970  
FXUS65 KCYS 070443  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
1043 PM MDT TUE JUN 6 2023  
   
UPDATE  
 
ISSUED AT 905 PM MDT TUE JUN 6 2023  
 
RAINFALL THIS EVENING IS COMING TO AN END. WENT AHEAD AND EXPIRED  
THE FLASH FLOOD WATCHES THAT WERE IN EFFECT FOR THE MULLEN BURN  
SCAR AND UPPER NORTH PLATTE RIVER VALLEY. UPDATES HAVE BEEN SENT.  
 
 
   
SHORT TERM  
(THIS EVENING THROUGH WEDNESDAY NIGHT)  
ISSUED AT 345 PM MDT TUE JUN 6 2023  
 
LATEST SATELLITE AND RADAR SHOWS NUMEROUS SHOWERS AND THUNDERSTORMS  
DEVELOPING INITIALLY OVER THE HIGH TERRAIN OF THE SIERRA MADRE,  
SNOWY, AND LARAMIE RANGES. DIURNAL CONVECTION WILL CONTINUE, BUT  
LIMITED 0-6 KM SHEAR AROUND 10 KT WILL KEEP STORMS PULSEY AND SINGLE  
CELLULAR. HOWEVER, SLOW STORM MOTIONS WILL POSE A RISK FOR POTENTIAL  
FLOODING NEAR THE MULLEN BURN SCAR. WHILE NOT AS MOIST AS THE PAST  
FEW DAYS WITH PWATS, FORECAST SOUNDINGS STILL SHOW FAIRLY GOOD  
MOISTURE THROUGH THE COLUMN TODAY. FARTHER EAST, A BOUNDARY HAS BEEN  
EVIDENT IN RADAR IMAGERY BETWEEN CHEYENNE AND LARAMIE AS A SUDO-  
DRYLINE ALONG THE SOUTH LARAMIE RANGE. ENHANCED SURFACE VORTICITY  
HAS BEEN NOTED WITH SURFACE SOUTHWESTERLIES TO THE EAST AND  
WESTERLIES FARTHER WEST. SO FAR, A FEW FAILED ATTEMPTS AT DEEPER  
CONVECTION HAVE BEEN MADE, BUT HI-RES GUIDANCE CONTINUES TO SUPPORT  
FURTHER STORM DEVELOPMENT IN THE AREA LATER THIS AFTERNOON. ONE  
CONCERN WILL BE THE POTENTIAL FOR LANDSPOUTS ALONG THIS BOUNDARY  
WITH ANY UPDRAFTS THAT COULD STRETCH THIS VORTICITY IN TO THE  
VERTICAL. LATEST SPC MESOANALYSIS HAS ALSO HIGHLIGHTED THIS AREA  
WITH THE NON-SUPERCELL TORNADO PARAMETER. OTHERWISE, HEAVY RAIN,  
SMALL HAIL, AND LIGHTNING WILL BE THE MAIN CONCERNS THROUGH THIS  
EVENING.  
 
THE ONGOING BLOCKING PATTERN CONTINUES WEDNESDAY WITH FAVORABLE  
UPPER LEVEL DIVERGENCE FROM THE UPPER LEVEL LOW OVER THE SOUTHWEST  
CONUS, ESPECIALLY ACROSS CARBON CO IN SOUTH-CENTRAL WY. STEEP MID-  
LEVEL LAPSE RATES WILL SUPPORT STORM DEVELOPMENT ONCE AGAIN WITH  
WIDESPREAD MLCAPE REACHING 500 J/KG. GREATER INSTABILITY WILL BE  
PRESENT WHERE LOW-LEVEL MOISTURE CAN SNEAK IN. WEAK FLOW ALOFT WILL  
ONCE AGAIN KEEP SHEAR LIMITED AND RESULT IN SLOW MOVING SINGLE CELL  
CONVECTION, ESPECIALLY WITH INITIAL DEVELOPMENT OVER THE HIGHER  
TERRAIN EARLY IN THE AFTERNOON BEFORE THE SHORTWAVE MOVES THROUGH.  
LOOKS TO BE ANOTHER DAY WHERE THE MULLEN BURN SCAR WILL NEED TO BE  
MONITORED FOR POTENTIAL FLOODING WITH HI-RES GUIDANCE DEPICTING  
NUMEROUS SHOWERS AND STORMS ACROSS CARBON AND ALBANY CO THROUGH THE  
EARLY EVENING. FARTHER EAST, STORM COVERAGE WILL BE LIMITED WITH A  
FEW ISOLATED STORMS POSSIBLE ALONG THE I-80 CORRIDOR EAST OF  
CHEYENNE. AFTERNOON TEMPERATURES WEDNESDAY WILL BE FAIRLY SIMILAR TO  
TODAY WITH HIGHS IN THE 70S TO LOW 80S.  
   
