Tornadoes and Flash Flood in Colorado, April 22, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GOODLAND KS
1100 PM MDT THU APR 22 2010

.DISCUSSION...
230 PM MDT THU APR 22 2010

H5 RIDGE AXIS WAS POSITIONED OVER THE CENTRAL ROCKIES WHILE
NORTHWEST H5 FLOW WAS OBSERVED ACROSS THE CENTRAL AND SOUTHERN
PLAINS THIS AFTERNOON.

WIDESPREAD TSRA IS EXPECTED AFTER 04-06Z IN LOW LVL WAA REGIME.
STORM MOTIONS SHOULD ALLOW PCPN TO IMPACT THE NORTHEAST ZONES AFTER
08-10Z. THE STRONGEST UPDRAFTS ARE EXPECTED TO IMPACT LOCATIONS
SOUTH OF INTERSTATE 70 WHERE STEEPEST H7-H5 LAPSE RATES/MUCAPE OF
400-500 J/KG MAY ALLOW A FEW HAILERS TO EXIST.

EARLY MORNING PCPN SHOULD LIFT NORTH AND EAST RAPIDLY WITH CLEARING
ANTICIPATED BY MID-LATE MORNING ACROSS THE SOUTHWEST ZONES. THIS
SHOULD ALLOW FOR DIURNAL HEATING/MODEST DESTABILIZATION AND MORE
ROBUST DEEP MOIST CONVECTION TO DEVELOP NORTHEAST OF SFC LOW AFTER
20-22Z. REMOVED MIDDAY POPS ACROSS THE WEST/SOUTHWEST ZONES WHILE
REINTRODUCING HIGHER POPS WEIGHTED ACROSS THE SOUTHWEST ZONES AFTER
21Z. THUNDERSTORM ACTIVITY SHOULD LIFT NORTH AND EAST BY 04-06Z WITH
LARGE SCALE SUBSIDENCE ANTICIPATED AFTER 06Z. WILL MAINTAIN LOW
PROBABILITIES THROUGH FRI MORNING WITH SCT TSRA ANTICIPATED UNDER H5
COLD POOL BY AFTERNOON.

H5 TROUGH IS PROGGED TO MOVE OVER THE AREA ON SAT WITH SCT SHRA
REMAINING IN THE FORECAST THROUGH THE AFTERNOON. LARGE SCALE FORCING
FOR SUBSIDENCE WILL SPREAD OVER THE REGION SAT EVENING BRINGING AN
END TO ANY LINGERING SHOWER ACTIVITY. WITH CLEARING SKIES AND LIGHT
LOW LVL FLOW, TEMPERATURES MAY FALL INTO THE LOW-MID 30S SUPPORTING
SCT FROST ACROSS THE WESTERN ZONES. THIS SCENARIO MAY BE REPEATED
TOWARD THE MIDDLE OF THE WEEK.

DAYS 4 THROUGH 7...A MID/UPPER TROUGH WILL TRANSLATE OUT OF THE
MISSISSIPPI VALLEY AREA AND OVER THE GREAT LAKES AT THE START OF
THE PERIOD WITH NORTHWEST MID/UPPER FLOW ANTICIPATED ACROSS THE
CENTRAL HIGH PLAINS. A NORTHWEST FLOW REGIME SHOULD LEAD TO
SEASONABLY COOL CONDITIONS WITH HIGHS IN THE 60S/LOWS IN THE
MID/UPPER 30S. A SHORTWAVE TROUGH OVER THE NORTHERN ROCKIES IS
PROGGED TO MOVE SOUTHEAST OVER THE CENTRAL HIGH PLAINS ON MON
BRINGING INCREASING CHANCES FOR PCPN AND LOW LVL CAA MAINTAINING
SEASONABLY COOL TEMPS ONCE AGAIN.

