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000
FXUS63 KLSX 230222
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
922 PM CDT WED MAY 22 2013

.UPDATE...
ISSUED AT 841 PM CDT WED MAY 22 2013

ISOLATED SHOWERS...MAINLY LIGHT CAN STILL BE EXPECTED ACROSS NERN
MO AND W CNTRL IL FOR THE REMAINDER OF THE NGT AS A WEAK SHORTWAVE
OVER ERN NEBRASKA DROPS SEWD THROUGH NERN MO AND W CNTRL IL LATE
TGT. MORE SIGNIFICANT SHOWERS JUST AHEAD OF A COLD FRONT EXTENDING
FROM A SFC LOW NEAR ORD SW THROUGH SAR AND FAM SHOULD REMAIN E-SE
OF OUR FORECAST AREA AS THE FRONT CONTINUES TO MOVE SLOWLY SEWD.
ALTHOUGH MUCH OF THE CUMULUS AND STRATOCUMULUS CLOUDS HAVE DISSIPATED
ACROSS SERN MO AND SWRN IL WITH LOSS OF DAYTIME HEATING...LOW-MID
LEVEL CLOUDS WILL CONTINUE TO ROTATE SEWD THROUGH AT LEAST THE
NRN HALF OF OUR FORECAST AREA FOR THE REST OF TGT...BEHIND THE
UPPER LEVEL LOW/TROUGH AND ASSOCIATED SFC LOW OVER THE GREAT LAKES
REGION. COOLER LOW TEMPERATURES ARE FORECAST FOR TGT COMPARED TO
THE PREVIOUS NGT...AND SLIGHTLY BELOW NORMAL FOR LATE MAY DUE TO
WEAK LOW LEVEL CAA BEHIND THE COLD FRONT AND LOWERING SFC DEW
POINTS. THE 00Z THU NAM MODEL RUN DROPS THE 8 DEGREE C 850 MB
ISOTHERM SEWD INTO SERN MO AND SRN IL BY 12Z THU.

GKS

&&

.SHORT TERM...(THROUGH LATE TONIGHT)
ISSUED AT 314 PM CDT WED MAY 22 2013

A FEW SHOWERS THAT POPPED UP ALONG AND AHEAD OF A REINFORCING COLD
FRONT WILL CONTINUE TO GRADUALLY MOVE EASTWARD...AND ANY LINGERING
SHOWERS SHOULD TAPER OFF QUICKLY AFTER SUNSET THIS EVENING WITH A
LOSS OF DIURNAL HEATING. THE LARGE LOW CONTINUING TO SPIN OVER THE
UPPER MIDWEST/GREAT LAKES WILL ACT TO KEEP MUCH OF THE REGION
UNDER PARTLY TO MOSTLY CLOUDY SKIES TONIGHT...THUS HAVE NOT GONE TOO
FAR BELOW GUIDANCE ON TONIGHT`S LOWS...WHICH WILL GENERALLY BE IN
THE LOW TO MIDDLE 50S ACROSS THE AREA. OBS TODAY OVER EASTERN AND
SOUTHEASTERN NEBRASKA HAVE INDICATED SOME POCKETS OF LIGHT
RAIN/DRIZZLE OCCURRING ON THE BACK SIDE OF THE LOW...THUS CANNOT
RULE OUT SOME LIGHT PRECIPITATION OVER THE NORTHERN TIER OF THE CWA
AS THE LOW BEGINS TO FINALLY LIFT NORTHEAST...MAINLY DURING THE LATE
OVERNIGHT HOURS TO JUST BEFORE DAYBREAK.

