Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 021912
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
212 PM CDT WED SEP 2 2015

.SHORT TERM:  (THROUGH LATE TONIGHT)
ISSUED AT 207 PM CDT WED SEP 2 2015

AN UPPER LEVEL RIDGE IS DOMINATING THE SOUTHERN CONUS WITH
SOMEWHAT STRONGER WESTERLIES ACROSS NORTHERN MO AND CENTRAL IL
WITH A WEAK UPPER LEVEL DISTURBANCE STRADDLING THE MO-IA BORDER.
AN EARLIER AREA OF SHRA/TSRA HAS SINCE DISSIPATED OVER NORTH-
CENTRAL AND NORTHEAST MO WHERE THERE REMAINS A RATHER THICK LAYER
OF HIGH CLOUDS STILL, WITH A DIURNAL CUMULUS CLOUD FIELD THAT HAS
DEVELOPED FURTHER TO THE SOUTH AND EAST...GENERALLY FOR AREAS S
OF I-70 IN MO AND SE OF I-55 IN IL. TEMPS HAVE RISEN TO ABOVE
AVERAGE VALUES ONCE AGAIN THIS AFTERNOON, WITH READINGS IN THE
UPPER 80S AND LOWER 90S FOR MOST LOCATIONS.

MAY SEE A LIMITED ISOLATED TSRA EVENT ONCE AGAIN LATE THIS
AFTERNOON UNTIL 00Z/7PM CDT WITH DRY CONDITIONS ANTICIPATED
OVERNIGHT WITH IT BEING VERY QUESTIONABLE WHETHER THE WEAK UPPER
LEVEL DISTURBANCE WILL BE ABLE TO KICK ANYTHING OFF OVERNIGHT.

TEMPERATURES OVERNIGHT SHOULD BE NEAR PERSISTENCE VALUES: MID 60S
IN THE EASTERN OZARKS TO THE MID 70S IN THE URBAN HEAT ISLAND OF
STL CITY, WITH NEAR 70 MOST EVERYWHERE ELSE.

TES

.LONG TERM:  (THURSDAY THROUGH NEXT WEDNESDAY)
ISSUED AT 207 PM CDT WED SEP 2 2015

THE PERSISTENT UPPER LEVEL RIDGE NOTED ACROSS THE CENTRAL CONUS
TODAY IS FORECAST TO REMAIN IN PLACE THROUGH THE WEEKEND. A
SPRAWLING SURFACE HIGH IS ALSO FORECAST TO REMAIN OVER THE
GREATER OHIO VALLEY REGION DURING THIS TIME. WITH LITTLE CHANGE IN
BOTH THE SURFACE AND THE UPPER AIR PATTERNS EXPECTED OVER THE
NEXT SEVERAL DAYS, IT IS LIKELY THAT THERE WILL BE LITTLE CHANGE
IN THE DAY-TO-DAY WX CONDITIONS. EXPECT HIGHS IN THE LOW TO MID
90S, OVERNIGHT LOWS AROUND 70, TRANSIENT CLOUDINESS, AND A
NOTICEABLY HUMID AIR MASS. THERE IS LITTLE CHANCE OF WIDESPREAD
RAINFALL UNTIL LATE THIS WEEKEND/EARLY NEXT WEEK.

MODELS SHOW THAT THE UPPER PATTERN STARTS TO BREAK DOWN LATE THIS
WEEKEND/EARLY NEXT WEEK IN RESPONSE TO A LOW PRESSURE SYSTEM
WHICH MOVES OVER THE PAC NW ON FRIDAY, THEN DIPS SOUTHWARD INTO
CA/NV BEFORE LIFTING BACK NORTHEASTWARD INTO THE NORTHERN PLAINS
OVER THE WEEKEND. THE LOW PRESSURE SYSTEM`S TRAILING COLD FRONT
EDGES TOWARD THE MO/IA BORDER ON MON NIGHT BEFORE LIFTING BACK
NORTHWARD AS A WARM FRONT ON TUESDAY. MCONV ON THE NOSE OF LLJS
SUPPORTS CHC POPS ON MON/TUE. A NEW SURFACE WAVE THEN DEVELOPS
ALONG THE STALLED BDRY AND RIDES NORTHEASTWARD DURING THE MIDDLE
OF THE WEEK, SENDING THE CDFNT THROUGH THE CWA ON WED/THU
(ALTHOUGH ECMWF/GFS DISAGREE ON THE SPEED OF THE FRONT). PCPN CHCS
FOR WED ARE TIED TO SFC FORCING WITH THE FRONT.

KANOFSKY

&&

.AVIATION:  (FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1250 PM CDT WED SEP 2 2015

VFR CONDITIONS, S-SW SURFACE WINDS, AND DRY WX ARE EXPECTED TO
CONTINUE AT THE TAF SITES THRU MUCH OF THE VALID PERIOD. LEFT THE
MVFR VSBYS EARLY THURSDAY MORNING IN PLACE AT ALL SITES BUT KSTL
FOR THIS PACKAGE TO BE RE-EVALUATED FOR THE 00Z PACKAGE WHEN
OBSERVATIONAL DATA COMES IN FOR SUCH PARAMETERS AS CROSSOVER TEMPS
AND A BETTER HANDLE ON CLOUD COVER IS ATTAINED.

TES

&&

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

$$

WFO LSX



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