704  
FXUS65 KCYS 172044  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
244 PM MDT SUN JUN 17 2018  
   
SHORT TERM
 
(THIS EVENING THROUGH MONDAY NIGHT)  
ISSUED AT 243 PM MDT SUN JUN 17 2018  
 
WET CONDITIONS TO CONTINUE ACROSS THE REGION FOR THE NEXT 24 HOURS  
AS QUASI-STATIONARY FRONT INTERACTS WITH A SERIES OF SHORTWAVES  
LIFTING NORTHEAST FROM A MEANDERING WESTERN US AREA OF LOW  
PRESSURE. THE CULPRIT OF THIS PERISTENT SLOW PATTERN PROGRESSION  
IS A REX BLOCK ACROSS WESTERN NOAM. 19Z SURFACE ANALYSIS SHOWS  
THE ENTIRE CWA WITHIN THE COOL/MOIST POST-FRONTAL AIR MASS N OF  
AFOREMENTIONED BOUNDARY, WHICH WAS DRAPED ACROSS NORTHERN AND  
CENTRAL CO. LATEST RADAR SHOWS ROBUST CONVECTION JUST SE OF THE  
CWA, A POCKET OF WEAK SHOWERS LIFTING NORTHEAST INTO THE CWA, AND  
A LINE OF THUNDERSTORMS ENTERING CARBON COUNTY.  
 
FOR TONIGHT, MODELS ARE CONSISTENT IN TRACKING SHORTWAVE ENERGY  
NORTHEAST INTO THE POST-FRONTAL AIR MASS, LIFTING CONVECTION  
ACROSS ALL OF SOUTHEAST WYOMING AND THE NEBRASKA PANHANDLE.  
RAINFALL RATES ARE NO LONGER ANTICIPATED TO NECESSITATE A FLASH  
FLOOD WATCH, SO WILL CANCEL IT WITH AFTERNOON ISSUANCE. THAT SAID,  
EXPECT PERIODIC LIGHT-MODERATE RAIN LATE THIS AFTERNOON AND  
EVENING AT MOST LOCATIONS. HAVE ALSO ADDED PATCHY FOG TO THE  
REGION AS THE MOIST LOW-LEVEL UPSLOPE IS A FAVORABLE PATTERN FOR  
DEVELOPMENT. WILL NEED TO KEEP AN EYE ON THE I-80 SUMMIT FOR  
POTENTIAL DENSE FOG LATER TONIGHT.  
 
BRIEF SUBSIDENCE ON THE BACK SIDE OF THE SHORTWAVE TROUGH AXIS  
WILL YIELD DRIER CONDITIONS LATE MONDAY MORNING THRU EARLY  
AFTERNOON. THIN RIBBON OF INSTABILITY DEVELOPS ONCE AGAIN LATE  
TOMORROW AFTERNOON/EVENING, AS A SECOND SHORTWAVE LIFTS ATOP AREA  
OF EAST/SOUTHEAST LOW-LEVEL UPSLOPE FLOW. ALTHOUGH CONVECTION  
WILL BE SLOW TO DEVELOP MONDAY, EXPECT THE POTENTIAL FOR STRONG OR  
MARGINALLY SEVERE T-STORMS, LIKELY DURING THE EVENING HOURS, AND  
PROBABLY RELATIVELY CLOSE TO THE CO STATELINE. SBCAPES ARE PROGD  
TO BE IN 1000-1500 J/KG ALONG WITH GOOD DIRECTIONAL SHEAR. THE GFS  
EVEN SHOWS CONVECTION BECOMING ELEVATED AND CONTINUING INTO THE  
PANHANDLE MONDAY NIGHT.  
   
