An upper level low in the Gulf of Alaska pumped in copious amounts of moisture with sub-tropical origins. Orographics played a major role in creating the lift that produced the precipitation over the Central Panhandle Mountains.
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The episode as NWS OTX wrote it up.
An upper level low in the Gulf of Alaska pumped in copious amounts of moisture with sub-tropical origins. Orographics played a major role in creating the lift that produced the precipitation over the Central Panhandle Mountains. Snow increased to between 3500 and 4000 feet during the day, which kept much of the heaviest snowfall in the mountains.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Spokane, WA wrote its last area forecast discussion before the first event at Apr 4, 1:42 AM PST, 1 hour 18 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
242 AM PDT MON APR 4 2011
.SYNOPSIS...
THE NEXT WET STORM SYSTEM WILL MOVE INTO THE FORECAST AREA THIS
MORNING AND LINGER INTO TUESDAY...WITH SNOW LEVELS FALLING
DRAMATICALLY MONDAY NIGHT. SIGNIFICANT SNOW ACCUMULATIONS ARE
POSSIBLE FOR THE IDAHO PANHANDLE MOUNTAINS BY TUESDAY. AT THE
LOWER ELEVATIONS...FLOODING WILL ONCE AGAIN BE POSSIBLE. THIS COOL
AND WET PATTERN WILL LAST MUCH OF THE WEEK.
&&
.DISCUSSION...
TODAY THROUGH TUESDAY...SATELLITE LOOPS ARE SHOWING A FAIRLY
ROBUST UPPER LEVEL LOW MOVING THROUGH THE GULF OF ALASKA AT THE
TIME WITH A 150KT JET TO THE SOUTH OF THE MAIN LOW. THIS JET IS
EXPECTED TO SLOWLY SAG INTO THE REGION TODAY AND HAS TAPPED INTO
SUBSTANTIAL SUB-TROPICAL MOISTURE ALL THE WAY FROM JUST NORTH OF
THE HAWAIIAN ISLANDS. AMSU PW'S ARE ON THE ORDER OF 1.00 TO 1.15
INCHES OF WATER AIMED DIRECTLY AT THE PACIFIC NORTHWEST. THIS WILL
RESULT IN A VERY WET WEATHER PATTERN FOR THE NEXT FEW DAYS.
WEAK ISENTROPIC UP-GLIDE ALONG THE 290K SURFACE WILL INCREASE
THIS MORNING FROM WEST TO EAST AS MOISTURE CONTINUES TO STREAM
INTO THE AREA. LIFT IS NOT GREAT...HOWEVER THE AMOUNT OF MOISTURE
THAT WILL MOVE INTO THE REGION OVER THE NEXT 12-24 HOURS WILL BE
SO GREAT THAT ONLY A LITTLE LIFT WILL RESULT IN HIGH QPF TOTALS.
PRECIPITATION MADE IT TO THE CASCADE CREST JUST AFTER MIDNIGHT.
SO FAR ONLY TRACE AMOUNTS TO A FEW HUNDREDTHS HAVE OBSERVED ON THE
WEST SIDE. IN ADDITION THE LOWER ATMOSPHERE REMAINS VERY DRY PER
CURRENT DEWPOINT DEPRESSION AND IT WILL TAKE SOME TIME TO MOISTEN
UP. STILL IT LOOKS LIKE THE TIMING OF LIGHT PRECIPITATION
BEGINNING AT THE WESTERN LOCATIONS AT OR AROUND 12Z THEN PUSHING
EAST THROUGH THE MORNING IS STILL ON TRACK. WE SHOULD EXPECT QUITE
A SHADOW EFFECT OFF THE CASCADES FOR THE LOWER EAST SLOPES AND THE
BASIN...WITH THE BEST ACCUMULATIONS FOR THE IMMEDIATE CASCADES AND
EAST OF A LINE FROM ABOUT OMAK TO THE TRI-CITIES. BUT JUST ABOUT
ALL LOCATIONS WILL RECEIVE SOME MOISTURE. A WEAK COLD FRONT
TONIGHT WILL TURN PRECIPITATION SHOWERY AND WITH CONTINUED UP-
SLOPING FLOW THE NORTHERN AND EASTERN MOUNTAINS WILL SEE COPIOUS
AMOUNTS OF RAIN AND SNOW. QPF AMOUNTS THROUGH TUESDAY AFTERNOON
WILL RANGE FROM LESS THAN .10 IN THE LOWER BASIN TO BETWEEN .50
AND AN INCH FOR CASCADE CREST AND THE HIGHER TERRAIN OF THE
NORTHERN AND PANHANDLE MOUNTAINS.
