Aug 22 Afternoon Weather Discussion

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
315 PM EDT SUN AUG 22 2010

.SYNOPSIS...
19Z WATER VAPOR AND H4 RUC ANALYSIS SHOWS AN AMPLIFIED UPPER LEVEL
PATTERN HAS NOW DEVELOPED ACROSS NORTH AMERICA. NORTHERN STREAM FLOW
CONSISTS OF DEEP TROUGHING ALONG THE PACIFIC COAST...FOLLOWED
DOWNSTREAM BY BROAD RIDGING INTO THE HIGH PLAINS...AND THEN ANOTHER
SIGNIFICANT TROUGH OVER THE NORTHEASTERN STATES. A NARROW EXTENSION
OF THIS TROUGH EXTENDS DOWN INTO THE CAROLINAS AND GEORGIA. IN THE
WAKE OF THIS EASTERN TROUGH...WV IMAGERY SHOWS AN EXPANSE OF
EXTREMELY DRY MID/UPPER LEVEL AIR FROM THE MID-SECTION OF THE
COUNTRY EASTWARD TO THE TN AND OH VALLEYS. SOME OF THIS DRIER AIR
WILL BE MAKING A RUN AT OUR FORECAST AREA...AND HOPEFULLY QUIET DOWN
MUCH OF THE DIURNAL SHOWER AND STORM ACTIVITY FOR THE FIRST PART OF
THE WEEK.

AT THE SURFACE...FORECAST AREA REMAINS IN A WEAK NORTHWEST FLOW
BETWEEN HIGH PRESSURE OVER THE CENTRAL GULF OF MEXICO...AND A WEAK
TROUGH FROM THE CAROLINA/GEORGIA COASTS. ALSO...A SUBTLE FRONTAL
BOUNDARY WAS LOCATED OVER CENTRAL AL AND GA. THIS FEATURE IS
ASSOCIATED WITH THE PASSING SHORTWAVE ENERGY ALOFT...AND WILL BE
MAKING SOME PROGRESS SOUTHWARD INTO THE OVERNIGHT. TOOK SOME TIME
TO GET CONVECTION GOING...HOWEVER RADARS ARE NOW SHOWING PLENTY OF
SCATTERED SHOWERS/STORMS ACROSS THE REGION. THESE STORM WILL DRIFT
SOUTHWARD INTO THE EVENING HOURS.

&&

.SHORT TERM (TONIGHT THROUGH TUESDAY NIGHT)...
TONIGHT INTO MONDAY...TROUGH OVER THE NORTHEASTERN STATES WILL PHASE
WITH ADDITIONAL ENERGY MOVING THROUGH ONTARIO...AND CLOSE OFF OVER
NEW YORK AND PENNSYLVANIA. GLOBAL GUIDANCE IN AGREEMENT WITH THIS
CLOSED LOW THEN DRIFTING SOUTHWARD ALONG THE ATLANTIC SEA-BOARD
THROUGH MONDAY. DEEP NORTHERLY FLOW ON THE WESTERN PERIPHERY OF THE
LOW WILL DRAG SOME OF THE DRIER AIR OVER THE TN VALLEY SOUTHWARD
OVER A GOOD PORTION OF THE FORECAST AREA...ESPECIALLY OUR WESTERN
AND NORTHERN ZONES. AT THE VERY LEAST...THIS DRIER AIR WILL HELP
SUPPRESS SIGNIFICANT CONVECTION OVER THESE NORTHERN AND WESTERN
ZONES FOR MONDAY AND TUESDAY. ZONES FURTHER SOUTH AND EAST...
ESPECIALLY SOUTH OF TALLAHASSEE/VALDOSTA MAY NOT EXPERIENCE THE
BRUNT OF THE DRIER AIR...HOWEVER AT LEAST SOME REDUCTION IN
CONVECTIVE COVERAGE IS EXPECTED BY TUESDAY.

FOR MONDAY...DRIER AIR ALOFT IS FORECAST TO ARRIVE ACROSS SOUTHEAST
ALABAMA...SOUTHWEST GEORGIA...AND THE FLORIDA PANHANDLE. FURTHER
SOUTH AND EAST TOWARD THE I-75 CORRIDOR...AND THE EASTERN BIG
BEND...THE DEEP LAYER MOISTURE WILL BE MORE STUBBORN TO BE REMOVED.
AT THE SURFACE...OLD FRONTAL BOUNDARY/TROUGH WILL LAY OUT JUST NORTH
OF THE I-10 CORRIDOR. WILL START THE DAY OFF WITH A SCATTERING OF
SHOWERS/STORMS OVER THE MARINE AREA AND MAINLY DRY CONDITIONS FOR
OUR LAND ZONES. UNLIKE PREVIOUS DAYS...THE DRY MID-LEVELS WILL KEEP
CONVECTION ON THE SUPPRESSED SIDE OVER OUR WESTERN AND NORTHERN
ZONES WHERE CURRENT GRIDS SHOW ONLY A SLIGHT CHANCE (15-25%) OF AN
AFTERNOON SHOWER. ALONG THE I-75 CORRIDOR AND DOWN INTO THE EASTERN
BIG BEND...THE DEEPER MOISTURE WILL ALLOW A BETTER COVERAGE OF
STORMS WITH POPS IN THE 30-50% RANGE. THESE AREAS WITH BETTER SHOWER
COVERAGE WILL SEE HIGH TEMPS INTO THE LOWER AND MIDDLE 90S...HOWEVER
FURTHER NORTH AND WEST...THE LACK OF SHOWERS AND CLOUDS WILL ALLOW
TEMPS TO REACH" onClick="return popup(this, 'notes')">REACH THE UPPER 90S. HEAT INDICES WILL BE WIDESPREAD
BETWEEN 105 AND 108 DEGREES.

