669  
FXUS63 KEAX 262002  
AFDEAX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO  
302 PM CDT WED APR 26 2017  
   
DISCUSSION
 
 
ISSUED AT 302 PM CDT WED APR 26 2017  
 
LARGE UPPER-LEVEL TROUGH CONTINUES TO WORK THROUGH THE CENTRAL  
U.S. THIS AFTERNOON WITH LINGERING LIGHT SHWR ACTIVITY CURRENTLY  
IMPACTING THE SOUTHERN 2/3RDS OF THE FORECAST AREA. ALL  
APPRECIABLE INSTABILITY NOW RESIDES WELL EAST OF THE FCST REGION,  
THUS WE CAN EXPECT LINGERING SHWRS FOR A FEW MORE HOURS THIS  
EVENING BEFORE ALL ACTIVITY EVENTUALLY SHIFTS EASTWARD. MAIN  
ISSUE WITH THIS AFTERNOON'S PACKAGE REVOLVES AROUND POSSIBLE FROST  
DEVELOPMENT EARLY THURSDAY MORNING AS HIGH PRESSURE GRADUALLY  
BUILDS INTO THE REGION. BIGGEST QUESTIONS INVOLVE WHETHER SKIES  
WILL CLEAR ENOUGH FOR THE CURRENT TEMP FORECAST TO MATERIALIZE,  
AND ALSO WHETHER WINDS WILL WEAKEN ENOUGH FOR FROST DEVELOPMENT.  
DESPITE THESE UNCERTAINTIES, ENOUGH EVIDENCE IS THERE TO SUPPORT  
PARTIAL CLEARING AFTER MIDNIGHT WHICH FACILITATED THE ISSUANCE OF  
A FROST ADVISORY FOR THE FAR NORTHWESTERN ZONES AFTER MIDNIGHT.  
 
PREVIOUSLY MENTIONED HIGH PRESSURE SHOULD RESULT IN DRY  
CONDITIONS ON THURSDAY BEFORE SHWRS REDEVELOP OVER THE REGION  
THURSDAY NIGHT INTO FRIDAY AS AN 850 LOW APPROACHES FROM THE WEST.  
ISENTROPIC ASCENT SHOULD INCREASE ACROSS THE REGION BEGINNING  
TOMORROW NIGHT AS A STRENGTHENING LOW-LEVEL JET INTERACTS WITH AN  
INVERTED TROUGH AND MIDLEVEL FRONT WHICH BOTH SHOULD BEGIN  
WORKING ACROSS OUR AREA TOMORROW EVENING. SHWR ACTIVITY SHOULD  
GRADUALLY COME TO AN END BY FRIDAY AFTERNOON AS THE LAGGING SFC  
LOW EVENTUALLY TRACKS OVER THE AREA. RAINFALL AMOUNTS WITH THIS  
SYSTEM SHOULD REMAIN LESS THAN A HALF INCH AS INSTABILITY SHOULD  
BE LIMITED THUS PREVENTING HEAVIER RAINFALL RATES.  
 
