Blizzard in Colorado, March 26 to 27, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GOODLAND KS
520 AM MDT THU MAR 26 2009

.DISCUSSION...03Z WATER VAPOR IMAGERY INDICATED LONG WAVE TROUGH
ACROSS THE CENTRAL US. STRONG SHORT WAVE TROUGH...WHICH WILL BE
PRIMARY WEATHER MAKER...WAS DIGGING INTO IDAHO. BOTH DDC AND DEN
INDICATE MID LEVEL LAPSE RATES HAVE INCREASED ACROSS THE
AREA...LBF INDICATES SIMILAR TREND ALTHOUGH SOUNDING MAY HAVE BEEN
CONTAMINATED BY WEAK CONVECTION NEAR THE AREA. 290 K 00Z
ISENTROPIC ANALYSIS INDICATES MODEST MOISTURE RETURN ALREADY
UNDERWAY...WITH NOSE OF 4 G/KG MIXING RATIOS NOSING UP INTO DDC.

MAIN FORECAST CONCERN WILL BE WINTER STORM/BLIZZARD CONDITIONS
EXPECTED TO DEVELOP THURSDAY AFTERNOON AND FRIDAY.

TODAY-FRIDAY NIGHT...MODELS HAVE TRENDED TOWARDS A SLOWER SOLUTION
WHICH WILL RESULT IN LONGER PERIOD OF FORCED ASCENT AND A BETTER
CHANCE FOR MORE SIG SNOWFALL ACROSS THE AREA. STILL SOME TIMING
DIFFERENCES BUT MUCH SMALLER THAN YESTERDAY SO A COMPROMISE IS IN
ORDER. AS PREVIOUS FORECASTER MENTIONED...MAIN DIFFERENCE BETWEEN
TWO SHORT TERM MODELS IS LOCATION OF STRONG FRONTAL ZONE AROUND H65
WITH GFS REMAINING TO THE SOUTH OF THE NAM.  A NOTICEABLE CHANGE FOR
BOTH THE GFS AND NAM IS THE MUCH LOWER STATIC STABILITY ACROSS THE
AREA. EPV* VALUES BTWN H7 AND H65 AS WELL AS H65 TO H6 SUGGEST
ATMOSPHERE WILL BE UNSTABLE TO WEAKLY STABLE...WHICH WOULD SUPPORT
STRONG BANDING AND POTENTIAL FOR HEAVY SNOW. STILL LARGE QUESTIONS
SURROUNDING THE TOTAL AMOUNT OF SNOW AS NAM HOLDS STRONG FORCING
OVER THE AREA MUCH LONGER AND FARTHER NORTH THAN OTHER MODELS...WITH
ECMWF CONTINUING TO KEEP HIGHER AMOUNTS CONFINED TO THE SOUTHWEST
SECTION OF THE CWA. NOT A CLEAR FAVORITE MODEL IN THIS
SCENARIO...AND ONGOING PRECIPITATION TO THE NORTH AND EAST OF THE
AREA WOULD SUGGEST THAT STABILITY MAY BE LOW ENOUGH THAT FORCING
MUCH WEAKER THAN WHAT IS EXPECTED THIS AFTERNOON IS SUFFICIENT TO
PRODUCE PRECIPITATION. GENERALLY TOOK SREF MEAN IDEA OF HIGHEST
AMOUNTS ACROSS THE SOUTHWEST TAPERING OFF TO THE NORTHEAST WITH A
RANGE OF ABOUT 2 INCHES IN THE NORTHEAST...TO NEARING A FOOT IN THE
SOUTHWEST. BIG QUESTION ABOUT AVAILABLE FORCING BY FRIDAY MORNING
WITH NAM HOLDING ON TO SOME ASCENT WHILE OTHER MODELS ALREADY IN A
MORE SUBSIDENT PATTER. WILL HOLD ON TO SNOW AND HIGHLIGHTS THROUGH A
PORTION OF THE DAY....BUT CONFIDENCE IS NOT AS HIGH AS THURSDAY
NIGHT PERIOD.

MODELS MAY DIFFER ON DETAILS ABOUT SNOW...BUT SEEM TO ME IN MUCH
BETTER AGREEMENT WITH RESPECT TO WIND STRENGTH OVERNIGHT TONIGHT. BUFKIT
SOUNDINGS INDICATE POTENTIAL WIND ADVISORY LEVEL WINDS THOUGH THE
NIGHT AS COLD AIR ADVECTION WILL KEEP LOWER BOUNDARY LEVEL WELL
MIXED. BUFR SOUNDINGS FROM NAM AND GFS SUGGEST NEAR ADVISORY LEVEL
WINDS OVERNIGHT...WITH GRIDDED MOS VALUES ALSO SUGGESTING WINDS
SUSTAINED NEAR 30 MPH. SO WHILE CONFIDENCE IN SNOW AMOUNTS NOT AS
HIGH AS I WOULD LIKE FOR WARNING CRITERIA...THINK STRONG WINDS WILL
MAKE BLIZZARD CONDITIONS LIKELY THOUGH THE NIGHT.

