Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 030447
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1147 PM CDT WED SEP 2 2015

.UPDATE:
Issued at 858 PM CDT Wed Sep 2 2015

WIDELY SCATTERED SHOWERS WERE ACROSS PARTS OF NORTH CENTRAL MO
AND SOUTH CENTRAL IA THIS EVENING. THIS ACTIVITY APPEARED TO BE
ASSOCIATED WITH LOW LEVEL MOISTURE CONVERGENCE AND WEAK WARM AIR
ADVECTION ON NOSE OF A 20-25 KT SOUTHWESTERLY LOW LEVEL JET. THE
PREVIOUS MODELS DID NOT HAVE A GOOD HANDLE ON THIS PRECIPITATION.
EVEN THE LATEST MODEL RUNS KEEP MOST OF THIS PRECIPITATION OUT OF
OUR FORECAST AREA TONIGHT. FOR NOW WILL JUST INCLUDE ISOLATED
SHOWERS/STORMS ACROSS NORTHEAST MO FOR THE REMAINDER OF THIS
EVENING. ANOTHER MILD AND MUGGY NIGHT WITH WEAK SOUTHERLY SURFACE
WINDS ON THE WESTERN OR NORTHWESTERN PERIPHERY OF THE SURFACE
RIDGE LOCATED JUST EAST/SOUTHEAST OF OUR AREA. LOWS WILL BE
SIMILAR TO THE PAST NIGHT...AND 5 TO 10 DEGREES ABOVE NORMAL FOR
EARLY SEPTEMBER.

GKS

&&

.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 06z TAFs through 06z Thursday Night)
Issued at 1139 PM CDT Wed Sep 2 2015

A few high-based spotty showers have developed across north
central MO this evening and are persisting as they drift
southeast. Present indications are they will avoid KUIN and will
hopefully dissipate before moving as far southeast as KCOU. Still
anticipating the potential for a short period of fog/br between
09-13z at all terminals except KSTL, with the possibility of
reducing the visibility to 4-6sm. Otherwise VFR flight conditions
to persist through Thursday with few-scattered diurnal cu from
midday into the afternoon.

Specifics for KSTL:

VFR flight conditions should prevail through the forecast period.

Glass

&&

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

$$

WFO LSX



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