Flooding in Idaho, January 16 to 20, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
425 PM PST SUN JAN 16 2011

.SYNOPSIS...
A NUMBER OF UNUSUALLY WARM PACIFIC STORM SYSTEMS WILL BRING
LOCALLY HEAVY RAIN AND HIGH MOUNTAIN SNOW INTO EARLY NEXT WEEK.
THE COMBINATION OF RAIN AND MELTING SNOW WILL RESULT IN INCREASED
RUNOFF OVER ALL LOCATIONS. LOCALIZED FLOODING IS POSSIBLE FROM
RISING RIVER LEVELS AND PONDING OF WATER DUE TO POOR DRAINAGE. A
SIGNIFICANT COLD FRONT WILL LOWER TEMPERATURES BY TUESDAY AND
BRING A GRADUAL DRYING TREND.

&&

.DISCUSSION...
TONIGHT...UPPER LEVEL JET FLOPPED OVER THE FLAT RIDGE AND TIED
INTO A WELL MAINTAINED SUBTROPICAL MOISTURE TAP MAKES SOME
PROGRESS TO THE SOUTHEAST TONIGHT BUT STILL REMAINS
OVERHEAD...PRIMARY NUISANCE ISSUE OF NOTE WOULD BE HOW THE UPPER
LEVEL JET INTERACTS WITH THE CASCADES AND POSSIBLY FORMS A LEE
WAVE THAT COULD BRING ABOUT SUBSTANTIAL SURFACE WINDS TO LOCATIONS
IN CLOSE PROXIMITY OF THE EAST SLOPES OF THE NORTHERN CASCADES.
THIS ISSUE LINGERS ON INTO TOMORROW AS WELL AND AS THUS WILL BE
DISCUSSED FURTHER. OTHERWISE AS WOULD BE EXPECTED WITH THE JET
PLACEMENT PRODUCING DOWNSLOPING SUBSIDENCE IN THE LEE AT THE
SURFACE FOR A GREAT PORTION OF THE LOWLANDS THE FORECAST SHOWS THE
DECREASED CHANCE OF PRECIPITATION WHILE GENERALLY HIGHER TERRAIN
IN NORTHERN IDAHO AND AT THE CREST OF THE CASCADES POP CHANGE
LITTLE. WIND ADVISORY LINGERS IN THE PALOUSE AND POINTS SOUTH TO
ACCOMMODATE THE HIGHEST WINDS ASSOCIATED WITH THIS SCENARIO INTO
THE EARLY PART OF THE EVENING BEFORE THE JET POSITIONING SHIFTS
THE PROBLEM WESTWARD LATER TONIGHT TO LOCATIONS NEAR WENATCHEE AND
THE WATERVILLE PLATEAU. /PELATTI

MONDAY THROUGH TUESDAY NIGHT...THE FIRE-HOSE OF SUB-TROPICAL MOISTURE
EXPERIENCED FOR THE PAST COUPLE DAYS WILL CONTINUE TO MOVE
STEADILY SOUTH THROUGH THIS PERIOD. ITS PRESENCE WAS ALREADY
BEGINNING TO WANE PER THE LATEST WATER VAPOR LOOPS AND MIMIC
PRECIPITABLE WATER DATA. WHEREAS YESTERDAY AFTERNOON SAW
PRECIPITABLE WATER VALUES AROUND 1.75 INCHES RIGHT OFF THE
COAST...THIS AFTERNOONS VALUES ARE NEARLY ONE-THIRD OF THAT.
DESPITE THE DEPARTURE OF THE MOISTURE...THE AIR MASS REMAINS
UNUSUALLY WARM AS WE REMAIN ON THE WARM SIDE OF A VERY STRONG
UPPER LEVEL JET. MOIST UPSLOPE FLOW WILL LIKELY KEEP SHOWERS GOING
THROUGH MONDAY EVENING AT THE CASCADE CREST AND OVER THE IDAHO
PANHANDLE. BUT PRECIPITATION AMOUNTS WILL NOT BE HEAVY.
HOWEVER...WITH SNOW LEVELS REMAINING AT OR ABOVE 4500 FT NEAR THE
CANADIAN BORDER AND AT LEAST 5500 FT ELSEWHERE...ABUNDANT SNOW
MELT WILL CONTINUE. WE WILL CONTINUE THE FLOOD WATCHES FOR THOSE
AREAS WHICH CURRENTLY HAVE NO FLOOD ADVISORIES...IE..THE NORTHERN
PARTS OF EASTERN WA AND THE NORTHERN ID PANHANDLE...HOWEVER WE
THINK THE RISK IS WANING WITH NOT MUCH RAIN TO BE ADDED TO THE
MIX.

