Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KLSX 281129
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
629 AM CDT FRI AUG 28 2015

.SHORT TERM:  (THROUGH LATE THIS AFTERNOON)
ISSUED AT 340 AM CDT FRI AUG 28 2015

MID AND HIGH CLOUDS ASSOCIATED WITH SHOWERS AND THUNDERSTORMS
CONTINUE TO STREAM IN ACROSS FORECAST AREA EARLY THIS MORNING AHEAD
OF COLD FRONT. DESPITE LOW LEVEL MOISTURE THAT WILL BE ON THE
INCREASE TODAY ON SOUTHERLY FLOW AHEAD OF THE COLD FRONT, THERE IS A
LOT OF DRY AIR TO OVERCOME. FEEL THAT BEST CHANCES OF SOME SHOWERS
AND A FEW THUNDERSTORMS WILL BE OVER CENTRAL AND NORTHEAST MISSOURI
AS WELL AS WEST CENTRAL ILLINOIS, BUT COVERAGE WILL BE SCATTERED.
OTHERWISE, TEMPERATURES TO REMAIN A BIT BELOW NORMAL IN THE LOW TO
MID 80S.

BYRD

.LONG TERM:  (TONIGHT THROUGH THURSDAY)
ISSUED AT 340 AM CDT FRI AUG 28 2015

THERE IS GOOD AGREEMENT IN THE 00Z GUIDANCE THAT FRONTAL
BOUNDARY AND ASSOCIATED SHORTWAVE SHOULD ALLOW THUNDERSTORMS
THREAT TO SLOWLY EXPAND OVER THE NORTHWEST HALF OF THE CWA
TONIGHT...WITH THE STL METRO LIKELY ON THE EASTERN EDGE OF THE
THREAT DURING THE PREDAWN HOURS.  DUE TO PROGGED LOW LEVEL
FORCING AHEAD OF THE FRONT, HAVE UPPED POPS INTO LIKELY CATEGORY
OVER OUR EXTREME NORTHWEST COUNTIES.

HOWEVER...FROM SATURDAY MORNING ON FEATURES AND MODEL SPECIFICS
BEGIN TO DIVERGE AND BECOME INCREASING NEBULOUS.  WHILE MODELS DO
AGREE THAT NORTHERN PORTION OF THE SHORTWAVE WILL CONTINUE TO PRESS
INTO THE LOWER GREAT LAKES DURING THE DAY...THEY DISAGREE WITH THEIR
HANDLING OF THE SOUTHERN PORTION OF THE SHORTWAVE ENERGY AS IT
STRETCHES SOUTHEAST AND POSSIBLY MERGING WITH ANOTHER WEAK
CIRCULATION ALONG THE GULF COAST (WHICH APPEARS TO ORIGINATE WITH
A BIT OF ENERGY THAT BREAKS OFF FROM THE BASE OF THE CURRENT EAST
COAST TROF). GFS AND NAM SUGGEST SOME TYPE OF REMNANT CIRCULATION
TAKING UP RESIDENCE IN THE VICINITY OF SW MO BY SUNDAY WITH
RESIDUAL SURFACE FRONT BECOMING STATIONARY OVER THE AREA...WHILE
ECMWF WANTS TO PUSH THE INCREASINGLY WEAK SHORTWAVE ENERGY AND
SURFACE BOUNDARY SOUTH WITH TIME.

IF NAM AND GFS SOLUTIONS DO COME TO FRUITION ON SUNDAY...AND IF NAM
LOW LEVEL MOISTURE FORECAST (WHICH IS OFTEN TOO HIGH) ALSO
VERIFIES...THEN THE DRY FORECAST ON SUNDAY WILL BE IN JEOPARDY.
HOWEVER...WOULD LIKE TO SEE ADDITIONAL SUPPORT FOR THESE WEAK
FEATURES AND TRENDS BEFORE REINTRODUCING CONVECTION ON SUNDAY.  SO
FOR NOW HAVE CONTINUED TO TREND THE FORECAST TO THE ECMWF
SOLUTION...NAMELY THUNDESTORM CHANCES EXPANDING SOUTHEAST ACROSS THE
CWA DURING THE DAY ON SATURDAY THEN GRADUALLY DIMINISHING FROM NW TO
SE LATE SATURDAY AFTERNOON AND SATURDAY NIGHT.

DESPITE THE DISCREPANCY IN THE UA PROGS ON SUNDAY...MEDIUM RANGE
SOLUTIONS REMAIN IN GOOD RUN TO RUN AND MODEL TO MODEL AGREEMENT
THAT WESTERN RIDGE WILLL BE EXPANDING EAST INTO THE MID MISSISSIPPI
AND OHIO VALLEYS DURING THE UPCOMING WEEK.  THIS SHOULD MEAN DRY
WEATHER FOR THE FA...ALONG WITH TEMPERATURES REBOUNDING TO LATE
SUMMER LEVELS WITH HIGHS IN THE UPPER 80S-LOWER 90S.

TRUETT
&&

.AVIATION:  (FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 621 AM CDT FRI AUG 28 2015

VFR CONDITIONS TO PERSIST THROUGH THE FORECAST PERIOD. IN THE
MEANTIME, NEXT FRONTAL BOUNDARY TO APPROACH REGION. SHOWERS AND
THUNDERSTORMS WILL BE SCATTERED IN NATURE AND HARD TO PIN DOWN IF
THEY WILL AFFECT TAF SITES, SO KEPT TAFS DRY FOR NOW. DID ADD
VICINITY TS MENTION FOR KUIN AND KCOU AFTER 06Z-07Z SATURDAY.
OTHERWISE, LIGHT SOUTHEAST TO SOUTH WINDS TO PICKUP TO BETWEEN 10
AND 15 KTS BY MID MORNING, BEFORE DIMINISHING THIS EVENING.

SPECIFICS FOR KSTL:
VFR CONDITIONS TO PERSIST THROUGH THE FORECAST PERIOD. IN THE
MEANTIME, NEXT FRONTAL BOUNDARY TO APPROACH REGION. SHOWERS AND
THUNDERSTORMS WILL BE SCATTERED IN NATURE AND HARD TO PIN DOWN IF
THEY WILL AFFECT METRO, SO KEPT TAF DRY FOR NOW. OTHERWISE, LIGHT
SOUTHEAST WINDS TO PICKUP FROM THE SOUTH BETWEEN 10 AND 15 KTS BY
16Z FRIDAY, BEFORE DIMINISHING THIS EVENING.

BYRD
&&

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

$$
WFO LSX


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.