Severe Thunderstorm Warning 262, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
235 PM CDT FRI MAY 18 2001

ON SATELLITE VAPOR IMAGERY A SHORT WAVE TROF WAS APPROACHING FROM THE
NORTHWEST...AS IT MADE ITS WAY AROUND THE UPPER RIDGE. VISIBLE IMAGERY
SHOWED A GRAVITY WAVE...COMING FROM AN MCS IN THE PLAINS...THAT HAD
PUSHED INTO THE GULF. IT HAD ADDED SOME STABILIZATION TO THE
ATMOSPHERE. UPPER LEVEL DIVERGENCE WAS NOTED ACROSS THE REGION.
DEWPOINTS WERE IN THE 60S. A FRONT WAS APPROACHING FROM THE PLAINS.

LOOKING AT THE SHORT TERM ALL OF THE MODELS INITIALIZED THE
CONVECTION WITH THE APPROACHING SHORT WAVE TROUGH...FAIRLY WELL. THE
ETA MODEL WAS THE BEST...EVEN THOUGH IT CONTINUED TO PAINT SOME RAIN
FROM SOUTHERN LOUISIANA LIKE IN THE 00Z RUN. ALL MODELS BUT THE AVN
SHOWED THE APPROACHING THE FRONT PUSHING INTO THE NORTHERN PART OF
THE FORECAST AREA AS THE SHORT WAVE TROF TROUGH EXITS THE REGION BY
SATURDAY NIGHT...BEFORE PUSHING BACK TO THE NORTH LATE SATURDAY
NIGHT INTO SUNDAY. AVN MODEL TRIES TO PHASE IN THE FRONT WITH THE
SHORTWAVE AND PUSHES THE FRONT EAST OF THE STATE BY 18Z
SATURDAY...THAT WAS DISCARDED. THERE WILL BE ENOUGH INSTABILITY FOR
SCATTERED THUNDERSTORMS FOR THE WEEKEND. SO TAKING IT PERIOD BY
PERIOD.

FOR TONIGHT...CLOUDS WILL INCREASE FROM THE NORTHWEST AS MOISTURE
INCREASES IN THE LOW TO MID LEVELS. THIS WAS VERIFIED BY AREA CROSS
SECTIONS. THE FRONT WILL BE PUSHING INTO THE NORTHWEST CORNER OF THE
STATE. THE SHORTWAVE TROUGH WILL REACH THE NORTHWEST PART OF THE COUNTY
WARNING AREA. GOOD UPPER LEVEL DIVERGENCE WILL CONTINUE OVER THE REGION
THROUGH TONIGHT. MID LEVEL TEMPS WILL BE AROUND -9 TO -12 FOR ADDED
INSTABILITY. ON THE ISENTROPIC FRONT CONDITIONAL PRESSURE DEFICITS
SHOW INCREASE MOISTURE AS SOME ISENTROPIC LIFT TAKES PLACE FROM
WEST TO EAST ON THE 300-310K FIELDS. CAPES WILL RUN AROUND 1500. SO
WILL PUT IN SCATTERED CONVECTIVE POPS NORTH FOR TONIGHT AND WIDELY
SCATTERED POPS ELSEWHERE. WILL RUN TEMPS A LITTLE WARMER THAN MOS DUE TO
CLOUD COVER.

FOR SATURDAY...MID LEVEL COLD POOL SHIFTS TO THE EAST ALONG WITH
UPPER DIVERGENCE...AS SHORT WAVE TROUGH CROSSES THE REGION. WEAK
ISENTROPIC LIFT CONTINUES FROM WEST TO EAST. THE FRONT WILL MOVE
ONTO THE NORTHWESTERN PART OF THE FORECAST AREA...FROM A KGWO-KCBM
LINE. THE UPPER JET SWITCHES BACK TO PURE NORTHWEST FLOW. CAPES
WILL HOLD AT 1000 TO 1500. SO WILL CONTINUE WITH SCATTERED
POPS...WITH THE BEST POPS AROUND THE FRONT. THE REST OF THE AREA
WILL BE OUTFLOW BOUNDARY INDUCED. ETA TEMPS LOOKED TO BE A LITTLE
HIGH...ESPECIALLY AROUND THE DELTA WITH THE CLOUD COVER. WILL GO
CLOSER TO SLIGHTLY COOLER MAV TEMPS.