PHILLIPSON

.LONG TERM...(THURSDAY THROUGH NEXT WEDNESDAY)
ISSUED AT 314 PM CDT WED MAY 22 2013

THU THROUGH FRI NIGHT...VORT MAXES MOVING ACROSS THE AREA TOMORROW
MAY SUPPORT ISOLATED SHOWERS HOWEVER THE TIMING OF THE VORT MAXES
ARE CURRENTLY FCST TO BE TEMPORALLY OUT OF SYNC WITH DIURNAL HEATING
WHICH WOULD TEND TO LIMIT PCPN COVERAGE. SOME CLOUD COVER SHOULD
PERSIST TOMORROW WITHIN CYCLONIC FLOW ALOFT IN THE WAKE OF A
DEPARTING LOW PRESSURE SYSTEM. A STRONG SFC HIGH THEN BUILDS INTO
THE MIDWEST AND BRINGS COOLER AIR TO MO/IL...EFFECTIVELY PUSHING A
FNTL BDRY IN SRN MO/NRN AR SWD AS A CDFNT. THE COOLEST OVERNIGHT
LOWS OUT OF THE NEXT SEVERAL DAYS WILL PROBABLY OCCUR LATE
TOMORROW NIGHT/EARLY FRI MORNING. TEMPERATURES SHOULD REMAIN
SEASONABLY COOL ON FRI UNDER THE INFLUENCE OF COOL ELY SFC FLOW.
GENERALLY DRY CONDITIONS ARE EXPECTED THROUGH FRI NIGHT HOWEVER
NOCTURNAL CONVECTION DRIVEN BY THE LLJ MAY CLIP THE NWRN CWA ON
LATE FRI NIGHT.

SAT THROUGH TUE...SFC WINDS WILL GRADUALLY BECOME SLY ACROSS THE CWA
AROUND THE BACK SIDE OF THE SFC HIGH ONCE IT SHIFTS FARTHER EWD. A
DVLPG LOW OVER THE PLAINS WILL REORIENT A BAROCLINIC ZONE SUCH THAT
IT STRETCHES THROUGH ERN KS AND WRN MO AS A WMFNT. TEMPERATURES WILL
WARM UP OVER THE WEEKEND AS THIS BDRY LIFTS INTO CENTRAL MO WITH THE
TEMPERATURE INCREASE AIDED BY THE STRONG SUN ANGLE AT THIS TIME OF
YEAR. MODELS ARE HINTING AT A FEW ILL-DEFINED VORT MAXES MOVING
ACROSS THE AREA OVER THE WEEKEND WHICH MAY SUPPORT SCT
THUNDERSTORMS. ADDITIONALLY...UPSTREAM NOCTURNAL MCS DVLPMT MAY ALSO
AFFECT OUR AREA THIS WEEKEND...EITHER AS DECAYING REMNANTS MOVING
INTO THE CWA OR BY GENERATING AN MCV WHICH FOCUSES TSRA DVLPMT
DURING THE FOLLOWING AFTN. POP12 CLIMATOLOGY FOR THIS TIME OF YEAR
IS AROUND 30 PERCENT AND THAT LOOKS REASONABLE GIVEN THE LACK OF
WELL-DEFINED FEATURES TO FOCUS PCPN DVLPMT AND THE UNCERTAINTY
REGARDING THE EFFECTS OF UPSTREAM MCS ACTIVITY. THE UPPER AIR
PATTN OVER THE CENTRAL PART OF THE COUNTRY WILL SHIFT FM RIDGING
TO SW FLOW BY THE MIDDLE OF THE WEEK AFTER A SHORTWAVE MOVES INTO
THE SWRN CONUS.

KANOFSKY

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 546 PM CDT WED MAY 22 2013

VFR CONDITIONS ARE EXPECTED MOST OF THE NIGHT BEFORE CEILINGS
BETWEEN 2000-3000FT CURRENTLY OVER IOWA MOVE SOUTHEASTWARD INTO
THE AREA. ISOLATED SHOWERS WILL BE IN THE AREA DURING THIS TIME
PERIOD...PARTICULARLY OVER NORTHEASTERN MISSOURI/WEST CENTRAL
ILLINOIS...SO HAVE MAINTAINED VCSH AT KUIN. ELSEWHERE CHANCES ARE
TOO LOW TO INCLUDE IN THE TAFS. OTHERWISE WINDS WILL VEER FROM
WEST TO NORTH WITH THE PASSAGE OF A COLD FRONT THAT MOVES SOUTH
THROUGH THE AREA BETWEEN 12-18Z.

SPECIFICS FOR KSTL...EXPECT MAINLY DRY AND VFR CONDITIONS THROUGH
TONIGHT. A COLD FRONT WILL MOVE THROUGH THE TERMINAL BEFORE 18Z.
CEILINGS WITH BE BETWEEN 2000-3000FT MOST OF THE DAY BEFORE
IMPROVING TO VFR BY THURSDAY EVENING.

BRITT

&&

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

$$

WFO LSX