000
FXUS63 KDDC 172059
AFDDDC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DODGE CITY KS
359 PM CDT FRI MAY 17 2013

...UPDATED SYNOPSIS AND SHORT TERM SECTIONS...

.SYNOPSIS...
ISSUED AT 356 PM CDT FRI MAY 17 2013

A MID LEVEL TROUGH AXIS CONTINUED TO MOVE INLAND ACROSS THE WESTERN
CONUS. A MID LEVEL BAROCLINIC ZONE EXTENDED FROM SOUTHERN CALIFORNIA
THROUGH SALT LAKE CITY REGION AND INTO THE NORTHERN DAKOTAS. 500MB
HEIGHT FALLS WERE MOST NOTABLE ACROSS THE DESERT SOUTHWEST REGION
WITH 12-HR HEIGHT FALLS ON THE ORDER OF 30 TO 50 METERS.  SHORTWAVE
RIDGING ENCOMPASSED THE WESTERN PLAINS FOR MUCH OF THE DAY TODAY.
MEANWHILE IN THE LOWER TROPOSPHERE...A SUBSTANTIAL AMOUNT OF LOW
LEVEL MOISTURE WAS FOUND ACROSS OKLAHOMA AND TEXAS.  DEWPOINT
TEMPERATURES IN THE 67 TO 71F RANGE WERE COMMON OVER A LARGE PORTION
OF SOUTHERN AND WESTERN OKLAHOMA...INTO NORTH TEXAS. THERE WAS A
WEAK FRONTAL BOUNDARY ACROSS THE RED RIVER REGION WHICH WAS LEFT
BEHIND FROM THE OLD UPPER LOW THAT AFFECTED THE REGION A COUPLE OF
DAYS AGO. SURFACE MOISTURE ADVECTION WAS STRONGEST ACROSS SOUTHWEST
KANSAS...AS DEWPOINT TEMPERATURE CONTINUED TO CLIMB AT DODGE CITY TO
63 DEGREES AS OF 2030 UTC.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 356 PM CDT FRI MAY 17 2013

TONIGHT:
A DENSE FOG ADVISORY WAS ISSUED FOR TONIGHT ACROSS MUCH OF SOUTHWEST
KANSAS. TEMPERATURES WILL CONTINUE TO SLOWLY FALL THROUGH THE 70S
THIS EVENING...BOTTOMING OUT IN THE 68 TO 71 DEGREE RANGE. ALL THE
SHORT-TERM MODELS ARE SUGGESTING DENSE FOG FORMATION AS VISIBILITY
FIELDS DROP SUBSTANTIALLY IN THE MODELS BETWEEN 06-09Z. THIS
CERTAINLY MAKES PHYSICAL SENSE GIVEN THE ANOMALOUSLY RICH MOISTURE
THAT WILL CONTINUE TO MOVE IN FROM OKLAHOMA ON THE SOUTHEAST WINDS.

TOMORROW INTO TOMORROW NIGHT:
DENSE FOG IN THE MORNING SHOULD SLOWLY BURN OFF IN THE 13-15Z TIME
FRAME GIVEN THE MORNING INSOLATION...BUT LOW STRATUS WILL HOLD ON
PRETTY TOUGH THROUGH MUCH OF THE MORNING HOURS GENERALLY NORTH OF A
SCOTT CITY TO DODGE CITY TO MEDICINE LODGE LINE.  EVENTUALLY...EVEN
THESE AREAS TO THE NORTH WILL SEE THE CEILING SCATTER OUT AS WARM
ADVECTION INCREASE WITH SOUTHWEST MOMENTUM INCREASING IN THE
BOUNDARY LAYER ACROSS FAR SOUTHWEST KANSAS.  THE LEAD UPPER
TROPOSPHERIC JET STREAK TIED TO THE LARGER SCALE TROUGH WILL BE
MOVING INTO COLORADO BY LATE MORNING...THIS LEAD JET WILL BE
ORIENTED FROM SSW TO NNE FROM NEW MEXICO THROUGH COLORADO INTO THE
WESTERN DAKOTAS.  A TEMPERATURE GRADIENT AT 700MB WILL EXIST ALONG
THIS LEAD JET STREAK.

