Severe Thunderstorm Warning 433, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
300 PM CDT WED JUL 19 2000

OVER THE CONUS AND SURROUNDING AREAS...UPPER PATTERN HAS FLATTENED
SINCE THE LAST TIME I WORKED...WITH UPPER LOW/WEAK TROUGH OVER
EASTERN CN...HIGH PRESSURE OVER SOUTHERN THIRD OF CONUS/NORTHERN
MEXICO...AND WEAK RIDGE OVER WESTERN CN. A COPIOUS QUANTITY OF
SHORTWAVES WORKING THROUGH THE FLOW...WITH FIRST TO AFFECT FA MOVING
OVER CENTRAL PLAINS AT THIS TIME. IN THE LOWER LEVELS...HIGH
PRESSURE STRETCHED FROM THE ATLANTIC INTO THE GULF OF MEXICO. SURFACE
FRONT STRETCHED FROM NEAR THE DELMARVA PENINSULA INTO THE OHIO RIVER
VALLEY INTO THE CENTRAL PLAINS. PRECIP H20 AMOUNTS OF 1.75"+
STRETCHING FROM SOUTHERN LA INTO MS/AL/TN INTO SOUTHERN OH.

SHORT RANGE MODELS ALL ADVERTISING A RETURN TO AMPLIFIED UPPER LEVEL
FLOW IN THE SHORT TERM AS STRONG TROUGH SWINGS SLOWLY AROUND EASTERN
CN LOW...PUSHING SURFACE FRONT SLOWLY SOUTH. HELPING THINGS ALONG IS
A STRONG SHORTWAVE MOVING(ETA STRONGEST/NGM WEAKEST) MOVING INTO THE
MID MISS RIVER VALLEY TONIGHT WITH A SECOND TO MOVE IN BEGINNING AT
F42 THURSDAY NIGHT INTO FRIDAY. AVN HOLD BEST DYNAMICS FARTHEST
NORTH...ETA FARTHEST SOUTH. NGM DOESN/T SEEM TO DO MUCH AT ALL WITH
SHORTWAVE. GOOD INSTABILITY AXIS LIES ACROSS FA THURS AND
FRIDAY...SO TSRA WILL BE IN THE FORECAST. MUCH COOLER THICKNESS
VALUES DO NOT PUSH THAT FAR INTO THE LOWER MISS RIVER VALLEY... BUT
JUST ENOUGH THAT ALONG WITH CLOUD COVER FROM CONVECTION...HEAT
ADVISORY WILL BE PROBABLY BE DROPPED AFTER TOMORROW.

WHAT IS GOING INTO THE FORECAST? WELL...I/M BASICALLY GOING TO LEAVE
POPS FOR TONIGHT A LAST MINUTE DECISION BASED UPON DEVELOPMENT
OCCURRING AT THIS TIME(TSRA POPPING OVER SOUTHEAST MS/SOUTHWEST AL).
TOMORROW THROUGH FRIDAY NIGHT...AM GOING A GENERAL WIDELY SCATTERED
TO SCATTERED WITH SOME TWEAKING FOR FRONTAL POSITION NORTH AND GULF
BREEZE ACTION SOUTH.

QPF DISCUSSION: CONVECTION A LITTLE SLOWER FIRING TODAY THAN ON
TUESDAY. PW'S ACROSS THE FORECAST AREA ARE STILL IN THE 1.75 TO 2.0
IN RANGE. AGREE WITH THE MODELS PLACEMENT OF MEASURABLE PRECIP IN
THE SOUTH AND EAST FOR TONIGHT. WILL GO WITH LESS THAN ONE TENTH IN
THOSE AREAS. THE APPROACHING BOUNDARY FROM THE NORTH WILL PROVIDE
ADDED FOCUS FOR TOMORROW IN THE NORTH WILL GO WITH AROUND ONE TENTH
FOR 18-00Z.

IN THE EXTENDED...MEDIUM RANGE MODEL RUNS TAKE UPPER PATTERN AND
CONTINUE TO AMPLIFY THE PATTERN. SYNOPTIC PICTURE PRETTY CONSISTENT
IN THE UPPER LEVELS...WITH TROUGH CONTINUING TO DIG IN TO EASTERN
CONUS AND REMAINING THERE...BUILDING RIDGE OVER THE SOUTHWESTERN
CONUS. MRF ENSEMBLES PRETTY CONSISTENT WITH THIS SCENARIO ALSO...AND
MAINTAIN A MEAN TROUGH OVER THE EASTERN CONUS/CN. MODELS ALSO START
THE EXTENDED WITH SURFACE FRONT PUSHED THROUGH MS(12Z AVN MOVES IT
TO CENTRAL MS BY F72/SAT MORN) TO ALONG OR JUST OFF GULF COAST
LINE...BUT SEEM TO HAVE A HARD TIME PUSHING FRONT ANY FARTHER SOUTH.
CANADIAN/NOGAPS PUT SOME GULF BREEZE SHOWERS ALONG THE COAST WITH
MRF MORE ENTHUSIASTIC WITH THE POPS. WILL KEEP MENTION OF PRECIP
ALL ZONES WITH BEST CHANCES SOUTH. TEMPS LOOK TO COOL TO NEAR
SEASONABLE AVERAGES THROUGH THE WEEKEND INTO THE FOLLOWING WORK WEEK.

PRELIMINARY NUMBERS...
JAN 074/098 073/097 073 1323
MEI 073/099 072/098 072 2323

.JAN...
AR...HEAT ADVISORY THURSDAY ZONES 074-075.
LA...HEAT ADVISORY THU+RSDAY ZONES 007>009-015-016.
MS...HEAT ADVISORY THURSDAY ZONES 018-019-025-034>036-040>042-047.

16/22