HYDROMETEOROLOGICAL DISCUSSION
NORTHWEST RIVER FORECAST CENTER PORTLAND OR
11:40 AM PDT SUN MAY 19 2013
...LOCAL FLOODING IS FORECAST TO RESUME ON THE OKANOGAN RIVER TOWARD THE END
OF THIS WEEK. HIGH WATER IS ALSO POTENTIALLY EXPECTED LATER THIS WEEK THROUGH
NORTHEAST TO NORTH-CENTRAL WASHINGTON, NORTHERN IDAHO AND NORTHWEST MONTANA...
...HYDROMETEOROLOGICAL CONDITIONS...PAST 24 HOURS...4 AM - 4 AM...
A LINGERING WEAK ONSHORE TROUGHY PATTERN ACROSS THE REGION RESULTED IN MORE
MIXES OF OCCASIONAL SCATTERED LIGHT VALLEY RAIN SHOWERS AND MOUNTAIN SNOW ACROSS
MUCH OF OUR FORECAST AREA. SATURDAY TEMPERATURES TENDED TO BE GENERALLY AROUND 5
TO 11 DEGREES BELOW NORMAL. THIS MORNING FREEZING LEVELS RANGED BETWEEN 6400
FEET AT QUILLAYUTE...TO 8400 FEET AT MEDFORD.
...OBSERVED HYDROLOGIC CONDITIONS...
RECESSIONS TENDED TO DOMINATE FLOWS ACROSS THE REGION...BUT NEAR THE U.S.
CANADIAN BORDER A NUMBER OF FLOWS STILL REMAIN CLOSE TO ACTION LEVELS.
...HYDROMETEOROLOGICAL FORECAST...MAY 19 - MAY 23...
SCATTERED LIGHT MIXED SHOWERS TRAIL OFF EASTWARD ACROSS THE REGION SUNDAY...
WITH MONDAY LOOKING TO BE MOSTLY DRY AS A TRANSIENT RIDGE WARMS UP MOST LOCA-
TIONS AROUND 4 TO 8 DEGREES ABOVE NORMAL. TUESDAY A COLD CORE GULF OF ALASKA LOW
WITH 4 TO 9 DEGREE BELOW NORMAL TEMPERATURES SAGS OCCASIONAL VALLEY RAIN AND
LOWERING MOUNTAIN SNOW INTO OUR NORTHWESTERN TIER TUESDAY. WEDNESDAY THE OCCLU-
SION OF THIS UNSETTLED LOW ENTRAINS SOME GULF OF MEXICO MOISTURE INTO AN EAST-
WARD SHIFTING RAIN PATTERN OVER THE UPPER COLUMBIA. EMBEDDED CONVECTION IN THIS
UPPER COLUMBIA DAY-4 FORECAST PROBLEM COULD RESULT IN LOCAL HEAVY RAIN IN SOUTH
EASTERN BRITISH COLUMBIA...NORTHWESTERN MONTANA...NORTHERN IDAHO...AND NORTH
EASTERN TO NORTH CENTRAL WASHINGTON.
...HYDROLOGIC CONDITIONS...
EXPECT EARLY TO MID PERIOD FLAT TO RECEDING FLOWS TO DOMINATE THE REGION...
BUT MINOR TUESDAY NORTHWESTERN TIER LOWER ELEVATION STREAM RISES ARE A PRELUDE
TO WHAT COULD BECOME LOCALLY SHARPENING NORTHEASTERN TIER UPPER COLUMBIA WEDNES-
DAY RISES FROM POTENTIALLY HEAVY LOCAL RAIN AT TIMES ACROSS SOUTHEASTERN BRITISH
COLUMBIA...NORTHWESTERN MONTANA...NORTHERN IDAHO...AND NORTHEASTERN TO NORTH-
CENTRAL WASHINGTON.
...6-10 DAY OUTLOOK...MAY 24 - MAY 28...
STILL LOOKS LIKE OUR REGION IS GOING TO BE DOMINATED BY THE SLOWLY DECAYING
REMNANTS OF AN UPPER LEVEL LOW CENTERED OVER OUR FORECAST AREA THAT CONTINUES
PINWHEELING GRADUALLY DIMINISHING SCATTERED MIXED SHOWERS OVER US THROUGH THIS
FORECAST PERIOD. AS THIS LOW GRADUALLY OPENS UP WE SHOULD SEE TEMPERATURES START
TO GRADUALLY WARM UP...ENDING THE PERIOD TYPICALLY AROUND 3 TO 7 DEGREES ABOVE
NORMAL.
ML/RF/TD
VISIT US ON THE WEB AT HTTP://WWW.NWRFC.NOAA.GOV FOR DETAILED
GRAPHICAL PRECIPITATION...FREEZING LEVEL...AND TEMPERATURE FORECASTS.
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