923  
FXUS63 KTOP 302332  
AFDTOP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TOPEKA KS  
632 PM CDT SUN APR 30 2017  
   
..UPDATE TO AVIATION FORECAST DISCUSSION
 
 
   
SHORT TERM
 
(THIS EVENING THROUGH MONDAY)  
ISSUED AT 325 PM CDT SUN APR 30 2017  
 
THE 500 MB UPPER LOW WAS OVER SOUTH CENTRAL KANSAS AT 18Z. THE LOW  
HAD BECOME VERTICALLY STACKED WITH THE SURFACE LOW IN THE SAME  
GENERAL AREA. THE RADAR MOSIAC WAS SHOWING SHOWERS NEAR THE LOW  
CENTER EXPANDING DIURNALLY EARLY THIS AFTERNOON. THIS SHOWER  
ACTIVITY SHOULD MOVE THROUGH NORTHEAST KANSAS LATE THIS AND EVENING  
ALONG WITH THE UPPER LOW. THE COVERAGE SHOULD DECREASE SOME THIS  
EVENING BUT WILL KEEP POPS GOING. THE BRUNT OF THE DEFORMATION ZONE  
PRECIPITATION SHOULD MISS OUR AREA TO THE NORTHWEST, BUT A  
DIMINISHING BAND OF PRECIPITATION IS FORECAST TO TRAVERSE NORTHEAST  
KANSAS TONIGHT. CLOUD ICE WILL BE MARGINAL FOR SN AND SINCE THE  
BOUNDARY LAYER TEMPERATURES REMAIN WARM ENOUGH TO KEEP THE  
PRECIPITATION RAIN, WILL NOT MENTION SN IN THE FORECAST. IT WOULD  
NOT BE SURPRISING TO SEE A LITTLE WET SNOW MIX IN UP ALONG THE  
NEBRASKA BORDER WHERE SURFACE TEMPS ARE IN THE UPPER 30S. ONCE THE  
FRONT MOVES THROUGH AS THE SURFACE LOW MOVES OUT, THE PRESSURE  
GRADIENT TIGHTENS WHICH SUPPORTS INCREASING WESTERLY WINDS. DRY  
WEATHER ON MONDAY WITH DECREASING CLOUDS. THE AIRMASS SHOULD MIX  
WELL ALLOWING GUSTY WINDS IN THE MIXED LAYER OF AROUND 30KT TO MIX  
TO THE SURFACE. TEMPERATURES ON MONDAY WILL STILL BE AROUND 10  
DEGREES F BELOW NORMAL FOR MAY 1.  
   
LONG TERM
 
(MONDAY NIGHT THROUGH SUNDAY)  
ISSUED AT 325 PM CDT SUN APR 30 2017  
 
BY MONDAY NIGHT, THE SURFACE AND MID-LEVEL LOWS WILL BE MOVING INTO  
THE GREAT LAKES REGION WITH WEST-NORTHWESTERLY FLOW IN PLACE ACROSS  
THE CENTRAL U.S. THESE LIGHT WESTERLY WINDS COMBINED WITH GENERALLY  
CLEAR SKIES WILL KEEP LOW TEMPERATURES MONDAY NIGHT IN THE LOW/MID  
40S. EXPECT DRY CONDITIONS MONDAY NIGHT THROUGH TUESDAY BEFORE THE  
NEXT SYSTEM APPROACHES THE REGION. DESPITE INCREASING CLOUD COVER  
THROUGH THE DAY, HIGHS SHOULD RISE INTO THE MID/UPPER 60S.  
 
