Severe Thunderstorm Warning 284, NWS Goodland, KS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GOODLAND KS
222 PM MDT TUE AUG 6 2013

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 222 PM MDT TUE AUG 6 2013

LATEST WV IMAGERY AND RAP ANALYSIS SHOWS NW FLOW STILL IN PLACE
ACROSS THE NORTHERN AND CENTRAL CONUS...WITH A RIDGE CENTERED OVER
TEXAS AND A WEAKENED CLOSED LOW OVER SOUTHERN ARIZONA. A VERY
MOIST/UNSTABLE AIRMASS REMAINS IN PLACE OVER OUR CWA WITH TD VALUES
ACROSS NW KANSAS IN THE MID 60S TO LOW 70S...AND SB CAPE VALUES IN
THE 2000-4000 J/KG RANGE FROM THE WEST TO THE EAST. A SURFACE
TROUGH IS CURRENTLY CENTERED ALONG THE KS/CO BORDER...WITH LOWER
TD VALUES AND MUCH MORE STABLE AIRMASS TO THE WEST OF THIS
FEATURE.

THUNDERSTORMS HAVE ALREADY DEVELOPED ALONG THIS TROUGH AXIS
IN OUR FAR SW CWA. I WOULD EXPECT ADDITIONAL THUNDERSTORM
ACTIVITY TO INITIATE ALONG AND EAST OF THIS FEATURE THROUGH THIS
AFTERNOON AND EVENING. LATEST HRRR INDICATED ACTIVITY FORMING AHEAD OF
THIS AXIS AND FORMING INTO A CLUSTER/LINE AND SHIFTING TO THE
SOUTH AND EAST. BASED ON NAM/GFS SUPPORTING BETTER COVERAGE IN THE
SOUTH...WHICH IS IN LINE WITH SHORT RANGE GUIDANCE I KEPT THIS
TREND. A COLD FRONT WILL APPROACH THE CWA TONIGHT...WITH ELEVATED
INSTABILITY/GOOD MOISTURE LINGERING I DECIDED TO KEEP THUNDERSTORM
MENTION THROUGH THE NIGHT. CONSIDERING STORM MOTION WITH
INDIVIDUAL CELLS AND MOISTURE AVAILABILITY I AM CONCERNED WE COULD
SEE LOCALIZED FLASH FLOODING THIS AFTERNOON/EVENING IN ADDITION TO
SEVERE HAIL/WIND THREAT. COVERAGE IS A QUESTION THOUGH...WITH ANY
CLUSTER/LINE LIKELY BEGINNING TO PROPAGATE QUICKER AS IT FORMS A
COLD POOL IN OUR SOUTH. AS A RESULT WE MAY NOT ACTUALLY SEE AS
WIDESPREAD OF A THREAT OF FLASH FLOODING TODAY/TONIGHT.

WEDNESDAY...COLD FRONT WILL DROP SOUTH OF OUR CWA AND BE NEAR THE
KS/OK BORDER BY LATE WED AFTERNOON. DEEP MOIST EASTERLY FLOW
ALONG/NORTH OF THIS FEATURE COMBINED WITH INCREASING LARGE SCALE
ASCENT WILL SUPPORT NUMEROUS TO WIDESPREAD SHOWERS/THUNDERSTORMS
ACROSS OUR SOUTHERN CWA. I AM CONCERNED THAT THE BEST COVERAGE MAY
BE TIED TO THE FRONT...WHICH WOULD PUT BETTER COVERAGE SOUTH OF OUR
CWA. HOWEVER THERE IS ENOUGH MOISTURE/FORCING ALOFT TO SUPPORT
HIGHER POPS ACROSS OUR SOUTHERN CWA IN THE AFTERNOON. A RESULT OF
THICK CLOUD COVER AND CAA THROUGH THE DAY WILL BE HIGH TEMPERATURES
WELL BELOW NORMAL (UPPER 60S TO MID 70S). PREVIOUS FORECAST HAD THIS
COOLER TREND...SO ONLY MINOR ADJUSTMENTS MADE. WHILE WE MAY NEED A
FLASH FLOOD WATCH FOR WED AFTERNOON DUE TO POSSIBLE TRAINING AND
WIDESPREAD HEAVY RAIN COVERAGE IN THE SOUTH...I FELT IT WAS BEST TO
CONCENTRATE PUBLIC ATTENTION ON ONGOING THUNDERSTORMS THIS
AFTERNOON/EVENING TO AVOID CONFUSION. WE MAY NEED TO ISSUE A WATCH
ON OVERNIGHT SHIFTS IF IT LOOKS LIKE OUR SOUTHERN CWA WILL REMAIN
FAVORABLE FOR A LARGE SCALE FLASH FLOOD THREAT.