SATURDAY NIGHT-SUNDAY...H5 TROUGH WILL SLOWLY SHIFT TO THE EAST
OVERNIGHT LEADING TO SUBSIDENCE AND CLEARING ACROSS THE AREA. WITH
WINDS RELAXING AND SKIES CLEARING...MAIN CONCERN WILL TEMPERATURES
AND THE IMPACT OF SNOW COVER ON FORECAST. IF SNOW COVER WAS NOT AN
ISSUE MID 40S TO LOW 50S WOULD BE PREVALENT ACROSS THE AREA...BUT
WITH EXPECTED SNOW COVER THINK TEMPS WILL STRUGGLE TO REACH THE 40S
IN MANY LOCATIONS.

JRM
&&

.AVIATION...FOR THE 12Z TAFS AT KGLD AND KMCK...STRATUS IS MOVING
SOUTH ACROSS NEBRASKA...AND IFR CEILINGS WILL REACH KMCK BY 14Z.
MAY HAVE SOME BREAKS AFTER 17Z...BUT CONDITIONS WILL LOWER FURTHER
AFTER 21Z AS SNOW DEVELOPS. LATEST RUC MODEL HAS SNOW DEVELOPING
AT KGLD AROUND 21Z...SO WILL FORECAST IFR CONDITIONS THERE. BOTH
SITES WILL DROP TO LIFR CONDITIONS AFTER 00Z.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 7 AM CDT
     FRIDAY FOR KSZ002.

     WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 1 PM CDT
     FRIDAY FOR KSZ003-004.

     BLIZZARD WARNING FROM 1 PM THIS AFTERNOON TO 7 AM CDT FRIDAY FOR
     KSZ001.

     BLIZZARD WARNING FROM 3 PM MDT /4 PM CDT/ THIS AFTERNOON TO 6 PM
     MDT /7 PM CDT/ FRIDAY FOR KSZ014>016-027>029-041-042.

     BLIZZARD WARNING FROM NOON TODAY TO NOON MDT FRIDAY FOR KSZ013.

NE...WINTER WEATHER ADVISORY FROM NOON MDT /1 PM CDT/ TODAY TO 6 AM
     MDT /7 AM CDT/ FRIDAY FOR NEZ079-080.

     WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 7 AM CDT
     FRIDAY FOR NEZ081.

CO...BLIZZARD WARNING FROM NOON TODAY TO 6 AM MDT FRIDAY FOR COZ090.

     BLIZZARD WARNING FROM NOON TODAY TO NOON MDT FRIDAY FOR COZ091-
     092.

&&

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE GOODLAND KS
1055 AM MDT THU MAR 26 2009

COZ090>092-KSZ001>004-013>016-027>029-041-042-NEZ079>081-271030-
YUMA-KIT CARSON-CHEYENNE CO-CHEYENNE KS-RAWLINS-DECATUR-NORTON-
SHERMAN-THOMAS-SHERIDAN-GRAHAM-WALLACE-LOGAN-GOVE-GREELEY-WICHITA-
DUNDY-HITCHCOCK-RED WILLOW-
1055 AM MDT THU MAR 26 2009 /1155 AM CDT THU MAR 26 2009/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EXTREME SOUTHWEST
NEBRASKA...NORTHWEST KANSAS AND EAST CENTRAL COLORADO.

.DAY ONE...TODAY AND TONIGHT

A POWERFUL WINTER STORM SYSTEM WILL MOVE OVER THE ROCKIES AND INTO
THE CENTRAL PLAINS TODAY AND TONIGHT. LIGHT TO MODERATE SNOW IN
EASTERN COLORADO WILL SPREAD INTO NORTHWEST KANSAS AND SOUTHWEST
NEBRASKA LATE THIS AFTERNOON AND EARLY EVENING. SNOW WILL CONTINUE
THROUGH THE NIGHT...WITH PERIODS OF HEAVY SNOW POSSIBLE MAINLY SOUTH
OF INTERSTATE 70. SNOWFALL AMOUNTS WILL VARY GREATLY ACROSS THE
AREA...RANGING FROM AROUND 2 INCHES EXPECTED AT MCCOOK AND UP TO 16
INCHES AT TRIBUNE AND LEOTI.

IN ADDITION TO THE SNOW...STRONG NORTHERLY WINDS OF 25 TO 35 MPH
WITH GUSTS TO AROUND 45 MPH WILL DEVELOP LATE THIS AFTERNOON AND
LAST THROUGH THE NIGHT. THIS WILL CREATE BLIZZARD CONDITIONS ALONG
AND SOUTH OF A YUMA TO HILL CITY LINE MAKING TRAVEL VERY HAZARDOUS
IF NOT IMPOSSIBLE TONIGHT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

STRONG WINDS AND SNOW WILL BEGIN TO DIMINISH ACROSS THE AREA
DURING THE MORNING HOURS WITH IMPROVING CONDITIONS EXPECTED BY
FRIDAY AFTERNOON...ALTHOUGH AREAS OF BLOWING SNOW WILL PERSIST
THROUGH SUNSET.

.SPOTTER INFORMATION STATEMENT...

ANY REPORTS OF SNOWFALL...POOR VISIBILITY IN BLOWING SNOW AND
STRONG WIND GUSTS WILL BE APPRECIATED.

JRM