782  
FXUS65 KCYS 270935 CCA  
AFDCYS  
 
AREA FORECAST DISCUSSION...CORRECTED  
NATIONAL WEATHER SERVICE CHEYENNE WY  
327 AM MDT SAT MAY 27 2017  
   
SHORT TERM
 
(TODAY THROUGH MONDAY)  
ISSUED AT 325 AM MDT SAT MAY 27 2017  
 
GOES-R WATER VAPOR IMAGERY DEPICTED A POSITIVELY-TILTED TROUGH AXIS  
FROM ND ACROSS SOUTHEAST MT, WESTERN WY INTO NORTHERN UT/NV. A WELL-  
DEFINED SHORTWAVE WAS ROTATING SOUTHEASTWARD ACROSS SOUTHWEST WY.  
A WAVY STATIONARY SURFACE FRONT EXTENDED EAST-WEST FROM THE MIDWEST  
ACROSS THE CENTRAL PLAINS AND ROCKIES TO THE SOUTHERN GREAT BASIN.  
A STRONG SOUTHERLY LOW-LEVEL JET AND FORCING FROM ENERGY ALOFT  
MAINTAINED STRONG CONVECTION OVER NORTHERN KS. REGIONAL RADARS  
DETECTED SCATTERED SHOWERS MOVING NORTHEAST FROM NORTHWEST CO INTO  
SOUTHEAST WY AND FAR WESTERN NE. SOME PATCHY FOG FORMED OVERNIGHT  
OVER PORTIONS OF FAR SOUTHEAST WY AND THE WESTERN NE PANHANDLE.  
TEMPERATURES WERE IN THE 30S AND 40S, WITH WESTERLY WINDS 5-15 MPH.  
 
THE UPPER TROUGH WILL SHIFT TO THE EAST ACROSS THE CWA TODAY AND  
INTO THE PLAINS THIS EVENING. CYCLONIC FLOW ALOFT AND A FEW WEAK  
DISTURBANCES ROTATING THROUGH THE TROUGH WILL MAINTAIN A COOL AND  
SHOWERY PATTERN TODAY. ISOLATED AFTERNOON THUNDERSTORMS ARE ALSO  
POSSIBLE WITH LOW-MID LEVEL LAPSE RATES NEAR 7 DEG C/KM AND CAPE  
VALUES 200-500 J/KG. STRONG CONVECTION IS NOT EXPECTED THOUGH WITH  
WEAK SHEAR AND INSTABILITY. HIGH TEMPERATURES TODAY WILL AVERAGE  
10-15 DEGREES BELOW SEASONAL NORMALS WITH MID 50S-MID 60S.  
NORTHWESTERLY WINDS WILL BE BREEZY THROUGH THE DAY WITH GUSTS TO  
30 MPH. SHOWERS WILL END THIS EVENING WITH SUBSIDENT AND MORE  
STABLE AIR MASS IN THE WAKE OF UPPER TROUGH PASSAGE.  
 
SUNDAY WILL TREND SOMEWHAT DRIER WITH A NORTHWEST FLOW ALOFT ON  
THE ANTICYCLONIC SIDE OF THE WESTERN CONUS UPPER RIDGE. IT WILL  
BE BREEZY ACROSS THE PLAINS WITH NORTHWEST WINDS GUSTING TO 25  
MPH. ANOTHER EMBEDDED SHORTWAVE INTERACTING WITH WEAK MOISTURE  
CONVERGENCE WILL FAVOR WIDELY SCATTERED AFTERNOON CONVECTION  
OVER THE MOUNTAINS AND FAR NORTH/NORTHEAST PLAINS. HIGH  
TEMPERATURES SUNDAY WILL BE 5-10 DEGREES WARMER WITH MID 60S-LOW  
70S.  
 
LITTLE CHANGE MONDAY WITH THE UPPER RIDGE STILL TO THE WEST AND  
CYCLONIC FLOW ALOFT FROM THE INFLUENCE OF A UPPER LOW NORTH OF  
LAKE SUPERIOR. A UPPER LEVEL DISTURBANCE AND SLIGHTLY MORE  
UNSTABLE ENVIRONMENT SUGGESTS HIGHER CONVECTIVE COVERAGE OVER  
SOUTHEAST WY, ESPECIALLY THE MOUNTAINS AND FOOTHILLS. HIGH  
TEMPERATURES MONDAY WILL BE A FEW DEGREES WARMER.  
   
LONG TERM
 
(MONDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 245 AM MDT SAT MAY 27 2017  
 
AN UPPER RIDGE OVER THE WESTERN CONUS WILL MOVE SLOWLY EAST ACROSS  
THE AREA DURING THE EARLY TO MIDDLE PART OF NEXT WEEK AND OVER THE  
PLAINS STATES BY FRIDAY. AT THE SURFACE, A COOL HIGH PRESSURE AREA  
WILL SETTLE SOUTHWARD OUT OF CANADA INTO THE NORTHERN AND CENTRAL  
PLAINS BY WEDS THEN SHIFT EAST THURSDAY AND FRIDAY. MAINLY DRY AND  
MILD CONDITIONS ARE EXPECTED OVER THE CWA MONDAY NIGHT AND TUESDAY,  
THOUGH A FEW SHOWERS MAY OCCUR NEAR THE COLORADO BORDER. DAILY  
CHANCES FOR SHOWERS AND TSTMS THEN RETURN FOR WEDS THROUGH FRIDAY  
AS IMPULSES LIFT NORTHEAST ACROSS THE REGION AND INTERACT WITH  
SOME INCREASED INSTABILITY. WARMER TEMPERATURES AND BETTER MOISTURE  
RETURN WILL RESULT FROM LEE TROUGHING OVER THE HIGH PLAINS.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)  
ISSUED AT 225 AM MDT SAT MAY 27 2017  
 
SOME LINGERING SHOWERS EARLY IN THE PERIOD MAINLY OVER THE NEB  
PANHANDLE. SCTD IFR CIGS EARLY IN THE PERIOD BUT IMPROVING DURING  
THE MORNING. SCTD SHOWERS AND A FEW TSTMS AGAIN LATER THIS MORNING  
THROUGH THE AFTERNOON.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 225 AM MDT SAT MAY 27 2017  
 
THE COOL AND SHOWERY WEATHER WILL CONTINUE TODAY. ISOLATED AFTERNOON  
THUNDERSTORMS ARE ALSO FORECAST, HOWEVER STRONG STORMS ARE NOT  
EXPECTED. SOMEWHAT DRIER AND MILDER WEATHER RETURNS SUNDAY AND MONDAY,  
WITH WIDELY SCATTERED AFTERNOON THUNDERSTORMS, MAINLY OVER THE HIGHER  
TERRAIN OF SOUTHEAST WYOMING. MINIMUM HUMIDITIES OF 40 TO 50 PERCENT  
TODAY WILL DECREASE TO 30 TO 35 PERCENT SUNDAY AND MONDAY.  
 

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

 
 

 
 
SHORT TERM...MAJ  
LONG TERM...RE  
AVIATION...RE  
FIRE WEATHER...MAJ  
 
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