BY LATE AFTERNOON...THE JET CORE WILL CONTINUE TO ADVANCE
NORTH-NORTHEASTWARD THROUGH NORTHEAST COLORADO INTO THE DAKOTAS. FAR
WESTERN KANSAS WILL BECOME UNDER THE INFLUENCE OF THE RIGHT-ENTRANCE
REGION OF THIS LEAD JET...PROVIDING THE NECESSARY UPWARD VERTICAL
MOTION TO PROMOTE ENHANCED LOWER TROPOSPHERIC DEVELOPMENT OF A
CYCLONE. THE LATEST NAM12 MODEL SUGGESTS A SURFACE LOW DOWN TO 994
OR 995MB BY LATE AFTERNOON SOMEWHERE ALONG THE COLORADO-KANSAS
BORDER...WITH A WARM FRONT EXTENDING EAST...THEN EAST-SOUTHEAST OF
THAT WHERE COOLER AIR WILL BE FROM ALL THE STRATUS FROM EARLIER IN
THE MORNING. STRONG SOUTHWEST MOMENTUM WILL ALLOW HOT, DRY AIR TO
ADVANCE NORTHEASTWARD TO ROUGHLY A JOHNSON-MONTEZUMA-SLAPOUT, OK
LINE BY 22Z. THE CONVERGENCE OF THESE TWO AIRMASS WILL BE THE FOCUS
FOR THE INITIAL THUNDERSTORMS. SURFACE-BASED CAPE IN THE
MOISTURE-LADEN AIRMASS WILL EXCEED 4000 J/KG WITH WIDESPREAD SURFACE
PARCELS OF MID 80S OVER UPPER 60S DEWPOINT (DEGF).

DEEP LAYER SHEAR WILL CERTAINLY BE THERE FOR SUPERCELL STORMS WITH
0-6KM AGL BULK SHEAR AROUND 45 KNOTS OR SO. VERY LARGE HAIL THE SIZE
OF BASEBALLS OR PERHAPS LARGER UP TO SOFTBALLS WILL CERTAINLY BE
POSSIBLE IN THE 6 TO 9PM TIME FRAME ONCE SUPERCELLS BECOME
ESTABLISHED. NOW TO THE TORNADO THREAT -- THERE IS REASON FOR GREAT
CONCERN ABOUT THE POSSIBILITY FOR LONG-LIVED, SIGNIFICANT TORNADOES
IN AN ENVIRONMENT THAT IS CHARACTERIZED BY SURFACE-BASED CAPE IN THE
3500-4500 J/KG RANGE ALONG WITH 0-1KM AGL HELICITY RAMPING UP TO THE
300-400 J/KG RANGE AS WELL (THANKS TO THE DYNAMIC LOW LEVEL JET THAT
DEVELOPS JUST AFTER SUNSET). THIS IS A TREMENDOUS AMOUNT OF
POTENTIAL ENERGY BOTH FROM KINEMATICS AND THERMODYNAMICS TO SUPPORT
EXTREMELY STRONG LOW LEVEL ROTATION IN SUPERCELL
THUNDERSTORMS...INCLUDING LONG-LIVED AND STRONG TORNADOES THAT
THRIVE DURING THE POST-SUNSET HOURS. THERE MAY ONLY BE ONE OR TWO
STORMS THAT THRIVE AFTER SUNSET...BUT THE DAMAGE POTENTIAL COULD BE
GREAT FROM JUST ONE ISOLATED SUPERCELL STORM.  EVENTUALLY DURING THE
03-06Z TIME FRAME...THE NOCTURNAL BOUNDARY LAYER COOLING WILL BE
SUFFICIENT ENOUGH TO LESSEN THE TORNADO THREAT...AND SUPERCELL
STORMS MAY DISSOLVE ALL TOGETHER BY 05 OR 06Z AS THE STORMS MOVE
TOWARD CENTRAL OR SOUTH-CENTRAL KANSAS.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 413 AM CDT FRI MAY 17 2013

