Flash Flood Warning 13, NWS Tulsa, OK

EASTERN OKLAHOMA/NORTHWEST ARKANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TULSA OK
402 AM CDT SAT APR 24 1999

PROBLEM(S) OF THE DAY:
TEMPERATURES
POPS
WILL THERE BE CONVECTION?

OBSERVATIONS INDICATE A VERY GOOD BAROCLINIC ZONE ACROSS THE
FORECAST AREA WITH A STATIONARY SURFACE FRONT ALONG THE FAR
SOUTHEASTERN EDGE OF OKLAHOMA. THERE SHOULD BE ENOUGH LIFT ASSOCIATED
WITH A PROCESSION OF RELATIVELY WEAK VORTICITY CENTERS FORECAST TO
MOVE NORTHEASTWARD ACROSS THE AREA...TO PRODUCE AT LEAST A 50/50
CHANCE OF RAIN AND POSSIBLY A THUNDERSTORM OR TWO ACROSS THE ENTIRE
AREA PERIODICALLY THROUGHOUT THE DAY AND INTO THE TONIGHT PERIOD.
LATE TONIGHT THE NGM...ETA AND TO A LESSER EXTENT THE AVN INDICATE A
STRONGER VORTICITY CENTER SWEEPING JUST INTO THE WESTERN ZONES BY
12Z. THERE IS CONSIDERABLE LIFT ASSOCIATED WITH THIS FEATURE AND
ELEVATED CONVECTION SHOULD RESULT. THEREFORE...WILL GO WITH LIKELY
POPS FROM KBVO TO KMLC AND KEEP 50 POPS EVERYWHERE ELSE FOR REASONS
DISCUSSED ABOVE.

TEMPERATURES WILL DEPEND GREATLY ON HOW FAR SOUTH THE LOW CLOUDS
STAY THROUGH THE DAY. THE ETA LOW-LEVEL RH PROGS INDICATE THAT THE
LOW CLOUDS SHOULD REMAIN IN PLACE ACROSS ALL BUT FAR SOUTHEAST
OKLAHOMA AND POSSIBLY WEST CENTRAL ARKANSAS. PERSISTENCE OF DIURNAL
RANGES LOOKS TO BE A GOOD FORECAST FOR TODAYS TEMPERATURES.
THEREFORE...LOOK FOR HIGHS NOT TO REACH 60 AGAIN TODAY ACROSS
NORTHEAST OKLAHOMA WITH IDB AGAIN POSSIBLY REACHING INTO THE 80S.
LOWS TONIGHT WILL ONCE AGAIN REFLECT A TINY DIURNAL RANGE WITH
PLENTY OF EXPECTED CLOUD COVER AND A PERSISTENT EASTERLY BREEZE.
TEMPERATURES FOR THE FIRST TWO PERIODS ARE GENERALLY LOWER THAN
MOS...EXCEPT FOR KFSM AND KIDB.

ELEVATED CONVECTION IN ASSOCIATION WITH THE AFOREMENTIONED STRONGER
SHORT-WAVE TROUGH WILL SWEEP NORTHEASTWARD ACROSS MOST OF EASTERN
BY MIDDAY SUNDAY...BUT MAY LINGER ACROSS THE NORTHEAST CORNER OF
OKLAHOMA AND THE NORTHWEST CORNER OF ARKANSAS WELL INTO THE
AFTERNOON.  TO DEAL WITH THIS...LIKELY POPS WILL BE FORECAST FOR ALL
BUT EXTREME SOUTHEAST OKLAHOMA...WHERE GOOD CHANCE POPS SHOULD BE
SUFFICIENT.  THE AREA SHOULD SEE A BREAK IN THE PRECIPITATION LATE
SUNDAY AND SUNDAY EVENING...BEFORE THE MAIN SHORT-WAVE TROUGH SWEEPS
NORTHEAST ACROSS THE AREA.  THE AVN INDICATES AN IMPRESSIVE DRY PUNCH
WRAPPING INTO THIS SYSTEM...SO THERE MAY BE AN ABRUPT END TO THE
PRECIPITATION CHANCES FROM SOUTHWEST TO NORTHEAST ACROSS THE AREA
EITHER LATE SUNDAY NIGHT OR EARLY MONDAY.  LIKELY POPS WILL BE
EXTENDED THROUGH SUNDAY NIGHT WITH JUST 20S AND 30S FOR EARLY ON
MONDAY.

