Winter Weather in Washington, January 14 to 15, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
350 PM PST MON JAN 14 2008

.SYNOPSIS...
A STRONG COLD FRONT WILL BRING MINOR ACCUMULATIONS OF SNOW TO MUCH
OF THE REGION THIS EVENING...AND THEN A BOUT OF VERY WINDY
CONDITIONS TO MOST OF THE REGION LATER TONIGHT. FOR THE REMAINDER
OF THE WORK WEEK A MAINLY DRY BUT COOLING TREND WILL TAKE HOLD.

&&

.DISCUSSION...
TONIGHT...ALL EYES ON THE STRONG AND FAST MOVING UPPER TROUGH AND
ASSOCIATED SURFACE COLD FRONT VISIBLE ON SATELLITE MOVING THROUGH
WESTERN WASHINGTON THIS AFTERNOON. GFS WILL BE MODEL OF CHOICE
WITH THIS SYSTEM GIVEN THE GOOD INITIALIZATION AND TIMING
COMPARISON VERSUS SATELLITE IMAGERY...AS WELL AS VERY GOOD RUN TO
RUN CONTINUITY OVER THE PAST TWO DAYS. TWO PROBLEMS ASSOCIATED
WITH THIS SYSTEM. FIRST IS PRECIPITATION POTENTIAL AND P-TYPE AT
AND IMMEDIATELY BEHIND THE FRONT. THIS IS A FAST MOVER WHICH WILL
PROBABLY PASS THROUGH WENATCHEE AROUND 5 PM OR SO AND THROUGH
SPOKANE AND PULLMAN BY 7 TO 9 PM THIS EVENING. DESPITE STRONG
FOCUS AND GOOD DYNAMIC SUPPORT ALOFT ALONG THE FRONT...AS WELL AS
AN ADEQUATE MOISTURE FEED...NO LOCATION WILL REMAIN UNDER
SUSTAINED PRECIPITATION LONG ENOUGH TO ALLOW SIGNIFICANT
ACCUMULATIONS OF WHAT WILL LIKELY BE SNOW OVER MOST
LOCATIONS...WITH A POSSIBLE MIX OF SNOW AND RAIN SOUTH OF
INTERSTATE 90. THERE ALSO IS A CHANCE FOR BRIEF FREEZING RAIN IN
THE DEEP BASIN WEST OF MOSES LAKE AS PRE-FRONT WARM ADVECTION MAY
WORK INTO THE MID LEVELS ABOVE THE COLD AIR TRAPPED AGAINST THE
CASCADES. HIGHEST ACCUMULATIONS EXPECTED IN THE VALLEYS OF THE
NORTHERN PANHANDLE AND NORTHEAST WASHINGTON...BUT EVEN THERE ONLY 1
TO 3 INCHES IN THE VALLEYS IS A PLAUSIBLE FOR CAST. THEN THE WIND
WILL START.

THIS IS AN UNUSUALLY STRONG AND FAST MOVING COLD FRONT FOR DEEP
WINTER...MORE COMMON IN A TRANSITION SEASON WHERE THERE IS MORE
OPPORTUNITY FOR CONTRASTING AIR MASS COLLISIONS. NON-THE-
LESS...THE CELLULAR NATURE OF THE CLOUDS BEHIND THE FRONT SUGGESTS
THE POST FRONT AIR MASS IS VERY DRY AND COLD...WITH THE DARKENING
ON WATER VAPOR INDICATIVE OF A LOW TROPOPAUSE IN THE TROUGH
CUSP...ALSO INDICATIVE OF A COLD ARCTIC MARITIME AIR MASS. ALL OF
THIS COLD DENSE AIR WILL SPILL OVER THE CASCADES AND RIDE GRAVITY
DOWN INTO THE COLUMBIA BASIN. THE GREATEST THREAT FOR STRONG WINDS
WILL EXIST OVER THE ZONES IMMEDIATELY IN THE LEE OF THE CASCADES
OVERNIGHT...AND WILL LIKELY SCOUR ANY REMAINING STRATUS AND
TRAPPED STAGNANT AIR. OVER THE EASTERN BASIN THE WINDS WILL BE
MORE GRADIENT INDUCED WITH THE UPPER TOUGH PROMOTING STRONG
CYCLOGENESIS IN THE LEE OF THE ROCKIES OVER THE CANADIAN PRAIRIE
PROVINCES. THUS MOST OF THE COLUMBIA BASIN IS NOW COVERED BY A
WIND ADVISORY FOR TONIGHT...AND THERE IS A POSSIBILITY OF SOME
LOCAL HIGH WIND CRITERIA NEAR THE CASCADES. LOW TEMPERATURES
TONIGHT ARE LARGELY LOW CONFIDENCE FORECASTS WITH A WELL MIXED AIR
MASS ALLOWING MOMENTARY SIGNIFICANT SPIKES AND DIPS IN THE POST
FRONT TURBULENT FLOW. /FUGAZZI