THE WARM REGIME WILL COME TO A RAPID END ON LATE MONDAY NIGHT AND
TUESDAY AS THE DEEP SHORTWAVE TROUGH CURRENTLY NEARING 170W
AMPLIFIES THE FLOW AND PUSHES THE STRONG UPPER LEVEL JET TO OUR
SOUTH. THIS ALLOWS THE WELL DEFINED ARCTIC BOUNDARY CURRENTLY
HUGGING THE CONTINENTAL DIVIDE IN ALBERTA AND THE NORTHERN THIRD
OF BC. AS A RESULT...OUR 850 MB TEMPS PLUNGE FROM CURRENT READINGS
IN THE 4-8C RANGE WHICH IS WELL ABOVE NORMAL...TO A MORE
SEASONABLE -2 TO -6C RANGE BY TUESDAY MORNING. THIS SURGE OF COLD
AIR COULD PRODUCE SOME PROBLEMS COME TUESDAY NIGHT AS SOME MODEL
SOLUTIONS ARE FORECASTING THE RAPID FORMATION OF A SURFACE-850 MB
LOW. SOME MODEL SOLUTIONS CLOSE OFF THIS LOW AND TRACK IT THROUGH
SOUTHERN WASHINGTON LATE TUESDAY INTO TUESDAY NIGHT...WHILE OTHERS
KEEP IT MUCH WEAKER AND FARTHER SOUTH. AT 12Z...THE MODELS WERE
SPLIT...BUT THE 18Z SOLUTIONS SHOW A LITTLE BETTER AGREEMENT AND
TAKE THE LOW ALMOST DUE EAST ALONG THE WA/OR BORDER. IF THIS COMES
TO FRUITION...WE HAVE A CHANCE OF SEEING A BAND OF MODERATE SNOWS
FORMING JUST NORTH AND EAST OF THE LOW TRACK AND POSSIBLY SOME
SNOW ADVISORIES...MAINLY SOUTH OF I90. HOWEVER AT THIS POINT THERE IS
TOO MUCH MODEL UNCERTAINTY AND MUCH DEPENDS ON HOW COLD THE
TEMPERATURES GET AHEAD OF THE SYSTEM.

ASIDE FROM PRECIP CHANCES...WE ARE A BIT CONCERNED ABOUT WINDS.
THE LOW-LEVEL JET WILL REMAIN ESTABLISHED OVER THE SE CORNER OF
THE CWA...WHICH WILL MAINLY IMPACT THE PALOUSE THROUGH MONDAY.
HOWEVER OF MORE INTEREST IS THE FORMATION OF MOUNTAIN WAVE
ACTIVITY IN THE IMMEDIATE LEE OF THE CASCADES. THIS IS A TRICKY
CALL. MOS GUIDANCE YIELDS LITTLE IF ANY CLUE INTO ITS
FORMATION...BUT THE FINER RESOLUTION MODELS HINT AT BETTER
CHANCES. OUR LOCAL WRF MODEL AND THE 4KM UW MM5 SOLUTIONS SHOW A
BREAKING MOUNTAIN WAVE FORMING SOMETIME AROUND 06-09Z TONIGHT AND
PERSISTING THROUGH 18Z-21Z ON MONDAY. THIS IS FAR FROM A CLASSIC
CASE FOR STRONG WINDS AS WE WOULD PREFER TO SEE A STRONG INVERSION
FORM AT CREST LEVEL. ALSO PROBLEMATIC WAS THE BUFR SOUNDINGS
INDICATE A SHALLOW NEAR GROUND INVERSION WILL PROTECT LOCATIONS
SUCH AS WENATCHEE FROM THE STRONGEST WINDS. FOR THAT REASON WE
WILL GO A WIND ADVISORY RATHER THAN A HIGH WIND WARNING. BUT WE
WILL MENTION THAT SPORADIC HIGH GUSTS ARE POSSIBLE ON THE
WATERVILLE PLATEAU AND HIGHER TERRAIN SURROUNDING WENATCHEE. FX