WITH SURFACE WINDS TURNING AROUND TO THE SOUTHEAST AND SOUTH SUNDAY
AND SUNDAY NIGHT THERE SHOULD BE A MODEST WARMING TREND...BUT SMALL
DIURNAL RANGES WILL STILL BE THE RULE THROUGH SUNDAY NIGHT.  LOOK FOR
GOOD WARM UP BEHIND THE SYSTEM ON MONDAY WHEN WEST SOUTHWESTERLY
LOW-LEVEL FLOW SHOULD RESULT IN TEMPERATURES ONCE AGAIN APPROACHING
80 DEGREES IN SOME AREAS.  UPPED HIGHS IN EXTENDED PERIODS TO BE
CONSISTENT WITH WARMUP ON MONDAY.  NO OTHER CHANGES WERE MADE TO
THE EXTENDED FORECAST.

FCSTID = 19
TUL   59  54  66  60 /  50  70  70  70
FSM   73  64  74  61 /  50  50  70  60
MLC   65  57  75  62 /  50  70  70  60
BVO   57  51  65  58 /  50  70  70  70
FYV   67  58  69  60 /  50  50  70  70
IDB   82  69  84  70 /  50  50  50  50
BYV   67  58  69  60 /  50  50  70  70
MIO   62  55  66  59 /  50  50  70  70
MKO   59  54  66  60 /  50  70  70  70
F10   59  54  66  60 /  50  70  70  70
HHW   82  69  84  70 /  50  50  50  50

.TUL...
AR...NONE.
OK...NONE.

--------------------
EXPERIMENTAL OUTPUT:

HAZARDOUS WEATHER EXPECTED NEXT 24 HOURS:  NONE
NGM fCONFIDENCE:  6 ON A SCALE OF 0 TO 10
ETA CONFIDENCE:  7 ON A SCALE OF 0 TO 10
AVN CONFIDENCE:  7 ON A SCALE OF 0 TO 10
FCST CONFIDENCE: 8 ON A SCALE OF 0 TO 10

ARZ001-002-010-011-019-020-029-OKZ049-053>076-251100-

EASTERN OKLAHOMA/NORTHWEST ARKANSAS HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TULSA OK
600 AM CDT SAT APR 24 1999

ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS PARTS OF SOUTHEAST
OKLAHOMA AND WEST CENTRAL ARKANSAS TODAY AND TONIGHT. ANY SEVERE
THUNDERSTORMS WILL LIKELY OCCUR IN AREAS SOUTH OF INTERSTATE
40.

.SYNOPSIS...
EARLY THIS MORNING...A STATIONARY FRONT WAS LOCATED FROM SOUTHERN
ARKANSAS ACROSS THE SOUTHEAST CORNER OF OKLAHOMA TO CENTRAL TEXAS.
THE FRONT MARKED THE BOUNDARY BETWEEN RELATIVELY COOL AND STABLE
AIR TO THE NORTH AND VERY MOIST AND UNSTABLE AIR TO THE SOUTH. WEAK
DISTURBANCES IN THE JET STREAM WILL MOVE ACROSS TEXAS AND SOUTHEAST
OKLAHOMA TODAY AND TONIGHT. SCATTERED THUNDERSTORMS ARE EXPECTED
ACROSS ALL OF THE AREA THROUGH TONIGHT...WITH A FEW STRONG TO SEVERE
THUNDERSTORMS POSSIBLE ACROSS SOUTHEAST OKLAHOMA AND WEST CENTRAL
ARKANSAS.

.DISCUSSION...
THE AIRMASS SOUTH OF THE FRONT WILL REMAIN MODERATELY UNSTABLE THROUGH
TONIGHT. ALTHOUGH TEMPERATURES ACROSS MOST OF THE OUTLOOK AREA WILL
REMAIN IN THE 60S AND 70S TODAY...LIFTING OF THE UNSTABLE AIR ABOVE
THE COOLER SURFACE AIR COULD RESULT IN STRONG ELEVATED THUNDERSTORMS.
THE DEGREE OF INSTABILITY SUGGESTS THE POSSIBILITY OF HAIL UP TO 1
INCH IN DIAMETER WITH ANY SEVERE THUNDERSTORMS.