TUESDAY THROUGH THURSDAY...THE OVERALL PATTERN THROUGH THIS
PORTION OF THE SHORT TERM FORECAST WILL BE STRONG RIDGING IN THE
EASTERN PACIFIC IN THE VICINITY OF 135W AND A LARGE AREA OF LOW
PRESSURE IN THE NORTHERN PLAINS. THIS PUTS THE INLAND NORTHWEST IN
A MAINLY DRY AND COOL NORTHERLY FLOW. THE MODELS ARE IN GOOD TO
VERY GOOD AGREEMENT WITH THE PATTERN. FOR TUESDAY THE EXITING COLD
FRONT WILL KEEP UP SLOPING PRECIPITATION ACROSS THE IDAHO
PANHANDLE THROUGH THE DAY WITH LIGHT ADDITIONAL SNOW ACCUMULATIONS
NEAR THE IDAHO/MONTANA BORDER. PRESSURE GRADIENTS ARE EXPECTED TO
SLOWLY EASE THROUGH THE DAY. AS SUCH EXPECT STRONG...GUSTY WINDS
LINGERING INTO THE MORNING HOURS BEFORE SUBSIDING THROUGH THE
REMAINDER OF THE DAY. THE SNOWING AND BLOWING SNOW ADVISORY IS
GOOD THROUGH 15Z AND THIS WILL HAVE TO BE MONITORED FOR
TIMING...BUT APPEARS TO BE ON TRACK. WITH THE COLD AIR ADVECTION
AND GUSTY WINDS EXPECT THE LOWER ATMOSPHERE TO MIX OUT COMPLETELY.
IN AREAS THAT MIXED OUT TODAY TEMPERATURES WILL BE ON THE ORDER OF
8-12 DEGREES COOLER ON TUESDAY...HOWEVER IN THE AREAS THAT WERE
TRAPPED IN THE FOG/STRATUS TEMPERATURES WILL ACTUALLY WARM UP A
DEGREES OR TWO.

TUESDAY NIGHT THROUGH WEDNESDAY HIGH PRESSURE STRENGTHENS OFF THE
COAST AND THE INLAND NORTHWEST CATCHES A BREAK FROM ANY TRANSIENT
SHORT WAVE DISTURBANCES...KEEPING THE FORECAST DRY AND COOL. SOME
LOW END POPS WERE HELD ON TO FOR UP SLOPING LIGHT PRECIPITATION
FOR SHOSHONE COUNTY...BUT CONFIDENCE THAT ANY MEASURABLE PRECIPITATION
WILL BE OBSERVED IS VERY LOW. THE SURFACE INVERSION WILL
STRENGTHEN ACROSS THE REGION BUT THE LOWER ATMOSPHERE APPEARS TO
DRY TO SUPPORT AND WIDESPREAD STRATUS/FOG DEVELOPMENT.