LONG TERM  
(THURSDAY THROUGH TUESDAY)  
ISSUED AT 345 PM MDT TUE JUN 6 2023  
 
THE LONG TERM FORECAST REMAINS LARGELY ON TRACK WITH UNSETTLED  
WEATHER CONTINUING THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK.  
 
THE SYNOPTIC WEATHER PATTERN WILL REMAIN MORE OR LESS FIXED THROUGH  
MOST OF THIS FORECAST PERIOD. THE STUBBORN RIDGE TO OUR NORTHEAST  
WILL MEANDER AROUND THE NORTHERN PLAINS TO SOUTHERN CANADIAN PRAIRIE  
OVER THE NEXT WEEK, FORMING AN OMEGA BLOCK ALONG WITH THE PERSISTENT  
CLOSED LOWS OVER THE CALIFORNIA COAST AND THE NORTHEAST CONUS. IN  
BETWEEN, OUR AREA WILL BE LARGELY UNDER NEARLY VERTICALLY STACKED  
SOUTHEASTERLY FLOW ON THE FRINGE OF THE PERSISTENT RIDGE. PICKING UP  
ON THURSDAY, THE MOISTURE PLUME WILL SHIFT EASTWARD AS THE SLOW  
MOVING CALIFORNIA CUTOFF LOW DRIFTS OUT WAY. A SUBTLE SHORTWAVE  
LIFTING NORTHWARD AS IT ROTATES AROUND THE UPPER LEVEL TROUGH IS  
LIKELY ON THURSDAY, WHICH MAY ENHANCE THE SOUTHEASTERLY FLOW ALOFT  
MAINLY OVER OUR WESTERN COUNTIES. INCREASING MID-LEVEL MOISTURE OVER  
THE HIGH PLAINS SHOULD ALLOW FOR A BIT MORE PRECIPITATION COVERAGE  
TO THE EAST EVEN AS SIGNIFICANT DRYING LIKELY REDUCES COVERAGE OVER  
CARBON COUNTY. THUS, HAVE POPS COMING UP SLIGHTLY MAINLY CENTERED  
AROUND THE LARAMIE RANGE AND ITS VICINITY. TRIMMED BACK FROM THE NBM  
SLIGHTLY, WHICH APPEARED A LITTLE AGGRESSIVE. THE SHORTWAVE  
MENTIONED ABOVE WILL LIFT THE MOISTURE PLUME A LITTLE FURTHER NORTH  
AND EAST FRIDAY, LEADING TO POPS EXPANDING TO A WIDER PORTION OF THE  
AREA. OVERALL, THE SEVERE THREAT LOOKS LOW FOR THURSDAY AND FRIDAY  
WITH VERY WEAK SHEAR IN PLACE. HOWEVER, LOCALLY HEAVY RAINFALL,  
SMALL HAIL, AND GUSTY WINDS WILL CONTINUE TO BE POSSIBLE.  
 