LONG TERM
 
(TUESDAY THROUGH SUNDAY)  
ISSUED AT 243 PM MDT SUN JUN 17 2018  
 
THE UPPER LOW WILL SLOWLY FILL AS IT WOBBLES ACROSS THE NORTHERN  
ROCKIES THROUGH MID-WEEK. MOIST UPSLOPE FLOW WILL CONTINUE INTO  
THE FRONT RANGE ON TUESDAY YIELDING ANOTHER ROUND OF AFTERNOON &  
EVENING THUNDERSTORMS. INSTABILITIES OF 1000-1500 J/KG SUGGEST  
ANOTHER ROUND OF A FEW STRONG TO POTENTIALLY LOCALLY SEVERE AGAIN  
ON TUESDAY. AFTERNOON THUNDERSTORMS LOOK TO BE A GOOD BET AGAIN ON  
WEDNESDAY, HOWEVER STRENGTH AND ORGANIZATION WILL BE LESS AS  
INSTABILITY GETS SHUNTED TO THE SOUTH. DRIER WEST/NORTHWEST FLOW  
WILL BUILD IN BY THE END OF THE WEEK. ALTHOUGH CANT COMPLETELY  
RULE OUT AN AFTERNOON OR EVENING THUNDERSTORM, COVERAGE WILL BE  
SIGNIFICANTLY LESS COMPARED TO THE BEGINNING OF THE WEEK.  
TEMPERATURES WILL WARM BACK INTO THE 70S MOST PLACES BY THURSDAY,  
WITH EVEN SOME 80S BY SATURDAY.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)  
ISSUED AT 1129 AM MDT SUN JUN 17 2018  
 
COMPLEX FORECAST TODAY WITH A STALLED FRONTAL ZONE TO THE  
SOUTHEAST AND MOIST NORTHEASTERLY UPSLOPE FLOW NORTH OF THE FRONT.  
MOST TERMINALS WILL REMAIN MVFR AND IFR WITH OCCASIONAL DROPS TO  
LIFR WITH PASSING STORMS AND SHOWERS. NUMEROUS SHOWERS AND  
THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AND CONTINUE OVERNIGHT.  
LOW CIGS UNDER 010 WILL CONTINUE TO BE AN ISSUE WITH THE ABUNDANT  
MOISTURE. KSNY KAIA WILL LIKELY SEE +TS THIS AFTERNOON AS A FEW  
STRONG TO SEVERE STORMS GET GOING ALONG THE FRONT. LOW  
VISIBILITIES WILL DEVELOP WITH FOG AND MIST TONIGHT DROPPING CIGS  
TO THE DECK. SKIES WILL BEGIN TO CLEAR MONDAY MID MORNING AS DRIER  
AIR MOVES IN. EXPECT SCT TO BKN CIGS TO 025 IN MOST SPOTS BY 18Z  
MONDAY.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 243 PM MDT SUN JUN 17 2018  
 
COOL AND MOIST PATTERN WILL BEGIN THE WORK-WEEK, ESPECIALLY WHERE  
UPSLOPE FLOW WILL PERSIST ACROSS THE EASTERN PLAINS. AREAS WEST OF  
THE LARAMIE RANGE WILL BEGIN TO SLOWLY DRY OUT BEGINNING AS EARLY  
AS TOMORROW, WHERE AFTERNOON HUMIDITIES OF 20-40 PERCENT WILL BE  
FAIRLY COMMON. SEE THAT TREND CONTINUING THROUGH MUCH OF THE WEEK,  
WITH EVEN THE EASTERN PLAINS BEGINNING TO DRY BY THE END OF THE  
WEEK. EXPECT PERIODIC SHOTS OF MAINLY AFTERNOON/EVENING  
PRECIPITATION AT LEAST THROUGH WEDNESDAY, ESPECIALLY FOR AREAS  
ALONG AND EAST OF THE LARAMIE RANGE. AFTER TODAY, WEDNESDAY LOOKS  
TO OFFER THE BEST PRECIPITATION CHANCES FOR THE SNOWIES.  
TEMPERATURES WILL REMAIN BELOW SEASONAL NORMS THROUGH MUCH OF THE  
WEEK, WITH SOME WARMING NOTED BY THE END OF THE WEEK.  
 

 
   
CYS WATCHES/WARNINGS/ADVISORIES
 
 
WY...NONE.  
NE...NONE.  
 

 
 

 
 
SHORT TERM...CAH  
LONG TERM...CAH  
AVIATION...ADL  
FIRE WEATHER...CAH  
 
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