MESOSCALE PRECIPITATION DISCUSSION 0152
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
917 PM EDT TUE MAY 15 2018

AREAS AFFECTED...NORTHWEST TX, TX PANHANDLE, & SOUTHWEST OK

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 160116Z - 160525Z

SUMMARY...CONVECTION IS ATTEMPTING TO CONCENTRATE BETWEEN
NORTHWEST TX AND THE TX PANHANDLE.  AS IT ATTEMPTS TO SHIFT
NORTHWARD, HOURLY TOTALS TO 1.75" WITH LOCAL AMOUNTS TO 3" ARE
EXPECTED.

DISCUSSION...CONVECTION IS BEING FOCUSED BY A WESTWARD MOVING
OUTFLOW BOUNDARY MOVING ACROSS NORTHWEST TX, ORGANIZED CONVECTION
DROPPING OUT OF THE TX PANHANDLE, AND A BOUNDARY NEAR 850 HPA
WHICH IS TRYING TO FILL IN CONVECTION IN BETWEEN.  PRECIPITABLE
WATER VALUES ARE 1-1.5" PER GPS DATA.  INFLOW AT 850 HPA IS
SOUTHEAST AT 20 KTS PER THE LUBBOCK TX VAD WIND PROFILE.  HOWEVER,
EFFECTIVE BULK SHEAR IN 40-60 KTS WHICH IS LEADING TO ORGANIZED
CONVECTION.

THE MESOSCALE GUIDANCE HAS BEEN WAY TOO FAR TO THE NORTH WITH THIS
ACTIVITY SO FAR, BELIEVING IT SHOULD BE A BIT FARTHER NORTH IN THE
TX PANHANDLE BEFORE SHIFTING INTO NORTHWEST OK. HOWEVER, THE 18Z
GFS GALVEZ-DAVISON INDEX VALUES ADVERTISE THE GREATEST INSTABILITY
NEAR THE CONGREGATING STORMS WHICH SHIFTS NORTHEAST INTO SOUTHWEST
OK WITH TIME, WHICH WAS A GUIDE FOR THE CONSTRUCTION OF THIS AREA.
 THE RECENT RAP GUIDANCE MASS FIELDS IMPLY THIS AS WELL.  THE
EXPECTATION IS FOR CONVECTION TO CONTINUE CONCENTRATING IN
NORTHWEST TX BEFORE ATTEMPTING TO LIFT NORTH TOWARDS SOUTHWEST OK
WITH TIME AS AN 850 HPA SLICE OF A FRONT LIFTS AND FLOW AT THAT
LEVEL VEERS WHILE CONVECTION PREFERENTIALLY PROPAGATES TOWARDS AN
AREA OF GREATER INSTABILITY NEAR CHILDRESS TX.  HOURLY RAIN TOTALS
UP TO 1.75" APPEAR POSSIBLE HERE AS CELLS CHAOTICALLY MERGE.  THE
HREF PROBABILITIES OF EXCEEDING 1" AND HOUR MAXIMIZE AROUND 04Z. 
THE MODEL SIGNAL FOR LOCAL AMOUNTS IN THE 3" STILL APPEARS
REASONABLE, EVEN IF MISPLACED.  USED A FOUR HOUR HORIZON DUE TO
GREATER UNCERTAINTY THAN USUAL IN THE EXPECTED CONVECTIVE
EVOLUTION. 

ROTH

ATTN...WFO...AMA...LUB...MAF...OUN...SJT...

ATTN...RFC...ABRFC...WGRFC...

LAT...LON   35000132 34819929 33989881 32330013 33370135
            33900228 34360260 34850213