Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 041759
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1259 PM CDT TUE AUG 4 2015

.SHORT TERM:  (THROUGH LATE THIS AFTERNOON)
ISSUED AT 358 AM CDT TUE AUG 4 2015


QUASI-STATIONARY FRONT LOOKS TO HELP PROVIDE FOCUS FOR
SCATTERED THUNDERSTORMS DURING THE DAY TODAY. BEST CHANCES FOR
STORMS THROUGHOUT MOST OF THE DAY TO BE IN CLOSE PROXIMITY TO THIS
FRONTAL BOUNDARY WHERE SFC CONVERGENCE IS MAXIMIZED. FRONT WILL
LIKELY WAVER AROUND A BIT AND MAY SAG BACK TO THE SOUTH AND WEST
(OR AT LEAST THE EFFECTIVE FRONT) DUE TO CONVECTIVE OUTFLOWS. MEAN
FRONTAL BOUNDARY LIKELY TO BE PLACED FROM THE NW TO SE ROUGHLY
THROUGH THE MIDDLE OF THE CWFA.

TEMPERATURE GUIDANCE ADVERTISING HIGHS IN THE 80S LOOKED REASONABLE
AND DID NOT DEVIATE TOO MUCH. WARMEST HIGHS WILL BE ACROSS CENTRAL
AND SOUTHEAST MISSOURI ON THE WARM SIDE OF THE BOUNDARY WITH LOW 80S
FURTHER TO THE NORTH AND EAST ACROSS NORTHEAST MISSOURI THROUGH
SOUTH-CENTRAL ILLINOIS.


GOSSELIN

.LONG TERM:  (TONIGHT THROUGH MONDAY)
ISSUED AT 358 AM CDT TUE AUG 4 2015


(TONIGHT - THURSDAY)

A LEAD SHORTWAVE TROUGH WILL APPROACH THE REGION EMBEDDED WITHIN WNW
FLOW ALOFT. DCPVA AHEAD OF THIS FEATURE COINCIDENT WITH A
STRENGTHENING SOUTHWESTERLY LLJ AT 850 HPA LOOKS TO PRODUCE A GOOD
CHANCE OF SHOWERS AND STORMS...PARTICULARLY LATE TONIGHT ALONG THE
MISSOURI RIVER.

UNFORTUNATELY...MODELS BEGIN TO DIVERGE QUITE SUBSTANTIALLY ALREADY
ON WEDNESDAY AND THEREAFTER. MAIN DIFFERENCES LIE WITH SPEED OF
SECONDARY SHORTWAVE TROUGH/ITS INTERACTION WITH LEAD SHORTWAVE AND
TRACK/SPEED OF LOW-LEVEL CYCLONE. WENT WITH A MODEL CONSENSUS FOR
POPS AND OTHER SENSIBLE WEATHER ELEMENTS FOR WEDNESDAY THROUGH
THURSDAY. REGARDLESS...THE MIDWEEK TIMEFRAME APPEARS TO BE QUITE
ACTIVE WITH THE PRIMARY CONCERN FOR HEAVY RAINFALL WHICH MAY RESULT
IN FLASH FLOODING AND RENEWED RIVER/STREAM FLOODING. LATE WEDNESDAY
AFTERNOON AND ESPECIALLY WEDNESDAY NIGHT APPEAR TO BE OF HEIGHTENED
CONCERN FOR HEAVY RAIN AS BOTH THE GFS/NAM HAVE STRONG MOISTURE
CONVERGENCE ON THE NOSE OF A 40-50 KT LLJ...GOOD UPPER-LEVEL
SUPPORT...PWAT VALUES OVER 2 INCHES...AND FAVORABLE THERMODYNAMIC
PROFILES ALL HIGHLIGHTING POSSIBILITY OF HEAVY RAIN.

DUE TO HIGH DEGREE OF UNCERTAINTY FOR MIDWEEK AND...AT LEAST AT THE
MOMENT...FAIRLY RECEPTIVE SOILS...WILL HOLD OFF ON ISSUING A FLASH
FLOOD WATCH FOR NOW. ONE MAY BE NEEDED HOWEVER DOWN THE ROAD IF
MODEL CONSENSUS RISES AND/OR PARTS OF THE CWFA RECEIVE SUFFICIENT
RAINFALL OVER THE NEXT 24 HOURS TO SATURATE SOILS.

