Area Forecast Discussion
Issued by NWS Dodge City, KS

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FXUS63 KDDC 201830
AFDDDC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DODGE CITY KS
130 PM CDT SAT SEP 20 2014

...UPDATE TO SHORT TERM...

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 122 PM CDT SAT SEP 20 2014

SHORT TERM MODELS INDICATE AN UPPER LEVEL SHORTWAVE TROUGH DIGGING
SOUTHEAST OUT OF THE NORTHERN PLAINS INTO THE UPPER MIDWEST TONIGHT.
MEANWHILE, AN ATTENDANT COLD FRONT IS PROJECTED TO PUSH SOUTHWARD
ACROSS WESTERN KANSAS OVERNIGHT PROVIDING THE FOCUS FOR POTENTIAL
THUNDERSTORM DEVELOPMENT. AMPLE MOISTURE WILL REMAIN AVAILABLE
AHEAD OF THE APPROACHING FRONTAL BOUNDARY WITH SURFACE DEWPOINTS
WELL UP INTO THE 60S(F) ACROSS CENTRAL AND MUCH OF SOUTHWEST
KANSAS. ALTHOUGH THE FLOW ALOFT IS NOT EXPECTED TO BE OVERLY
FAVORABLE, ENOUGH INSTABILITY WITH CAPE VALUES IN EXCESS OF 1000
J/KG AND STEEP LOW LEVEL LAPSE RATES MAY BE ENOUGH TO SUPPORT
ISOLATED THUNDERSTORMS IN A BAND OF INCREASED H7 FRONTOGENESIS
BEHIND THE FRONTAL BOUNDARY TONIGHT. THE BETTER CHANCE FOR STORM
DEVELOPMENT WILL BE ACROSS CENTRAL KANSAS WHERE MOISTURE WILL BE
MORE READILY AVAILABLE WITH CHANCES TAPERING OFF WESTWARD WHERE
SURFACE DEWPOINTS LOWER INTO THE UPPER 50S(F) CLOSER TO THE
COLORADO BORDER.

TEMPERATURES TONIGHT WILL BE SLIGHTLY COOLER THAN THE LOWER 60S(F)
EXPERIENCED ACROSS CENTRAL AND SOUTHWEST KANSAS THIS MORNING AS
COOLER AIR FILTERS SOUTHWARD BEHIND THE PASSING COLD FRONT TONIGHT.
LOOK FOR LOWS DOWN INTO THE MID TO UPPER 50S(F) ACROSS CENTRAL
KANSAS NEAR THE I-70 CORRIDOR WITH THE LOWER 60S(F) STILL LIKELY
FURTHER SOUTH CLOSER TO THE OKLAHOMA BORDER. THE COOLER AIR BEHIND
THE FRONT WILL HELP LOWER HIGH TEMPERATURES TOMORROW AS WELL. THE
NAM/GFS SHOW H85 TEMPERATURES ONLY UP INTO THE MID TEENS(C) ACROSS
CENTRAL KANSAS TO THE UPPER TEENS(C) IN EXTREME SOUTHWEST KANSAS.
WITH LINGERING CLOUD COVER PLAYING A POSSIBLE FACTOR EARLY IN THE
DAY, HIGHS ARE ONLY EXPECTED TO REACH UP INTO THE MID TO UPPER
70S(F) ACROSS WEST CENTRAL KANSAS SUNDAY AFTERNOON WITH THE LOWER
80S(F) IN SOUTH CENTRAL KANSAS.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 406 AM CDT SAT SEP 20 2014

AN EXTENDED EAST ASIAN JET FROM CHINA TO NEAR THE DATELINE BREAKS
INTO HIGHLY AMPLIFIED BLOCKY FLOW AROUND 160W WITH ANTICYCLONIC WAVE
BREAKS AROUND 30N/170W AND OFF THE SOUTHERN CALIFORNIA COAST.
CONSIDERABLE UNCERTAINTY EXISTS IN THE EXTENDED PERIOD AS A BLOCKY,
AMPLIFIED FLOW EVOLVES OVER NORTH AMERICA, AND CONFIDENCE IN
SYNOPTIC SCALE DETAILS IS VERY LOW BEYOND DAY 5. TROPICAL
THUNDERSTORM ACTIVITY SHOWS LITTLE COHERENT ORGANIZATION THAT
PROJECTS ONTO A MADDEN-JULIAN OSCILLATION. IT DOES APPEAR THAT A
KELVIN WAVE HAS PROPAGATED RAPIDLY THROUGH THE WESTERN HEMISPHERE
AND IS APPROACHING AFRICA, AND THUNDERSTORM ACTIVITY SHOULD
INCREASE IN THE WESTERN INDIAN OCEAN BY LATE SEPTEMBER. HOWEVER,
THERE IS LITTLE AGREEMENT AMONG NUMERICAL MODELS ON EVOLUTION OF
ANY COHERENT SIGNAL THROUGH EARLY OCTOBER. GLOBAL RELATIVE ANGULAR
MOMENTUM IS TRENDING UP AND IS APPROACHING CLIMATOLOGICAL VALUES
WITH A LARGE INCREASE AROUND 40N. MOUNTAIN TORQUE PEAKED A FEW
DAYS AGO BUT STILL REMAINS STRONGLY POSITIVE. THE ATMOSPHERE STILL
IS BEST REPRESENTED BY PHASE 4 OF THE WEICKMANN-BERRY PHASE SPACE
DIAGRAM, WHICH FAVORS ANTICYCLONIC FLOW IN THE WESTERN UNITED
STATES.

