Winter Storm in Colorado, April 23, 2010

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PUEBLO CO
901 PM MDT THU APR 22 2010

.UPDATE...
UPDATED TO EXPIRE TORNADO WATCH.

&&

.SHORT TERM...
UPDATED TO EXPIRE TORNADO WATCH.

.LONG TERM...
NO UPDATES AT THIS TIME.

&&

.AVIATION...
NO UPDATES AT THIS TIME.

&&

.PREV DISCUSSION... /ISSUED 314 PM MDT THU APR 22 2010/

SHORT TERM...
(TONIGHT AND FRIDAY)

CURRENTLY...SEVERE WEATHER EVENT UNDERWAY ON THE PLAINS WITH TORNADO
PRODUCING SUPERCELLS REPORTED. SURFACE LOW LOCATED NEAR KPUB AT
2130Z WITH WARM FRONT LIFTING NORTH ALONG THE ARKANSAS RIVER
ALLOWING BEST INSTABILITY TO POOL ALONG AND NORTH OF THE BOUNDARY.
0-6KM SHEARS MAXIMIZED NORTH OF THE WARM FRONT...AS EASTERLY SURFACE
WINDS GUST TO 30 KNOTS...BOOSTING SHEAR ABOVE 50 KNOTS. DRIER AIR
HAS PUSHED EAST AND COVERS MUCH OF THE EASTERN PLAINS SOUTH OF THE
ARKANSAS RIVER...WITH DRYLINE PUSHING NEARLY TO THE KS BORDER AT
2030Z. NOT SEEING MUCH CONVECTION OVER THE MOUNTAINS
CURRENTLY...THOUGH PRECIP IS BEGINNING TO DEVELOP OVER NEW MEXICO
AHEAD OF THE UPPER JET.

SURFACE LOW REMAINS IN THE VICINITY OF KPUB THROUGH THE NIGHT AS
UPPER LOW EJECTS INTO SERN CO BY FRI MORNING. EXPECT SEVERE THREAT
TO SHIFT MAINLY NORTH AND EAST OF THE AREA DURING THE EVENING...AS
INSTABILITY GETS PUSHED INTO NORTHEAST COLORADO. BEST UPWARD MOTION
SHIFTS WESTWARD TO THE CENTRAL AND EASTERN MOUNTAINS OVERNIGHT WITH
SNOW LEVELS FALLING BELOW 9000 FEET BY MORNING. QPF VALUES FROM NAM
AND GFS BOTH SUGGEST WARNING CRITERIA SNOWFALL POSSIBLE LATE TONIGHT
AND ESPECIALLY FRIDAY OVER THE RAMPART/SAWATCH/MOSQUITO RANGES AND
PIKES PEAK...SO WILL HOIST A WINTER STORM WARNING FOR HIGHER
ELEVATION ZONES. WILL SEE SOME SNOW AS LOW AS 7000 FEET OVER THE
PALMER DIVIDE...THOUGH NOT SURE IF ACCUMULATIONS WILL BE ENOUGH FOR
HIGHLIGHTS. OTHER AREA TO WATCH IS OVER THE WET MOUNTAINS...AS NAM
HITS THE EAST SLOPES HARD EARLY FRI MORNING. IN GENERAL EXPECT COOL
UNSETTLED WEATHER THROUGH THE DAY FRIDAY...WITH WIDESPREAD SHOWERS
OVER LOWER ELEVATIONS AND HIGHER ELEVATION SNOWS.

LONG TERM...
(FRIDAY NIGHT THROUGH THURSDAY)

A MIX OF WINTER WEATHER AND SPRINGTIME CONVECTION SPELLS A
CONTINUATION OF UNSETTLED CONDITIONS FOR THE FORECAST AREA THROUGH
THE EXTENDED PERIOD.

FRIDAY NIGHT THROUGH SATURDAY...MODELS AGREE ON PLACING THE UPPER
LOW OVER THE SE CORNER OF COLORADO FRI NIGHT...THEN TRACK IT
EASTWARD ACROSS KS THROUGH SAT. THIS WILL KEEP WRAPAROUND NORTHERLY
FLOW IN PLACE FOR THE CWA. SCATTERED TO LIKELY POPS THROUGH FRI
NIGHT LOOKS REASONABLE...THEN AS THE LOW PULLS AWAY ON SAT GRIDS
REFLECT A GRADUAL DECREASING OF PROBABILITY AND COVERAGE...WITH
FINALLY JUST SOME ISOLATED SHOWERS FOR THE CENT MTS SAT NIGHT.
EXPECT EXTENSIVE CLOUD COVER AND COOLER AFTN MAX TEMPS IN THE 50S TO
RIGHT AROUND 60 F.