SNOW LEVELS WILL START OUT AROUND 2000 FEET OR A LITTLE LOWER THIS
MORNING...BEFORE INCREASING TO 3500-4000 FEET THROUGH THE DAY. DEWPOINTS
MAINLY IN THE MID 20S TO LOWER 30S WILL RESULT IN WET-BULB
EFFECT....ALLOWING PRECIPITATION TO BEGIN MOST PLACES BUT THE
LOWER ELEVATIONS AS SNOW OR A RAIN/SNOW MIX....BEFORE SWITCHING TO
MOSTLY RAIN THROUGH THE MORNING HOURS. ACCUMULATIONS BELOW
3000-3500 FEET WILL BE MAINLY ON NON-ROAD SURFACES AND WITH ONLY
LIGHT PRECIPITATION AT THE START OF THIS EVENT SNOW SHOULD BE VERY
LIGHT. SNOW ACCUMULATIONS BY TUESDAY AFTERNOON MAY REACH AS HIGH
AS 5 TO 9 INCHES FOR THE CENTRAL PANHANDLE MOUNTAINS. EARLY SEASON
CRITERIA IS ONLY 6+ INCHES FOR 24 HOURS. A WATCH WAS ISSUED
PREVIOUSLY FOR LATE SEASON CONDITIONS ABOVE 4500 FEET FOR THE
CENTRAL PANHANDLE MOUNTAINS AND WHILE I THINK THE PRECIPITATION
WILL BE MORE THAN ADEQUATE I AM NOT SO CONFIDENT WITH THE SNOW
LEVELS. AS SUCH I WILL CONTINUE THE WATCH FOR THE TIME BEING.
THE MAIN WEATHER ISSUE FOR THE NEXT FEW DAYS WILL BE FLOODING. THE
RAINFALL OVER THE PAST WEEK OR SO HAS SATURATED THE GROUND AND ANY
ADDITIONAL QPF WILL ONLY ADD TO FLOODING CONCERNS. FLOOD WARNINGS
AND WATCHES ARE ALREADY IN PLACE AND THIS WILL BE MONITORED
CLOSELY FOR FURTHER UPDATES. /TOBIN
TUESDAY NIGHT THROUGH THURSDAY...A WEAK SHORTWAVE IMPULSE WILL MOVE
THROUGH THE REGION TUESDAY NIGHT INTO WEDNESDAY WITH CONTINUED
UNSETTLED WEATHER FOR THE INLAND NORTHWEST. POST-FRONTAL WESTERLY
FLOW WILL FOCUS PRECIPITATION ON THE EASTERN ZONES WHILE CREATING A
RAIN SHADOW OVER THE BASIN. SNOW LEVELS WILL FALL TO AROUND 1500
FEET OVERNIGHT BUT QPF WILL BE RATHER LIGHT IN THE LOWER ELEVATIONS
AND ANY SIGNIFICANT ACCUMULATING SNOW SHOULD BE ABOVE 4000 FEET.
WEDNESDAY NIGHT A BROAD UPPER LEVEL TROUGH WILL DROP SOUTH THROUGH
THE REGION. THE LOW PRESSURE CENTER WILL TRACK SOUTH ACROSS WESTERN
WASHINGTON AND OREGON. WHILE MOST OF THE TROUGH CUSP DYNAMICS WILL
REMAIN CLOSE TO THE LOW CENTER...THERE WILL BE ADEQUATE LIFT AND
MOISTURE FOR A GOOD CHANCE OF SHOWERS ACROSS MOST OF THE FORECAST
AREA. THE COLD POOL ALOFT WILL FOSTER INSTABILITY SHOWERS THAT COULD
BRING A QUICK BURST OF SNOW OR GRAUPEL EVEN TO LOWER VALLEY
LOCATIONS. AS THE SURFACE LOW TRACKS THROUGH THE AREA...DEFORMATION
ZONES WILL DEVELOP WITH BANDED PRECIPITATION POSSIBLE. ANY
CONVECTIVE BANDING THAT DEVELOPS OR CONTINUES DURING THE OVERNIGHT
HOURS COULD PRODUCE ACCUMULATING SNOW BUT AGAIN...MODEL QPF IS
LIGHT...IN THE 0.10 TO 0.15 INCH RANGE FOR THE VALLEYS. TEMPERATURES
WILL CONTINUE THE COOL TREND.
