Tornadoes and Hail in Kansas, August 11 to 12, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DODGE CITY KS
245 PM CDT SUN AUG 11 2002

MAIN FORECAST CHALLENGE IS HOW MUCH OF A COOL DOWN WILL BE FELT
ACROSS SOUTHWEST KS BY TUESDAY.

DAYS 1-2...
KGLD RADAR AND SAT LOOP EARLIER TODAY SHOWING AN OUTFLOW BOUNDARY
MOVING INTO OUR NORTHERN CWA. LEE TROF/DEVELOPING DRY LINE EXTENDED
SOUTH ACROSS ERN COLORADO. BEST MOISTURE AND WEAKEST CAP HOWEVER WAS
PLACE OVER OUR EASTERN CWA WHICH IS WHERE BEST AFTERNOON CU HAVE
BEEN DEVELOPING THIS AFTERNOON AS CONVECTIVE TEMPERATURE BEGINS TO
GET EXCEEDED. MODELS CONTINUE TO PROG A WEAK VORT LOBE TO CROSS
WESTERN KS LATER THIS EVENING SO WITH COOLER 7H TEMPS AND BETTER
MOISTURE PRESENT IN OUR EAST CAN NOT RULE OUT SOME CONVECTION
DEVELOPING HERE. ALSO HARD TO IGNORE OUR BOUNDARIES TO OUR WEST AND
NORTH, ESPECIALLY OUR NORTH. CURRENT FORECAST ALREADY HAS SMALL POPS
GOING IN THE EAST AND WILL KEEP THIS GOING BUT WILL ALSO NOW MENTION
SMALL POPS IN THE WEST.

MAJOR CHANGES BEGIN TO SHAPE ON MONDAY AS OUR COLD FRONT ENTERS NW
KS BY 12Z MON AND OUR NEXT MAJOR UPPER WAVE DROPS SOUTH INTO WY.
AVN/ETA/NGM STILL PLACES FROPAS AT GCK, HYS AND EHA AROUND 18Z, DDC
AROUND 21Z AND P28 AROUND 00Z. WILL THEREFORE CONTINUE TO FOLLOW
THIS TIMING. MODELS ALSO SHOWING BETTER MOIST CONV DEVELOP DURING
THE AFTERNOON AS OUR FRONT MOVES SOUTH/SOUTHEAST OF DDC WITH LIS
DECREASING TO -4 TO -6C/KM. ALTHOUGH COULD STILL SEE SOME CONVECTION
EARLIER IN THE DAY WITH THIS FRONT AS IT CROSSES THE CWA, IT APPEARS
THE BETTER DYNAMICS WILL BE LOCATED IN OUR S/SE CWA IN THE
AFTERNOON. WILL THEREFORE PLACE HIGH CHC POPS IN THE SE AND ONLY SLT
CHC POPS IN THE NW.

BY MONDAY NIGHT OUR WY (THE MORE SIG VORT LOBE) WILL DROP SOUTH INTO
EAST CENTRAL CO BY 12Z TUE. RIGHT ENTRANCE REGION OF 25H JET ALSO
WILL BE PLACED NEAR WESTERN KS BY 12Z TUES. WITH LIFT PRESENT AND
MOISTURE POOLING BEHIND OF COLD FRONT WILL THEREFORE GO WITH HIGH
CHC/LIKELY POPS LATE MONDAY NIGHT ACROSS ALL THE CWA. WILL ALSO
CONTINUE HIGH CHC/LIKELY POPS INTO TUESDAY AS THIS WAVE MOVES EAST
ACROSS THE STATE ON TUESDAY. CLOUDS, PCPN AND CURRENT OBS IN SRN
CANADA IN THIS AIR MASS LOOKS AS IF TEMPS WILL REMAIN WELL BELOW
NORMAL ON TUESDAY. THE 12Z FWC/MAV NOT LOOKING TO BAD ON FORECAST
HIGHS. GUIDANCE MAY EVEN BE A BIT TOO WARM IN THE SOUTH WHERE PCPN
AND CLOUDS MORE LIKELY TO HOLD ON ALL DAY. WILL THEREFORE FOLLOW THE
GUIDANCE TREND BUT WILL TRIM A FEW MORE DEGREES OFF ACROSS THE
SOUTH. WILL TAPER OFF PCPN AND EVEN TRY TO BRING A CLEARING TREND
BEHIND OUR S/W TROF WHICH WILL BE CROSSING THE CWA EARLY IN THE DAY.

THANKS FOR THE CORD...ICT, OUN.

DAYS 3-7...

SIGNIFICANT REGIME TRANSITION, ESPECIALLY ACROSS THE EAST ASIAN/
PACIFIC/NORTH AMERICAN SECTOR, IS WELL UNDERWAY AT THIS TIME.  THIS
CHANGE MAY BE LINKED TO THE RELATIVELY PERSISTENT (ABOUT 2-3 WEEKS)
AND VERY LARGE AREA OF DEEP MOIST TROPICAL CONVECTION FROM ROUGHLY
160 DEG W TO 60 DEG E, FROM ABOUT 10 DEG SOUTH OF THE EQUATOR TO
ROUGHLY 25 DEG N.