A MID/UPPER RIDGE IS PROGGED TO AMPLIFY ACROSS THE ROCKIES TUE-WED
WITH PHASE DIFFERENCES ACROSS THE GREAT PLAINS. A SUBTLE RISE IN
TEMPS IS ANTICIPATED THROUGH THE PERIOD WITH SEASONABLE VALUES IN
THE UPPER 60S/UPPER 30S TO LOWER 40S.

&&

.AVIATION...
1100 PM MDT THU APR 22 2010

FOR THE 06Z TAFS...RAIN AND THUNDERSTORMS SOUTHWEST OF CWA ARE
MOVING NORTHEAST...AND SHOULD OVERSPREAD THE GLD TERMINAL AFTER 07Z
ALONG WITH IFR CEILINGS/VISIBILITES. CURRENT RUC INDICATES
RAIN/THUNDERSTORMS AS WELL AS IFR CEILINGS SHOULD HOLD OFF OVER MCK
TERMINAL UNTIL AFTER 10Z...HOWEVER RUC IS CURRENTLY A LITTLE SLOW ON
THE PROGRESS OF CURRENT PRECIP EDGE...SO I LEFT VCTS IN THE MCK TAF
THROUGH 10Z TO COVER THE CHANCE FOR EARLIER ARRIVAL. AFTER 15Z...
TIMING AND COVERAGE OF THUNDERSTORM ACTIVITY BECOMES PROBLEMATIC
OVER BOTH TERMINALS...WITH MODELS DIFFERING ON DISSIPATION OF
OVERNIGHT ACTIVITY...AND REDEVELOPMENT OF DAYTIME THUNDERSTORMS.
WITH THE VIGOROUS NATURE OF THE SYSTEM BUILDING TO THE WEST...AND
RANGE OF SCENARIOS...I DECIDED TO KEEP VCTS IN TAFS THROUGH
03Z...WITH LATER FORECASTS NEEDED TO NAIL DOWN
THE DETAILS.

DR
&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
NE...NONE.
CO...NONE.
&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GOODLAND KS
1037 AM MDT WED APR 21 2010

COZ090>092-KSZ001>004-013>016-027>029-041-042-NEZ079>081-221245-
YUMA-KIT CARSON-CHEYENNE CO-CHEYENNE KS-RAWLINS-DECATUR-NORTON-
SHERMAN-THOMAS-SHERIDAN-GRAHAM-WALLACE-LOGAN-GOVE-GREELEY-WICHITA-
DUNDY-HITCHCOCK-RED WILLOW-
1037 AM MDT WED APR 21 2010 /1137 AM CDT WED APR 21 2010/

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

THUNDERSTORMS WILL ONCE AGAIN DEVELOP THIS AFTERNOON AND SPREAD
ACROSS THE AREA OVERNIGHT. LIMITED INSTABILITY ARE EXPECTED TO KEEP
THUNDERSTORMS FROM BECOMING SEVERE THROUGH THE EARLY EVENING. AS
THUNDERSTORM CONTINUE TO DEVELOP OVERNIGHT...THE THREAT FOR LARGE
HAIL WILL INCREASE.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

A STRONG UPPER LEVEL STORM SYSTEM WILL MOVE INTO THE REGION
THURSDAY AND THURSDAY NIGHT. THIS SYSTEM IS EXPECTED TO CAUSE
SCATTERED TO NUMEROUS THUNDERSTORMS ACROSS THE AREA. SOME OF
THESE STORMS COULD BECOME SEVERE DURING THE AFTERNOON AND EVENING
HOURS. AT THIS TIME...THE MAIN THREATS WILL BE DAMAGING WINDS AND
VERY LARGE HAIL.

ADDITIONAL CHANCES FOR THUNDERSTORMS WILL CONTINUE FROM FRIDAY
INTO FRIDAY NIGHT. HOWEVER...THESE STORMS ARE NOT EXPECTED TO
BECOME SEVERE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THIS AFTERNOON OR EVENING.