094  
FXUS65 KPUB 181023  
AFDPUB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PUEBLO CO  
423 AM MDT SAT AUG 18 2018  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 420 AM MDT SAT AUG 18 2018  
 
STILL A FEW WEAK REMNANTS OF OVERNIGHT CONVECTION DRIFTING AROUND  
THE SE PLAINS THIS MORNING, AND WILL RETAIN SOME LOW POPS THROUGH  
SUNRISE FOR THE FAR SERN CORNER OF THE AREA. ATTENTION THEN TURNS  
NORTHWESTWARD, AS STRONG SHORT WAVE WILL RIDE OVER THE UPPER RIDGE  
TODAY AND TONIGHT, EVENTUALLY CLOSING OFF A MID LEVEL LOW OVER THE  
CENTRAL PLAINS BY EARLY SUN MORNING. WELL DEFINED TROUGH AND  
ASSOCIATED CONVECTION ALREADY SHOWING UP NICELY THIS MORNING IN  
SATELLITE IMAGERY FROM ERN WY SOUTH INTO WRN CO/ERN UT, WITH  
OCCASIONAL CG LIGHTNING PUSHING THROUGH WRN CO AS OF 10Z. FOR TODAY,  
ENHANCED UPWARD MOTION WITH THE UPPER WAVE SPREADS EASTWARD THROUGH  
THE MOUNTAINS EARLY THIS AFTERNOON, THEN ACROSS THE I-25 CORRIDOR  
AND EASTERN PLAINS FROM MID-AFTERNOON INTO THE EVENING. SHOULD SEE  
FAIRLY ORGANIZED BAND OF TSRA DEVELOP OVER THE MOUNTAINS IN THE  
EARLY AFTERNOON, WITH STORMS INTENSIFYING AS THEY MOVE EAST INTO THE  
MORE UNSTABLE AIR MASS ON THE PLAINS. THREAT OF STRONG/SEVERE  
CONVECTION AND POTENTIAL FOR HEAVY RAIN THEN SHIFTS ACROSS THE  
PLAINS TOWARD THE KS BORDER DURING THE EVENING AND OVERNIGHT HOURS.  
SPC SWODY1 MARGINAL RISK OF SEVERE OVER THE PLAINS LOOKS REASONABLE  
TODAY/TONIGHT, AS 0-6KM SHEAR INCREASES TO AROUND 40 KTS BY 00Z,  
WHILE CAPE CLIMBS INTO THE 1-2K J/KG RANGE. ALTHOUGH BRIEF HEAVY  
RAINFALL WILL BE POSSIBLE OVER THE MOUNTAINS, HEAVIEST RAIN  
POTENTIAL WILL LIKELY OCCUR OVER THE PLAINS, AS CONVECTION ORGANIZES  
INTO AN MCS BY EVENING. CONVECTION THEN ENDS FROM WEST TO EAST  
OVERNIGHT, AS BULK OF TSRA ACTIVITY SHIFTS EAST IN KS/OK/TX. MAX  
TEMPS TODAY WILL RUN JUST A COUPLE DEGF COOLER THAN FRI WITH MORE  
CLOUD COVER ACROSS THE REGION.  
   
LONG TERM
 
(SUNDAY THROUGH FRIDAY)  
ISSUED AT 420 AM MDT SAT AUG 18 2018  
 
SUNDAY AND MONDAY...FORECAST MODELS ARE ARE IN GOOD AGREEMENT  
DURING THIS PERIOD LEADING TO HIGH CONFIDENCE IN THE FORECAST. THE  
LONG TERM FORECAST PERIOD BEGINS WITH THE EXIT OF A POTENT SHORTWAVE  
TROUGH EAST OUT OF COLORADO AND RIDGE RECOVERY OVER THE SOUTHWEST  
US. HEIGHT RISES, Q-VECTOR DIVERGENCE, AND MOISTURE-SCOURING DEEP  
NORTHERLY FLOW WILL LEAD TO DRIER CONDITIONS ACROSS THE FORECAST  
AREA SUNDAY AND MONDAY. RESIDUAL ENERGY ON THE BACKSIDE OF THE  
SYSTEM MAY SPAWN AN ISOLATED STORM OR TWO OVER THE EASTERN MOUNTAINS  
SUNDAY, WHILE WEAK ENERGY IN THE NORTHWEST FLOW WILL HELP TO DEVELOP  
A FEW ISOLATED THUNDERSTORMS ACROSS THE HIGH TERRAIN ON MONDAY.  
SURFACE WINDS OUT OF THE NORTH WILL BE QUITE BREEZY ON SUNDAY, IN  
THE 20-35 MPH SUSTAINED RANGE, ACROSS THE I-25 CORRIDOR AND  
EASTERN PLAINS. TEMPERATURES WILL BE COOLER WITHIN THE NORTHERLY  
FLOW REGIME, WITH HIGHS IN THE LOW 80S ACROSS THE PLAINS AND HIGH  
VALLEYS, AND MID 70S IN COLORADO SPRINGS.  
 