LARGE DIFFERENCES IN DETERMINISTIC MODEL SOLUTIONS DEVELOP LATE NEXT
WEEK AS SHARP RIDGING EVOLVES 130-140W AND ANOTHER TROUGH DIGS
INTO THE WESTERN UNITED STATES. THE ECMWF HAS VACILLATED BETWEEN A
RIDGE IN THE SOUTHWESTERN UNITED STATES WITH A PROGRESSIVE TROUGH
LIFTING NORTHEAST OVER THE RIDGE AND A DEEP TROUGH IN THE CENTRAL
ROCKIES BY 28-29 SEPTEMBER. THE GFS ENSEMBLE MEMBERS ALL HAVE A
DEEP TROUGH SOMEWHERE BETWEEN 110W AND 120W BY 27 SEPTEMBER, BUT
THE GEM ENSEMBLES DIFFER WIDELY BETWEEN MAINTAINING A RIDGE AND A
MEAN TROUGH OVER THE WESTERN PART OF THE COUNTRY. THE DIFFERENCES
IN MODEL SOLUTIONS AND LACK OF STRONG LARGE SCALE SIGNALS IN
OBSERVATIONAL DATA MAKE GUESSING AT HOW THE FLOW WILL EVOLVE
EXTREMELY DIFFICULT. THE BEST GUESS IS THAT RIDGING WILL PERSIST
FROM MEXICO INTO THE SOUTHWEST UNITED STATES AND THAT THE TROUGH
NEXT WEEKEND WILL LIFT OUT TO THE NORTHEAST INSTEAD OF WALLOWING
INTO THE CENTRAL PART OF THE COUNTRY, BUT THERE IS VERY LIMITED
CONFIDENCE IN THIS SOLUTION. REGARDLESS OF HOW THE TROUGH EVOLVES,
IT WILL BE A TRANSITORY FEATURE, AND THE BASE STATE FLOW WITH A
RIDGE IN THE WESTERN UNITED STATES AND A TROUGH IN THE EASTERN
PART OF THE COUNTRY IS LIKELY TO RETURN BY EARLY OCTOBER.

CONFIDENCE IS HIGHER IN EVOLUTION OF THE FLOW THROUGH THE FIRST PART
OF NEXT WEEK. THE VIGOROUS UPPER LEVEL TROUGH IN SASKATCHEWAN WILL
DIG INTO THE UPPER MIDWEST SUNDAY, AND A SECOND SURGE OF COOL AIR
WILL INVADE KANSAS SUNDAY MORNING. DRIER AIR WILL MOVE INTO MOST OF
WESTERN KANSAS BEHIND AN INITIAL COLD FRONT THAT WILL PASS THIS
AFTERNOON AND EVENING, BUT THERE MAY BE SOME SHOWERS IN THE ELEVATED
FRONTOGENETIC REGION BEHIND THE SECOND COLD SURGE IN FAR SOUTHWEST
KANSAS YET SUNDAY MORNING. COLD AIR ADVECTION SUNDAY WILL KEEP
TEMPERATURES SEVERAL DEGREES BELOW VALUES OBSERVED SATURDAY. STRATUS
LIKELY WILL FORM IN FAR SOUTHWEST KANSAS SATURDAY NIGHT AND PERSIST
AT LEAST INTO SUNDAY AFTERNOON IN THE SOUTHWEST CORNER OF THE STATE.

