Heavy Snow in Idaho, April 29, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
316 AM PDT TUE APR 29 2008

.SYNOPSIS...A COLD FRONT WILL BRING SCATTERED SHOWERS TO THE
INLAND NORTHWEST TODAY AND TONIGHT...THE FIRST IN A SERIES OF
DISTURBANCES THAT WILL BRING COOLER...BREEZY AND SHOWERY WEATHER
TO THE REGION THROUGH MID WEEK. A SLOW WARMING AND DRYING PERIOD
IS FORECAST FOR THE END OF THE WEEK UNDER WESTERLY FLOW ALOFT.

&&

.DISCUSSION...
TODAY AND TONIGHT...THE FOCUS REMAINS ON THE VORT MAX NOW INSIDE
130W CLOSING IN ON THE OREGON COAST WHICH WILL TRACK E THRU OREGON
AND FAR SERN WA BY WED MORNING. FOLLOWING THE EXIT N INTO BC OF
THE SHORT-WAVE TROF THAT MOVED THRU THE REGION MON...A NEARLY
STALLED LOW-MID LEVEL FRONT HAS GENERATED A PERSISTENT BAND OF
SHOWERS FROM SPOKANE N INTO SERN BC. GUIDANCE WAS DOING POOR ON
ITS INITIALIZATION OF THIS PCPN...MOVING IT E WAY TOO FAST. WE
FULLY EXPECT THIS BAND TO BEGIN TO INCREASE ITS EWD MOVEMENT AS
THE INBOUND OREGON VORT NEARS. AS IT DOES HOWEVER...LG-SCALE
FORCING FOR ASCENT WILL STEADILY INCREASE AND LIKELY SHIFT THE
BEST CHANCE OF PCPN TO SERN WA AND THE CNTRL ID PANHANDLE ALONG
THE SRN TAIL OF THE AFOREMENTIONED FRONT. ITS NOT UNTIL LATE TODAY
AND TONIGHT THAT THE VORT MAX MOVES SE OF MY CWA...LEAVING MUCH OF
MY CWA UNDER AN INCREASINGLY UNSTABLE AND COOLER AIR-MASS. ITS
ALSO THE SAME TIME THAT WE EXPECT THE LOW-LEVEL FLOW TO VEER TO
THE W AND NW...FAVORING N ID...THE NRN BLUE MTNS AND THE CAMAS
PRAIRIE AS THE MOST LIKELY AREA FOR HEAVIER PCPN. SNOW LEVELS NOW
WELL ABOVE 5-6K FT MSL WILL LOWER TO AT LEAST 3K FT MSL
TONIGHT...AND PUT THE CAMAS PRAIRIE UNDER THE THREAT OF SNOW. FOR
NOW WEVE KEEP BELOW ADVSY ACCUMULATIONS ABOVE AROUND 3000 FT INTO
WED MORNING FOR ID ZONE 27...AND LIMITED ID ZONE 4 MTN
ACCUMULATIONS TO 4 INCHES AS A ZONE AVERAGE. THE SAME CAA THAT
WILL LOWER SNOW LEVELS WILL ALSO HELP TO INCREASE SFC WINDS WELL
INTO THE BREEZY CATEGORY TODAY AND TONIGHT. THERMODYNAMIC
PROFILES STILL SHOW ONLY A MARGINAL THREAT OF THUNDER BY THIS
AFTERNOON. BZ

WEDNESDAY THROUGH FRIDAY...MODEL CHANGES FOR THE PERIOD HAVE
AGAIN BEEN FAIRLY MINOR...SO THE CHANGES TO THIS PORTION OF THE
FORECAST HAVE LIKEWISE BEEN RELATIVELY INSIGNIFICANT. THE BIGGEST
CHANGES HAVE REALLY BEEN TO TRY TO REFLECT SOME SORT OF A DIURNAL
POP CHANGE FOR CONVECTIVE PRECIPITATION WEDNESDAY THROUGH
WEDNESDAY NIGHT WITH A PEAK IN CONVECTIVE SHOWER ACTIVITY AND
COVERAGE WEDNESDAY AFTERNOON. LIKEWISE...THE CHANCES OF
THUNDERSTORMS HAVE REALLY ONLY BEEN MAINTAINED DURING THE PEAK
HEATING HOURS OF THE DAY ON WEDNESDAY.

THE BIG STORY DURING THIS PORTION OF THE FORECAST WILL CONTINUE TO
BE UNSEASONABLY COOL CONDITIONS DOMINATING THE NORTHWEST THROUGH
THURSDAY. MODEL 850 MB TEMPERATURES LINGER IN THE 0C TO +4C RANGE
FOR BOTH WEDNESDAY AND THURSDAY BEFORE SLOWLY REBOUNDING FRIDAY AS
THE NEXT SHORT WAVE APPROACHES THE AREA WITH WARM ADVECTION
ISENTROPIC PRECIPITATION BEGINNING TO BREAK OUT FROM WEST TO EAST.
WITH THE WARM ADVECTION OCCURRING AHEAD OF THE SHORT WAVE
UNDERCUTTING AN UPPER LEVEL RIDGE THAT HAD TRIED TO BUILD OVER THE
CWA BY THAT JUNCTURE...PRECIPITATION WILL LIKELY NOT BE VERY
SIGNIFICANT GIVEN THE WEAK NATURE OF THE DISTURBANCE DUE TO THE
FACT THAT IT WILL HAVE TO BREAK DOWN A RIDGE TO GET HERE...HOWEVER
WEAK FLOW AT 850 MB WILL LIKELY NOT SUPPORT MUCH OF A RAIN SHADOW
EAST OF THE CASCADES...SO CHANCES OF RAIN WILL EVEN BE IN THE
FORECAST FOR WENATCHEE AND OMAK.