THURSDAY NIGHT THROUGH SUNDAY...PRECIPITATION WILL DIMINISH
OVERNIGHT THURSDAY AS THE LOW RETREATS TO THE SOUTH TAKING THE
MOISTURE AND FORCING WITH IT. BY FRIDAY THE LOW SINKS WELL TO OUR
SOUTH AND A RIDGE STARTS TO BUILD OVER THE REGION. NORTHERLY FLOW
WILL BRING A DRIER AND MORE STABLE AIR MASS INTO THE REGION. WHILE
MUCH OF THE AREA WILL REMAIN DRY AND THERE WILL BE SOME
SUNSHINE...NORTHERLY FLOW WILL KEEP TEMPERATURES ON THE COOL SIDE
BUT CLOSER TO SEASONAL NORMALS. DRY WEATHER SHOULD CONTINUE THROUGH
SUNDAY. THEN THE RIDGE AXIS MOVES EAST INTO MONTANA LATE SUNDAY
AND THE NEXT PACIFIC SYSTEM APPROACHES THE COAST. /KELCH
&&
.AVIATION...
AN EXPANSIVE AREA OF VIRGA IS PUSHING EAST INTO THE AREA THIS LATE
EVENING...AND WILL CONTINUE TO OVERSPREAD THE ENTIRE AREA OVERNIGHT.
SOME -SN SHOULD BEGIN TO FALL OUT AFTER 10Z IN FAR EASTERN WA/NORTH
IDAHO...AND BECOME STEADIER AFTER 12Z. FOR KEAT AND KMWH...AND
PRECIP WILL BE SPOTTY AT BEST WITH A PRONOUNCED RAIN SHADOW EAST OF
THE CASCADES. PRECIP WILL GRADUALLY TRANSITION TO -RA AT ALL SITES
ON MONDAY AS FREEZING LEVELS RISE. CIGS WILL FALL STEADILY TONIGHT
AS PRECIP SPREADS IN...BUT LIKELY RISE SLIGHTLY ON MONDAY AFTERNOON
WITH BETTER MIXING IN THE LOW LEVELS AS WELL AS SOME HEATING IN THE
LOWEST LEVELS MAKING LOW LEVEL SATURATION DIFFICULT. WINDS WILL
STEADILY PICK UP DURING THE AFTERNOON MONDAY AT ALL SITES. /FRIES
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 46 37 50 34 44 30 / 70 80 30 60 50 40
COEUR D'ALENE 44 37 47 32 42 29 / 90 100 50 60 60 50
PULLMAN 47 39 47 34 43 30 / 80 100 60 40 60 50
LEWISTON 55 42 53 37 50 33 / 60 80 40 30 60 50
COLVILLE 50 36 50 34 48 30 / 70 70 40 60 50 40
SANDPOINT 43 35 44 32 41 30 / 100 100 60 80 60 50
KELLOGG 40 33 41 30 39 27 / 100 100 80 80 60 60
MOSES LAKE 56 39 56 36 53 29 / 40 40 0 10 30 30
WENATCHEE 55 37 52 36 50 32 / 40 30 0 10 20 30
OMAK 56 35 54 35 51 30 / 60 40 10 20 20 30
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...FLOOD WATCH FROM 11 AM PDT THIS MORNING THROUGH TUESDAY
AFTERNOON CENTRAL PANHANDLE MOUNTAINS...COEUR D'ALENE
AREA...IDAHO PALOUSE...LEWIS AND SOUTHERN NEZ PERCE
COUNTIES...LEWISTON AREA...NORTHERN PANHANDLE.
WINTER STORM WATCH FROM THIS AFTERNOON THROUGH TUESDAY AFTERNOON
ABOVE 4500 FEET FOR THE CENTRAL PANHANDLE MOUNTAINS.