TROUGHING WILL DEVELOP IN THE LEE OF THE ROCKIES AS THE UPPER LEVEL
LOW OFF THE SOUTHERN CALIFORNIA COAST PROPAGATES INTO THE CENTRAL
ROCKIES MONDAY MORNING. A NARROW CORRIDOR OF LOW LEVEL MOISTURE WILL
SPREAD NORTH THROUGH EASTERN COLORADO AND EXTREME WESTERN KANSAS
MONDAY. CONSIDERABLE MID LEVEL DIRECTIONAL SHEAR WILL EVOLVE MONDAY
AS THE UPPER LEVEL TROUGH APPROACHES AND MID LEVEL WINDS INCREASE.
IF THE STRATUS DISSIPATES AND ALLOWS HEATING OF THE BOUNDARY LAYER,
SUFFICIENT INSTABILITY WILL DEVELOP TO SUPPORT FORMATION OF AT
LEAST A FEW SEVERE THUNDERSTORMS IN EASTERN COLORADO THAT
SUBSEQUENTLY WILL PROPAGATE INTO WESTERN KANSAS LATE MONDAY
AFTERNOON OR EVENING. AN AREA OF THUNDERSTORMS LIKELY WILL MOVE
ACROSS WESTERN KANSAS INTO CENTRAL SECTIONS OF THE STATE BY
TUESDAY MORNING AS THE UPPER LEVEL TROUGH MOVES INTO THE CENTRAL
PLAINS AND CLOSES OFF NEAR THE BLACK HILLS.

THE UPPER LEVEL TROUGH WILL BE SLOW TO MOVE EAST WITH RISING HEIGHTS
IN THE EASTERN UNITED STATES AND A RIDGE AMPLIFYING FROM THE
SOUTHWESTERN STATES INTO THE NORTHERN PLAINS. ANOTHER MINOR TROUGH
ROTATING AROUND THE UPPER LEVEL CYCLONE WILL MOVE INTO KANSAS
TUESDAY AND SUPPORT ADDITIONAL THUNDERSTORM DEVELOPMENT. THE UPPER
LEVEL CYCLONE WILL OPEN UP AND EVOLVE INTO AN ELONGATED TROUGH
ACROSS THE CENTRAL PART OF THE COUNTRY WEDNESDAY. AN UPPER LEVEL
ANTICYCLONE WILL DEVELOP IN THE NORTHERN PLAINS THURSDAY, AND PART
OF THE UPPER LEVEL TROUGH WILL RETROGRADE BACK TO KANSAS THURSDAY.
AS SUCH, THE CHANCE FOR THUNDERSTORMS WILL EXTEND INTO AT LEAST
FRIDAY AND POSSIBLY SATURDAY BEFORE THE UPPER LEVEL TROUGH FINALLY
LIFTS OUT AS THE NEXT TROUGH DIGS INTO THE WESTERN UNITED STATES.

THERE IS NO REALLY COOL AIR TO TAP, AND THE LOW LEVELS OF THE
ATMOSPHERE WILL REMAIN FAIRLY WARM THROUGH THE WEEK. TEMPERATURES
WILL BE NEAR SEASONAL AVERAGES WITH DAY TO DAY VARIATIONS DEPENDENT
MORE ON CLOUD COVER THAN ANY AIR MASS CHANGES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1225 PM CDT SAT SEP 20 2014

ISOLATED THUNDERSTORMS WILL BE POSSIBLE LATE THIS AFTERNOON IN THE
VICINITY OF KDDC AS A SURFACE TROUGH PUSHES EASTWARD ACROSS
SOUTHWEST KANSAS. ISOLATED THUNDERSTORMS WILL BE POSSIBLE AGAIN LATE
TONIGHT IN THE VICINITY OF KGCK AND KDDC AS A WEAK COLD FRONT MOVES
SOUTHWARD ACROSS WESTERN KANSAS. OTHERWISE, VFR CONDITIONS WILL
PREVAIL AT ALL TAF SITES THROUGH EARLY SUNDAY MORNING. MVFR CIGS MAY
BE POSSIBLE TOWARD DAYBREAK SUNDAY MORNING AS LOW LEVEL STRATUS
IS EXPECTED TO DEVELOP ALONG AND BEHIND THE FRONTAL BOUNDARY.
WINDS WILL TURN NORTHEASTERLY 5 TO 15KT ACROSS WEST CENTRAL AND
PORTIONS OF SOUTHWEST KANSAS LATE THIS AFTERNOON AS THE
AFOREMENTIONED SURFACE TROUGH EDGES EASTWARD ACROSS WESTERN
KANSAS. A COLD FRONT IS THEN PROJECTED TO MOVE THROUGH WESTERN
KANSAS EARLY SUNDAY MORNING TURNING WINDS NORTHEASTERLY 5 TO 15KT
ACROSS THE REST OF CENTRAL AND SOUTHWEST KANSAS.

&&

.PRELIMINARY POINT TEMPS/POPS...
DDC  60  80  54  80 /  30  20  10  20
GCK  58  78  55  77 /  30  20  10  40
EHA  57  77  59  75 /  30  20  20  30
LBL  60  80  57  80 /  30  20  10  30
HYS  56  77  49  76 /  30   0   0  10
P28  62  82  54  81 /  30  20   0   0

&&

.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...JJOHNSON
LONG TERM...RUTHI
AVIATION...JJOHNSON



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