Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KKEY 281936
AFDKEY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
236 PM EST WED JAN 28 2015

.DISCUSSION...WATER VAPOR IMAGERY HIGHLIGHTS AN IMPRESSIVE STREAK OF
DRY AIR ROUNDING THE BASE OF THE FLORIDA PENINSULA. THIS ARID SWATH
HINTS AT THE LARGE SCALE SUBSIDENCE BETWEEN THE UPPER LEVEL RIDGE TO
OUR WEST AND THE DEPARTING LONG WAVE TROUGH. AT THE SURFACE...HIGH
PRESSURE IS FAVORED ACROSS THE SOUTHEASTERN UNITED STATES. AVAILABLE
SURFACE OBSERVATIONS INDICATE HIGH PRESSURE IS SPILLING SOUTH THROUGH
THE APPALACHIANS. SURFACE WINDS ARE FROM THE NORTHEAST AND HAVE
FREQUENTLY GUSTED NEAR 20 KNOTS. SKIES ARE SUNNY AND THE RADAR IS
ECHO FREE. TEMPERATURES HAVE SLUGGISHLY RISEN THROUGH THE
60S...BRRRR.

.SHORT TERM (TONIGHT THROUGH FRIDAY NIGHT)...LOW THETA-E AIR HAS
ENGULFED THE FLORIDA PENINSULA...IN FACT...DEWPOINTS HAVE FALLEN INTO
THE LOWER 30S AT MOST LOCATIONS. GIVEN THE LOCATION OF THE BUILDING
HIGH PRESSURE SYSTEM...A DENSITY BLOW APPEARS LIKELY TONIGHT. THE
HIGH WILL SLIDE EAST INTO THE WESTERN ATLANTIC THURSDAY AND THURSDAY
NIGHT...LEADING THE WAY FOR A DECELERATING FRONTAL BOUNDARY WHICH
WILL STALL ACROSS FLORIDA FRIDAY AND FRIDAY NIGHT. THUS...LOWS 55 TO
59 TONIGHT...FOLLOWED BY ANOTHER COOL AFTERNOON ON THURSDAY. WE
ADVERTISE LOWER 70S ON THURSDAY...BUT FIND IT HARD TO BELIEVE WE WILL
VEER TO EAST GIVEN THE SIGNIFICANTLY COOLED GULF SIDE WATER
TEMPERATURES. IF WINDS REMAIN NORTHEAST...THEN HIGHS WILL STRUGGLE TO
GET OUT OF THE 70S. NEVERTHELESS...A MODERATING TREND IS LIKELY
FRIDAY AND FRIDAY NIGHT. RAIN CHANCES ARE NIL THROUGH THE SHORT TERM.

&&

.LONG TERM (SATURDAY THROUGH WEDNESDAY)...A CUTOFF LOW ACROSS THE
BAJA WILL DIRECT LOWER HEIGHTS INTO THE SOUTHEASTERN UNITED STATES.
AS A RESULT...THE SUBTROPICAL RIDGE WILL ERODE AND RECEDE TO THE
SOUTH SATURDAY THROUGH MONDAY.  THE CUTOFF IS PROGGED TO
PHASE...OPEN...AND SLIDE INTO THE MISSISSIPPI RIVER VALLEY TUESDAY
THROUGH WEDNESDAY. THIS SCENARIO WOULD FAVOR CYCLOGENESIS ACROSS THE
NORTHWESTERN GULF OF MEXICO. THUS...A MAINLY WEAK WIND FIELD WOULD
TEND TO STRENGTHEN IN RESPONSE TO THE DEVELOPING LOW PRESSURE SYSTEM.
FOR NOW...WE HAVE RETAINED THE PREVIOUS FORECAST WHICH ADVERTISES
MILD WEATHER AND NO RAIN CHANCE. WE AGREE WITH THE PREVIOUS
DISCUSSION WHICH HIGHLIGHTS ISENTROPIC ASCENT AT SOME TIME OVER THE
WEEKEND. HOWEVER...WE HAVE NOT INTRODUCED RAIN CHANCES BASED ON OUR
LOW CONFIDENCE IN TIMING.

&&

.MARINE...ANOTHER SURGE IN NORTH TO NORTHEAST BREEZES IS EXPECTED
TONIGHT...THUS SMALL CRAFT SHOULD EXERCISE CAUTION FOR INCREASING
WINDS. FROM SYNOPSIS...A HIGH PRESSURE SYSTEM OVER THE EASTERN
UNITED STATES WILL DROP SOUTHWARD TONIGHT THROUGH SATURDAY...AS A
RESULT... FRESH NORTHERLY BREEZES WILL GRADUALLY DECREASE AND VEER TO
THE EAST. THEREAFTER...HIGH PRESSURE WILL REBUILD ACROSS THE WESTERN
NORTH ATLANTIC.

&&

.AVIATION...VFR CONDITIONS WITH CLEAR SKIES WILL PREVAIL AT ISLAND
TERMINALS THIS AFTERNOON. NORTH WINDS ON THE LOW SIDE OF 10 TO 15
KNOTS GUSTING TO 15 TO 20 KNOTS WILL RELAX A BIT THIS AFTERNOON...BUT
STRENGTHEN BACK TO 10 TO 15 KNOTS AND OCCASIONALLY GUSTY TONIGHT.


&&

.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  59  72  62  74 / 0 0 0 0
MARATHON  58  71  62  73 / 0 0 0 0

&&

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

$$

PUBLIC/MARINE.........CLR
AVIATION/NOWCASTS.....11
DATA COLLECTION.......PARKE

VISIT US ON THE WEB AT WWW.WEATHER.GOV/KEYWEST

FOLLOW US ON FACEBOOK AND TWITTER AT...

WWW.FACEBOOK.COM/NWSKEYWEST
WWW.TWITTER.COM/NWSKEYWEST


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.