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000
FXUS63 KLSX 161738
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1238 PM CDT THU MAY 16 2013

.UPDATE...
ISSUED AT 1102 AM CDT THU MAY 16 2013

ONGOING CLUSTER OF CONVECTION ACROSS ILLINOIS WILL CONTINUE TO
DEVELOP FURTHER NORTH ON ITS OWN OUTFLOW...TOWARD AREA OF INSTABILITY
THAT PER SPC MESOANAYLSIS GRAPHICS HAS INCREASED TO AROUND 1000
J/KG. ALSO EXPECT AN UPTICK IN CONVECTION THIS AFTERNOON ALONG
AND NORTH OF A WEAK SURFACE TROF THAT LIES ACROSS NORTHEAST
MISSOURI AND WEST CENTRAL ILLINOIS. FURTHER SOUTH...DENSE CIRRUS
WILL INHIBIT DESTABILIZATION AND KEEP THUNDERSTORM CHANCES LOWER
BUT AREA OF RAIN SHOWERS IN NORTH CENTRAL ARKANSAS WILL PIVOT
NORTH INTO THE SOUTHERN CWA BY EVENING.

TEMPERATURES WILL GENERALLY TOP OUT NEAR 80...BUT WHERE IT RAINS
OR CLOUDS ARE THICKER TEMPERATURES WILL REMAIN IN 70S.

CVKING

&&

.SHORT TERM...(THROUGH LATE THIS AFTERNOON)
ISSUED AT 333 AM CDT THU MAY 16 2013

MAIN CONCERN WILL BE COVERAGE OF THUNDERSTORMS TODAY.  THUNDERSTORMS
THAT WERE OVER THE NORTHERN CWA ALONG THE COLD FRONT LAST EVENING
HAVE SHIFTED NORTH OF THE AREA EARLY THIS MORNING.  EXPECT SCATTERED
SHOWERS AND THUNDERSTORMS TO REDEVELOP OVER THE AREA LATER THIS
MORNING/AFTERNOON WITH INCREASED ASCENT AS UPPER LOW OVER OKLAHOMA
MOVES EASTWARD INTO ARKANSAS.  LATEST RUNS OF THE RAP/LOCAL WRF SHOW
THAT THERE WILL BE INCREASING 925-850MB MOISTURE CONVERGENCE AHEAD
OF THE LOW OVER SOUTHEAST MO/SOUTHWEST IL.  A SECOND FOCUS FOR
DEVELOPMENT WILL BE ALONG THE SURFACE FRONT OVER THE NORTHERN CWA
BEFORE IT LIFTS NORTH OF THE AREA TONIGHT.  WILL GO NO HIGHER THAN
CHANCE POPS AT THIS POINT GIVEN THAT OVERALL FORCING AND INSTABILITY
ARE NOT PARTICULARLY IMPRESSIVE AND THE INSTABILITY IS PARTIALLY
CAPPED.

CURRENT TEMPERATURES ARE RELATIVELY WARM...AND MIXING DOWN 850MB
TEMPERATURES SUPPORT GOING HIGHS WHICH ARE CLOSE TO MOS GUIDANCE.

