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Hydrometeorological Discussion
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AGUS76 KPTR 171608
HMDPTR
HYDROMETEOROLOGICAL DISCUSSION
NORTHWEST RIVER FORECAST CENTER PORTLAND OR
09:09 AM PDT FRI MAY 17 2013

...LOCAL FLOODING CONTINUES ON THE OKANOGAN RIVER. HIGH WATER
EXPECTED AGAIN NEXT WEEK THROUGH NORTHEAST WASHINGTON, NORTHERN
IDAHO AND NORTHWEST MONTANA...

...HYDROMETEOROLOGICAL CONDITIONS...PAST 24 HOURS...4 AM - 4 AM...

A BROAD UPPER LEVEL LOW PRESSURE SYSTEM MOVED ONSHORE YESTERDAY...
BRINGING CONTINUED COOL SHOWERY WEATHER TO THE REGION. HIGH
ELEVATION AREAS THROUGH THE GRAND TETONS AND OREGON CASCADES A
QUARTER INCH OF PRECIPITATION OR MORE...THOUGH MOST AREAS HAD
RELATIVELY LIGHT RAIN. TEMPERATURES RANGED FROM NEAR TO 10 DEGREES
BELOW NORMAL. FREEZING LEVELS RANGED FROM AROUND 7000 FEET NEAR
THE COAST TO AROUND 10000 FEET OVER THE GREAT DIVIDE.

...OBSERVED HYDROLOGIC CONDITIONS...

THOUGH MOST BASINS SAW RECESSIONS YESTERDAY...MANY NEAR THE U.S.
CANADIAN BORDER REMAIN NEAR TO ABOVE ACTION LEVELS.

...HYDROMETEOROLOGICAL FORECAST...MAY 17 - MAY 21...

A MOISTER THAN NORMAL ATMOSPHERE AND A LOW PRESSURE TROUGH WILL
HELP TO BRING CONTINUED SHOWERY WEATHER THROUGH THE REGION TODAY
AND SATURDAY. AS THIS SYSTEM MOVES EAST SUNDAY...THE BASIN WILL
SEE IMPROVING...DRIER CONDITIONS. DRIER CONDITIONS SHOULD CONTINUE
THROUGH MONDAY WITH SLIGHTLY WARMER TEMPERATURES.  MONDAY NIGHT
ANOTHER LOW PRESSURE SYSTEM WILL MOVE ONSHORE. MOISTURE WILL BEGIN
TO TRAIN INTO THE REGION TUESDAY HELPING TO BRING MORE LIGHT TO
MODERATE SHOWERS TO THE REGION.

...HYDROLOGIC CONDITIONS...

RELATIVELY DRY CONDITIONS WITH NEAR NORMAL TEMPERATURES WILL HELP
TRIBUTARIES RECEDE OVER THE NEXT FEW DAYS. MAINSTEM RIVERS WILL
CONTINUE TO RUN HIGH WITH THE PREVIOUS WEEK`S SNOWMELT AND RAIN
RUNOFF.

BY TUESDAY...PRECIPITATION WILL BEING TO INCREASE AGAIN INTO
SOUTHERN BRITISH COLUMBIA AND NEAR THE CONTINENTAL DIVIDE IN
NORTHWEST MONTANA AND NORTHERN IDAHO.  THIS WILL HELP START RISES
AGAIN THROUGH THE RIVERS IN THESE AREAS.

...6-10 DAY OUTLOOK...MAY 22 - MAY 26...

MODELS IN THE EXTENDED PERIOD ARE IN GOOD AGREEMENT...THOUGH IF
THEY SHIFT SLIGHTLY IT COULD MEAN BIG DIFFERENCES IN THE WEATHER
AND HYDROLOGIC OUTCOMES.  CURRENT MODELS SUGGEST SOUTHERN BRITISH
COLUMBIA...NORTHERN IDAHO AND NORTHWEST MONTANA WILL SEE HEAVY
PRECIPITATION WEDNESDAY AS THE INCOMING LOW PRESSURE SYSTEM
INTERACTS WITH A SUBTROPICAL MOISTURE FEED OVER THIS AREA.

CURRENT MODELS ALSO SUGGEST THIS LOW WILL MOVE EAST QUICKLY BY
THURSDAY...BRINGING AN UNSTABLE...UNORGANIZED AIRMASS OVER THE
REGION.  IF THIS VERIFIES WE`LL SEE LIGHT PRECIPITATION AND NEAR
NORMAL TEMPERATURES THROUGH THE END OF THE 10 DAY PERIOD.

VS/CO/JS/BA/RF/SK

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
