734  
FXUS64 KLZK 202003  
AFDLZK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LITTLE ROCK AR  
303 PM CDT FRI OCT 20 2017  
   
SHORT TERM
 
TODAY THROUGH SUNDAY NIGHT  
 
EARLY AFTERNOON WATER VAPOR SATELLITE IMAGERY AND 12Z SUBJECTIVE  
RAOB ANALYSIS SHOWED A LARGE UPPER TROUGH OVER THE NORTHWESTERN  
CONUS AND A SHORTWAVE TROUGH LOCATED OVER THE SOUTHERN HIGH  
PLAINS. A LARGE UPPER LEVEL RIDGE WAS IN PLACE OVER THE  
SOUTHEASTERN CONUS...EXTENDING NORTH OVER THE GREAT LAKES REGION.  
REGIONAL RADARS SHOWED ISOLATED RAIN SHOWERS EXTENDING FROM EAST  
TEXAS TO THE NORTH OVER WESTERN ARKANSAS AND INTO MISSOURI. RAIN  
WAS EXTREMELY LIGHT WITH ONLY SPRINKLES MAKING IT DOWN TO THE  
SURFACE AS THE RAIN SHOWERS WERE ELEVATED OVER A VERY DEEP LAYER  
OF DRY AIR AS OBSERVED BY THE LZK MORNING WEATHER BALLOON. THE  
SOUTHERN HIGH PLAINS SHORTWAVE TROUGH AND RETREATING UPPER LEVEL  
RIDGING WERE AIDING IN THE MOISTENING AND COOLING OF THE  
THERMODYNAMIC PROFILE ALOFT THOUGH AND WILL HELP SET THE STAGE FOR  
HEAVIER RAINFALL SATURDAY NIGHT INTO SUNDAY.  
 
FOR TONIGHT...PERSISTENT WARM AND MOIST AIR ADVECTION WILL CAUSE  
CLOUDS TO INCREASE THROUGHOUT THE OVERNIGHT HOURS. THE INCREASE IN  
SOUTHERLY WINDS NEAR SUNRISE AND RETURN OF LOW-LEVEL CLOUDS ON A  
WEAK LOW-LEVEL JET WILL KEEP OVERNIGHT TEMPERATURES WARM AND IN  
THE LOWER TO MID 60S FOR LOWS TONIGHT/SATURDAY MORNING. THE  
INCREASE IN CLOUDS WILL PREVENT TEMPERATURES FROM GETTING TOO WARM  
ON SATURDAY...BUT SOME BREAKS IN THE CLOUDS AND FILTERED SUNSHINE  
WILL STILL ALLOW TEMPERATURES TO CLIMB UP INTO THE MID TO UPPER  
70S BY SATURDAY AFTERNOON DUE TO THE WARM START TO THE DAY. THE  
SOUTHERN HIGH PLAINS SHORTWAVE TROUGH IS EXPECTED TO MOVE  
NORTHEAST OF ARKANSAS TONIGHT. THIS WILL TAKE SOME OF THE LIFT WE  
ARE SEEING WITH TODAY'S SHOWERS AWAY FROM THE REGION, LIKELY  
KEEPING MOST AREAS DRY DURING THE DAY ON SATURDAY. HOWEVER  
PERSISTENT WARM AND MOIST AIR ADVECTION WILL KEEP AT LEAST SOME  
WEAK LIFT IN PLACE OVER THE STATE...SO KEPT A 20 PERCENT CHANCE OF  
RAIN IN THE FORECAST TO ACCOUNT FOR THE POTENTIAL FOR AN ISOLATED  
SHOWER OR STORM WITH THE RETURN OF DEEPER MOISTURE.  
 
THE LARGE UPPER TROUGH CURRENTLY OVER THE NORTHWESTERN CONUS WILL  
DIG SOUTHEAST DURING THE DAY ON SATURDAY. A STRONG SHORTWAVE  
TROUGH IS EXPECTED TO ROTATE THROUGH THE BASE OF THE LARGER UPPER  
TROUGH AND SPREAD STRONG LARGE SCALE FORCING FOR ASCENT OVER  
EASTERN OKLAHOMA AND WESTERN ARKANSAS SATURDAY EVENING THROUGH THE  
OVERNIGHT HOURS. THIS STRONG LIFT COMBINED WITH DEEP SOUTHERLY  
FLOW WILL MOISTEN UP THE TROPOSPHERE RESULTING IN DEEP MOIST  
ADIABATIC LAPSE RATES OVER THE STATE AND VERY LITTLE CAP. THIS  
WILL ALLOW FOR VERY EFFICIENT PRECIPITATION PROCESSES RESULTING IN  
A VERY HIGH CONFIDENCE IN MOST LOCATIONS ACROSS THE STATE SEEING  
THUNDERSTORM ACTIVITY SATURDAY NIGHT INTO SUNDAY MORNING. HAVE  
ANYWHERE FROM 80 TO 100 POPS IN THE FORECAST FROM SATURDAY NIGHT  
TO SUNDAY AS THIS UPPER LEVEL SYSTEM MOVES OVER THE AREA.  
 