TUESDAY...ECMWF/GFS BOTH SHOW THE DRY AIR FIRMLY IN PLACE ACROSS THE
WESTERN HALF OF THE FORECAST AREA...AND MAKING SOME BETTER PROGRESS
TOWARD THE SUWANNEE RIVER VALLEY. WILL KEEP POPS WELL BELOW CLIMO
OVER THE WEST (10-20%) AND THEN SLOWLY INCREASE THE RAIN CHANCES TO
35-40% OVER OUR FAR SOUTHEASTERN AREAS (PERRY/MAYO/CROSS CITY). ONCE
AGAIN TEMPERATURES WILL REACH THE MID/UPPER 90S OVER A WIDE SWATH OF
THE AREA.

&&

.LONG TERM (WEDNESDAY THOUGH NEXT WEEKEND)...
THE LARGE SCALE LONG TERM PERIOD BEGINS IN THE AMPLIFIED NRN STREAM
WITH RIDGING FROM PAC NW EWD TO CNTRL PLAINS...TROUGH OVER NRN GREAT
LAKES AND ANOTHER TROUGH DIGGING SWD FROM NY ESE TO ALONG ATLC COAST
OF GA WITH 577DM LOW OVER DE FOLLOWED BY AMPLIFIED RIDGE OVER WRN
ATLC. SRN STREAM SHOWS RIDGING FROM HIGH NV/UT BORDER SEWD TO VCNTY
APALACHICOLA. LOOKING SWD...587DM LOW OVER WRN GULF. ALL THIS LEAVES
MUCH OF CWA IN WEAKNESS TO EAST OF RIDGE AND S OF ERN TROUGH.
HOWEVER THE PATTERN QUICKLY CHANGES. ERN UPPER LOW IS FORECAST TO
WEAKEN INTO AN OPEN WAVE ON WED AND LIFT TO THE NORTHEAST BEING
ABSORBED BY UPSTREAM TROUGH BY THURS. LATEST MODELS MUCH MORE
AGGRESSIVE IN DRYING OUT LOCAL ATMOSPHERE. BY FRI...TROUGH NOW
OFFSHORE ALLOWING UPSTREAM RIDGE TO SPREAD ESE (WITH NWLY STEERING
FLOW) AND BUILD DOWN EAST COAST AND INTO CARIB AS DRIER AIR WORKS IN
FROM NW-SE. AND...FORMER WRN GULF LOW PROGGED TO LIFT NEWD ALONG
GULF COAST PROVIDING ADDITIONAL SOURCE OF MOISTURE APPEARS ONLY
BEGINS TO IMPACT SRN CWA ON SAT.

AT SURFACE...PERIOD BEGINS WITH CLOSED LOW IN WRN ATLC JUST
OFF N ENGLAND WITH TRAILING FRONTAL BOUNDARY SWWD INTO CNTRL AL/GA.
PRE-FRONTAL TROUGH EXTENDING FROM FRONT SWWD ACROSS MARINE AREA.
INITIAL POSITION OF UPPER TROUGH ALLOWS FRONT TO DROP SWD IN NRN
GULF WATERS ON WED. THEN AS UPPER TROUGH AND THEN CLOSED LOW LIFTS
NEWD...FRONT STALLS OVER WATERS WITH DRIER AIR FILTERING SWD IN ITS
WAKE. THIS DIFFERENT FROM 24HRS AGO...MODELS FORMALLY HINTED AT
DEVELOPING TROPICAL WAVE FORMING ALONG REMNANTS OF COLD FRONT/SHEAR
ZONE IN WRN GULF AND MOVING NEWD ADVECTING MOISTURE BACK TOWARDS
LOCAL AREA. LATEST GFS AND NAM NOW SHOW WAVE REMAINING WEST OF CWA
WITH SUPPRESSED PATTERN OVER CWA. IF WAVE MOVES NEWD INTO CWA...IT
WONT BE UNTIL SAT OR BEYOND. SO WITH MID-UPPER RIDGE DOMINANT...THEN
A TRANSITION INTO A NLY STEERING FLOW WITH SHALLOW SEA BREEZE
FOCUSED ALONG FL COAST. OF COURSE THIS PATTERN IMPLIES INCREASING
TEMPS AND BELOW NORMAL POPS...WITH RAIN STARTING AND ENDING LATER
INTO NIGHT AND INCREASED CHANCE FOR SEVERE STORMS.