FOR SATURDAY NIGHT...THE FRONT WILL BEGIN TO PUSH BACK NORTH OF THE
FORECAST AREA AS SOUTHERLY FLOW IN THE LOW LEVELS INCREASE AHEAD OF
THE NEXT SYSTEM. MIDLEVEL TEMPS WILL WARM UP AGAIN...AS THE UPPER
RIDGE REGAINS ITS INFLUENCE ACROSS THE REGION. SO WILL PUT IN WIDELY
SCATTERED POPS WITH LOW SCATTERED POPS IN THE EAST...DUE TO THE SHORT
WAVE EXITING THE REGION AND BEST MID LEVEL TEMPS. MOS TEMPS APPEAR
TO BE ON TRACK.

FOR SUNDAY AND SUNDAY NIGHT...ANOTHER SHORT WAVE WILL CROSS THE
REGION FROM THE WEST. SOUTHERLY FLOW WILL INCREASE SOME AHEAD
OF AN AREA OF LOW PRESSURE IN THE PLAINS...AT AROUND 30 KTS IN
THE LOW LEVELS. NO REAL COLD POOL IS EXPECTED...SO WILL PUT IN
WIDELY SCATTERED POPS ONLY FOR THE PERIOD. MOS TEMPS LOOK TO BE
ON TRACK HERE AS WELL.

QPF 24HR DISCUSSION...RAINFALL AMOUNTS WILL BE ON THE LIGHT SIDE
AVERAGING FROM LESS THAN .10 INCH SOUTH TO LESS THAN .25 INCH NORTH.
THIS WAS SHOWN BY ALL THE MODELS. PRECIPITABLE WATER WILL AVERAGE
FROM .75 TO 1.8 INCHES. NCEP AMOUNTS WERE GENERALLY SIMILAR.

.EXTENDED DISCUSSION MONDAY THROUGH FRIDAY...
LOOKING AT THE MEDIUM RANGE MODELS. THE CHANCES OF RAIN COME TO
AN END AS A STRONG COLD FRONT PUSHES THROUGH THE REGION MONDAY INTO
TUESDAY. THE MODELS HAVE DIFFERENT OPINIONS ON THE TIMING. IT WILL
BE ASSOCIATED WITH A DEEP TROUGH...WHICH WILL SETTLE OVER THE
EASTERN HALF OF THE NATION. DRYING CONDITIONS WILL BE EXPECTED ON
WEDNESDAY...BEFORE ANOTHER FRONT APPROACHES. THE FRONT WILL PUSH
INTO THE REGION ON FRIDAY. SO WITH THE INCREASE IN MEAN MOISTURE AND
INSTABILITY GRADUALLY INCREASING...WILL PUT IN A CHANCE OF SHOWERS
THURSDAY AND SHOWERS/THUNDERSTORMS FRIDAY.

PRELIM NUMBERS...
JAN  68/88/67/89/67  2432
MEI  67/88/65/89/66  2432

.JAN...
MS...NONE.
LA...NONE.
AR...NONE.
17

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
191200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE JACKSON MS
823 PM CDT FRI MAY 19 2001

...THUNDERSTORMS...
ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE TONIGHT ALONG AND NORTH
OF A CROSSETT ARKANSAS...GREENVILLE...GRENADA MISSISSIPPI LINE.
LARGE HAIL AND DAMAGING WINDS WILL BE THE PRIMARY THREAT IN THESE
AREAS.

AN APPROACHING UPPER LEVEL DISTURBANCE WILL COMBINE WITH AN UNSTABLE
AIRMASS TO PRODUCE SCATTERED THUNDERSTORMS OVERNIGHT.

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT
WWW.SRH.NOAA.GOV/JAN. THIS INCLUDES THE GRAPHICAL HAZARDOUS WEATHER
OUTLOOK.