FXUS63 KLSX 231806
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1206 PM CST WED DEC 23 2009
.UPDATE...
/1126 AM CST WED DEC 23 2009/
WILL BE EXPANDING THE FLOOD WATCH TO INCLUDE THE REST OF MY
CENTRAL MO COUNTIES. RADAR ESTIMATES ARE SHOWING A BAND OF 1 TO 2
INCHES OF RAIN HAS FALLEN OVER CALLAWAY...OSAGE AND MONTGOMERY
COUNTIES SO FAR...WITH A FEW BASINS AT OR JUST ABOVE FLASH FLOOD
GUIDANCE. IT IS STILL RAINING IN THIS AREA AND ADDITIONAL
CONVECTION HAS DEVELOPED OVER NERN OK. REST OF FLOOD WATCH STILL
LOOKS VALID GIVEN THAT MANY AREAS HAVE ALREADY RECEIVED UP TO AN
INCH OF RAINFALL.
BRITT
&&
.DISCUSSION...
/448 AM CST WED DEC 23 2009/
WAA SHRA WITH EMBEDDED TSRA ONGOING EARLY THIS MORNING INVOF
QUASISTATIONARY BDRY STRETCHED ACROSS KS/MO/IL WITH MORE DISCRETE
CONVECTION NOTED ACROSS NERN OK CLOSER TO THE SFC LOW. WFO LSX HAD
ACCUMULATED 0.7 INCHES OF RAIN AS OF 10Z AFTER A FEW CONVECTIVE
ELEMENTS PASSED DIRECTLY OVER THE OFFICE AND PROVIDED A FIRSTHAND
LOOK AT THE MODERATE TO HEAVY RAINFALL RATES OCCURING ACROSS PARTS
OF THE CWA. SREF/NAM/LOCAL WRF KEEP THIS BDRY NEARLY STATIONARY
THROUGH THE MORNING WITH SOME NWD MOVEMENT BY AFTERNOON. TEMPS WILL
CONTINUE RISING THROUGH THE DAY AND REMAIN NEARLY STEADY OVERNIGHT
AS S-SELY WINDS TRANSPORT WARM AND MOIST AIR NWD. GIVEN THE OBSERVED
DOWNPOURS OVER FROZEN GROUND EARLY THIS MORNING...HAVE CONTINUED THE
GOING FLOOD WATCH.
WATER VAPOR IMAGERY DEPICTS AN IMPRESSIVE STORM SYSTEM OVER THE SWRN
US AND A SHORTWAVE IN CANADA OVER THE BC/AB BORDER. CANADIAN
SHORTWAVE WAS POISED TO DROP SWD AND INTERACT WITH THE SRN SYSTEM
/FUJIWHARA EFFECT/ BEFORE THE VORTICITY CENTERS MERGE OVER THE
MIDWEST BY FRIDAY. WHILE MODELS HANDLE THESE SYSTEMS COMPARABLY...I
HAVE TWO SIGNIFICANT CONCERNS WITH RESPECT TO SYSTEM EVOLUTION.
FIRST...FLOW REMAINS BLOCKED OVER ERN CANADA WITH NO SIGNS OF
DECREASED MOISTURE CONTRAST ON WATER VAPOR IMAGERY...SUGGESTING THAT
BLOCKING WILL CONTINUE FOR THE NEAR FUTURE DESPITE PROGRESSIVE
SOLUTION DEPICTED BY ECMWF/GFS/GEM/UKMET. SECOND...23/00Z GEM AND
23/06Z GFS HAVE SHOWN A SEWD TREND WITH THE LOCATION OF THE SFC LOW
AS COMPARED TO PREVIOUS RUNS. A MORE SEWD TRACK FOR THE SFC LOW
WOULD RENEW CONCERNS FOR ACCUMULATION OF ADVISORY CRITERIA SNOWFALL
AFTER THE HEAVY RAIN ENDS...ESPECIALLY IN WRN PARTS OF THE CWA.
