TUESDAY)  
WITHIN A PROGRESSIVE AND ZONAL WESTERLY FLOW ALOFT, THE  
AFOREMENTIONED HIGH PRESSURE SYSTEM WILL SLIDE SWIFTLY INTO THE  
WESTERN ATLANTIC OCEAN WITH AN EXTENSIVE RIDGE AXIS REACHING  
ACROSS THE EXTREME SOUTHEAST UNITED STATES BEFORE RETREATING  
SOUTHEASTWARD INTO THE BAHAMAS EARLY NEXT WEEK. WITH THIS PATTERN,  
LOW LEVEL MOISTURE ALONG WITH A DECAYING STABLE LAYER WILL PROMPT  
ISOLATED 10 TO PERHAPS 20 PERCENT POPS BUT WITH NO SIGNIFICANT  
RAINFALL EXPECTED. HIGH TEMPERATURES WILL RANGE FROM THE MID 70S  
THIS WEEKEND TO NEAR 80 EARLY NEXT WEEK WITH OVERNIGHT LOWS  
HOVERING AROUND 70 DEGREES.  
 

 
   
MARINE
 
 
DESPITE A BRIEF AND SUBTLE RESPITE IN THE WINDS, A SIGNIFICANT  
WIND SURGE WILL OVERSPREAD OUR ENTIRE MARINE DISTRICT EARLY THIS  
EVENING, SUBSEQUENTLY A SMALL CRAFT ADVISORY WILL BE REQUIRED  
BEGINNING WITH THE 430 PM MARINE PACKAGE. STRONG NORTH WINDS WILL  
PREVAIL TONIGHT AND EARLY THURSDAY MORNING, BEFORE ABATING  
APPRECIABLY LATE THURSDAY INTO FRIDAY. THEREAFTER, MODERATE MOSTLY  
EAST WINDS WILL KICK OFF THIS WEEKEND WITH WIND SPEED UNCERTAINTY  
INCREASING ON SUNDAY. STAY TUNED.  
 

 
   
AVIATION
 
 
VFR WILL PREVAIL AT EYW & MTH THROUGH THE TERMINAL FORECAST PERIOD.  
NE WINDS SUSTAINED NEAR 10 KNOTS EARLY THIS MORNING WILL BECOME  
NORTHERLY AND INCREASE TO NEAR 15 KNOTS AFTER 18Z, WITH GUSTS  
APPROACHING 25 TO 30 KNOTS AFTER 18/00Z.  
 

 
   
CLIMATE
 
 
IN 1983, THE DAILY RECORD LOW TEMPERATURE OF 53 DEGREES WAS LAST  
RECORDED IN KEY WEST. TEMPERATURE RECORDS HAVE BEEN KEPT SINCE  
1872.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
KEY WEST 72 55 60 58 / - 0 0 0 MARATHON 72 53 60 58 / - 0 0 0  
 

 
   
KEY WATCHES/WARNINGS/ADVISORIES
 
 
FL...NONE.  
GM...NONE.  
 

 
 

 
 
PUBLIC/MARINE/FIRE...APA  
AVIATION/NOWCASTS....MCLOVIN  
 
VISIT US ON THE WEB AT WEATHER.GOV/KEY  
 
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WWW.FACEBOOK.COM/NWSKEYWEST  
WWW.TWITTER.COM/NWSKEYWEST  
 
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