MESOSCALE PRECIPITATION DISCUSSION 0201
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
426 PM EDT SAT MAY 26 2018

AREAS AFFECTED...NORTHERN NV...SOUTHEAST OR...SOUTHWEST ID

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

VALID 262025Z - 270125Z

SUMMARY...SLOW MOVING SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS WILL PRODUCE LOCALLY HEAVY RAINFALL THROUGH THIS
AFTERNOON OVER THE NORTHERN GREAT BASIN AND PARTS OF THE NORTHERN
ROCKIES.  SOME INSTANCES OF FLASH FLOODING WILL BE POSSIBLE.

DISCUSSION...REGIONAL RADAR IMAGERY IS INDICATING RAPIDLY
DEVELOPING CONVECTION OVER NORTHEAST NEVADA AND EXTENDING
NORTHWARD INTO THE CENTRAL IDAHO MOUNTAINS EARLY THIS AFTERNOON. 
THE MOST RECENT RAP ANALYSIS AND BLENDED TPW SHOWED PRECIPITABLE
WATER VALUES ON THE ORDER OF 0.75 TO 0.90 INCHES, WHICH IS NEAR
TWO STANDARD DEVIATIONS ABOVE NORMAL. CELLS DEVELOPING IN THIS
AIRMASS HAVE PRODUCED HOURLY RAINFALL RATES OF 0.75 TO 1.50 INCHES
PER HOUR.

THIS CONVECTION IS BEING DRIVEN BY DEEP LAYER ASCENT IN THE MID TO
UPPER LEVELS AHEAD OF A LARGE UPPER LOW OVER WESTERN NEVADA, WITH
MUCH OF THIS REGION UNDER THE FAVORABLE LEFT EXIT REGION OF THE
UPPER JET.  SHORTWAVE IMPULSES ROTATING AROUND THE UPPER LOW ARE
PROVIDING ADDITIONAL ASCENT AND ENHANCED LOW LEVEL CONVERGENCE. 
IN ADDITION, MIXED LAYER CAPE IS ALSO IN THE 500 TO 1000 J/KG
RANGE BASED ON THE LATEST SPC MESOANALYSIS.

MOST OF THE AVAILABLE HIGH RESOLUTION GUIDANCE (INCLUDING THE MOST
RECENT HRRR AND EXPERIMENTAL HRRR) SHOWED THE POTENTIAL FOR LOCAL
1 TO 2 INCH RAINFALL AMOUNTS, WITH THE HIGHEST AMOUNTS NEAR THE
IDAHO/NEVADA BORDER.  THIS MUCH RAINFALL COULD RESULT IN LOCAL
FLASH FLOOD ISSUES, WHICH COULD BE ENHANCED IN AREAS WITH BURN
SCARS.

HAMRICK

ATTN...WFO...BOI...LKN...MSO...PIH...REV...TFX...

ATTN...RFC...CBRFC...CNRFC...MBRFC...NWRFC...

LAT...LON   46691380 46341285 45591267 44631286 43741343
            42611395 41531421 40811465 40501544 40421661
            40631764 41371834 42591816 44181688 45821574
            46531475