OTHER ELEVATED THUNDERSTORMS WILL BE POSSIBLE IN AREAS WELL NORTH OF
THE FRONT ACROSS NORTHEAST OKLAHOMA AND NORTHWEST ARKANSAS. A FEW
OF THESE STORMS COULD PRODUCE SMALL HAIL...BUT LIMITED INSTABILITY
AND WEAK UPPER FORCING SHOULD KEEP THUNDERSTORMS IN THESE AREAS BELOW
SEVERE LEVELS.

.EMERGENCY MANAGEMENT AGENCY AND SPOTTER ACTIVATION...
SINCE ANY STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED TO REMAIN
ISOLATED THROUGH TONIGHT...SPOTTER ACTIVATION IS NOT EXPECTED.
AN UPDATED HAZARDOUS WEATHER OUTLOOK WILL BE ISSUED AT 1 PM.

ARZ001-002-010-011-019-020-029-OKZ049-053>076-251100-

EASTERN OKLAHOMA/NORTHWEST ARKANSAS HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TULSA OK
600 AM CDT SAT APR 24 1999

ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS PARTS OF SOUTHEAST
OKLAHOMA AND WEST CENTRAL ARKANSAS TODAY AND TONIGHT. ANY SEVERE
THUNDERSTORMS WILL LIKELY OCCUR IN AREAS SOUTH OF INTERSTATE
40.

.SYNOPSIS...
EARLY THIS MORNING...A STATIONARY FRONT WAS LOCATED FROM SOUTHERN
ARKANSAS ACROSS THE SOUTHEAST CORNER OF OKLAHOMA TO CENTRAL TEXAS.
THE FRONT MARKED THE BOUNDARY BETWEEN RELATIVELY COOL AND STABLE
AIR TO THE NORTH AND VERY MOIST AND UNSTABLE AIR TO THE SOUTH. WEAK
DISTURBANCES IN THE JET STREAM WILL MOVE ACROSS TEXAS AND SOUTHEAST
OKLAHOMA TODAY AND TONIGHT. SCATTERED THUNDERSTORMS ARE EXPECTED
ACROSS ALL OF THE AREA THROUGH TONIGHT...WITH A FEW STRONG TO SEVERE
THUNDERSTORMS POSSIBLE ACROSS SOUTHEAST OKLAHOMA AND WEST CENTRAL
ARKANSAS.

.DISCUSSION...
THE AIRMASS SOUTH OF THE FRONT WILL REMAIN MODERATELY UNSTABLE THROUGH
TONIGHT. ALTHOUGH TEMPERATURES ACROSS MOST OF THE OUTLOOK AREA WILL
REMAIN IN THE 60S AND 70S TODAY...LIFTING OF THE UNSTABLE AIR ABOVE
THE COOLER SURFACE AIR COULD RESULT IN STRONG ELEVATED THUNDERSTORMS.
THE DEGREE OF INSTABILITY SUGGESTS THE POSSIBILITY OF HAIL UP TO 1
INCH IN DIAMETER WITH ANY SEVERE THUNDERSTORMS.

OTHER ELEVATED THUNDERSTORMS WILL BE POSSIBLE IN AREAS WELL NORTH OF
THE FRONT ACROSS NORTHEAST OKLAHOMA AND NORTHWEST ARKANSAS. A FEW
OF THESE STORMS COULD PRODUCE SMALL HAIL...BUT LIMITED INSTABILITY
AND WEAK UPPER FORCING SHOULD KEEP THUNDERSTORMS IN THESE AREAS BELOW
SEVERE LEVELS.

.EMERGENCY MANAGEMENT AGENCY AND SPOTTER ACTIVATION...
SINCE ANY STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED TO REMAIN
ISOLATED THROUGH TONIGHT...SPOTTER ACTIVATION IS NOT EXPECTED.
AN UPDATED HAZARDOUS WEATHER OUTLOOK WILL BE ISSUED AT 1 PM.