Saturday, October 23, 2010

Area Forecast Discussion - South Central/Southwest Missouri

FXUS63 KSGF 231114
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
614 AM CDT SAT OCT 23 2010

..UPDATE TO AVIATION...

DISCUSSION...
/ISSUED 240 AM CDT SAT OCT 23 2010/

SHORT TERM (TODAY THROUGH MONDAY)...

DECIDEDLY COMPLEX STORM SYSTEM CONTINUING TO AFFECT MUCH OF THE
NATIONS MID SECTION EARLY THIS MORNING. WATER VAPOR IMAGERY
DEPICTS LARGE UPPER LEVEL GYRE OVER THE NEBRASKA PANHANDLE...WITH
SERIES OF SHORTWAVES ROTATING AROUND THE PARENT CIRCULATION. ONE
WAVE CURRENTLY APPROACHING THE CWA FROM THE SOUTHWEST THIS
MORNING...RESULTING IN GRADUAL EXPANSION OF SHOWERS/THUNDERSTORMS
OVER MAINLY THE WESTERN HALF OF THE CWA. BIGGEST ISSUE RIGHT NOW
IS STUBBORN DRY LOW LEVEL AIR MASS THAT IS SEEMINGLY REFUSING TO
MOISTEN...WITH 10+ DEGREE DEWPOINT DEPRESSIONS AT THE
SURFACE...AND 00Z SGF RAOB STILL INDICATING DEWPOINT DEPRESSIONS
IN THE 5-8 DEGREE C RANGE UP THROUGH ABOUT 600 MB/13KFT. WHILE
AIRMASS WILL ULTIMATELY MOISTEN UP DURING THE DAY TODAY...THINK
THAT THIS WILL CONTINUE TO RESULT IN MUCH SLOWER DEVELOPMENT OF
PRECIPITATION THAN THE STRENGTH OF THIS SYSTEM WOULD OTHERWISE
SUGGEST.

LEAD WAVE APPROACHING THE AREA THIS MORNING EXPECTED TO PASS
THROUGH THE CWA BY MID TO LATE MORNING. STRONGER WAVE CURRENTLY
NEAR RED RIVER VALLEY IS ON THE HEELS OF THE FIRST...AND SHOULD
BEGIN TO APPROACH THE AREA BY MIDDAY TODAY. DESPITE SOMEWHAT
SHEARED CHARACTER OF THIS VORT...LARGE SCALE LIFT FROM PVA AND
APPROACH OF UPPER LEVEL SPEED MAX SHOULD BE ENOUGH TO GENERATE
SCATTERED THUNDERSTORMS THIS AFTERNOON. SEVERE WEATHER THREAT
CONTINUES TO LOOK LESS IMPRESSIVE WITH TIME...THOUGH STILL RATHER
AMBIGUOUS AND MOST CERTAINLY DEPENDENT ON QUALITY OF INSTABILITY
THAT WILL BE PRESENT. DRY AIR AT THE SURFACE AND IN THE LOW LEVELS
MAY WELL MAKE APPRECIABLE CAPE TOUGH TO COME BY...BUT IF STORMS
ARE ABLE TO GET GOING...STRONGEST WOULD BE CAPABLE OF MAINLY A
LARGE HAIL AND GUSTY WIND THREAT. TORNADO THREAT APPEARS TO BE
RATHER LOW CONSIDERING WHAT SHOULD BE LCLS ABOVE 1 KM. THAT BEING
SAID...WILL CERTAINLY BE KEEPING AN EYE ON THINGS DURING THE DAY
CONSIDERING DEGREE OF WIND SHEAR THAT WILL BE IN PLACE.

GUIDANCE CONTINUES TO HOLD BACK MID/UPPER LEVEL TROUGH AXIS
THROUGH LATE SUNDAY NIGHT/EARLY MONDAY MORNING. MID LEVEL JET
STREAK/SHORTWAVE EXPECTED TO ROTATE THROUGH THE MAIN TROUGH SUNDAY
AFTERNOON AS IT APPROACHES THE CWA...WHICH WILL LIKELY SPAWN YET
ANOTHER ROUND OF SCATTERED THUNDERSTORMS ACROSS THE REGION. NOT
UNLIKE TODAY...SEVERE WEATHER THREAT LOOKING NOT TERRIBLY
HIGH...THOUGH NOT NON-ZERO DEPENDING ON DEGREE OF INSTABILITY
PRESENT. AGREE WITH SPC DY2 OUTLOOK THAT THREAT WOULD LIKELY BE IN
THE FORM OF WIND AND LARGE HAIL AND BE CONFINED TO AREAS ALONG AND
SOUTH OF U.S. 60...WITH THE BULK OF THE SEVERE WEATHER REMAINING
SOUTH OF THE SGF CWA.