THERE WILL BE TWO AREAS OF FOCUS THAT WILL CONTRIBUTE TO  
PRECIPITATION CHANCES DURING THE TUESDAY NIGHT THROUGH WEDNESDAY  
NIGHT PERIOD. AT THE SURFACE, LOW PRESSURE WILL BE TRACKING INTO TX  
WITH AN ASSOCIATED WARM FRONT STRETCHING NORTHEASTWARD ACROSS OK AND  
SHOULD HOVER NEAR THE KS/MO/AR/OK BORDERS. MODELS SHOW SCATTERED  
PRECIPITATION DEVELOPING ALONG AND NORTH OF THIS BOUNDARY, WITH  
SHOWERS EXTENDING NORTHWARD INTO CENTRAL AND EAST CENTRAL KS TUESDAY  
NIGHT INTO WEDNESDAY. DO NOT ANTICIPATE THUNDERSTORMS WITH THIS  
PRECIPITATION DUE TO LITTLE TO NO INSTABILITY PRESENT THAT FAR NORTH  
OF THE BOUNDARY. THE SECOND AREA OF FOCUS IS WITH AN EMBEDDED  
SHORTWAVE THAT MODELS SHOW DEVELOPING OVER MONTANA TUESDAY MORNING  
AND DEEPENING INTO A MID-LEVEL TROUGH AS IT DIVES SOUTHEAST INTO THE  
HIGH PLAINS AND CENTRAL PLAINS TUESDAY NIGHT INTO WEDNESDAY. THIS  
ADVANCING MID-LEVEL TROUGH WILL PROVIDE ENOUGH FORCING TO BRING  
ADDITIONAL PRECIPITATION CHANCES INTO NORTH CENTRAL KS ON WEDNESDAY,  
WITH PRECIPITATION SHIFTING EASTWARD ACROSS THE CWA BY WEDNESDAY  
EVENING. MODEL SOUNDINGS SHOW SOME WEAK INSTABILITY ALOFT OVER NORTH  
CENTRAL KS AS THIS TROUGH PASSES OVERHEAD, SO HAVE ADDED A SLIGHT  
CHANCE OF THUNDERSTORMS TO THAT REGION WEDNESDAY AFTERNOON. MUCH OF  
THIS SCATTERED PRECIPITATION WILL END WEDNESDAY NIGHT AS THE MID-  
LEVEL TROUGH PROGRESSES EAST OF THE CWA AND DEVELOPS A CLOSED-LOW.  
MODELS ARE NOW SHOWING THE POTENTIAL FOR SOME LIGHT ISOLATED  
PRECIPITATION TO DEVELOP ON THE BACK SIDE OF THIS EXITING LOW ON  
THURSDAY ACROSS FAR NORTHEAST AND EAST CENTRAL KS, SO HAVE SOME  
SLIGHT-CHANCE POPS IN PLACE. AS THIS DEEP MID-LEVEL TROUGH ADVANCES  
ACROSS THE EASTERN U.S., A BROAD MID-LEVEL RIDGE WILL SLIDE INTO THE  
CENTRAL U.S. MODELS CONTINUE TO SHOW A BLOCKING PATTERN SETTING UP,  
WITH THIS RIDGE REMAINING ANCHORED OVER THE CENTRAL U.S. LATE WEEK  
THROUGH NEXT WEEK, WITH THE NEXT CLOSED MID-LEVEL LOW REMAINING OVER  
THE WESTERN U.S.  
 
AS FOR TEMPERATURES, THE MID-WEEK PRECIPITATION WILL KEEP HIGHS  
COOLER IN THE 60S, BUT EXPECT A MODERATING TREND ONCE THE RIDGE  
BUILDS IN, WITH HIGH TEMPERATURES RISING INTO THE LOW 70S BY FRIDAY  
AND INTO THE MID/UPPER 70S OVER THE WEEKEND.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)  
ISSUED AT 631 PM CDT SUN APR 30 2017  
 
MAIN CONCERNS FOR THE FORECAST PERIOD ARE BREEZY NORTHWEST WINDS  
AND CIGS. LOWER CIGS COME IN LATER THIS EVENING AND REMAIN EVEN AS  
WINDS INCREASE OUT OF THE NW TOWARD SUNRISE. CIGS CLEAR BY LATE IN  
THE FORECAST BUT WINDS REMAIN GUSTY THROUGH THE AFTERNOON.  
 

 
   
TOP WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM...JOHNSON  
LONG TERM...HENNECKE  
AVIATION...67  
 
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