Flash Flood Warning 42, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
230 PM CDT FRI OCT 27 2000

IN THE SHORT TERM...DIFFERENTIAL HEATING BOUNDARY FROM TULSA TO GUTHRIE
TO MEDFORD HAS BEEN THE REGION OF MOST CONVECTION EARLIER TODAY AND
WITH ADDITIONAL INSOLATION SOUTH OF BOUNDARY AND CONVECTION CONTINUING
ACROSS NORTHEAST OKLAHOMA...BOUNDARY HAS STRENGTHENED. EXPECT TO GO
LIKELY TO CATEGORICAL POPS THIS AREA FOR THIS EVENING. OTHERWISE THE
OVERNIGHT PERIOD WILL BE DOMINATED BY A VERY MOIST AIRMASS AND WEAK
LIFT...ENOUGH TO KEEP POPS GOING ALL AREAS. LOW LEVEL JET WILL LIKELY
INCREASE LATE TONIGHT OUT WEST AND MAY HELP TO INCREASE COVERAGE OF
TSRA TOWARD 12Z BUT THIS IS MORE LIKELY TOWARD MIDDAY.

ALL INGREDIENTS FOR WIDESPREAD RAINFALL APPEAR TO BE COMING TOGETHER
LATE SATURDAY/SATURDAY NIGHT...WITH NEGATIVELY TILTED UPPER LOW FORCING
LARGE SCALE RISING MOTION IN A VERY MOIST ATMOSPHERE ALONG WITH COOL
TEMPERATURES IN THE MID LEVELS. PLAN TO CONTINUE WITH 50 TO 70 POPS MOST
AREAS SATURDAY WITH THE BRUNT OF RAIN EXPECTED TO DEVELOP SATURDAY
EVENING/OVERNIGHT...THEN ENDING ACROSS THE SOUTHEAST SUNDAY. EXPECT
SEVERE WEATHER AND FLOODING TO ACCOMPANY THIS SYSTEM.

EXTENDED...THE NEXT MAJOR SYSTEM TO AFFECT THE AREA SHOULD BE UPPER LOW
CURRENTLY IN THE GULF OF ALASKA. THERE SHOULD BE A BREAK IN THE PRECIP
SUNDAY/MONDAY...PARTICULARLY ACROSS THE NORTHWEST HALF OF AREA WHICH
SHOULD RECEIVE THE LARGEST AMOUNT OF COOLER/STABLE LOW LEVEL AIR. BUT
BY LATE MONDAY/EARLY TUESDAY UPPER LOW APPROACHING FROM THE WEST SHOULD
ALLOW WAA/DEEP MOISTURE ADVECTION TO SPREAD NORTHWARD ACROSS THE AREA.
FEELING IS THAT UPPER LOW RETREATING NORTHWARD WILL ALLOW TIGHT
MOISTURE/THERMAL GRADIENT TO REMAIN CLOSE TO RED RIVER...IN FACT TOO
CLOSE FOR ME TO FEEL COMFORTABLE WITH A DRY FORECAST FOR LAST MONDAY AS
LOW LEVEL WINDS BEGIN TO BACK. WILL HAVE SMALL POPS ACROSS THE SOUTH
LATE MONDAY FOR THIS REASON. WILL ALSO CONTINUE WITH CHANCE POPS MONDAY
NIGHT.

TUESDAY SILL LOOKING WET WITH STRONG LIFT/DEEP MOISTURE AVAILABLE.
THERE AREA STILL DIFFERENCES REGARDING THE STRENGTH/SPEED/ORIENTATION OF
UPPER LOW...BUT MODELS ARE GENERALLY CONSISTENT IN BRINGING SYSTEM
THROUGH TUESDAY WHICH IS SIMILAR TO YESTERDAYS' VERSIONS. WILL
THEREFORE INCREASE POPS INTO THE LIKELY CATEGORY OUT WEST AND A GOOD
CHANCE EAST OF THE INTERSTATE 35. BY WEDNESDAY MRF MOVES SYSTEM THROUGH
THE REMAINDER OF AREA WITH LATEST CANADIAN SENDING THE UPPER LOW
NORTHWARD INTO THE NORTHERN PLAINS WHILE AMPLIFYING ANOTHER UPPER LOW
ACROSS THE SOUTHWEST. THE CANADIAN SUGGESTS FRONT MAY HANG UP ACROSS
THE SOUTHEAST. THIS SOLUTION WOULD ALSO SUPPORT UPPER RIDGE REMAINING
ACROSS THE DEEP SOUTH WITH UPPER LEVEL DIFFLUENCE REMAINING OVER MUCH OF
THE AREA. PLAN TO GO SOMEWHERE IN THE MIDDLE AND EXTEND CHANCE POPS
ACROSS THE SOUTHEAST HALF OF AREA FOR WEDNESDAY.

GAG 61/68/52/70 4791
PNC 61/71/58/68 75*3
OKC 60/71/60/68 35*3
SPS 61/72/60/72 4690

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