ACTIVE WEATHER BY THURSDAY AFTERNOON AT LEAST SHOULD PUSH OFF TO THE
SOUTH AND EAST WITH SUBSIDENCE BEHIND STOUT SECONDARY VORT MAX.
THURSDAY AFTERNOON LOOKS FAIRLY DRY WITH ONLY SCHC/CHC POPS AND HIGH
TEMPERATURES SLIGHTLY BELOW NORMAL.


(FRIDAY - MONDAY)

UPPER-LEVEL ANTICYCLONE BEGINS TO FLEX ITS MUSCLES ACROSS THE
SOUTHERN PLAINS BEGINNING FRIDAY AND HEADING INTO THIS UPCOMING
WEEKEND. COMPLEXITY OF FORECAST STAYS QUITE HIGH THOUGH AS MID-
MISSISSIPPI VALLEY STAYS ON THE NORTHEASTERN PERIPHERY OF
AFOREMENTIONED HIGH. TOO DIFFICULT TO PIN DOWN EXACTLY WHEN THERE
WILL BE CHANCES FOR SHOWERS/STORMS...DUE TO HIGH DEGREE OF
UNCERTAINTY WITH TIMING OF DISTURBANCES WITHIN THE "RING OF FIRE".

TEMPERATURES WILL LIKELY BE ON THE INCREASE BOTH DAY AND NIGHT
COMPARED TO THE MIDDLE OF THIS WEEK AS HEIGHTS RISE AND 850-HPA
TEMPERATURES WARM BACK OF +20C. NEAR NORMAL TEMPERATURES ARE MOST
LIKELY FOR THIS PERIOD...BUT BUST POTENTIAL DURING EACH DAY WILL BE
HIGH AS IN THE ABSENCE OF CLOUDS/STORMS TEMPS MAY SOAR WELL INTO THE
90S WHEREAS A CONVECTIVE COMPLEX COMING DOWN FROM THE MID-MISSOURI
VALLEY AT THE RIGHT TIME COULD HAVE HIGHS IN THE 70S/LOW 80S. DUE TO
VERY HIGH LEVEL OF UNCERTAINTY WITH POPS/CLOUD COVER...RELIED ON
MODEL CONSENSUS FOR TEMPERATURES.


GOSSELIN

&&

.AVIATION:  (FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1247 PM CDT TUE AUG 4 2015

SPECIFICS FOR KUIN: ONGOING SH/TS AT TAF ISSUANCE WILL PERSIST FOR
THE NEXT FEW HOURS BEFORE DIMINISHING WITH THE LOSS OF DAYTIME
HEATING. A SECOND ROUND OF PRECIPITATION IS EXPECTED LATE OVERNIGHT
BUT THE TIMING IS UNCERTAIN NEAR KUIN BECAUSE IT IS FARTHER NORTH.

SPECIFICS FOR KCOU: TWO PERIODS OF SH/TS ARE EXPECTED DURING THE
NEXT 24 HOURS. THE FIRST PERIOD WILL OCCUR THIS AFTERNOON DUE TO
DIURNAL HEATING INVOF A QUASISTATIONARY BOUNDARY AHEAD OF AN UPPER
LEVEL DISTURBANCE. THESE STORMS WILL LIKELY DIMINISH AFTER SUNSET.
THE NEXT PERIOD WILL OCCUR LATE TONIGHT AND LAST INTO TOMORROW.
THESE SH/TS WILL OCCUR AHEAD OF A SECOND UPPER LEVEL DISTURBANCE.
THE TIMING FOR THE OVERNIGHT PRECIPITATION IS STILL UNCERTAIN BUT
WILL PROBABLY NOT BEGIN UNTIL AFTER 03Z AT KCOU.

SPECIFICS FOR KSTL, KSUS, KCPS: TWO PERIODS OF SH/TS ARE EXPECTED
DURING THE NEXT 24-30 HOURS. THE FIRST PERIOD WILL OCCUR THIS
AFTERNOON DUE TO DIURNAL HEATING INVOF A QUASISTATIONARY BOUNDARY
WITH SUPPORT FROM AN UPPER LEVEL DISTURBANCE. THESE STORMS WILL
LIKELY DIMINISH AFTER SUNSET. THE NEXT PERIOD WILL OCCUR LATE
TONIGHT AND LAST INTO TOMORROW. THESE SH/TS WILL OCCUR AHEAD OF A
SECOND UPPER LEVEL DISTURBANCE. THE TIMING FOR THE OVERNIGHT
PRECIPITATION IS STILL UNCERTAIN BUT WILL PROBABLY NOT BEGIN UNTIL
AFTER 06Z IN THE ST LOUIS METRO AREA.

KANOFSKY

&&

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

$$

WFO LSX



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