BRITT

.LONG TERM...(TONIGHT THROUGH WEDNESDAY)
ISSUED AT 333 AM CDT THU MAY 16 2013

WEAKENING FRONT WILL MOVE N-NE OF OUR AREA TGT.  MAY STILL HAVE
WIDELY SCATTERED THUNDERSTORMS DURING THE EVNG.  SCATTERED SHOWERS
AND STORMS MAY CONTINUE ACROSS SERN MO LATE TGT AHEAD OF THE UPPER
LEVEL LOW/TROUGH MOVING SLOWLY EWD THROUGH SRN MO AND NRN AR AS
DEPICTED BY THE NCEP 4 KM WRF. SCATTERED SHOWERS AND STORMS MAY
DEVELOP AGAIN ON FRI INTO FRI EVNG AS A WEAK SHORTWAVE DROPS SEWD
THROUGH NRN MO AND INTO IL. THE UPPER LEVEL RIDGE SHOULD REBUILD
OVER MO FRI NGT AND SAT...AND THIS COUPLED WITH PERSISTENT SLY
SFC/LOW LEVEL FLOW WILL LEAD TO WARMER HIGH TEMPERATURES FOR THE
WEEKEND WITH ABOVE NORMAL TEMPERATURES ESPECIALLY ON SUN. MAY HAVE
ISOLATED TO WIDELY SCATTERED DIURNAL SHOWERS AND STORMS SAT AFTN
INTO SAT EVNG. SCATTERED SHOWERS AND STORMS MAY OCCUR SUN AFTN
ACROSS NERN AND CNTRL MO AS A SW FLOW SHORTWAVE MOVES NEWD
THROUGH THIS AREA AHEAD OF AN UPPER LEVEL TROUGH MOVING SLOWLY
EWD INTO THE NRN PLAINS. THE POPS SHOULD INCREASE SUN NGT AND MON
AS THE UPPER LEVEL TROUGH/LOW MOVES NEWD THROUGH THE NRN PLAINS
WITH STRENGTHENING SWLY LOW LEVEL FLOW BRINGING INCREASING LOW
LEVEL MOISTURE INTO OUR AREA. THE LATEST GFS MODEL RUN IS A LITTLE
WEAKER WITH THIS STORM SYSTEM AND ITS ASSOCIATED COLD FRONT...AND
WILL LEAN MORE TOWARD THE STRONGER ECMWF SOLUTION. ALTHOUGH THERE
MAY BE WEAK SW FLOW SHORTWAVES AND ASSOCIATED WEAK SFC TROUGHS
MOVING THROUGH OUR AREA...THE MAIN COLD FRONT WILL NOT LIKELY
MOVE SEWD THROUGH OUR AREA TIL TUE. THERE WILL LIKELY BE STRONG TO
SEVERE CONVECTION AHEAD AND ALONG THIS COLD FRONT. COOLER...NEAR
NORMAL TEMPERATURES CAN BE EXPECTED BEGINNING TUE AND CONTINUING
FOR THE REST OF THE EXTENDED FORECAST AS A SLOW MOVING UPPER LEVEL
LOW AND ASSOCIATED SFC LOW MOVE SEWD THROUGH IA AND NRN IL ON WED
WITH COOLER AIR FILTERING INTO OUR REGION BEHIND THE COLD FRONT.

GKS

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1235 PM CDT THU MAY 16 2013

BELIEVE GREATEST COVERAGE OF CONVECTION THIS AFTERNOON WILL BE IN
UIN AREA...WHERE BEST HEATING/INSTABILITY WILL CO-EXIST IN VICINITY OF
FRONTAL BOUNDARY AND/OR RESIDUAL OUTFLOW FROM LAST NIGHTS
CONVECTION. AMS-TYPE ACTIVITY CERTAINLY POSSIBLE FURTHER S TO THE
I-70 CORRIDOR...BUT BELIEVE THAT THESE STORMS WILL BE MUCH MORE
HIT AND MISS. OUTSIDE OF A TSRA THREAT AT SUS FOR THE NEXT 30-45
MIN OR SO BASED ON LATEST DEVELOPMENT...WILL KEEP COU AND STL AREA
TAFS DRY FOR THE AFTERNOON/EARLY EVENING HOURS. OUTSIDE OF STORMS
EXPECTING A SCT-BKN CU DECK 4-5KFT...WITH BROADER RAIN SHIELD
ASSOCIATED WITH UPPER LOW REMAINING S OF ALL TAF SITES.

WITH LOW LEVEL MOISTURE SPIRALLING AROUND LOW...IN THE STL AREA
HAVE CONTINUED TREND OF EARLIER FORECASTS OF INTRODUCING MVFR CIGS
DURING THE PREDAWN HOURS.  HAVE TRIED TO BE A BIT MORE OPTIMISTIC
AT UIN AND COU...WITH CIGS ALSO DROPPING BUT REMAINING LOW END
VFR.

SPECIFICS FOR KSTL...CURRENT ACTIVITY IN THE METRO AREA WILL MISS STL
TAF TO THE WEST. WHILE CAN`T TOTALLY RULE OUT ADDITIONAL
DEVELOPMENT THIS AFTERNOON...DUE TO ITS SPOTTY NATURE WILL KEEP
STL TAF DRY ATTM AND NOWCAST THIS THREAT AS NEEDED.  OTHERWISE...
EXPECTING A BKN CU DECK 4-5KFT INTO THE EVENING...WITH MVFR CIGS
DEVELOPING DURING THE PREDAWN HOURS.

TRUETT

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
IL...NONE.
&&

$$

WFO LSX