WEDNESDAY THROUGH SUNDAY...FOLLOWING A RELATIVELY QUIET AND
COOL START TO THE PERIOD...THE PATTERN WILL BECOME INCREASINGLY
WETTER AND WARMER TO END THE WEEK AND START THE WEEKEND. WEDNESDAY
STARTS OFF WITH A HIGHLY AMPLIFIED JET STREAM ACROSS THE PACIFIC
FEATURING AN UPPER-LEVEL TROUGH NEAR THE DATELINE AND RIDGE OF
HIGH PRESSURE CENTERED ALONG 135W. A STRONG SUBTROPICAL MOISTURE
FETCH WILL BE TRACKING UP THE WESTERN FLANK OF THE RIDGE AND
REMAIN DIRECTED INTO WESTERN CANADA. THIS LEAVES THE INLAND NW ON
THE EASTERN FLANK OF THE RIDGE...UNDER A DRY...COOL N/NW FLOW
REGIME. AWAY FROM LINGERING SNOW SHOWERS ACROSS THE CAMAS PRAIRIE
AND BLUE MTNS...A MAJORITY OF THE REGION WILL EXPERIENCE FAIR
SKIES AND DRY CONDITIONS WITH TEMPERATURES NEAR NORMAL.

FOR SUNDAY ONWARD...THE UPPER-LEVEL RIDGE OF HIGH PRESSURE ALONG
135W WILL BECOME FLATTENED SHIFTING THE SUBTROPICAL MOISTURE FETCH
AND GRAVY TRAIN OF STORM SYSTEMS FROM BRITISH COLUMBIA...TOWARD
THE PAC NW. MODELS ARE IN FAIR TO GOOD AGREEMENT ON THE LARGE-
SCALE FLOW WITH SOME EXPECTED DIFFERENCES ON THE TIMING OF EACH
DISTURBANCE. BY ANY MEANS...LOOSE AGREEMENT AMONGST GUIDANCE
SUGGEST ONE WAVE OF MOISTURE COMES THROUGH THURSDAY...A SECOND
FRIDAY...THEN A THIRD/FOURTH SATURDAY AND SUNDAY. THE FIRST TWO
WAVES WILL BE WEAKER AND MOVE INTO A COOLER ENVIRONMENT RESULTING
IN THE CHANCE FOR LIGHT SNOW FOR MOST VALLEY LOCATIONS NORTH OF
INTERSTATE 90. HOWEVER...BY THE WEEKEND...THE THIRD AND FOURTH
SYSTEMS WILL MOVE INTO THE REGION TIED TO A RICH SUBTROPICAL
MOISTURE FETCH AND SNOW LEVELS WILL BE ON THE RISE WITH MOST
VALLEYS TRANSITIONING TO RAIN BY SUNDAY. UNLIKE THE CURRENT MILD
PATTERN...MID LEVEL FLOW WILL BE MORE NW TO SE ALLOWING COOLER AIR TO
REMAIN IN PLACE...ESPECIALLY NEAR THE CANADIAN BORDER...KEEPING
P-TYPES MAINLY SNOW FOR THE NORTHERN MOUNTAINS. THIS WILL NOT BE
THE CASE IN THE VALLEYS WHERE TEMPERATURES WILL WARMING ABOVE
FREEZING...AND GENERALLY ABOVE JANUARY NORMAL'S. /SB

&&

.AVIATION...
00Z TAFS...A STRONG WESTERLY JET ALOFT WILL CONTINUE TO SETTLE
SOUTHWARD OVER THE INLAND NW.  THIS WILL KEEP A RATHER STRONG
PRESSURE GRADIENT SETUP AT THE SURFACE AND BREEZY TO LOCALLY GUSTY
WINDS FOR ALL TERMINALS.  THESE WNDS WILL WILL BE SLOWER TO
MATERIALIZE IN THE IMMEDIATE FOOTHILLS OF THE EAST SLOPES AND
WENATCHEE VALLEY WHERE SHALLOW INVERSIONS WILL KEEP THE BL
DECOUPLED RESULTING IN AREAS OF DENSE FG.  AS A RESULT...WIND SHEAR
WILL BE THE MAIN CONCERN UNTIL AFT 06Z WHEN THE STRONG WINDS ALOFT
ARE EXPECTED TO MIX TO THE SFC.  AS FOR PCPN...WESTERLY FLOW
WILL KEEP THE MAIN PCPN THREAT ALONG THE CASCADE CREST AND IDAHO
PANHANDLE WITH MOSTLY DRY CONDITIONS IN BTWN.  STRATUS WILL BE
POSSIBLE ALONG THE KGEG-KCOE CORRIDOR BUT CONFIDENCE IS GENERALLY
LOW WITH SOME DRIER AIR ADVECTING IN FROM THE WEST.  ANY LOW CLOUDS
THAT DO FORM...THE BREEZY SFC FLOW SHOULD KEEP VIS AOA 6SM.  /SB

