Saturday, May 29, 2010

Area Forecast Discussion - South Central/Southwest Missouri

FXUS63 KSGF 291729
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
1229 PM CDT SAT MAY 29 2010

..UPDATE TO AVIATION...

UPDATE...
CUMULUS FIELD WAS SPREADING WEST ACROSS SOUTH CENTRAL MISSOURI AT
MIDDAY AS LOW LEVEL MOISTURE ADVECTED WESTWARD AROUND AN UPPER
LEVEL LOW CENTERED OVER THE DEEP SOUTH. ISOLATED CONVECTION WILL BE
POSSIBLE LATER THIS AFTERNOON AND EVENING ACROSS THE EASTERN
OZARKS. OTHERWISE THE FORECAST IS ON TRACK WITH ONLY MINOR FORECAST
GRID ADJUSTMENTS FOR THE AFTERNOON.

FOSTER

&&

DISCUSSION...

A VERY NICE MEMORIAL DAY WEEKEND WILL CONTINUE TODAY AS HIGH
PRESSURE SLOWLY SLIDES TO THE EAST OF THE OZARKS. A FEW AFTERNOON
CUMULUS WILL BE ABOUT ALL THE ATMOSPHERE WILL BE ABLE TO GENERATE
THIS AFTERNOON.

FOR THE SECOND HALF OF THE HOLIDAY WEEKEND...A CUTOFF UPPER LEVEL
LOW OVER THE GULF COAST WILL SLOWLY OOZE WEST AS ANOTHER STRONGER
AND MORE PROGRESSIVE UPPER LEVEL LOW OVER THE NORTHWESTERN U.S.
BEGINS TO FLATTEN OUT THE UPPER LEVEL RIDGE WHICH HAS BROUGHT
GENERALLY WARM AND DRY WEATHER TO THE REGION OVER THE LAST WEEK.
AS THIS OCCURS...A SURFACE LOW...NOW OVER WYOMING...WILL MOVE EAST
INTO THE CENTRAL PLAINS AND ATTEMPT TO PUSH A WEAK COLD FRONT INTO
THE OZARKS SUNDAY NIGHT INTO MONDAY. BOTH THE ECMWF AND GFS STALL
THE FRONT OUT ACROSS THE REGION WHICH WILL THEN ACT AS A FOCUSING
MECHANISM FOR AFTERNOON SHOWERS AND THUNDERSTORMS INTO THE
BEGINNING OF THE WEEK.

WITH THE EXPECTED WEAK FORCING AND INITIALLY DRY MID AND UPPER
LEVEL CONDITIONS...DONT ANTICIPATE MUCH IN THE WAY OF SEVERE
THUNDERSTORM DEVELOPMENT FROM SUNDAY NIGHT INTO TUESDAY.
HOWEVER...WITH A BOUNDARY MOVING INTO THE REGION AND INCREASING
LOW LEVEL MOISTURE AND INSTABILITY REALLY CANT RULE OUT STRONG TO
ISOLATED SEVERE THUNDERSTORMS COMPLETELY. WILL INDICATE THIS IN
THE HAZARDOUS WEATHER OUTLOOK AND WILL WATCH UPCOMING MODELS FOR
ANY INCREASE IN SEVERE POTENTIAL.

LEE SIDE CYCLOGENESIS...IN ADVANCE OF A FAIRLY WEAK UPPER LEVEL
WAVE...OCCURS TUESDAY WITH THE STALLED OUT FRONT ACROSS THE REGION
LIFTING NORTH OF THE AREA AS A WARM FRONT. THE SURFACE LOW THE GFS
DEVELOPS IS QUITE A BIT STRONGER THAN THAT OF THE ECMWF. AS A
RESULT OF THIS...THE GFS PUSHES A COLD FRONT THROUGH THE OZARKS
WEDNESDAY NIGHT AS A UPPER LEVEL RIDGE OVER THE ROCKY MOUNTAIN
REGION BUILDS AND DEVELOPS A NORTHWEST FLOW PATTERN BY THE END OF
THE WEEK OVER THE REGION. THE ECMWF DEVELOPS THE SURFACE LOW BUT
IS MUCH WEAKER WITH IT. AS A RESULT...THE ECMWF SWINGS THE WEAKER
SURFACE LOW NORTH OF THE REGION WHICH NEVER REALLY GETS THE COLD
FRONT THROUGH THE OZARKS AND STALLS IT OUR IN THE AREA.

GIVEN THE TIME OF YEAR...AM A BIT HESITANT TO BUT THE GFS SOLUTION
AT FACE VALUE AND HAVE GONE WITH A BLEND OF THE GFS/ECMWF FOR THE
FORECAST. AN INTERESTING NOTE HOWEVER IS THE DEVELOPMENT OF A
NEGATIVE NAO...POSITIVE PNA PATTERN AS DEPICTED BY CPC FOR THE
FIRST WEEK OF JUNE. THIS WOULD SUPPORT THE DEVELOPMENT OF THE
WESTERN RIDGE...EASTERN TROUGH PATTERN SHOWN BY THE MODELS. ITS
IS ALSO THE PATTERN WE HAVE SEEN PREDOMINATE FOR MUCH OF THE LAST
9 MONTHS AT LEAST.

WOULD EXPECT THAT IF THE REGION DOES SLIP BACK INTO NORTHWEST FLOW
AS THE MODELS ARE INDICATING...THE REGION COULD SEE A PERIOD OF
COOLER TEMPERATURES AS CANADIAN AIR MASSES SLIDE INTO THE CENTRAL
PLAINS AND THE TENNESSEE VALLY REGION BY THE END OF THE WEEK AND
INTO NEXT WEEKEND.

HATCH

&&

AVIATION...

FOR THE 1800Z TAFS...THE UPPER LEVEL AND SURFACE
RIDGES EXTENDING FROM THE WESTERN GREAT LAKES SSW TO TEXAS WHICH
HAVE DOMINATED THE WEATHER OVER THE OZARKS AND EASTERN KANSAS
OVER THE PAST TWO DAYS WILL CONTINUE TO WEAKEN WITH THE NORTHERN
HALF OF THESE RIDGE FLATTENING OUT AND TOPPLING EASTWARD. A WEAK
CUTOFF UPPER LEVEL LOW CURRENTLY CENTERED OVER MISSISSIPPI WILL
GRADUALLY BROADEN IN CIRCULATION WHILE DRIFTING WNW AND VERY SLOWLY
OPENING INTO A TROUGH. THIS LOW...WHICH IS ALREADY BRINGING
INCREASING HIGH CLOUDINESS TO THE FORECAST AREA WILL BRING SOME
INCREASE IN LOWER LEVEL MOISTURE TO THE FORECAST AREA LATER ON
SUNDAY WITH ISOLATED TO SCATTERED CONVECTION POSSIBLE LATER IN
THE AFTERNOON. EXPECT TO REMAIN IN VFR CONDITIONS THROUGHOUT THE
FORECAST PERIOD AS LOW LEVEL ATMOSPHERIC CONDITIONS ARE CURRENTLY
RELATIVELY DRY AND ARE FORECAST TO REMAIN DRY INTO EARLY TOMORROW
MORNING.

COLUCCI/FOSTER

&&

SGF WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&

$$


Weather Information from www.artmorris.com