MESOSCALE PRECIPITATION DISCUSSION 0047
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
359 PM EST WED FEB 08 2017
 
AREAS AFFECTED...COASTAL RANGE OF OR....NORTHERN CA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 082100Z - 090600Z
 
SUMMARY...PERSISTENT MODEST OROGRAPHICALLY INDUCED SHOWERS WILL
CONTINUE FOR A FEW HOURS BEFORE DRYING STARTS TO LIFT NORTH ACROSS
CA BY 00Z.  STRENGTHENING LOW LEVEL JET WILL TIGHTEN MOISTURE
PLUME AND INCREASE MOISTURE FLUX AND RAIN RATES AFTER 04Z AS COLD
FRONT APPROACHES. 

DISCUSSION...BLENDED TPW LOOP AND SURFACE OBSERVATIONS DENOTE A
SUBTLE BOUNDARY/ FRONT LIFTING NORTHWARD ALONG THE NW CA COAST
THAT DEMARCATES THE BIFURCATION OF THE MOISTURE STREAMS...WITH THE
TAIL END OF THE CA STREAM CONTINUING TO ADVECT NORTHWARD ON
BACKING LOW LEVEL FLOW (85-7H) FROM WSW AT 35KTS TO SSWLY AT 25
KTS AROUND 00Z...DECREASING FURTHER AFTERWARD.  TPWS WILL DECREASE
BELOW AN INCH AND RAIN RATES WILL BECOME LESS THAN .1"/HR LEADING
TO AN ADDITIONAL 1-2" ACROSS THE NORTHERN SIERRA PROLONGING
FLOODING CONCERNS THERE FOR A FEW MORE HOURS.

NW CA/OR COASTAL RANGES...LEAKING INTO CASCADES... WV LOOP SHOWS
STRENGTHENING JET STREAK AND BAROCLINIC LEAF GROWTH BETWEEN
130-140W STEADILY ADVANCING NORTHWARD.  AMSU 89GHZ ANALYSIS
INDICATES WARM/OCCLUDED FRONT NEARING THE COLUMBIA RIVER
VALLEY...WITH WELL DEFINED COLD FRONT EXTENDING SW TOWARD 30N140W.
 BLENDED TPW ANALYSIS SHOWS BROAD AREA OF 1.0"+ VALUES WITHIN THE
WARM SECTOR THOUGH GENERALLY BROAD WITH RAP ANALYSIS SUGGESTING
FLOW IN THE 35-40KT RANGE ACROSS THE REGION.  THIS SHOULD LEAD TO
STEADY .2-.4"/HR RAINFALL RATES IN THE COASTAL RANGE OF
OREGON...SATURATING THE AREA FOR STRONGER RAINFALL/FLOODING
CONCERNS WITH THE NEXT SURGE. AS SUCH AN ADDITIONAL 1.5-2.5" ARE
POSSIBLE OVER THE NORTHERN SIERRAS INTO TRINITY/MT. SHASTA REGION.

GOES-W WV LOOP SHOWS STRENGTHENING UPPER LEVEL JET AND BAROCLINIC
LEAF EXPANSION BETWEEN 130-140W.  AS THE JET/SHORTWAVE ENERGY
LIFTS NORTH GENTLE EASTWARD PROGRESSION OF HEIGHT FALLS WILL
SUPPORT STRENGTHENING AND NARROWING THE LOW LEVEL JET JUST AHEAD
OF THE COLD FRONT AT THE LEADING EDGE OF 50-60KT 85H AND 7H 60KT
JET STREAK.  RAP/ARW CAMS SUGGEST THIS WILL REACH SW OREGON BY
03-04Z.  THIS LEADING EDGE ALSO APPEARS TO BE A GOOD MARKER FOR
1.25" TPW WITH 1.5" VALUES AS FAR NORTH AS 38N.  THIS ALLOWS FOR
VERY STRONG DYNAMIC MOISTURE FLUX THAT WILL AFFECT SSW FACING
OROGRAPHY ALONG THE COASTAL RANGE TO SUPPORT RATES THAT WILL
STEADILY INCREASE FROM .25 TO .5" TOWARD 09Z...PARTICULARLY ACROSS
FAVORED TERRAIN OF SW OREGON.  HI-RES CAMS ARE IN GENERAL
AGREEMENT THOUGH THE HRRR IS A BIT LESS ROBUST WITH THE FLOW AND
MST FLUX AND THEREFORE HAS REDUCED TOTALS.  AS SUCH UTILIZING THE
HREF AND SSEO MEANS WOULD SUGGEST A GENERAL 3-5" ACROSS SW
OREGON/NW CA AND 2-3" ALONG THE OR COASTAL RANGE THROUGH
06Z...WITH PEAK FLUX AFTER THIS TIME FRAME. 

GALLINA

ATTN...WFO...EKA...MFR...PQR...REV...STO...

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

LAT...LON   46152345 45912314 45302312 44432323 44012332 
            43572350 42982359 42652330 42262296 41842269 
            41842206 41662155 41222121 40622070 40152040 
            39492020 38802013 38712047 38922094 39492153 
            40522229 40492294 40092319 39872377 39992408 
            40352449 40762426 41252417 41812420 42162442 
            42672458 43022473 43942435 44712424 45572406 
            46022386