&&

.PRELIMINARY POINT TEMPS/POPS...
SPOKANE        42  48  30  36  25  33 /  20  30  10  60  40  10
COEUR D'ALENE  42  46  30  35  27  33 /  30  60  20  60  50  10
PULLMAN        43  49  31  38  28  35 /  20  60  20  60  70  10
LEWISTON       47  58  35  42  32  40 /  20  50  20  60  70  20
COLVILLE       37  46  28  34  23  34 /  20  20  10  50  40  10
SANDPOINT      41  43  31  34  26  32 /  70  70  30  40  50  10
KELLOGG        41  42  29  34  29  33 / 100  90  70  60  60  30
MOSES LAKE     34  49  29  38  27  36 /  10  10   0  50  30   0
WENATCHEE      37  53  30  35  27  35 /  10  10  10  60  30  10
OMAK           37  43  27  34  23  31 /  20  20  10  30  20   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...FLOOD WATCH THROUGH TUESDAY AFTERNOON COEUR D'ALENE AREA...
     NORTHERN PANHANDLE.

     WIND ADVISORY UNTIL 4 PM PST MONDAY ABOVE 2000 FEET FOR THE
     IDAHO PALOUSE.

WA...FLOOD WATCH THROUGH TUESDAY AFTERNOON EAST SLOPES NORTHERN
     CASCADES...NORTHEAST MOUNTAINS...SPOKANE AREA.

     WIND ADVISORY UNTIL 4 PM PST MONDAY ABOVE 2000 FEET FOR THE
     LOWER GARFIELD AND ASOTIN COUNTIES...WASHINGTON PALOUSE.

     WIND ADVISORY FROM 10 PM THIS EVENING TO 4 PM PST MONDAY
     WATERVILLE PLATEAU...WENATCHEE AREA.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SPOKANE WA
621 AM PST SUN JAN 16 2011

IDZ001>004-026-027-WAZ031>038-041>044-171430-
NORTHERN PANHANDLE-COEUR D'ALENE AREA-IDAHO PALOUSE-
CENTRAL PANHANDLE MOUNTAINS-LEWISTON AREA-
LEWIS AND SOUTHERN NEZ PERCE COUNTIES-NORTHEAST BLUE MOUNTAINS-
LOWER GARFIELD AND ASOTIN COUNTIES-WASHINGTON PALOUSE-
MOSES LAKE AREA-UPPER COLUMBIA BASIN-SPOKANE AREA-
NORTHEAST MOUNTAINS-OKANOGAN HIGHLANDS-WENATCHEE AREA-
EAST SLOPES NORTHERN CASCADES-OKANOGAN VALLEY-WATERVILLE PLATEAU-
621 AM PST SUN JAN 16 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH IDAHO...
NORTH CENTRAL IDAHO...CENTRAL WASHINGTON...EAST CENTRAL
WASHINGTON...NORTH CENTRAL WASHINGTON...NORTHEAST WASHINGTON AND
SOUTHEAST WASHINGTON.

.DAY ONE...TODAY AND TONIGHT

PERIODS OF RAIN AND WINDY CONDITIONS WILL IMPACT MUCH OF THE
INLAND NORTHWEST TODAY. ON THE PALOUSE AND HIGHER TERRAIN OF
SOUTHEAST WASHINGTON GUSTS OF 45 MPH ARE POSSIBLE THIS AFTERNOON.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

MILD AND WET WEATHER WILL CONTINUE THROUGH MONDAY WITH OCCASIONAL
RAIN SHOWERS...HIGH SNOW LEVELS AND BREEZY WINDS. THE COMBINATION
OF THE MELTING SNOW AND RAIN WILL CONTRIBUTE TO RISES ON MANY
CREEKS AND SMALL STREAMS.

AN UPPER LEVEL DISTURBANCE WILL MOVE THROUGH THE REGION LATE
TUESDAY INTO TUESDAY NIGHT...FOLLOWED BY COOLER MORE SEASONAL
TEMPERATURES. THERE IS THE POTENTIAL FOR LIGHT TO MODERATE SNOW IN
THE MOUNTAINS.

DRIER AND COOLER WEATHER IS FORECAST BY WEDNESDAY THROUGH THE REST
OF THE WEEK. THIS SHOULD HELP RUNOFF AND WATER LEVELS ON CREEKS
AND STREAMS TO SUBSIDE.