MESOSCALE PRECIPITATION DISCUSSION 0113
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
316 PM EDT SAT MAY 23 2015
 
AREAS AFFECTED...EASTERN COLORADO...SOUTHEAST WYOMING....FAR
WESTERN NEBRASKA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 231915Z - 240115Z
 
SUMMARY...POSSIBLE FLASH FLOOD WITH LOW GUIDANCE AND EXPECTED CELL
MERGERS TOWARD 00Z.

DISCUSSION...WELL DEFINED COLD UPPER LOW OVER UT/CO LINE ALLOWING
FOR GOOD INSTABILITIES TO DEVELOP AS SOUTH-SOUTHEASTERLY MOISTURE
TRANSPORT INCREASES INTO EASTERN COLORADO.  THIS HAS ALREADY
RAISED SURFACE TDS INTO THE LOW 50S AND TPWS ARE AT OR SLIGHTLY
ABOVE .75" PER GPS AND BLENDED TPW LOOP.  CLEAR SKIES HAVE ALLOWED
INCREASED SURFACE HEATING LEADING TO SBCAPES OVER 1000 J/KG AT
THIS TIME.  THESE LEVELS OF MOISTURE AND INSTABILITIES SHOULD
SUPPORT DISCRETE CONVECTIVE CELLS AS THEY MOVE OFF THE HIGHER
TERRAIN LIKELY EVOLVING INTO A LINEAR COMPLEX MOVING TO THE
NORTHEAST AND EAST. RATES OF .75-1.0"/HR ARE POSSIBLE AND GIVEN
THE SATURATED SOILS IN THE LAST FEW WEEKS...FLASH FLOOD GUIDANCE
COULD BE EXCEEDED IN SPOTS. 

OF CONCERN TOWARD THE END OF THE PERIOD... ADDITIONAL CONVECTION
ON A SURFACE MOISTURE CONVERGENCE BOUNDARY ALONG THE SOUTH PLATTE
RIVER SHOULD BE IN LOW STEERING ENVIRONMENT  WITH SLOWER CELL
MOTIONS TOWARD THE NORTH OR NORTH-NORTHWEST EVENTUALLY INTO THE
DEFORMATION ZONE FORMING FROM SOUTHEAST WYOMING INTO NORTHEAST
COLORADO.  THE POTENTIAL FOR THE LINEAR COMPLEX TO MERGE WITH
THESE ISOLATED CELLS WILL POSE THE GREATEST FLASH FLOOD THREAT. 
THIS SCENARIO IS IN ALIGNMENT WITH RECENT (16Z AND 17Z) HRRR AND
THE FSL-EXPERIMENTAL HRRR RUNS.   

GALLINA

ATTN...WFO...BOU...CYS...GLD...PUB...RIW...

ATTN...RFC...ABRFC...MBRFC...

LAT...LON   42510479 41140299 40210238 38360226 38270398 
            39050475 39840504 40890584 41470700 42440688