THIS AREA OF THUNDERSTORMS IS GENERALLY BEING FORCED BY
ANOMALOUSLY WARM SEA SURFACE TEMPERATURES, ESPECIALLY FOR THOSE
AROUND THE DATELINE, AND ALSO THE INDIAN MONSOON SYSTEM.  THERE IS
NOT MUCH EVIDENCE (YET) OF A MADDEN-JULIAN OSCILLATION (MJO).
FOR SOME ADDITIONAL DETAIL ABOUT THE PLANETARY-SCALE CIRCULATION,
PLEASE REFER TO THE FORECAST REASONING SECTION OF
HTTP://WWW.CRH.NOAA.GOV/DDC/WEEK2HTML.

THIS TRANSITION IS LEADING TO THE ESTABLISHMENT OF ROUGHLY A
MIDDLE/UPPER TROPOSPHERIC DATELINE TROUGH/140 DEG W RIDGE/100 DEG W
TROUGH, NORTH OF ABOUT 30 DEG.  IN ADDITION, THE EXTRATROPICAL
WESTERLIES ARE MIGRATING SOUTHWARD INTO THE LOWER 48 STATES, AT
LEAST FOR THIS UPCOMING WEEK.  UNDERSTANDING THE SUMMER BASE STATE,
THE ABOVE MENTIONED WAVE TRAIN CAN BE VIEWED AS A VERSION OF THE
PACIFIC/NORTH AMERICAN TELECONNECTION (WEAKLY NEGATIVE PHASE).  THIS
SITUATION WILL ALLOW PERHAPS SEVERAL SYNOPTIC-SCALE COLD FRONTS TO
MIGRATE ACROSS THE PLAINS DURING MY FORECAST PERIOD.  OF COURSE,
TIMING WILL BE DIFFICULT, AS WELL AS POSITIONING.

A FINAL POINT TO MAKE IS THAT THIS REGIME WILL BE SLOWLY
RETROGRESSIVE, SUCH THAT ABOUT A WEEK FROM NOW THE MID/UPPER
TROPOSPHERIC TROUGH AXIS INITIALLY AROUND 100 DEG W SHOULD BE ALONG
THE WEST COAST OF NORTH AMERICA, WITH HEIGHT RISES FIRST OVER THE
SOUTHEAST US, AND THEN EVENTUALLY THE CENTRAL PLAINS (AGAIN -- WHAT
HAS BEEN OBSERVED MUCH OF THIS SUMMER).

ALL OF THE OPERATIONAL GLOBAL NWP ARE CONVERGING TO THIS SCENARIO,
AFTER A PERIOD OF LOW SKILL.  THE LATTER IS OFTEN THE CASE DURING A
REGIME TRANSITION.  UNDERSTANDING THEIR BIASES, ETC., I HAVE NO REAL
NWP PREFERENCE.  HOWEVER, I THINK THE DETERMINISTIC ECMWF FROM 1200
UTC 10 AUGUST INITIAL CONDITIONS AND THE 1200 UTC 11 AUGUST AVN ARE
THE CLOSEST TO THE REAL ATMOSPHERE.

GOING EXTENDED FORECAST IS REASONABLE.  ONE OF THE SOURCE REGIONS OF
THE UPCOMING COOL AIR INTRUSION, WHICH AFFECTS MY CWA DAYS 1 AND 2,
IS COMING FROM THE ARCTIC LATITUDES OF NORTHWESTERN CANADA.  THUS I
WILL LIKELY LOWER MINIMUM TEMPERATURES INTO THE 50S FOR WEDNESDAY
MORNING (SHOULD NOT BE ANY RECORD LOWS), AND CORRESPONDINGLY LOWER
THE MAX TEMPERATURES FOR THAT DAY.  I WILL LEAVE IN THE MENTION OF
THUNDERSTORMS FOR THE OVERNIGHT HOURS OF WEDNESDAY INTO THURSDAY.
TEMPERATURES SHOULD WARM TO AT LEAST NORMAL FROM THURSDAY ONWARD.
FINALLY, ALL FACTORS CONSIDERED, I WILL INTRODUCE ANOTHER
OPPORTUNITY OF THUNDERSTORMS FOR MY CWA ON DAY 6.  OUR LOCAL 8-10
DAY (8/19-21) FORECAST WILL READ ABOVE NORMAL TEMPERATURES AND BELOW
NORMAL PRECIPITATION (BACK TO THE RIDGE).

PRELIMINARY GUIDANCE FOR COORDINATION ONLY. OFFICIAL FORECASTS ARE
CONTAINED WITHIN THE DODGE CITY ZONE FORECAST.

DDC   67  82  58  72 /  30  20  50  30
GCK   65  80  58  72 /  30  20  50  40
EHA   65  81  58  70 /  20  30  70  70
LBL   67  86  61  69 /  20  50  70  70
HYS   68  83  58  71 /  30  30  50  30
P28   70  90  63  69 /  20  50  70  70

.DDC...NONE.

FCSTID =18/23