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Hydrometeorological Discussion
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AGUS76 KPTR 201818
HMDPTR
HYDROMETEOROLOGICAL DISCUSSION
NORTHWEST RIVER FORECAST CENTER PORTLAND OR
11:15 AM PDT MON MAY 20 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 SOME
MIXES OF OCCASIONAL SCATTERED LIGHT VALLEY RAIN SHOWERS AND MOUNTAIN SNOW ACROSS
OUR FORECAST AREA. SUNDAY TEMPERATURES TENDED TO BE GENERALLY AROUND 3 TO 7
DEGREES BELOW NORMAL. THIS MORNING FREEZING LEVELS RANGED BETWEEN 8600 FEET AT
SPOKANE...TO 12800 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 20 - MAY 24...

MONDAY STILL LOOKS TO BE MOSTLY DRY AS A TRANSIENT RIDGE WARMS UP MOST LOCA-
TIONS AROUND 3 TO 6 DEGREES ABOVE NORMAL. TUESDAY A COLD CORE GULF OF ALASKA LOW
WITH 9 TO 10 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 AND LOWERING SNOW PATTERN OVER THE UPPER COLUMBIA. POTENTIAL
EMBEDDED CONVECTION IN THIS UPPER COLUMBIA FORECAST PROBLEM COULD RESULT IN
OCCASIONAL LOCAL HEAVY RAIN IN SOUTH EASTERN BRITISH COLUMBIA...NORTHWESTERN
MONTANA...NORTHERN IDAHO...AND NORTH EASTERN TO NORTH CENTRAL WASHINGTON WEDNES-
DAY TO FRIDAY. LOOK FOR COLDEST 7 TO 16 DEGREE BELOW NORMAL TEMPERATURES AROUND
WEDNESDAY.

...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 TO FRIDAY RISES FROM POTENTIALLY HEAVY LOCAL RAIN AT TIMES ACROSS SOUTH-
EASTERN BRITISH COLUMBIA...NORTHWESTERN MONTANA...NORTHERN IDAHO...AND NORTH-
EASTERN TO NORTH-CENTRAL WASHINGTON.

...6-10 DAY OUTLOOK...MAY 25 - MAY 29...

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 OCCASIONAL 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 NEAR TO 6 DEGREES ABOVE
NORMAL.

ML/RF/CO/BG

VISIT US ON THE WEB AT HTTP://WWW.NWRFC.NOAA.GOV FOR DETAILED
GRAPHICAL PRECIPITATION...FREEZING LEVEL...AND TEMPERATURE FORECASTS.


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National Weather Service Weather Forecast Office