WA...FLOOD WATCH FROM 11 AM PDT THIS MORNING THROUGH TUESDAY
AFTERNOON EAST SLOPES NORTHERN CASCADES...WASHINGTON
PALOUSE.
&&HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE SPOKANE WA 407 PM PDT SUN APR 3 2011 IDZ001>004-026-027-WAZ033-042315- NORTHERN PANHANDLE-COEUR D'ALENE AREA-IDAHO PALOUSE- CENTRAL PANHANDLE MOUNTAINS-LEWISTON AREA- LEWIS AND SOUTHERN NEZ PERCE COUNTIES-WASHINGTON PALOUSE- 407 PM PDT SUN APR 3 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH IDAHO... NORTH CENTRAL IDAHO AND SOUTHEAST WASHINGTON. .DAY ONE...TONIGHT THE RECENT WET WEATHER HAS CAUSED MANY RIVERS AND STREAMS TO RUN HIGH IN THE NORTHERN IDAHO PANHANDLE. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY A FLOOD WATCH IS IN EFFECT THROUGH TUESDAY...WITH MORE RAIN AND HIGH ELEVATION SNOW EXPECTED. TOTAL PRECIPITATION AMOUNTS BETWEEN A HALF INCH AND AN INCH ARE LIKELY OVER THE IDAHO PANHANDLE. THE HEAVIEST PRECIPITATION WILL FALL MONDAY NIGHT. THERE WILL BE A HEIGHTENED POTENTIAL FOR ROCK SLIDES AND MUD SLIDES MONDAY NIGHT SINCE THE SOIL HAS BECOME SATURATED DURING THE RECENT WET WEATHER. FORTUNATELY...SNOW LEVELS WILL NOT BE ABOVE 4000 FEET FOR VERY LONG. SNOW MELT SHOULD NOT BE A BIG CONTRIBUTOR TO THE RUNOFF IN NORTH IDAHO. LOOK FOR MORE RISES ON CREEKS AND SMALL STREAMS DURING THE EARLY TO MID PART OF THE WEEK...BUT WIDESPREAD RIVER FLOODING IS NOT ANTICIPATED AT THIS TIME. WAZ031-032-034>038-041-043-044-042315- NORTHEAST BLUE MOUNTAINS-LOWER GARFIELD AND ASOTIN COUNTIES- MOSES LAKE AREA-UPPER COLUMBIA BASIN-SPOKANE AREA- NORTHEAST MOUNTAINS-OKANOGAN HIGHLANDS-WENATCHEE AREA- OKANOGAN VALLEY-WATERVILLE PLATEAU- 407 PM PDT SUN APR 3 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL WASHINGTON...EAST CENTRAL WASHINGTON...NORTH CENTRAL WASHINGTON... NORTHEAST WASHINGTON AND SOUTHEAST WASHINGTON. .DAY ONE...TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY MORE RAIN IS EXPECTED MONDAY AND TUESDAY...WITH AMOUNTS BETWEEN A HALF INCH AND AN INCH LIKELY IN THE NORTHERN BLUE MOUNTAINS. OTHERWISE...GUSTY WINDS WILL BE POSSIBLE LATE MONDAY AND TUESDAY ACROSS THE COLUMBIA BASIN IN ADDITION TO THE NORTHERN BLUE MOUNTAINS. WAZ042-042315- EAST SLOPES NORTHERN CASCADES- 407 PM PDT SUN APR 3 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL WASHINGTON. .DAY ONE...TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY A FLOOD WATCH IS IN EFFECT THROUGH TUESDAY...WITH MORE RAIN AND HIGH ELEVATION SNOW EXPECTED. PRECIPITATION AMOUNTS IN EXCESS OF ONE INCH ARE LIKELY NEAR THE CASCADE CREST. THERE WILL BE A HEIGHTENED POTENTIAL FOR ROCK SLIDES AND MUD SLIDES MONDAY THROUGH TUESDAY SINCE THE SOIL HAS BECOME SATURATED DURING THE RECENT WET WEATHER.
The national radar mosaic for the moment the first event began.
1 heavy snow. Local standard time, as filed.
SNOTELS in the area received approximately a half to one foot of total snowfall between Monday morning and early Tuesday morning.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2011Every state in 2011This day in weather historyWarnings in Idaho, April 2011
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 294435.