SUNDAY...NW FLOW ALOFT SETTLES IN BEHIND THE DEPARTING SYSTEM...BUT
THE FORECAST WARMING NOW LOOKS TO BE VERY TEMPORARY. ISOLATED
SHOWERS CONTINUE FOR THE CENT MTS...BUT THE EXTENDED MODELS PERSIST
IN BRINGING AN UPPER DISTURBANCE DOWN ACROSS THE N ROCKIES SUN EVE.
IN FACT...GFS AND ECMWF MODELS ARE NOW IN VERY CLOSE AGREEMENT IN
PLACEMENT OF THIS FEATURE...SO DECIDED TO INTRODUCE ISOLATED POPS
ALONG THE PALMER DVD SUNDAY NIGHT. OTHERWISE...MOST AREAS WILL STAY
DRY WITH MAX TEMPS IN THE 60S PUSHING 70 F.

MONDAY AND TUESDAY...TEMPORARY RIDGING OVER THE 4 CORNERS OUT AHEAD
OF THE NEXT LOW PRES SYSTEM THAT WILL MOVE ONSHORE ACROSS CA TUE
MORNING. HOWEVER...THE UPPER DISTURBANCE FROM SUNDAY WILL RETREAT
ACROSS THE CENTRAL US ON MON...BUT NOT BEFORE COLD SFC HI PRES
PUSHES INTO EASTERN CO. THIS SHOULD KEEP THE EASTERN PLAINS OF CO
CLOUDY AND COOLER WITH AT LEAST AN ISOLATED SHOT OF SOME PCPN.
ADJUSTED TEMP AND POP GRIDS TO INDICATE THIS.

WEDNESDAY AND THURSDAY...THE NEXT UPPER LOW SYSTEM MOVES ONSHORE AND
STAGNATES OVER THE GREAT BASIN REGION...WITH AN INDICATION THAT IT
ELONGATES AND PERHAPS ENCOMPASSES THE WESTERN THIRD OF THE COUNTRY.
NO CHANGES AT THIS TIME...BUT LOGICAL TRENDING WOULD BE FOR AN
INCREASE IN W-SW FLOW ACROSS THE STATE...AS WELL AS POPS ALONG THE
CONTDVD. 27

AVIATION...
LOW LEVELS HAVE DRIED OVER THE MOUNTAINS AND AT KALS AND KPUB...SO
WILL REMOVE TSRA MENTION THROUGH THE EVENING. STILL SOME THREAT OF
STORMS AT KCOS...SO WILL KEEP VCTS THROUGH MID EVENING. AS UPPER
LOW LIFTS NORTH ACROSS THE AREA OVERNIGHT...EXPECT SHOWERS TO
SPREAD BACK SOUTH OVER MOST OF THE AREA BY 12Z FRIDAY. WIDESPREAD
RAIN AND MOUNTAIN SNOW WILL PRODUCE FAIRLY SOLID MVFR CONDITIONS
ACROSS MOST OF SOUTHERN COLORADO ON FRIDAY...WITH AREAS OF IFR
CONDITIONS OVER THE HIGHER TERRAIN DUE TO LOW VISIBILITY IN SNOW
SHOWERS.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 9 AM MDT SATURDAY FOR COZ061-063.

WINTER STORM WARNING UNTIL 9 AM MDT SATURDAY FOR COZ058>060-081-
082.

&&

50/50

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PUEBLO CO
759 PM MDT THU APR 22 2010

