Severe Thunderstorm Warning 259, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
359 PM CDT WED MAY 24 2000

CAPES NOW OVER 5000 J/KG N OF SURFACE FRONT SPLITTING OK FROM SW-NE.
SURFACE DEWPOINTS AOA 70F BEING DRAWN W-WARD ON N SIDE OF FRONT.
PERSISTENCE OF ELEVATED CONVECTION INTO W KS AND NW OK TODAY, AND
ONGOING MID-LEVEL CLOUD DEVELOPMENT FARTHER E ACROSS KS AND N OK,
BEARS TESTIMONY TO AVAILABLE LIFT ABOVE CAP. SOME ACCAS IN THESE
CLOUD FIELDS, INDICATING ATMOSPHERE IS JUST WAITING TO GO.

QUESTION, AS ALWAYS, IS WHETHER CAP WILL BREAK. MODELS INDICATE
SUBSTANTIAL COOLING BY 00Z AT 700MB ACROSS N OK, BUT THIS COOLING IS
NOT CONFIRMED BY OUN 20Z SOUNDING. IF MODELS ARE RIGHT, ANY RAPID
CONVECTIVE DEVELOPMENT LIKELY WOULD BE DELAYED UNTIL 22-00Z ACROSS N
OK. PROFILERS INDICATE MID-UPPER WINDS GRADUALLY STRENGTHENING AS
NOSE OF SUBTROPICAL JET HEADS ACROSS NM. ALTHOUGH WINDS 700 MB AND
BELOW ARE RATHER CHAOTIC BASED ON PROFILERS/VWPS, STRONGLY BACKED
SURFACE AND BL WINDS SET UP FAVORABLE DIRECTIONAL SHEAR. CONSIDERING
AVAILABLE INSTABILITY, ANY STORMS THAT CAN TAP THE BL WILL BE
CAPABLE OF ALMOST ANYTHING THIS EVENING.

SITUATION TONIGHT LIKELY TO EVOLVE INTO A HEAVY RAIN THREAT AS
CONVECTION ORGANIZES INTO AN MCS. COMPOSITE FIELDS RESEMBLE A MADDOX
FRONTAL-TYPE EVENT, OR PERHAPS A MESOHIGH TYPE IF SURFACE FRONT IS
REINFORCED BY OUTFLOW. VERY IMPRESSIVE SPEED CONVERGENCE PROGGED AT
850 MB AT NOSE OF SOUTHWESTERLY 850 JET. PW VALUES PROGGED TO
INCREASE TO 2 OR MORE OVER E OK BY 06Z IN REGION OF MAXIMUM
MOISTURE CONVERGENCE. MOST LIKELY HEAVY RAIN TRACK WOULD APPEAR TO
BE ACROSS N CENTRAL INTO NE OK AND THE OZARKS BY 12Z, AS CONVECTION
RIDES ALONG N EDGE OF CAP. WE THINK THE ETA IS LIKELY NUDGING THE
SFC-850MB BAROCLINIC ZONE TOO FAR S, WHICH FURTHER SUPPORTS A MORE
NORTHERN SWATH OF +RA. HOWEVER, NOT SO SURE THAT EVENING CONVECTION
MIGHT PROPAGATE MORE TO THE RT OF THE MEAN FLOW AND EAT INTO THE CAP
AND TOWARD THE LLJ. ERGO, CENTRAL OK. DUE TO UNCERTAINTY OF
LOCATION, AND FACT THAT ORGANIZED CONVECTION HAS YET TO DEVELOP, WE
WILL HOLD OFF ON ANY FLASH FLOOD WATCHES FOR NOW.

WHAT HAPPENS THU WILL BE HEAVILY CONTINGENT ON WHAT HAPPENS TONIGHT.
MODELS WANT TO HOLD THE SURFACE BOUNDARY ACROSS CENTRAL OR SOUTHERN
OK AND TRY TO LIFT IT SLOWLY N DURING THE DAY, BUT LINGERING EFFECTS
OF CONVECTION TONIGHT MAY HAVE OTHER IDEAS. CONTINUED PRESENCE OF
DECENT BAROCLINIC ZONE ARGUES FOR KEEPING POPS IN, ESPECIALLY NEAR
AND N OF FRONT. TEMPORARY BUILDING OF MID LEVEL RIDGE PROBABLY
INDICATES THAT THE CAP WILL RETURN, AT LEAST ACROSS S ZONES.

GRADUAL BACKING OF UPPER FLOW TO SW SUPPORTS GRADUAL RETURN OF THE
WARM SECTOR TO ENTIRE AREA BY FRI. MAY WELL HAVE ANOTHER MCS THU
NIGHT, BUT MORE LIKELY TO OUR N. SURFACE LOW EXPECTED TO LIFT INTO
EXTREME NW OK BY 12Z FRI WITH WARMFRONT E ACROSS EXTREME S KS.
SUBTROPICAL SPEED MAX ENTERING S PLAINS BY FRI MORNING COULD MAKE
FOR AN INTERESTING DAY FRI AS SHORTWAVES IN SW FLOW PROVIDE FORCING.
CAP ONCE AGAIN WILL BE THE KEY ISSUE. WILL KEEP LOW POPS MAINLY W
AND N FOR FRI, SLIGHTLY HIGHER FRI NIGHT BASED ON CLIMO AND
POTENTIAL FOR NOCTURNAL WEAKENING OF CAP. POPS CONTINUED AREAWIDE
SAT AND IN SE EARLY SUN AS COLD FRONT CROSSES AREA. FOR NOW, DRY SUN
AND MEMORIAL DAY.

FCSTID = 24
OKC   65  84  70  92 /  50  40  40  20
HBR   65  88  70  95 /  30  20  30  20
SPS   69  95  72  96 /  20  10  20  20
GAG   60  84  67  95 /  40  30  40  30
PNC   63  82  68  93 /  50  40  40  30
DUA   71  90  73  93 /  20  20  10  10

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

LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
828 PM CDT WED MAY 24 2000

TIME (CDT) .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0815 PM    5 NE CARNEGIE             OK   1.00 INCH HAIL
05/24/00   CADDO                          PUBLIC REPORT

COLE