SATURDAY INTO SATURDAY NIGHT CONTINUE TO LOOK LIKE AN ACTIVE
WEATHER PERIOD ACROSS THE GREAT PLAINS AS THE UPPER TROUGH CURRENTLY
DIGGING INTO THE WEST COAST, SWINGS EAST INTO THE ROCKIES. THIS IS
IN RESPONSE TO A 100+ KNOT JET STREAK ON THE BACK SIDE OF THE WAVE
THIS MORNING, BEGINNING TO ROUND THE BASE OF THE TROUGH ON SATURDAY.
THE ARRIVAL OF THIS SYSTEM WILL PUSH A PACIFIC FRONT EASTWARD INTO
THE PLAINS AND STRETCH FROM THE DAKOTAS INTO EASTERN COLORADO
WHILE ALSO INDUCING STRONG LOW-LEVEL CYCLOGENESIS OVER NORTHWEST
KANSAS SATURDAY AFTERNOON. A DRYLINE EXTENDING SOUTH OF THIS CYCLONE
WILL SLIP EASTWARD INTO WESTERN KANSAS BY MID AFTERNOON ROUGHLY
ALONG THE HIGHWAY 83 CORRIDOR. THIS BOUNDARY WILL BE THE DIVIDING
LINE BETWEEN TWO EXPECTED EXTREMES OF HIGH IMPACT WEATHER.

ON THE MOIST SIDE OF THE BOUNDARY, UPPER 50 TO MID 60 DEGREE
DEWPOINTS ALONG WITH TEMPERATURES IN THE 90S WILL RESULT IN HIGH TO
EXTREME INSTABILITY VIA MLCAPE VALUES OF 3000-3500 J/KG EXPECTED BY
MID AFTERNOON. A STRONG ELEVATED MIXED LAYER WILL REMAIN OVER THE
CENTRAL PLAINS VIA 700 HPA TEMPERATURES OF +12C TO +14C WITH THIS
EML EFFECTIVELY CAPPING THE ATMOSPHERE THROUGH MOST OF THE DAY.
HOWEVER, AS THE WAVE APPROACHES THE PLAINS BY LATE AFTERNOON, LARGE
SCALE ASCENT AND MID/UPPER LEVEL HEIGHT FALLS MAY ERODE ENOUGH OF
THE CAP TO GENERATE ISOLATED TO POSSIBLY SCATTERED CONVECTION EAST
OF HIGHWAY 83 ALTHOUGH WOULD NOT BE SHOCKED IF CONVECTION FAILS TO
GENERATE. OVERALL SEVERE CONVECTIVE POTENTIAL IS HIGHLY CONDITIONAL
NOT ONLY ON CONVECTIVE COVERAGE BUT ALSO DUE TO STRONGER 6-12 KM AGL
WINDS REMAINING BEHIND THE DRYLINE. NONETHELESS, SHEAR PROFILES ARE
MODESTLY FAVORABLE FOR ROTATING UPDRAFTS AND ANY SUPERCELL LASTING
FOR MORE THAN AN HOUR COULD PRODUCE HAIL UP TO BASEBALL SIZE
ALONG WITH AN ISOLATED TORNADO.

ON THE DRY SIDE OF THE BOUNDARY, POTENTIAL EXISTS FOR CRITICAL FIRE
WEATHER CONDITIONS ACROSS FAR SOUTHWEST KANSAS. DEEP THERMAL MIXING
BEHIND THE DRYLINE WILL RESULT IN TEMPERATURES IN THE MID TO UPPER
90S COMBINING WITH DRY AIR TO PRODUCE MINIMUM HUMIDITY LEVELS OF
10-15 PERCENT FOR SEVERAL HOURS DURING THE AFTERNOON TO EARLY
EVENING. THIS ALONG WITH WIND GUSTS ABOVE 25 MPH IN THE AFTERNOON
COULD PRODUCE RED FLAG CONDITIONS FOR A SEVERAL HOURS AND OPTED TO ISSUE
A FIRE WEATHER WATCH FOR LOCATIONS GENERALLY WEST OF HIGHWAY 83.

