MESOSCALE PRECIPITATION DISCUSSION 0448
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1221 PM EDT SUN JUL 10 2016
 
AREAS AFFECTED...WESTERN AND CENTRAL ID 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 101620Z - 102220Z
 
SUMMARY...HEAVY RAINS WILL BECOME MORE WIDESPREAD AND CONCENTRATED
OVER THE NEXT SEVERAL HOURS. SOME FLASH FLOODING WILL BE POSSIBLE
OVER SOME OF THE HIGHER TERRAIN AND ESPECIALLY NEAR BURN-SCAR
AREAS.

DISCUSSION...COOLING CLOUD TOPS ARE EXPANDING ACROSS MUCH OF
NORTHEAST OR AND INTO PORTIONS OF WESTERN ID AS A RATHER
IMPRESSIVE 90 TO 110 KT 250MB JET STREAK ROUNDS THE BASE OF THE
STRONG UPPER LOW OVER THE PACIFIC NORTHWEST. IN FACT...500 MB
HEIGHT ANOMALIES OVER THE PACIFIC NORTHWEST ARE LOCALLY AS MUCH AS
3 STD DEV BELOW NORMAL WHICH INDICATES JUST HOW STRONG THE FORCING
HAS BEEN WITH THIS SYSTEM. 

LEFT-FRONT QUAD JET DYNAMICS WILL OVER SPREAD MUCH OF WESTERN AND
CENTRAL ID THROUGH EARLY AFTERNOON PROVIDING ROBUST DEEP LAYER
ASCENT...AND THIS COUPLED WITH OROGRAPHICS/UPSLOPE FLOW AND AT
LEAST MODEST DEGREE OF INSTABILITY SHOULD RESULT IN AN EXPANSION
OF HEAVY RAINFALL. 

PWATS OVER THE REGION ARE SOMEWHAT ELEVATED COMPARED TO
NORMAL...AND THE CIRA LPW PRODUCT DOES SHOW SOME CONCENTRATED
MOISTURE IN THE 700/300 MB LAYER WHICH WOULD SUPPORT GREATER
RAINFALL EFFICIENCY. FORECASTS FROM THE ESRL EXPERIMENTAL HRRR AND
THE NCEP HRRR SUGGEST HOURLY RAINFALL AMOUNTS THROUGH EARLY AND
MID-AFTERNOON MAY REACH 0.75 INCHES/HR OVER THE HIGHER TERRAIN OF
ESPECIALLY CENTRAL ID INVOLVING THE SAWTOOTH AND SALMON RIVER
MOUNTAINS AND ADJACENT SOUTHWEST FACING SLOPES WHICH ARE EXPECTED
TO BE ORIENTED MORE ORTHOGONAL TO THE 700/500 MB MEAN FLOW. THE
SAME GUIDANCE SUPPORTS 6-HOUR RAINFALL AMOUNTS OF AS MUCH AS 1.5
TO 1.75 INCHES.

FLASH FLOODING WILL BE POSSIBLE GIVEN THE LOCALLY INTENSE RAINFALL
RATES OVER THE TERRAIN...AND RUNOFF MAY BE ENHANCED ESPECIALLY
NEAR AREA BURN-SCARS. 

ORRISON

ATTN...WFO...BOI...MSO...PIH...TFX...

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

LAT...LON   45971491 45921426 45491379 44841407 44061492 
            43701545 43441610 43481652 43621673 43801686 
            44441693 45121655 45631594