000
FXUS63 KLSX 182014
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
314 PM CDT SAT MAY 18 2013

.SHORT TERM...(THROUGH LATE TONIGHT)
ISSUED AT 312 PM CDT SAT MAY 18 2013

(TONIGHT)

THE PRIMARY CONCERN TONIGHT IS POTENTIAL THUNDERSTORM DEVELOPMENT
NORTH OF A NW-SE ORIENTED WARM FRONT THAT WILL LIFT ACROSS THE CWA
OVERNIGHT. GIVEN THE UNSTABLE AIRMASS IN PLACE OVER THE REGION
/MUCAPES ON THE ORDER OF 2500-3000J/KG AS PER THE RUC...GFS...AND
LOCAL WRF MODELS FOR TONIGHT/ ADDITIONAL WAA AND A VEERING LLJ COULD
CERTAINLY PROVIDE ENOUGH LIFT TO FIRE SOME STORMS DURING THE LATE
OVERNIGHT AND EARLY MORNING HOURS. THE 4KM WRF-NNM AND HRRR DEVELOP
SCATTERED STORMS TONIGHT NORTH OF THE FRONT...PARTICULARLY THROUGH
THE 09Z-12Z TIME FRAME. THUS...HAVE MAINTAINED TRENDS IN TONIGHT`S
FORECAST...INTRODUCING SCHC POPS AFTER MIDNIGHT WITH A FOCUSED AREA
OF CHC POPS MARCHING NORTHWARD THROUGH THE LATE OVERNIGHT HOURS AND
TOWARD DAYBREAK.

OTHERWISE...ANOTHER WARM NIGHT IS AHEAD FOR THE AREA...WITH LOW
TEMPERATURES EXPECTED TO DROP INTO THE MIDDLE 60S FOR SOUTHWEST
ILLINOIS TO UPPER 60S OVER MID MISSOURI AND FOR THE STL METRO AREA.

JP

.LONG TERM...(SUNDAY THROUGH NEXT SATURDAY)
ISSUED AT 312 PM CDT SAT MAY 18 2013

ON SUNDAY...WARM FRONT TO LIFT NORTH OF FORECAST AREA BY
MIDDAY...SO JUST HAVE SLIGHT CHANCE POPS DURING THE MORNING
HOURS...THEN BEST CHANCES OF STORMS IN CENTRAL/NORTHEAST MO...WEST
CENTRAL IL DURING THE AFTERNOON HOURS CLOSER TO THE MAIN WEATHER
SYSTEM. THE ACTIVITY RAMPS UP DURING SUNDAY EVENING AND THE
OVERNIGHT HOURS AS A SHORTWAVE ROTATES AROUND THE UPPER SYSTEM
THROUGH THE FORECAST AREA...THOUGH BEST CHANCES REMAIN OVER
CENTRAL/NORTHEAST MO...WEST CENTRAL IL ON NOSE OF LOW LEVEL JET.
WITH DECENT SHEAR AND INSTABILITY...AS WELL AS LOW LEVEL
MOISTURE...SEVERE STORMS ARE POSSIBLE OVER THIS AREA...WITH THE
MAIN THREAT BEING LARGE HAIL. OTHERWISE...WITH WARM FRONT LIFTING
NORTH OF FORECAST AREA AND 850 TEMPS APPROACHING 20C...WILL SEE
TEMPS WARM UP INTO THE MID TO UPPER 80S. LOWS SUNDAY NIGHT TO
REMAIN MILD...IN THE MID TO UPPER 60S.

ON MONDAY...ACTIVITY TO TAPER OFF A BIT...BEFORE RAMPING BACK UP
LATE MONDAY AFTERNOON AND THROUGH THE OVERNIGHT HOURS WITH NEXT
SIGNIFICANT SHORTWAVE AND ANOTHER ROUND OF SEVERE WEATHER POSSIBLE.
WITH MODELS CONTINUING TO SLOW DOWN THIS SYSTEM...WILL SEE THE
STORMS PERSIST THROUGH WEDNESDAY BEFORE TAPERING OFF AS FRONTAL
BOUNDARY FINALLY MOVES THROUGH. TEMPERATURES TO REMAIN ABOVE NORMAL
THROUGH THE FIRST PART OF THE WORK WEEK...BEFORE COOLING OFF TO NEAR
NORMAL TEMPS IN THE 70S FOR THE LAST HALF OF THE WORK WEEK.

WITH SLOW EXIT OF SYSTEM AND FRONTAL BOUNDARY STALLED OUT JUST SOUTH
OF FORECAST AREA ON THURSDAY...CHANCE POPS OVER SOUTHEAST HALF OF
FORECAST AREA STILL LOOKS GOOD. OTHERWISE...DRY WEATHER EXPECTED
FRIDAY AND SATURDAY.

BYRD
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1243 PM CDT SAT MAY 18 2013

FOG HAS DISSIPATED ACROSS THE REGION...THOUGH CIGS HAVE BEEN A BIT
SLOW TO RECOVER...PARTICULARLY ACROSS NORTHEAST MO AND OVER THE
OZARKS. LATEST VISIBLE SATELLITE IMAGERY SHOWS AN EXTENSIVE
CUMULUS FIELD DEVELOPING OVER THE MISSISSIPPI VALLEY...THOUGH
EXPECT THE GRADUAL IMPROVEMENT IN CIGS TO CONTINUE THIS
AFTERNOON...WITH JUST SOME SCT VFR CLOUDS EXPECTED.

A NW-SE ORIENTED WARM FRONT WILL SHIFT NORTHWARD ACROSS THE REGION
OVERNIGHT TONIGHT...AND MODELS CONTINUE TO INDICATE THE
DEVELOPMENT OF SOME SHRA/TSRA ALONG AND AHEAD OF THE ADVANCING
WARM FRONT. FOR NOW...HAVE INCLUDED MENTION OF VCSH FOR AREA TAF
SITES DURING THE EARLY MORNING HOURS...AND WILL DEFER TO LATER TAF
ISSUANCES TO FURTHER PIN DOWN TIMING AND/OR MENTION OF TSRA.
OTHERWISE...WINDS WILL REMAIN SOUTHEASTERLY TODAY AND VEER TO
THE SOUTH ON SUNDAY...INCREASING TO ABOUT 10-12KT WITH SOME GUSTS
AS RETURN FLOW SETS IN.

SPECIFICS FOR KSTL...

CIGS ARE EXPECTED TO CONTINUE TO IMPROVE TO SCT VFR THIS
AFTERNOON...WITH LIGHT SOUTHEAST WINDS. OVERNIGHT TONIGHT A WARM
FRONT WILL DRIFT NORTH ACROSS THE AREA...AND MODELS CONTINUE TO
INDICATE SOME SHRA/TSRA DEVELOPMENT ACCOMPANYING THE FRONT. HAVE
CURRENTLY INCLUDED VCSH MENTION FOR KSTL FROM 10-13Z...THOUGH
TIMING WILL LIKELY NEED REFINED IN LATER TAF ISSUANCES...ALONG
WITH POTENTIAL THUNDER MENTION WHEN COVERAGE/INTENSITY BECOMES
MORE CLEAR. WINDS WILL VEER TO THE SOUTH TOMORROW BEHIND THE
ADVANCING WARM FRONT...INCREASING TO 10-12KT AND GUSTING TO
20-22KT BY THE AFTERNOON.

JP
&&

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

$$
WFO LSX