LOOKING FORWARD TO NEXT WEEKEND...THE MODELS HAVE GENERALLY TRENDED
TOWARD BRINGING RIDGING OF SOME VARIETY TOWARD THE PACIFIC
NORTHWEST BY THE END OF THE WEEKEND...HOWEVER BEFORE THAT
POINT...NORTHWESTERLY WAVES IN A BROAD NORTHWEST FLOW THAT
BECOMES BRIEFLY ESTABLISHED ARE LIKELY TO KEEP THINGS COOL AND
UNSETTLED. /FRIES

&&

.AVIATION...
AN UPPER LEVEL TROUGH WILL MOVE OVER THE REGION DURING THE NEXT 24
HOURS. THIS MORNING...MAINLY ISOLATED SHOWERS ARE EXPECTED OVER THE
COLUMBIA BASIN WITH SCATTERED SHOWERS OVER THE IDAHO PANHANDLE AND
CASCADES. CEILINGS AND VSBY WILL REMAIN VFR. SHOWERS WILL BECOME
MORE WIDESPREAD LATER TODAY...ESPECIALLY S OF SPOKANE INCLUDING
THE KPUW AND KLWS TAFS. WE WILL ADD TEMPO MVFR CEILINGS FOR THESE
AREAS LATE TODAY AND OVERNIGHT. SUSTAINED SFC WINDS 14-20KT WILL
BECOME MORE LIKELY BY MIDDAY FOR ALL SITES...ON THE BACK-SIDE OF
THE EXITING COLDFNT. ISOLD THUNDER THREAT WILL REMAIN IN THE FCST
FOR TODAY ALSO. BZ

&&

.PRELIMINARY POINT TEMPS/POPS...
SPOKANE        52  33  48  31  51  33 /  60  50  50  30  20  10
COEUR DALENE  51  33  46  31  51  32 /  60  50  50  30  20  10
PULLMAN        49  32  48  32  52  35 /  60  60  50  30  10  10
LEWISTON       55  37  54  36  58  37 /  70  50  30  30  10  10
COLVILLE       52  30  51  30  56  31 /  50  40  50  30  20  10
SANDPOINT      49  31  47  31  49  31 /  60  60  40  30  30  10
KELLOGG        46  31  43  30  47  31 /  70  70  60  40  20  10
MOSES LAKE     56  34  56  31  61  35 /  20  10  20  10  10  10
WENATCHEE      56  37  55  37  60  38 /  20  10  20  10  10  10
OMAK           56  31  56  30  61  32 /  20  20  20  10  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE SPOKANE WA
612 AM PDT TUE APR 29 2008

IDZ001>003-026-WAZ031>038-041>044-301315-
NORTHERN PANHANDLE-COEUR DALENE AREA-IDAHO PALOUSE-LEWISTON AREA-
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-
612 AM PDT TUE APR 29 2008

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

EXPECT BELOW NORMAL TEMPERATURES AND OCCASIONAL SHOWERY PRECIPITATION.
FREEZING LEVELS WILL BE LOW ENOUGH TO KEEP AN ONGOING THREAT OF
SNOW IN THE FORECAST FOR ALL LOWER ELEVATIONS...ESPECIALLY DURING THE
OVERNIGHT HOURS.

IDZ004-027-301315-
CENTRAL PANHANDLE MOUNTAINS-LEWIS AND SOUTHERN NEZ PERCE COUNTIES-
612 AM PDT TUE APR 29 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH IDAHO AND
NORTH CENTRAL IDAHO.

.DAY ONE...TODAY AND TONIGHT

THE NEXT R0UND OF COLD AND SHOWERY WEATHER IS ALREADY MOVING INTO
THE REGION...AND WILL LINGER THE REST OF THE WEEK. EXPECT SNOW
LEVELS TO FALL AS LOW AS 2500 FEET BY LATE TONIGHT...WITH A
CHANCE FOR MODERATE SNOW ACCUMULATIONS ON THE CAMAS PRAIRIE OF
NORTH IDAHO SOUTHEAST OF LEWISTON. ALSO...SIGNIFICANT SNOW
ACCUMULATIONS WILL BE POSSIBLE FOR THE CENTRAL IDAHO PANHANDLE
MOUNTAINS INCLUDING ALL PASSES.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

EXPECT BELOW NORMAL TEMPERATURES AND OCCASIONAL SHOWERY PRECIPITATION.
FREEZING LEVELS WILL BE LOW ENOUGH TO KEEP AN ONGOING THREAT OF
SNOW IN THE FCST FOR ALL LOWER ELEVATIONS...ESPECIALLY DURING THE
OVERNIGHT HOURS.