BIGGER CONCERNS MAKE THEIR INITIAL APPEARANCE EARLY SATURDAY WITH  
THE THREAT FOR MODERATE AND POTENTIALLY LOCALLY HEAVY RAINFALL  
CONTINUING THROUGH MUCH OF THE UPCOMING WEEKEND. MAIN CULPRIT  
CONTINUES TO BE A STALLED SURFACE FRONT WHICH TODAY'S MODEL RUNS  
SUGGEST WILL BE QUITE A BIT SOUTH OF OUR AREA, MAINLY SOUTH OF THE  
I-44 CORRIDOR BEFORE FEATURE BEGINS TO LIFT NORTH AS A WARM FRONT  
BY EARLY SUNDAY MORNING. SOUTH OF THE FRONT, FCST MODELS CONTINUE  
TO SHOW IMPRESSIVE MOISTURE ADVECTION OUT AHEAD OF A DEEP LONGWAVE  
TROUGH APPROACHING FROM THE FOUR CORNERS REGION. WITH PWAT VALUES  
ON THE ORDER OF 3 TO 4 STANDARD DEVIATIONS ABOVE NORMAL WITH AN  
EVEN STRONGER LOW-LEVEL JET, THE INGREDIENTS APPEAR TO BE IN PLACE  
FOR A WIDESPREAD HEAVY RAIN EVENT ACROSS THE OZARKS AND MID-  
MISSISSIPPI VLY. FROM TODAY'S MODEL VIEWPOINT, MUCH OF OUR REGION  
APPEARS TO BE SPARED THE HEAVIEST RAINS, WHICH MAKES SENSE BASED  
ON THE EXPECTED FRONTAL POSITION FOR LATEST GUIDANCE TRENDS.  
DESPITE THIS, LONG DURATION RAINFALL LOOKS INCREASINGLY LIKELY  
THIS AFTERNOON, WHICH OVER TIME, WILL CERTAINLY ADD UP. LATEST  
EVENT TOTAL QPF FCST CALLS FOR OVER 3 INCHES SOUTH OF THE ROUTE 50  
CORRIDOR, WITH TOTALS AS HIGH AS AN INCH AND A HALF UP ALONG THE  
IOWA BORDER. THIS RAINFALL WILL CERTAINLY LEAD TO A RESPONSE ON  
AREA RIVERS AND STREAMS, BUT BEST POTENTIAL FOR ANY CONVECTIVE  
RAINFALL RATES WILL REMAIN SOUTH OF OUR AREA THANKS TO THE  
SOUTHWARD POSITION OF THE FRONT. IN FACT, MUCH OF THE UPCOMING  
EVENT LOOKS TO BE THUNDER FREE, EXPECT FOR AREAS ALONG AND SOUTH  
OF ROUTE 50 WHERE SOME ELEVATED INSTABILITY MAY BE ABLE TO SNEAK  
NORTH ENOUGH TO LEAD TO SOME EMBEDDED STORMS.  
 
RAIN SHWRS EVENTUALLY COME TO AN END LATE SUNDAY NIGHT AS MAIN  
SFC LOW TRACKS AWAY FROM THE REGION. STRONG COLD ADVECTION ON THE  
BACKSIDE OF THIS SYSTEM WILL LEAD TO A CHILLY START TO NEXT WEEK  
WITH TEMPERATURES GRADUALLY INCREASING BY MIDWEEK AS WARM AIR  
ADVECTION INCREASES AHEAD OF THE NEXT SYSTEM THAT SHOULD BEGIN  
IMPACTING THE AREA TUES NGT/EARLY WED.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)  
ISSUED AT 1231 PM CDT WED APR 26 2017  
 
MVFR STATUS DECK OVER AREA TERMINALS THIS AFTERNOON ALL IN  
ASSOCIATION WITH A UPPER TROUGH THAT CONTINUES TO WORK EAST  
THROUGH THE REGION. LATEST FCST SOUNDINGS SUGGEST STRATUS WILL  
CONTINUE THROUGH THE AFTERNOON WITH SOME IMPROVEMENT TO LOW-END  
VFR POSSIBLE AFTER THE 21Z TIME FRAME. EVENTUALLY OVERNIGHT EXPECT  
A GRADUAL CLEARING TREND AS DRIER AIR BEGINS TO WORK INTO THE  
AREA. AFTER THIS OCCURS, VFR CAN BE EXPECTED THROUGH THE DURATION  
OF THE FCST PERIOD. NORTHWEST WINDS OF ROUGHLY 15 KTS THIS  
AFTERNOON WILL BEGIN TO WEAKEN THIS EVENING.  
 

 
   
EAX WATCHES/WARNINGS/ADVISORIES
 
 
KS...FROST ADVISORY FROM 1 AM TO 8 AM CDT THURSDAY FOR KSZ025-102.  
 
MO...FROST ADVISORY FROM 1 AM TO 8 AM CDT THURSDAY FOR MOZ001>004-011-  
012-020.  
 

 
 

 
 
DISCUSSION...32  
AVIATION...32  
 
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