.LONG TERM...(FRIDAY THROUGH MONDAY)
ISSUED AT 220 AM MDT TUE AUG 6 2013

MODELS ARE IN REASONABLY GOOD AGREEMENT WITH THE SYNOPTIC
SCALE PATTERN DURING THE EXTENDED PERIOD. MINOR DIFFERENCES EMERGE
BY THE WEEKEND WHEN ECMWF IS STRONGER AND MORE AMPLIFIED THAN THE
GFS WITH UPPER RIDGE THAT BUILDS OVER OUR AREA. OTHERWISE...TYPICAL
DIFFERENCES EXIST WITH TIMING AND PLACEMENT OF SUBTLE SHORTWAVES IN
THE MID/UPPER FLOW LEADING TO UNCERTAINTY AS TO WHEN THE MOST
WIDESPREAD CONVECTION WILL OCCUR.

BY EARLY FRIDAY...DEEP MOISTURE WILL HAVE SHIFTED EAST OF THE AREA
AS RELATIVELY STRONG SHORTWAVE DEPARTS. COOL NORTHEASTERLY SURFACE
FLOW EARLY SHOULD SHIFT TO SOUTHEASTERLY LATE FRIDAY CAUSING A
RETURN OF LOW LEVEL MOISTURE AND HIGHER THETA-E VALUES. SOME
CONVECTION MAY DEVELOP FRIDAY AND FRIDAY EVENING IN THE VICINITY OF
LEE TROUGH / SURFACE CONVERGENCE OVER THE WESTERN PORTION OF THE
AREA. SIGNIFICANT FORCING IS ABSENT AND A RELATIVELY DRY COLUMN WITH
DEEP MIXED LAYER WILL LIKELY LIMIT COVERAGE OF CONVECTION. ON
SATURDAY...MOISTURE INCREASES FURTHER AND MID/UPPER FLOW
STRENGTHENS. LEE TROUGH SHARPENS AND MODELS INDICATE ONE OR TWO
SMALL PERTURBATIONS IN THE WESTERLY FLOW ALOFT...ALL OF WHICH
SUPPORTS A BETTER CHANCE OF CONVECTION ACROSS THE AREA. GFS IS MORE
PROGRESSIVE FOR SUNDAY AND MONDAY SHOWING DEEP MIXING ACROSS THE
WESTERN HALF OF THE AREA SUNDAY WITH CONVECTION CONFINED TO THE
EASTERN PORTION OF THE AREA WHERE BETTER MOISTURE RESIDES. ECMWF
HAS THE UPPER RIDGE AXIS FURTHER WEST AND THE GFS ENSEMBLE MEAN IS
IN BETWEEN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1144 AM MDT TUE AUG 6 2013

SCATTERED THUNDERSTORMS WILL DEVELOP ALONG TROUGH AXIS OVER NW
KS/SW NE THIS AFTERNOON AND INCREASE IN COVERAGE THROUGH THIS
EVENING AS THE ACTIVITY TRANSITIONS EAST. CURRENTLY COVERAGE IS
STILL TOO MUCH OF A QUESTION AT EITHER TERMINAL WITH BETTER
CHANCES FURTHER SOUTH AND EAST...SO I LIMITED MENTION TO VCTS.
LATE TONIGHT FOG/STRATUS IS EXPECTED TO REDEVELOP...WITH LOWER
CIGS/VIS AT BOTH TERMINALS BY SUNRISE. GUIDANCE CURRENTLY SUPPORTS
MVFR CONDITIONS...HOWEVER CONSIDERING THE MOIST NATURE OF THE
AIRMASS IF WINDS GO COMPLETELY CALM WE COULD SEE LOWER CONDITIONS
DEVELOP. FOR NOW I CHOSE TO STAY IN LINE WITH CURRENT
GUIDANCE...HOWEVER WE WILL NEED TO MONITOR THIS.

&&

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

SHORT TERM...DR
LONG TERM...BRB
AVIATION...DR

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