TUESDAY AND WEDNESDAY...FORECAST CONFIDENCE REMAINS MODERATE-HIGH AS  
MODELS REMAIN IN GOOD AGREEMENT, WITH SOME DIFFERENCES BEGINNING TO  
DEVELOP IN THE POSITION OF THE MID-LEVEL RIDGE BY LATE WEDNESDAY.  
THE RIDGE SHIFTS EAST SLIGHTLY SOUTH OF COLORADO CAUSING MID-  
LEVEL FLOW OVER THE STATE TO BECOME MORE WEST-NORTHWEST. THE FLOW  
BECOMES DISTURBED OVER COLORADO AS AN UPPER LEVEL JET SAGS SOUTH.  
AT THE SAME TIME, SURFACE FLOW BECOMES SOUTHERLY/SOUTHEASTERLY  
FROM THE TEXAS GULF COAST INTO SOUTHERN COLORADO, RETURNING  
MOISTURE TO THE REGION. THUNDERSTORMS WILL HAVE NO PROBLEM  
DEVELOPING EACH DAY OVER THE HIGH TERRAIN UNDER THE INFLUENCE OF  
STRONG DAYTIME HEATING, SHORTWAVE ENERGY, AND UPPER LEVEL JET  
DYNAMICS AND A RETURN OF ABOVE AVERAGE TPW. STORMS WILL BE STEERED  
ONTO THE I-25 CORRIDOR AND EASTERN PLAINS DURING EACH AFTERNOON  
AND EVENING. WHILE SHEAR WILL BE FAVORABLE BOTH DAYS WITH THE JET  
OVERHEAD, INSTABILITY WILL BE MARGINAL AT BEST ON WEDNESDAY, AS  
SURFACE DEW POINTS ARE STILL RECOVERING. STILL, WITH SUCH  
FAVORABLE SHEAR, COULD GET A LOW-END SEVERE STORM OR TWO.  
INSTABILITY WILL BE BETTER ON WEDENSDAY AS SURFACE DEW POINTS  
INCREASE AFTER ANOTHER DAY OF RETURN FLOW. THEREFORE, WEDNESDAY  
LOOKS LIKE THERE MAY BE A BETTER CHANCE FOR STORMS TO BE SEVERE.  
TEMPERATURES WILL BE WARMER THIS PERIOD, WITH HIGHS IN THE MID TO  
UPPER 80S ACROSS THE PLAINS, AND LOW 80S IN COLORADO SPRINGS AND  
THE HIGH VALLEYS.  
 
THURSDAY AND FRIDAY...MODEL SOLUTIONS DIVERGE MORE DURING THIS  
PERIOD WITH THE POSITION OF THE HIGH AND PROGRESSION OF  
DISTURBANCES, LEADING TO LESS CONFIDENCE IN THE FORECAST COMPARED TO  
ABOVE. IT APPEARS AS THOUGH LESS MOISTURE WILL BE IN PLACE WITH THE  
EXIT OF THE TUES/WED STORM SYSTEM. WHILE THE ECMWF MAINTAINS A  
SHORTWAVE OFF THE WEST COAST AND INTO THE NORTHERN ROCKIES ON  
THURSDAY, THE GFS WEAKENS THE SHORTWAVE BY THE TIME IT MAKES IT THIS  
FAR EAST. THIS LEADS TO MORE WIDESPREAD CONVECTIVE COVERAGE IN THE  
ECMWF VS THE GFS OVER THE HIGH TERRAIN ON THURSDAY, THOUGH BOTH  
MODELS KEEP THE PLAINS DRY. THE GEFS ALSO SHOWS CONSIDERABLE SPREAD  
WITH THE PROGRESSION OF THE MID-LEVEL PATTERN BY THIS TIME.  
REGARDLESS, THE RIDGE REMAINS CENTERED SOMEWHERE SOUTH OF COLORADO  
WITH WESTERLY TO NORTHWEST FLOW OVERHEAD LEADING TO THUNDERSTORM  
CHANCES AT LEAST OVER THE HIGH TERRAIN.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)  
ISSUED AT 420 AM MDT SAT AUG 18 2018  
 
PATCHY MVFR STRATUS WILL OCCASIONALLY IMPACT BOTH KCOS AND KPUB  
THROUGH 15Z, WITH SOME IFR CIGS POSSIBLE JUST WEST AND NORTH OF KCOS  
THROUGH SUNRISE. CONDITIONS THEN BECOME VFR AT ALL TERMINALS INTO  
EARLY AFTERNOON BEFORE CONVECTION BEGINS TO MOVE OFF THE MOUNTAINS  
AND APPROACH TAF SITES 19Z-20Z. WILL INCLUDE VCTS AT ALL TERMINALS  
FOR THE AFTERNOON AND EARLY EVENING, WITH BEST CHANCE FOR TSRA AT  
BOTH KCOS AND KPUB. STORMS TODAY COULD BE STRONG, WITH HAIL AND  
GUSTY WINDS POSSIBLE AT KCOS AND KPUB LATE THIS AFTERNOON.  
 

 
   
PUB WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM...PETERSEN  
LONG TERM...LINE  
AVIATION...PETERSEN  
 
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