WEDNESDAY NIGHT INTO THURSDAY...THE MODELS ARE FAIRLY CONSISTENT
SHOWING WEAK WARM AIR ADVECTION ACROSS THE FORECAST AREA THROUGH
THIS TIME PERIOD. THIS WILL HELP TO STRENGTHEN THE SURFACE
INVERSION. THE COMBINATION OF THE STRENGTHENING INVERSION...LIGHT
WINDS AND LINGERING SNOW PACK WILL RESULT IN FOG/STRATUS BEGINNING
TO EXPAND ACROSS THE THE COLUMBIA BASIN...SPOKANE AREA AND THE
NORTHERN VALLEYS. WHILE MODEL GUIDANCE DOES SHOW A WARMING
TREND THIS WILL BE MAINLY REALIZED AT THE HIGHER ELEVATIONS ABOVE
THE SURFACE INVERSION. BELOW THE INVERSION TEMPERATURES WILL SEE
LITTLE DIURNAL CHANGE. IN ADDITION A WEAK MID LEVEL SHORT WAVE
DISTURBANCE WILL BRUSH THE NORTHEAST ZONES WEDNESDAY NIGHT INTO
EARLY THURSDAY MORNING. UP SLOPING FLOW INTO THE EASTERN MOUNTAIN
ZONES WILL COMBINE WITH THE WEAK LIFT PROVIDED BY THE SHORT WAVE
TO SUPPORT LIGHT POPS ACROSS THE PANHANDLE MOUNTAINS. OTHERWISE
THE FORECAST REMAINS DRY. TOBIN

THURSDAY NIGHT THROUGH MONDAY...STRONG UPPER RIDGE OFF THE COAST
NEAR 135W WILL RESULT IN A DRY NORTHWEST FLOW THROUGH FRIDAY
NIGHT. THEN ON SATURDAY THE UPPER RIDGE RETROGRADES TO NEAR 140W
AND AMPLIFIES IN RESPONSE TO A DIGGING TROUGH NEAR 160W. THIS WILL
RESULT IN A NORTHERLY FLOW FROM SATURDAY THROUGH MONDAY. A SHORT
WAVE DROPPING DOWN IN THE NORTHERLY FLOW WILL BRING A CHANCE OF
SNOW TO THE AREA OVER THE WEEKEND. A COLDER AND DRIER AIR MASS FROM
CANADA WILL MOVE SOUTH BEHIND THIS SHORT WAVE LATE IN THE WEEKEND
AND MONDAY. BUT HOW COLD STILL REMAINS VERY UNCERTAIN...WITH 850MB
TEMPS OVER EASTERN WA ON MONDAY RANGING FROM -6C OFF 12Z
ECMWF...TO -20C OFF A FEW GFS ENSEMBLE MEMBERS. 12Z CANADIAN
SOLUTION LOOKS QUITE COLD SIMILAR TO GFS ENSEMBLE MEAN...WITH UKMET
SHOWING A SHARPER TROUGH AS WELL COMPARED TO ECMWF. BUT GIVEN
GREAT PERFORMANCE OF ECMWF IN EXTENDED CAN NOT DISCOUNT ITS IDEA
EITHER. FOR NOW...WENT WITH A MIDDLE GROUND APPROACH WITH
TEMPERATURES ON MONDAY.  JW

