FXUS64 KMEG 220615
AFDMEG
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
1215 AM CST TUE DEC 22 2009
.UPDATE...
UPDATED FOR 06Z TAF DISCUSSION.
&&
.PREV DISCUSSION... /ISSUED 920 PM CST MON DEC 21 2009/
DISCUSSION...
DENSE FOG DEVELOPED RAPIDLY THIS EVENING IN SUB FREEZING
TEMPERATURES ACROSS NORTHWEST TENNESSEE WHERE DAYTIME TEMPERATURES
STRUGGLED TO REACH THE UPPER 30S. EXPECT THE FOG AND OTHER AREAS
ACROSS THE MIDSOUTH TO DROP TO AT LEAST FREEZING UNDER MOSTLY
CLEAR SKIES SHORTLY AFTER MIDNIGHT. FOG SHOULD DEVELOP IN THIS
AREA...THUS ISSUED A FREEZING FOG ADVISORY FOR MUCH OF THE
MIDSOUTH. THE DELTA REGION...INCLUDING MEMPHIS METRO WILL REMAIN
ABOVE FREEZING AND TEMP/DEW POINT SPREADS SHOULD BE ENOUGH THAT
FOG WILL NOT HINDER VISIBILITIES MUCH.
UPDATED FORECAST HAS BEEN SENT ALONG WITH THE FREEZING FOG
ADVISORY UNTIL 8 AM TUESDAY.
AC
&&
.PREV DISCUSSION... /ISSUED 353 PM CST MON DEC 21 2009/
DISCUSSION...
ACTIVE WEATHER IN STORE FOR THE CHRISTMAS WEEK. GOES WATER VAPOR
IMAGERY SHOWED AN UPPER LEVEL TROF JUST OFF OF THE PACIFIC NORTHWEST
COAST AT DISCUSSION TIME. THIS FEATURE WILL COME ASHORE TONIGHT...
AND DIG INTO THE FOUR CORNERS REGION THROUGH LATE TUESDAY EVENING.
SHORTWAVE UPPER LEVEL RIDGING WILL BRIEFLY BUILD DOWNSTREAM OF
DIGGING UPPER LOW...LEADING TO MILD AFTERNOON TEMPS ACROSS THE
MIDSOUTH...ASSUMING NO PESKY LOW STRATUS AS OCCURRED TODAY OVER
NORTHERN WEST TN. HIGH CLOUDS WILL INCREASE HOWEVER...IN ADVANCE
OF A LEAD SHORTWAVE. THIS SHORTWAVE WILL INTERACT WITH INCREASING
LOW/MID LEVEL MOISTURE TO TOUCH OFF SCATTERED LATE EVENING SHOWERS
WEST OF THE MS RIVER. THIS ACTIVITY SHOULD GRADUALLY EXPAND EAST
OF THE MS RIVER OVERNIGHT. WITH MOIST SOUTHERLY FLOW...ALL AREAS
OF THE MIDSOUTH SHOULD REMAIN ABOVE FREEZING.
WEDNESDAY WILL SEE STRENGTHENING UPPER LEVEL DIFFLUENCE ACROSS THE
MIDSOUTH... AS THE UPPER LOW LIFTS INTO TX. EXPECT SHOWERS TO
EXPAND IN COVERAGE ACROSS THE MIDSOUTH DURING THE DAY. LOW LEVEL
PRESSURE GRADIENT WILL TIGHTEN WEDNESDAY AFTERNOON AND EVENING NIGHT...
AHEAD OF A DEEPENING SURFACE LOW LIFTING INTO MO. A SECONDARY
SURFACE LOW WILL LIKELY FORM BY THIS TIME...OVER CENTRAL MS.
ALTHOUGH SLIGHT ELEVATED INSTABILITY WILL BE POSSIBLE OVER THE
MIDSOUTH...GREATEST ELEVATED INSTABILITY...PERHAPS SURFACE
BASED...WILL OCCUR TO THE SOUTH...NEARER TO GULF COAST. ALTHOUGH
LOW LEVEL SHEAR PROFILES WILL BE IMPRESSIVE...THE MAJORITY OF THE
DIRECTIONAL SHEAR WILL OCCUR IN THE STABLE LOW LEVEL INVERSION.
SHEAR PROFILES ABOVE THIS INVERSION WILL BE NEAR UNIDIRECTIONAL.
HAVE TENDED TOWARD THE MORE CONSERVATIVE MET GUIDANCE WINDS OVER
THE MAV WEDNESDAY AND WEDNESDAY NIGHT. EXPECT THE STRONGEST WINDS
JUST OFF THE SURFACE NEAR THE THE TOP OF THE LOW LEVEL INVERSION.