SUNDAY AND SUNDAY NIGHT WILL REMAIN ACTIVE OVER THE GREAT PLAINS AS
THE AFOREMENTIONED JET STREAK CONTINUES TO DIVE SOUTHEAST INTO THE
BASE OF THE UPPER TROUGH.  THE EXIT REGION OF THIS JET WILL CONTINUE
TO DEEPEN THE SURFACE LOW INITIALLY OVER WESTERN KANSAS SUNDAY
MORNING ALTHOUGH IT SHOULD LIFT QUICKLY NORTHEAST INTO THE NORTHERN
PLAINS BY SUNDAY EVENING. THIS WILL ALLOW AN ASSOCIATED PACIFIC
FRONT TO PUSH SOUTHEAST THROUGH WESTERN KANSAS BY EARLY AFTERNOON
ON SUNDAY. UNDER THIS SCENARIO DEEPER MOISTURE WILL BE SHUNTED INTO
THE EASTERN HALF OF KANSAS LEAVING ONLY WEAK CONDITIONAL
INSTABILITY OVER THE WESTERN HALF OF THE STATE. CAN/T COMPLETELY
RULE OUT SOME HIGHER BASED THUNDERSTORMS WITH THE INITIAL FRONTAL
PASSAGE SUNDAY BUT SUNDAY EVENING TO OVERNIGHT LOOK DRY FOR
PORTIONS OF KANSAS WEST OF HIGHWAY 281. OTHERWISE, TEMPERATURES
WILL BE SLIGHTLY COOLER BEHIND THE FRONT FOR SUNDAY WITH HIGHS IN
THE 80S ANTICIPATED.

MONDAY INTO TUESDAY WILL TURN QUIET AS THE REMNANT CLOSED
CIRCULATION FROM THE WEEKEND SYSTEM, SLOWLY WOBBLES AROUND THE
NORTHERN PLAINS. THE PACIFIC FRONT SHOULD STALL OVER THE SOUTHERN
PLAINS LEAVING DEEPER MOISTURE TRAPPED WELL SOUTH OF KANSAS.
HOWEVER, JET DYNAMICS MAY PRODUCE ENOUGH ASCENT TO TRIGGER SOME
WEAK HIGH BASED THUNDERSTORMS ON MONDAY BUT THEN DRY FOR TUESDAY
WITH HIGHS GENERALLY IN THE 70S TO LOWER 80S BOTH DAYS. QUESTIONS
STILL EXIST FOR WEDNESDAY INTO THURSDAY WITH THE EVOLUTION OF THE
UPPER PATTERN ALTHOUGH THEY GENERALLY AGREE ON A RIDGE BUILDING OVER
THE PLAINS AS A TROUGH DIGS INTO THE PACIFIC NORTHWEST. WHETHER
THE LEE TROUGH CAN DEEPEN ENOUGH UNDER THIS SETUP TO PULL THE
FRONT AND ASSOCIATED DEEPER MOISTURE BACK NORTH INTO KANSAS FOR
THUNDERSTORM DEVELOPMENT IS UNKNOWN. WILL LEAVE THIS PORTION OF
THE FORECAST RELATIVELY UNCHANGED DUE TO THE UNCERTAINTIES EXISTING
AT THIS POINT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 104 PM CDT FRI MAY 17 2013

A SIGNIFICANT AMOUNT OF LOW LEVEL MOISTURE WILL MOVE INTO
SOUTHWEST KANSAS TONIGHT. THIS WILL RESULT IN THE WIDESPREAD
DEVELOPMENT OF DENSE FOG...PARTICULARLY IN THE 08-13Z TIME FRAME
LATE TONIGHT/EARLY SATURDAY MORNING. WILL CARRY ONE-QUARTER MILE
VISIBILITY IN THE TAF FOR DDC AND GCK TERMINALS. DENSE FOG WILL
ERODE SHORTLY AFTER SUNRISE...BUT LOW STRATUS MAY PERSIST IN THE
HYS AREA THROUGH LATE MORNING.


&&

.PRELIMINARY POINT TEMPS/POPS...
DDC  67  91  60  83 /  10  20  30  20
GCK  67  93  58  81 /  10  20  20  20
EHA  66  94  58  81 /  10  10  10  10
LBL  67  97  58  84 /  10  10  10  10
HYS  66  90  63  81 /  10  20  40  30
P28  70  91  65  87 /  10  20  30  20

&&

.DDC WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY FROM 11 PM CDT /10 PM MDT/ THIS EVENING TO 9
AM CDT /8 AM MDT/ SATURDAY FOR KSZ043>045-061>064-074>080-
084>090.

FIRE WEATHER WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY
EVENING FOR KSZ061-062-074-075-084-085.

&&

$$

SYNOPSIS...UMSCHEID
SHORT TERM...UMSCHEID
LONG TERM...AJOHNSON
AVIATION...UMSCHEID