&&

.AVIATION...
A STRONG COLD FRONT PASSAGE WILL OCCUR THIS EVENING.  TIMING OF
FRONT LOOKS TO TRACK THROUGH KEAT NEAR 01Z...KMWH NEAR
02Z...KGEG/KSFF NEAR 04Z...AND KPUW/KLWS NEAR 05Z.  NEAR AND JUST
BEFORE FRONT PASSAGE LOW LEVEL WIND SHEAR WILL BE AN ISSUE WITH
STRONG SW WINDS JUST ABOVE THE SFC.  ALSO PRIOR TO FRONT PASSAGE...A
LOW LEVEL TEMPERATURE INVERSION WILL PERSIST ACROSS THE VALLEYS OF
NORTHERN WASHINGTON...THE COLUMBIA BASIN...AND VALLEYS NEAR THE
CASCADES.  THUS AREAS OF IFR STRATUS OR FOG WILL PERSIST BUT WITH
IMPROVEMENT LIKELY AS FRONT TRACKS THROUGH THE AREA.  REPORTS FROM
LEAVENWORTH AND KELN SUGGEST -PL AND -FZRA MIXED IN AND THIS WILL BE
POSSIBLE THIS EVENING AT KEAT/KMWH.  ELSEWHERE A BRIEF PERIOD OF SN
OR LOCALLY +SN IS POSSIBLE WITH FRONT PASSAGE AT KGEG/KSFF/KCOE/KPUW
WITH IFR VSBYS.  BEHIND THE FRONT PASSAGE...GUSTY WEST WINDS WILL
OCCUR WITH GUSTS TO 40-45KTS.  THIS WILL BE SUFFICIENT TO SCOUR OUT
THE LOW LEVEL INVERSION WITH CLEARING SKIES AND VFR CONDITIONS
OVERNIGHT THROUGH TUESDAY AFTERNOON.  JW

&&

.PRELIMINARY POINT TEMPS/POPS...
SPOKANE        25  29  13  26  14  29 /  60  10   0   0   0   0
COEUR DALENE  24  28  15  27  14  30 /  70  10  10  10  10  10
PULLMAN        28  29  14  28  19  32 /  60  20   0  10  10  10
LEWISTON       32  35  23  34  24  38 /  40  20   0  10  10  10
COLVILLE       20  27  11  25   9  28 /  80   0   0  20  20   0
SANDPOINT      24  26  11  25  11  28 /  90  10  10  20  20  10
KELLOGG        23  23  15  25  13  28 /  90  40  10  20  20  10
MOSES LAKE     26  32  13  29  13  32 /  40   0   0   0   0   0
WENATCHEE      27  31  17  28  14  33 /  50   0   0   0   0   0
OMAK           23  28   8  25   8  28 /  60   0   0   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...SNOW AND BLOWING SNOW ADVISORY FROM 7 PM THIS EVENING TO 7 AM
     PST TUESDAY FOR CENTRAL PANHANDLE MOUNTAINS...NORTHERN
     PANHANDLE.

     WIND ADVISORY FROM 7 PM THIS EVENING TO 4 AM PST TUESDAY FOR
     COEUR DALENE AREA...IDAHO PALOUSE...LEWIS AND SOUTHERN NEZ
     PERCE COUNTIES.

WA...SNOW AND BLOWING SNOW ADVISORY FROM 7 PM THIS EVENING TO 7 AM
     PST TUESDAY FOR NORTHEAST MOUNTAINS.

     WIND ADVISORY FROM 7 PM THIS EVENING TO 4 AM PST TUESDAY FOR
     LOWER GARFIELD AND ASOTIN COUNTIES...MOSES LAKE AREA...
     SPOKANE AREA...UPPER COLUMBIA BASIN...WASHINGTON PALOUSE...
     WATERVILLE PLATEAU...WENATCHEE AREA.

&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE SPOKANE WA
550 PM PST MON JAN 14 2008

IDZ001>004-026-027-WAZ031>038-041>044-160200-
NORTHERN PANHANDLE-COEUR DALENE 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-
550 PM PST MON JAN 14 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...TONIGHT

FOLLOWING A QUICK SHOT OF WINTERY PRECIPITATION EARLY THIS EVENING
ASSOCIATED WITH A VIGOROUS COLD FRONT...EXPECT WINDS TO INCREASE
DRAMATICALLY OVERNIGHT ONCE THIS FRONT PASSES INTO MONTANA.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A VIGOROUS COLD FRONT WILL BRING WINDY CONDITIONS TO THE INLAND
NORTHWEST TUESDAY MORNING FOLLOWED BY CONSIDERABLY COLDER
TEMPERATURES THROUGH FRIDAY.