Flash Flood Warning 49, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
330 PM CDT SAT JUN 19 1999

A FAIRLY SUBSTANTIAL MESS LIES ACROSS OUR FORECAST AREA THIS
AFTERNOON.  A WEAK LOW IS JUST NORTH OF HOBART... AND A RATHER
STRONG OUTFLOW BOUNDARY EXTENDS ROUGHLY FROM CORDELL TO LAKE
TEXOMA.  WIDESPREAD CLOUDINESS FROM THE MORNING CONVECTIVE COMPLEX
REMAINS OVER MUCH OF THE EASTERN PART OF THE FORECAST AREA... AS
BRAND NEW STORMS DEVELOP NEAR THE OUTFLOW BOUNDARY.  TEMPERATURES
VARY DRAMATICALLY FROM THE MID 60S NEAR PONCA CITY TO THE MID 90S AT
ALTUS.

HAVE GENERALLY SIDED WITH THE ETA MODEL FOR MOST FORECAST
PARAMETERS.  EXPECT THE SURFACE LOW TO DISSIPATE OVERNIGHT AS
GENERALLY SOUTH TO SOUTHEAST FLOW SETS IN.

RAIN CHANCES TONIGHT ARE BASED MAINLY ON THE LOCATION OF MESOSCALE
FEATURES... WHILE LATER PERIODS ARE BASED MOSTLY ON ETA POSITIONING
OF LOW LEVEL MOISTURE.  SINCE A WEAKNESS IN THE UPPER RIDGE IS
FORECAST BY ALL MODELS THROUGHOUT THE FORECAST PERIODS... FEEL THAT
THE RIDGE WILL NOT BE SUFFICIENT TO STIFLE ALL RAIN CHANCES.  HIGHER
POPS WILL BE IN THE SOUTH... WHERE MOST OF THE MOISTURE IS FORECAST
TO HANG OUT.  HAVE ALSO OPTED TO INCLUDE 20 PERCENTS TOMORROW AND
MONDAY FOR THE NORTHEAST PART OF THE FORECAST AREA... DUE TO THE
POSSIBILITY OF A STAMPEDING MCS COMING DOWN FROM THE CENTRAL PLAINS.

HAVE ALSO ADDED POPS... 20 PERCENT... TO MUCH OF THE EXTENDED
PERIODS... EXCEPT IN THE NORTH.  AGAIN... THIS IS DUE MAINLY TO THE
PROBABLE INABILITY OF THE UPPER RIDGE TO ELIMINATE ALL PRECIPITATION.

TEMPERATURES SHOULD WARM SLOWLY OVER THE NEXT FEW DAYS.  HAVE SCALED
THE WARMUP BACK A BIT FROM THE PREVIOUS FORECAST... DUE MOSTLY TO
THE RAIN RISK THING.

FCSTID = 23 = CMS

OKC   68  85  69  90 /  30  30  20  30
HBR   66  89  67  90 /  40  10  20  20
SPS   70  89  70  90 /  40  40  40  40
GAG   64  89  67  90 /  10  10  10  10
PNC   63  82  67  86 /  10  20  20  20
DUA   63  85  68  88 /  40  50  40  30

.OUN...
OK...NONE.
TX...NONE.

OKZ004-009-010-014>016-021-022-033>036-201130-

THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
12 30 PM CDT SAT JUN 19 1999

THUNDERSTORMS APPROACHING SEVERE CAN BE EXPECTED SOUTH OF A LINE
FROM ADA TO CHICKASHA TO CHEYENNE. THIS INCLUDES ALL OF SOUTHERN
OKLAHOMA AS WELL AS WESTERN NORTH TEXAS. HAIL WILL BE THE MAIN
THREAT.

DISCUSSION...THUNDERSTORMS ARE CURRENTLY MOVING ACROSS EASTERN
OKLAHOMA EARLY THIS AFTERNOON. AN OUTFLOW BOUNDARY OF COOL AIR FROM
THE MORNING THUNDERSTORMS WILL LIE ACROSS SOUTHERN OKLAHOMA DURING
THE AFTERNOON. THIS BOUNDARY IS EXPECTED TO ACT TO PROVIDE LIFT FOR
ADDITIONAL THUNDERSTORM ACTIVITY DURING THE AFTERNOON INTO EARLY
EVENING HOURS.

THE AIRMASS OVER SOUTHERN OKLAHOMA AND NORTH TEXAS IS RELATIVELY
UNSTABLE...BUT WIND SHEAR IS RELATIVELY WEAK. THUS THE STRONGEST
STORMS THAT DO DEVELOP ARE EXPECTED TO PRODUCE HAIL SMALLER THAN
DIME SIZE. THE STORMS SHOULD ALSO BE SHORT-LIVED.

PURPURA