NONETHELESS...WEDNESDAY AND THURSDAY WILL STILL BE ONE OF THE
WINDIEST PERIODS OF THE YEAR.
THE MAIN FRONT/DRYLINE WILL SWING THROUGH THE MIDSOUTH DURING THE
DAY THURSDAY...DRIVING A LINE OF SHOWERS AND EMBEDDED THUNDERSTORMS
EAST. AS MENTIONED ABOVE...INSTABILITY WILL BE MARGINAL AT BEST...AND
ELEVATED. STILL EXPECT A CHANCE OF STRONG WINDS... PARTICULARLY IN
THE STRONG SUBSIDENCE BEHIND THE ADVANCING SURFACE FRONT/DRYLINE...
THURSDAY AFTERNOON AND EARLY EVENING.
LATEST SEVERAL GFS RUNS PINWHEEL THE UPPER LOW OVER THE UPPER
MIDWEST FRIDAY AND SATURDAY. NORTHERN PORTIONS OF THE MIDSOUTH
WILL BE IN SUFFICIENT PROXIMITY TO THE UPPER LOW FOR SCATTERED
SNOW FLURRIES CHRISTMAS EVENING AND SATURDAY. OTHERWISE... THE
CHANCES OF A WHITE CHRISTMAS ACROSS THE MIDSOUTH APPEAR TO BE
VERY LOW.
FORECAST CONFIDENCE FALLS FOR THE LATE WEEKEND AND EARLY NEXT WEEK
PERIODS...WITH THE ECMWF AND GFS MODELS SHOWING RUN TO RUN
INCONSISTENCIES AND POOR AGREEMENT WITH EACH OTHER ON TODAY/S 12Z
RUNS. HAVE TEMPERED MEX GUIDANCE HIGH TEMPS FOR EARLY NEXT WEEK...
GIVEN LIMITED CONFIDENCE IN THE UPPER RIDGE BUILDING IN.
PWB
&&
.AVIATION...
06Z TAF CYCLE
VFR CONDITIONS WILL PREVAIL THROUGH LATE TONIGHT WITH SOME
FOG/FREEZING FOG REDUCING VISBYS TO MVFR CATEGORIES EARLY TUESDAY
MORNING. ICING ON AIRCRAFT COULD BECOME A PROBLEM WHERE FREEZING
FOG DEVELOPS AND PERSISTS. WINDS SHOULD REMAIN EASTERLY TO SOUTHEASTERLY
OVERNIGHT. FOG SHOULD MIX OUT BY MID MORNING WITH VFR CONDITIONS
WITH THICKENING AND LOWERING MID AND HIGH CLOUDS BY AFTERNOON
EXPECTED. WINDS SHOULD ALSO INCREASE FROM THE SOUTH...ESPECIALLY
BY TUESDAY AFTERNOON. RAIN CHANCES WILL INCREASE AFTER SUNSET
TUESDAY EVENING AT JBR AND MEM TERMINALS WITH MVFR CIGS AND VISBYS
POSSIBLE.
JLH
&&
.PRELIMINARY POINT TEMPS/POPS...
MEM 49 60 53 60 / 60 90 90 90
MKL 45 57 54 59 / 40 80 80 90
JBR 46 55 49 57 / 70 90 90 90
TUP 45 56 50 62 / 30 70 80 90
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...FREEZING FOG ADVISORY UNTIL 8 AM CST THIS MORNING FOR CLAY-
CRAIGHEAD-GREENE-LAWRENCE-MISSISSIPPI-POINSETT-RANDOLPH.
MO...FREEZING FOG ADVISORY UNTIL 8 AM CST THIS MORNING FOR DUNKLIN-
PEMISCOT.
MS...FREEZING FOG ADVISORY UNTIL 8 AM CST THIS MORNING FOR ALCORN-
BENTON MS-CALHOUN-CHICKASAW-ITAWAMBA-LAFAYETTE-LEE MS-
MARSHALL-MONROE-PONTOTOC-PRENTISS-TIPPAH-TISHOMINGO-UNION-
YALOBUSHA.
TN...FREEZING FOG ADVISORY UNTIL 8 AM CST THIS MORNING FOR CARROLL-
CHESTER-CROCKETT-DECATUR-DYER-FAYETTE-GIBSON-HARDEMAN-
HARDIN-HAYWOOD-HENDERSON-HENRY-LAKE-MADISON-MCNAIRY-OBION-
WEAKLEY.
&&
$$