WITH A NOTICEABLY DRIER PATTERN THAN PREV RUN...PREVIOUS POPS WILL
BE LOWERED AND TEMPS INCREASED. NOW WDLY SCT TO LOW SCT DAYTIME POPS
UNTIL SAT AFTN...THEN SCT POPS. WITH ABSENCE OF FRONTAL CLOUDS...
MINIMUM TEMPS WILL NOW DROP TO AT OR SLIGHTLY ABOVE CLIMO (INLAND
CLIMO AROUND 69). CONVERSELY...HIGHS WILL RISE TO WELL ABOVE CLIMO
(CLIMO IS 90 DEGREES). EXPECT MID 90S INLAND WED THRU FRI DROPPING
TO LOW 90S ON SAT. HIGHEST HEAT INDICES WILL RISE INTO THE 103 TO
106 DEGREE RANGE WED AND THURS LOWERING TO AROUND 100 DEGREES FRI
AND SAT.

&&

.MARINE...
THE FORECAST WATERS WILL LIE BETWEEN A STALLED FRONTAL BOUNDARY TO
THE NORTH AND THE SUBTROPICAL RIDGE AXIS TO THE SOUTH THROUGH THE
NEXT SEVERAL DAYS. THE NEARBY FRONTAL BOUNDARY WILL KEEP SCATTERED
TO NUMEROUS SHOWERS AND STORMS IN THE FORECAST.

&&

.AVIATION...
AS WAS MENTIONED ON THE EARLIER DISCUSSION...FOR THE REMAINDER OF
THE AFTERNOON AND EVENING HOURS TODAY...THE TIMING OF THE SCATTERED
SHOWERS AND THUNDERSTORMS WILL BE THE GREATEST CONCERN AT THE
TERMINALS. ALTHOUGH THE OVERALL COVERAGE OF THE SHOWERS AND STORMS
IS NOT EXPECTED TO BE AS NUMEROUS AS WAS EARLIER THOUGHT... SOME OF
THE STORMS THAT DO DEVELOP COULD BE FAIRLY STRONG WITH GUSTY WINDS.
WITH RESPECT TO TIMING...MADE SOME MINOR CHANGES FROM THIS MORNING`S
PACKAGE MAINLY TO DELAY THE ONSET OF THE CONVECTION AT MOST OF THE
TERMINALS BY 1 TO 3 HRS IN MOST CASES. FOR THE OVERNIGHT PERIOD...
DECIDED TO USE A BLEND OF GUIDANCE AND PERSISTENCE...WHICH BRINGS
MOST OF THE TERMINALS DOWN TO A PERIOD OF MVFR CONDITIONS...EXCEPT
FOR ECP (WHICH WILL REMAIN AT VFR FOR THE TIME BEING)...AND VLD
(WHICH WILL HAVE A PERIOD OF PREVAILING MVFR WITH A TEMPO FOR
IFR/LIFR CIGS).

&&

.FIRE WEATHER...
CONFIDENCE CONTINUES TO INCREASE THAT THE COLD FRONT TO THE NORTH
WILL PASS CLEANLY THROUGH THE TRI-STATE AREA ON MONDAY WHICH WILL
ALLOW SIGNIFICANTLY DRIER AIR TO MOVE INTO THE REGION ON TUESDAY.
ALTHOUGH NO RED FLAG CONDITIONS ARE EXPECTED AT THIS TIME...
AFTERNOON RELATIVE HUMIDITIES MAY BRIEFLY DROP INTO THE MID TO UPPER
30S ACROSS WELL INLAND AREAS OF THE FLORIDA PANHANDLE.

&&

.PRELIMINARY POINT TEMPS/POPS...
TALLAHASSEE 75 97 76 96 75 / 30 40 20 30 10
PANAMA CITY 79 94 78 94 77 / 30 20 10 20 10
DOTHAN 75 98 73 97 72 / 30 10 10 10 10
ALBANY 76 97 74 97 73 / 30 20 10 10 10
VALDOSTA 75 95 75 94 73 / 40 40 30 40 10
CROSS CITY 76 93 74 92 75 / 40 50 30 40 10
APALACHICOLA 77 93 78 93 78 / 30 30 20 20 10

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
GA...NONE.
FL...NONE.
GM...NONE.


WTVY-TV 285 N Foster Street Dothan, AL 36303 334-792-3195
Copyright © 2002-2014 - Designed by Gray Digital Media - Powered by Clickability 101265014 - wtvy.com/a?a=101265014
Gray Television, Inc.