LATER SHIFTS WILL NEED TO MONITOR THESE TRENDS. THAT SAID...I STILL
EXPECT RAIN TO CHANGE TO SNOW LATE TOMORROW NIGHT AS COLD AIR
WRAPS AROUND THE BACK SIDE OF THE DEPARTING LOW. TIGHT PRESSURE
GRADIENT WILL CREATE STRONG GUSTY WINDS THU NIGHT THROUGH FRI NIGHT.
NO CHANGES MADE PAST 00Z SUN.
KANOFSKY
&&
.AVIATION...
/1145 AM CST WED DEC 23 2009/
FOR THE 18Z TAFS...
KSTL/KSUS...VSBYS AND CIGS HAVE IMPROVED TO MVFR AT SURROUNDING
OB SITES...HAVE PREVAILED SUCH CONDITIONS THRU 3Z WITH TEMPO IFR
FOR THE NEAR-TERM. COMPLEX FCST AS ANOTHER SFC LOW WILL DEEPEN
ACRS ERN TX AND LIFT NWD THRU THE MID-MS VLY. PRESENTLY SFC BNDRY
IS DRAPED ACRS CENTRAL MO THRU SRN IL...JUST SOUTH OF KSUS/KSTL.
AS THE SECOND SFC LOW LIFTS NWD WILL FIND THE REGION IN THE WARM
SECTOR WITH INCREASING SLY WINDS GUSTING AT TIMES WITH PREVAILING
IFR CONDITIONS. WE SHALL SEE THE ADVECTION OF A VERY MOIST AND
SLIGHTLY UNSTABLE AIRMASS ACRS THE TAF LOCALES RESULTING IN HEAVY
RAINS AND SCATTERED TSRA. WITH AFORMENTIONED CONDITIONS HAVE GONE
VCTS FOR NOW AND DO NOT EXPECT LIFR.
KCOU...SFC FRONTAL BNDRY JUST SOUTH BEHIND WHICH MVFR CONDITIONS
EXIST. HAVE PREVAILED MVFR WITH TEMPO IN THE NEAR-TERM FOR IFR-
LIFR IN ASSOCIATED WITH THE PRESENT HEAVY RAIN BAND PER RADAR
RETURNS. EXPECT THIS PRECIP TO ADVECT EWD...WILL NEED TO MONITOR
PSBL CONVECTIVE WEATHER IMPACTS TO THE EAST. WITH SFC LOW LIFTING NWD
AS WITH KSTL/KSUS EXPECT HEAVY RAINS AND SCATTERED TSRA THRU FCST
AREA. HAVE FOLLOWED THRU WITH IFR CONDITIONS AND VCTS AFTER 3Z
IMPROVING SLIGHTLY INTO 13Z WITH INCREASING SLY WINDS.
KUIN...LIFR CONDITIONS TO PREVAIL OVER THE NEXT SEVERAL HOURS AS
FCST AREA IS WELL NORTH OF THE STATIONARY BNDRY TO THE SOUTH AND
ENCOMPASSED IN A MUCH COOLER AIR MASS. DO NOT EXPECT CONDITIONS TO
IMPROVE UNTIL THE SECONDARY LOW TRACKS NWD WITH ASSOCIATED WARM
SECTOR AND STRONG SLY WINDS BY 14Z.
SIPPRELL
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR AUDRAIN-BOONE-
CALLAWAY-COLE-CRAWFORD-FRANKLIN-GASCONADE-IRON-JEFFERSON-
KNOX-LEWIS-LINCOLN-MADISON-MARION-MONITEAU-MONROE-
MONTGOMERY-OSAGE-PIKE-RALLS-REYNOLDS-SHELBY-ST. CHARLES-ST.
FRANCOIS-ST. LOUIS-ST. LOUIS CITY-STE. GENEVIEVE-WARREN-
WASHINGTON.
IL...FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR ADAMS IL-BOND IL-
BROWN IL-CALHOUN IL-CLINTON IL-FAYETTE IL-GREENE IL-JERSEY
IL-MACOUPIN IL-MADISON IL-MARION IL-MONROE IL-MONTGOMERY IL-
PIKE IL-RANDOLPH IL-ST. CLAIR IL-WASHINGTON IL.
&&
$$
WFO LSX