THERE IS A CHANCE FOR SOME SEVERE STORMS SATURDAY NIGHT INTO  
SUNDAY MORNING ACROSS NORTHWESTERN ARKANSAS. WITH STRONG LIFT AND  
LITTLE CAP TO WORK WITH...CONVECTION SHOULD ORGANIZE INTO A LONG  
LINE OR SEVERAL CLUSTERS OF STORMS IN A LINE. EITHER WAY THE STORM  
MODE WILL FAVOR A PRIMARY HAZARD OF DAMAGING STRAIGHT LINE WINDS  
AND LOCALIZED HEAVY RAINFALL AND FLOODING. THERE IS SOME SMALL  
THREAT FOR TORNADOES BUT WITH THE STORM SYSTEM PRIMARILY MOVING  
THROUGH DURING THE OVERNIGHT HOURS...SURFACE BASED INSTABILITY  
WILL BE LIMITED. THUNDERSTORM ACTIVITY WILL CONTINUE ACROSS THE  
STATE ON SUNDAY...BUT THE THREAT FOR SEVERE WEATHER IS EXPECTED TO  
REMAIN LOW.  
 
IF THE UPPER LEVEL SYSTEM IS SLOWER THAN EXPECTED  
SIMILAR TO WHAT THE 12Z NAM SHOWS...THERE MAY BE A LOW THREAT OF  
SEVERE STORMS ACROSS EASTERN ARKANSAS SUNDAY AFTERNOON. IF THE  
SYSTEM IS ON PACE WITH THE 12Z GFS FORECAST THEN IT LOOKS LIKELY  
THAT LOW-LEVEL COLD AIR WILL OUTPACE THE UPPER LEVEL COLD AIR AND  
STORMS ON SUNDAY WILL REMAIN ELEVATED KEEPING THE SEVERE WEATHER  
THREAT LOW. EITHER WAY...ON AND OFF RAIN CHANCES ARE A GOOD BET  
ACROSS MUCH OF THE STATE ON SUNDAY...SO IF YOU HAVE OUTDOOR PLANS,  
SATURDAY IS YOUR BETTER BET FOR A WARM AND DRY DAY OUTSIDE! HIGHS  
ON SUNDAY WILL RANGE FROM THE 60S IN THE NORTHWEST TO THE LOWER  
70S IN THE SOUTHEAST. COOLER AND DRIER AIR WILL MOVE ACROSS  
ARKANSAS BEHIND THIS UPPER LEVEL SYSTEM SUNDAY NIGHT INTO MONDAY.  
 
CAVANAUGH  
 

 
   
LONG TERM
 
MONDAY THROUGH FRIDAY  
 
BY SUNDAY NIGHT, RAIN WILL START TO TAPER OFF SOME, AS THE COLD  
FRONT MOVES EASTWARD. HOWEVER, BY THIS TIME, THE TROUGH DIGGING DOWN  
INTO THE MIDSOUTH REGION IS EXPECTED TO FORM A CUTOFF LOW. THERE'S  
SOME SPREAD IN MODEL SOLUTIONS BEYOND THIS POINT, BUT MOST ARE  
CLUSTERING IN ON THE LOW MOVING OUT OF THE REGION MONDAY AFTERNOON  
OR NIGHT. AT THAT POINT, RAIN CHANCES WILL COME TO AN END.  
 
COLDER AIR WILL MOVE INTO THE REGION ON TUESDAY. THIS WILL BE EVEN  
MORE SO ON TUESDAY NIGHT, AS A CUTOFF LOW FORMS OVER THE GREAT LAKES  
REGION AND THE UPPER FLOW BECOMES MORE MERIDIONAL. LOWS ON WEDNESDAY  
MORNING WILL FALL INTO THE 40S, WITH HIGHS MAINLY IN THE 60S DURING  
THE AFTERNOON. A FEW PLACES IN THE NORTHWEST MAY EVEN STAY IN THE  
50S.  
 
THE AFOREMENTIONED CUTOFF LOW WILL MOVE EASTWARD ON WEDNESDAY AND  
THE UPPER FLOW WILL BECOME MORE ZONAL. SURFACE HIGH PRESSURE PASSING  
THROUGH WILL BRING MORE OF A SOUTHERLY COMPONENT TO THE WINDS, WHICH  
WILL ALLOW TEMPERATURES TO MODERATE.  
 
ANY MODERATION, THOUGH, WILL BE SHORT-LIVED, AS ANOTHER POWERFUL  
UPPER TROUGH DIGS DOWN INTO THE SOUTHERN PLAINS AT THE END OF THE  
WEEK. THIS WILL PUSH ANOTHER COLD FRONT INTO THE REGION, WITH  
SHOWERS AND THUNDERSTORMS EXPECTED. BEHIND THAT SYSTEM (IN OTHER  
WORDS, JUST BEYOND THE END OF THE PERIOD), THERE COULD BE A MORE  
SIGNIFICANT PUSH OF COLD AIR. BUT, THAT'S A DISCUSSION WE WILL HAVE  
TO HAVE AT ANOTHER TIME.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
BATESVILLE AR 62 75 65 69 / 10 20 90 90  
CAMDEN AR 66 78 69 73 / 20 30 80 80  
HARRISON AR 60 74 57 60 / 20 20 100 60  
HOT SPRINGS AR 64 76 66 66 / 20 30 90 70  
LITTLE ROCK AR 64 78 68 72 / 10 20 80 80  
MONTICELLO AR 65 80 69 74 / 10 30 50 90  
MOUNT IDA AR 63 75 64 63 / 20 30 90 70  
MOUNTAIN HOME AR 64 75 61 63 / 20 20 100 70  
NEWPORT AR 61 77 66 73 / 10 20 80 90  
PINE BLUFF AR 64 79 68 74 / 10 20 70 80  
RUSSELLVILLE AR 63 76 65 65 / 20 20 90 70  
SEARCY AR 62 77 66 72 / 10 20 80 80  
STUTTGART AR 63 78 68 75 / 10 20 70 90  

 
   
LZK WATCHES/WARNINGS/ADVISORIES
 
NONE.  

 
 

 
 
SHORT TERM...CAVANAUGH / LONG TERM...57  
 
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