MESOSCALE PRECIPITATION DISCUSSION 0165
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
834 PM EDT MON JUN 01 2015
 
AREAS AFFECTED...EASTERN WASHINGTON...NORTHERN IDAHO...NORTHWEST
MONTANA...NORTHEAST OREGON 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 020033Z - 020633Z
 
SUMMARY...CONVECTIVE COVERAGE WITH PASSAGE OF UPPER-LEVEL TROF
OVER THE NEXT FEW HOURS TO PRODUCE INCREASED RAINFALL EFFICIENCY
TO POSSIBILITY EXCEED THE VERY LOW FLASH FLOOD GUIDANCE IN THE
AREA.  

DISCUSSION...EVOLUTION OF UPSCALE CONVECTIVE GROWTH AHEAD OF
NEGATIVELY TILTED UPPER-LEVEL TROF MOVING NORTH ACROSS OREGON INTO
WASHINGTON CONTINUES ON PACE PER EARLIER SPENES AND EXCESSIVE
RAINFALL OUTLOOK.  DEEP CONVECTIVE COMPLEX MOVING OFF HIGHER
ELEVATIONS OF NORTHEAST OREGON WILL AID DEEP MOISTURE CONVERGENCE
ACROSS NORTHERN AND EASTERN WASHINGTON INTO THE HIGHER TERRAIN
OVER NORTHERN IDAHO IN THE NEXT HOUR.  THIS IS TAPPING THE POCKET
OF 1000-1500 J/KG INSTABILITIES ACROSS EASTERN WASHINGTON AS WELL
AS THE .8-1.0" TOTAL PWATS IN PLACE ALLOWING FOR INCREASED
EFFICIENCY OF CONVECTIVE CORES FOR 1.0-1.25"/HR RATES.  WITH THE
STRONG MID-LEVEL RIDGE AXIS FROM SOUTHEAST BRITISH COLUMBIA INTO
CENTRAL MONTANA SEEN IN WV...INCREASINGLY DIFFLUENT AND SLOWING
FLOW WILL PROVIDE GOOD UPDRAFT OUTFLOW AS WELL AS DECREASING
FORWARD MOTIONS OF THE CELLS TO ALLOW TOTALS TO POTENTIALLY EXCEED
THE LOW FLASH FLOOD GUIDANCE VALUES ACROSS THE DISCUSSION REGION.

FURTHER EAST ALONG THE EASTERN SLOPES OF THE CASCADES...INCREASED
INSTABILITIES AND DEEP MOISTURE CONVERGENCE NEAR A WEAK VORT LOBE
HAS BEEN ENOUGH FOR A SMALL AREA OF CONVECTIVE GROWTH.  300-850MB
CLOUD BARING MEAN WIND IS VERY SLOW (5-10KTS TO THE
NORTH-NORTHWEST) ALLOWING FOR THE HIGHER PROBABILITIES OF SLOW
MOTION AND CELL MERGERS. 

AS INSTABILITIES ARE EXHAUSTING TOWARD 04-06Z... SOUTHWESTERLY LOW
LEVEL FLOW WILL INCREASE CONVERGENCE ALONG OROGRAPHY IN NORTHEAST
WASHINGTON INTO NORTH CENTRAL IDAHO TO ALLOW FOR FOR HIGHER RAIN
TOTALS INTO THE MOUNTAINS EVEN THOUGH INSTABILITY BEGINS TO WANE. 
THIS TREND IN LINE WITH RECENT HI-RESOLUTION GUIDANCE TRENDS
PARTICULARLY THE HRRR AND ARW.   

GALLINA

ATTN...WFO...BOI...MSO...OTX...PDT...SEW...

ATTN...RFC...NWRFC...

LAT...LON   49471567 48311407 47231481 46071550 45031730 
            44961894 45871915 46881792 47771798 47911866 
            47381976 46862023 47512100 48312137 49022148 
            49271969 49431770