HEADING INTO THE WEEKEND, THE MAJOR FORECAST CHALLENGE WILL BE HOW  
FAR WEST THE INFLUENCE OF THE EASTERN CUTOFF LOW WILL EXTEND. MODELS  
HAVE TRENDED MORE TOWARDS A SOLUTION THAT BRINGS A SHORTWAVE AROUND  
THE FAR WESTERN FRINGE OF A NEW CUTOFF LOW DROPPING INTO THE GREAT  
LAKES REGION THIS WEEKEND. THIS COULD BRING A BACKDOOR FRONT THROUGH  
UNDERNEATH THE STILL PERSISTENT RIDGE TO OUR NORTH. THE MOISTURE  
PLUME ALOFT IS ALSO LIKELY TO PUSH BACK TO THE SOUTHWEST. GEFS MEAN  
PW AT SCOTTSBLUFF PEAK AT 00Z SUNDAY NEAR 1.0", WHICH EVEN HIGHER  
VALUES OFF TO THE NORTHEAST INCLUDING CHADRON. FORECAST SOUNDINGS  
HAVE THE SKINNY CAPE LOOK OF A HEAVY RAINFALL POTENTIAL OVER THE  
HIGH PLAINS STARTING SATURDAY AFTERNOON. HAVE FAIRLY WIDESPREAD HIGH  
POPS SATURDAY, BUT AGAIN TONED BACK FROM THE NBM A TAD TO KEEP MOST  
AREAS IN THE "LIKELY" CATEGORY JUST TO UNCERTAINTY STEMMING FROM A 4-  
DAY LEAD TIME. ON SUNDAY, MODELS HAVE TRENDED A BIT COOLER ON THE  
BACKSIDE OF THIS SHORTWAVE. 700-MB TEMPERATURES PER THE GEFS MEAN  
DROP TO +4C AT CHADRON, AND A GOOD NUMBER OF MODELS GET CLOSE TO  
+2C. MOST MODELS HAVE INSTABILITY DECREASING SIGNIFICANTLY ON  
SUNDAY, BUT WE MAY SEE SOME FAIRLY WIDESPREAD STRATIFORM RAINFALL  
DEVELOP WITH MOIST UPSLOPE FLOW AND SOME MODEST ISENTROPIC LIFT OVER  
THE AREA. THE NORTHEASTERN BOUNDARY OF THE MOISTURE PLUME IS LIKELY  
TO BE FAIRLY SHARP, WHICH INTRODUCES SOME UNCERTAINTY MAINLY IN THE  
NORTHERN PANHANDLE. LOOKS LIKE A COOL AND FAIRLY WET DAY SUNDAY WITH  
ON AND OFF SHOWERS LIKELY ESPECIALLY CLOSER TO THE MOUNTAINS.  
 
WE THEN FLIP BACK TO THE INFLUENCE OF THE WESTERN CUTOFF LOW INTO  
EARLY NEXT WEEK AS IT DRIFTS BACK TO THE NORTHEAST PER MODEL  
FORECASTS ON MONDAY AND TUESDAY. TEMPERATURES SHOULD WARM SOMEWHAT  
ON MONDAY AND MORESO ON TUESDAY. WHILE ENSEMBLE MOISTURE VALUES  
DECREASE SLIGHTLY FROM THE WEEKEND, THEY REMAIN LARGELY ABOVE NORMAL  
SUPPORTING ADDITIONAL ROUNDS OF AFTERNOON CONVECTION ACROSS THE  
AREA. ENSEMBLES HAVE NOW COME INTO MUCH BETTER AGREEMENT IN BREAKING  
DOWN THE OMEGA BLOCK AND RETURNING WESTERLY FLOW TO THE AREA BY THE  
MIDDLE OF NEXT WEEK. THE MOISTURE COULD BE A LITTLE SLOWER TO  
DEPART, BUT SOME FORM OF A PATTERN CHANGE DOES NOW APPEAR LIKELY.  
 
 
   
AVIATION  
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)  
ISSUED AT 1043 PM MDT TUE JUN 6 2023  
 
VFR CONDITIONS EXPECTED TO PERSIST THROUGH OVERNIGHT HOURS FOR ALL  
SOUTHEAST WYOMING AND WESTERN NEBRASKA TAF TERMINALS, WITH THE  
EXCEPTION OF KAIA. DUE TO CLEAR SKIES AND LIGHT UPSLOPE WINDS  
OVERNIGHT, SIMILAR CONDITIONS TO LAST NIGHT, OPTED TO ADD FG INTO  
THE TAF FOR KAIA FROM 09Z TO 13Z. TOMORROW'S FORECAST IS VERY  
SIMILAR TO TODAY'S WITH ISOLATED TO SCATTERED SHOWERS AND  
THUNDERSTORMS IN PORTIONS OF SOUTHEAST WYOMING, MAINLY ALONG AND  
WEST OF THE LARAMIE RANGE BETWEEN 18Z AND 03Z.  
 
 
   
FIRE WEATHER  
 
ISSUED AT 345 PM MDT TUE JUN 6 2023  
 
NO FIRE WEATHER CONCERNS WITH WIDESPREAD PRECIPITATION CHANCES  
CONTINUING WITH THE ONGOING PATTERN ACROSS SOUTHEAST WYOMING AND  
WESTERN NEBRASKA.  
 
 
   
CYS WATCHES/WARNINGS/ADVISORIES  
 
WY...NONE.  
NE...NONE.  
 
 
 
 
UPDATE...GCC  
SHORT TERM...MB  
LONG TERM...MN  
AVIATION...LK  
FIRE WEATHER...MB  
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