FOR MONDAY...TROUGH AXIS SHOULD BE OVER OR JUST EAST OF THE CWA BY
MID MORNING...RESULTING IN WHAT LOOKS AT THIS POINT LIKE A DRY
DAY. SOUTHERLY FLOW WILL REMAIN IN PLACE DURING THE DAY AS YET
ANOTHER STRONG STORM SYSTEM BEGINS TO APPROACH THE REGION FROM THE
WEST MONDAY NIGHT.

BOXELL

LONG TERM (MONDAY NIGHT THROUGH THURSDAY)...

00Z MED RANGE MODEL OUTPUT SHOWING GOOD CONTINUITY FROM RUN TO RUN
AND MODEL TO MODEL. THIS IN SPITE OF A RATHER FAST AND CHANGABLE
PATTERN...WHICH IS USUALLY PRONE TO INCREASED UNCERTAINTY. A
SYSTEM WILL STRENGTHEN AND SLIDE ACROSS THE NORTHERN TIER OF
STATES FROM MONDAY NIGHT INTO MIDWEEK. THIS WILL SEND A COLD
FRONT THROUGH THE REGION IN THE TUE NIGHT/EARLY WED TIME FRAME.
MOISTURE RETURN IS SOMEWHAT IN QUESTION AND GIVEN THE SPEED OF
THIS SYSTEM...WILL MAINTAIN CHC POPS ACROSS THE EASTERN HALF OF
THE AREA. STRONG LOW PRESSURE OVER THE UPPER MIDWEST WILL FILL
DURING THE MIDWEEK TIME FRAME WITH A BROAD UPPER TROUGH ACROSS
MUCH OF THE MIDWEST. THE BRUNT OF ANY COLD AIR SHOULD STAY TO OUR
NORTH AND AREA TEMPERATURES WILL HOVER NEAR SEASONAL AVGS. AS THE
SYSTEM GRADUALLY LIFTS ENE THROUGH THE GREAT LAKES STATES AND INTO
SE CANADA DURING MID/LATE WEEK THE PATTERN LOOKS TO AMPLIFY A BIT.
THIS SHOULD RESULT IN A GRADUAL WARMING TREND AS SFC HIGH PRESSURE
MOVES EAST OF THE AREA.

GAGAN

&&

AVIATION...

FOR THE 12Z TAFS...

SCATTERED SHRA/TSRA EXPECTED TO CONTINUE ACROSS THE REGION THIS
MORNING...WITH BEST CHANCES FOR PRECIPITATION TO INITIALLY BE AT
KJLN THROUGH MID MORNING. AFTER THAT...PRECIPITATION WILL BE
POSSIBLE AT ALL TERMINALS...THOUGH WITH UNCERTAINTIES WITH REGARD TO
TIMING/COVERAGE...HAVE ONLY INCLUDED VCTS MENTION FOR NOW. EXPECT
GENERALLY VFR CONDITIONS TODAY...THOUGH CIGS/VIS COULD DROP TO
MVFR BRIEFLY IN SHRA/TSRA.

ALONG WITH SHRA/TSRA...SURFACE WIND SPEEDS AS WELL AS LLWS TO BE A
SIGNIFICANT CONCERN TODAY. THROUGH ABOUT 14Z...LLWS WILL CONTINUE
WITH A SOUTHERLY 45-50 KT LOW LEVEL JET IN PLACE. AFTER
14Z...SURFACE HEATING SHOULD BE ENOUGH TO MIX DOWN SOME OF THAT
ENERGY...RESULTING IN SOUTHERLY SURFACE WINDS INCREASING TO 15-20
KT WITH GUSTS BETWEEN 25 AT 30 KT LATE MORNING AND THIS AFTERNOON.
AFTER SUNDOWN TONIGHT...SURFACE GUSTS SHOULD SUBSIDE
SOMEWHAT...BUT LLWS WILL REESTABLISH ITSELF WITH YET ANOTHER 40-50
KT LOW LEVEL JET OVER THE AREA.

BOXELL

&&

SGF WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&

$$

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