COZ058>089-093>099-240200-
WESTERN MOSQUITO RANGE/EAST LAKE COUNTY ABOVE 11000 FT-
LEADVILLE VICINITY/LAKE COUNTY BELOW 11000 FT-
EASTERN SAWATCH MOUNTAINS ABOVE 11000 FT-
WESTERN CHAFFEE COUNTY BETWEEN 9000 AND 11000 FT-
CENTRAL CHAFFEE COUNTY BELOW 9000 FT-
WESTERN MOSQUITO RANGE/EAST CHAFFEE COUNTY ABOVE 9000 FT-
SAGUACHE COUNTY WEST OF CONTINENTAL DIVIDE BELOW 10000 FT-
SAGUACHE COUNTY EAST OF CONTINENTAL DIVIDE BELOW 10000 FT-
LA GARITA MOUNTAINS ABOVE 10000 FT-
UPPER RIO GRANDE VALLEY/EASTERN SAN JUAN MOUNTAINS BELOW 10000 FT-
EASTERN SAN JUAN MOUNTAINS ABOVE 10000 FT-
DEL NORTE VICINITY/NORTHERN SAN LUIS VALLEY BELOW 8500 FT-
ALAMOSA VICINITY/CENTRAL SAN LUIS VALLEY BELOW 8500 FT-
SOUTHERN SAN LUIS VALLEY-
NORTHERN SANGRE DE CRISTO MOUNTAINS BETWEEN 8500 AND 11000 FT-
NORTHERN SANGRE DE CRISTO MOUNTAINS ABOVE 11000 FEET-
SOUTHERN SANGRE DE CRISTO MOUNTAINS BETWEEN 7500 AND 11000 FT-
SOUTHERN SANGRE DE CRISTO MOUNTAINS ABOVE 11000 FT-
NORTHWESTERN FREMONT COUNTY ABOVE 8500 FT-
WESTERN/CENTRAL FREMONT COUNTY BELOW 8500 FT-
WET MOUNTAIN VALLEY BELOW 8500 FEET-
WET MOUNTAINS BETWEEN 6300 AND 10000 FT-
WET MOUNTAINS ABOVE 10000 FT-
TELLER COUNTY/RAMPART RANGE ABOVE 7500 FT/PIKES PEAK BETWEEN
7500 AND 11000 FT-PIKES PEAK ABOVE 11000 FT-
CANON CITY VICINITY/EASTERN FREMONT COUNTY-
NORTHERN EL PASO COUNTY/MONUMENT RIDGE/RAMPART RANGE BELOW
7500 FT-
COLORADO SPRINGS VICINITY/SOUTHERN EL PASO COUNTY/RAMPART RANGE
BELOW 7400 FT-PUEBLO AND VICINITY/PUEBLO COUNTY BELOW 6300 FT-
WALSENBURG VICINITY/UPPER HUERFANO RIVER BASIN BELOW 7500 FT-
TRINIDAD VICINITY/WESTERN LAS ANIMAS COUNTY BELOW 7500 FT-
CROWLEY COUNTY-LA JUNTA VICINITY/OTERO COUNTY-
EASTERN LAS ANIMAS COUNTY-WESTERN KIOWA COUNTY-
EASTERN KIOWA COUNTY-LAS ANIMAS VICINITY/BENT COUNTY-
LAMAR VICINITY/PROWERS COUNTY-SPRINGFIELD VICINITY/BACA COUNTY-
759 PM MDT THU APR 22 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL...EAST
CENTRAL...SOUTH CENTRAL AND SOUTHEAST COLORADO.

.DAY ONE...TONIGHT

ISOLATED THUNDERSTORMS...PRODUCING GUSTY WINDS...CLOUD TO GROUND
LIGHTING AND SMALL HAIL WILL BE POSSIBLE THROUGH MIDNIGHT...MAINLY
ACROSS TELLER AND EL PASO COUNTIES.

A STRONG AND SLOW MOVING UPPER LEVEL LOW PRESSURE SYSTEM WILL
TRACK ACROSS THE AREA FROM TONIGHT THROUGH EARLY SATURDAY
MORNING...PRODUCING OCCASIONAL MODERATE TO HEAVY SNOW AND BLOWING
SNOW OVER THE CENTRAL MOUNTAINS AND ACROSS TELLER
COUNTY...ESPECIALLY LATE TONIGHT THROUGH THE DAY FRIDAY. SNOW
ACCUMULATIONS OVER A FOOT ARE LIKELY BY MIDDAY SATURDAY...MAINLY
ABOVE 9000 FEET.

OVER THE PALMER DIVIDE AND NORTHERN EL PASO COUNTY...RAIN MAY
CHANGE TO SNOW LATE TONIGHT AND AGAIN FRIDAY NIGHT...WITH 2 TO 4
INCHES OF HEAVY WET SNOW POSSIBLE.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL AGAIN BE
POSSIBLE ACROSS THE AREA MONDAY THROUGH WEDNESDAY...WITH THE BEST
COVERAGE EXPECTED OVER THE HIGHER TERRAIN. THE MAIN THREATS FROM
THUNDERSTORMS WILL BE CLOUD TO GROUND LIGHTNING AND GUSTY WINDS TO
NEAR 40 MPH...WITH SMALL HAIL UP TO 1/2 INCH IN DIAMETER POSSIBLE
WITH THE STRONGEST STORMS.

.SPOTTER INFORMATION STATEMENT...

WEATHER CONDITIONS MEETING REPORTING CRITERIA FOR SPOTTERS WILL BE
LIKELY LATE TONIGHT AND EARLY FRIDAY MORNING OVER THE CENTRAL
MOUNTAINS...PIKES PEAK AND TELLER COUNTY.

50/10

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