941  
FXUS65 KCYS 191735  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
1135 AM MDT WED JUN 19 2019  
   
UPDATE
 
 
ISSUED AT 1011 AM MDT WED JUN 19 2019  
 
WILL CONTINUE TO MONITOR THE POTENTIAL FOR STRONG WIND GUSTS ALONG  
I-80 BETWEEN RAWLINS AND LARAMIE THIS AFTERNOON. AS OF 10 AM,  
WINDS HAVE INCREASED BETWEEN 20 TO 30 MPH IN A FEW AREAS NEAR ELK  
MOUNTAIN AND ARLINGTON. NOT CONFIDENT ENOUGH FOR A WARNING QUITE  
YET, MAINLY BECAUSE OF TO THE UNUSUAL PATTERN AND TYPICAL  
FREQUENCY OF THESE TYPE OF EVENTS FOR THIS TIME OF THE YEAR.  
 
OTHERWISE, A MARGINAL RISK OF STRONG TO SEVERE THUNDERSTORMS  
STILL EXISTS TODAY ACROSS EAST CENTRAL WYOMING AND THE FAR  
NORTHERN NEBRASKA PANHANDLE, MAINLY FOR NORTH OF A LINE FROM  
JUST NORTH OF DOUGLAS WYOMING SOUTHEAST TOWARDS ALLIANCE NEBRASKA.  
MAIN CONCERN IS STRONG GUSTY WINDS, BUT THUNDERSTORM COVERAGE  
SHOULD BE PRETTY ISOLATED.  
 

 
   
SHORT TERM
 
(TODAY THROUGH FRIDAY EVENING)  
ISSUED AT 320 AM MDT WED JUN 19 2019  
 
...HIGH WIND WATCH FOR ARLINGTON THIS AFTERNOON THROUGH THURSDAY  
EVENING...  
 
AN ACTIVE AND UNUSUAL PATTERN FOR THIS TIME OF YEAR IS SET TO  
TAKE SHAPE ACROSS SOUTHEASTERN WYOMING AND THE ROCKY MOUNTAINS  
LATER THIS AFTERNOON AND CONTINUE TO THE WEEKEND. ANOMALOUSLY  
DEEP TROUGHING AND STRONG JET ENERGY WILL DEVELOP THIS MORNING  
AND AFTERNOON ACROSS WESTERN WYOMING. STRONG WEST WINDS WILL  
DEVELOP AS 700 AND 500 MB FLOW INCREASE AHEAD OF THE MAIN TROUGH.  
DEEP SURFACE MIXING FROM THE DRYING WEST WIND AND RESIDUAL  
ELEVATED UNSTABLE LAYERS WILL HELP TO TRANSPORT 35 TO 45 KTS OF  
MOMENTUM TO THE SURFACE. LOW LEVEL PRESSURE GRADIENTS WILL ALSO  
INCREASE THROUGH THE EVENING AND OVERNIGHT AS A DEEP LEE LOW  
DEVELOPS OVER EASTERN WYOMING. LOW LEVEL WINDS IN GAP AREAS WILL  
LIKELY ACCELERATE IN RESPONSE TO THE MIXING AND SUPPORTIVE LOW  
LEVEL PRESSURE GRADIENTS. A HIGH WIND WATCH WAS ISSUED FOR  
ARLINGTON TO ACCOUNT FOR THE THREAT OF STRONG WIND IMPACTS TO  
TRAILERS AND RECREATION VEHICLES OUTSIDE THE NORMAL CLIMATOLOGICAL  
TIMING.  
 
A FEW SHOWERS AND POSSIBLY HIGH BASED THUNDERSTORMS MAY ALSO  
DEVELOP IN THE AFTERNOON AND EVENING HOURS MAINLY OVER THE EASTERN  
PLAINS WHERE RESIDUAL MOISTURE REMAINS THE HIGHEST. PSEUDO  
DRYLINE/ SURFACE TROUGH WILL LIKELY INITIATE SCATTERED STORMS OVER  
THE EASTERN PLAINS WITH THE POTENTIAL FOR DAMAGING WINDS THANKS  
TO LARGE LOW LEVEL INVERTED V SIGNATURES. AGREE WITH SPC ON  
MAINTAINING THE MARGINAL SEVERE PROBS THROUGH THE AFTERNOON.  
STORMS WILL QUICKLY FADE WITH THE LOSS OF DAYTIME HEATING AND  
LITTLE PRECIPITATION IS EXPECTED OVERNIGHT.  
 
THURSDAY WILL AGAIN BE WINDY FOR THE INTERIOR VALLEYS AND FOOT  
HILLS AS THE MAIN BRUNT OF THE JET AND LEE LOW CONSOLIDATE OVER  
THE REGION. THE REST OF THE AREA SHOULD REMAIN WARMER AND MOSTLY  
DRY THROUGH THE DAY. THURSDAY AFTERNOON WILL LIKELY BE THE BEST  
TIME FOR STRONG GUSTS TO REACH THE SURFACE WITH WELL ESTABLISHED  
UPPER AIR SUPPORT AND DEEP MIXING FROM WARM TEMPERATURES.  
THIS HIGH WIND SUPPORTIVE PATTERN WILL QUICKLY FADE THURSDAY  
EVENING AS LIFT AND STEEP MID LEVEL LAPSE RATES FROM THE  
APPROACHING TROUGH OVERSPREAD THE REGION. SHOWERS AND  
THUNDERSTORMS WILL LIKELY DEVELOP THURSDAY EVENING AND CONTINUE  
THROUGH FRIDAY MORNING AS THE LEE LOW MOVES TO THE EAST DRAGGING A  
COLD FRONT SOUTH AND EAST ACROSS THE AREA. LOW LEVEL FLOW WILL  
ADVECT DEEP MOISTURE BACK INTO THE REGION TRANSITIONING BACK TO A  
WET AND STORMY PATTERN THROUGH THE WEEKEND. EXPECT COOLER  
TEMPERATURES AND PRECIPITATION ON FRIDAY AS CONTINUED TROUGHING  
AND MOISTURE RETURN SUPPORTS SHOWER AND THUNDERSTORM ACTIVITY.  
   
LONG TERM
 
(SATURDAY THROUGH NEXT WEDNESDAY)  
 
SUMMARY: MAIN FOCUS WILL BE ON SATURDAY AND SUNDAY TIME FRAME WITH  
GREATER SHOWER AND THUNDERSTORM LIKELIHOOD WHILE EARLY TO MID NEXT  
WEEK LOOKS DRIER AND WARMER. HAZARDS ON SATURDAY AND PERHAPS SUNDAY  
COULD BE POCKETS OF HEAVY RAINFALL AND A FEW STRONG THUNDERSTORMS.  
SUNDAY IS MORE CONDITIONAL AT THIS TIME DEPENDING ON PATTERN  
EVOLUTION AND TIMING.  
 
WEATHER DETAILS: QUITE ACTIVE PATTERN TO END THE WORK WEEK GOING  
INTO THE WEEKEND WITH A LARGE-SCALE TROUGH OVER THE NORTHERN PLAINS  
BACK ACROSS THE PACIFIC NORTHWEST PER MULTI-MODEL CONSENSUS. SEVERAL  
VORTICITY MAXIMUMS AND EMBEDDED SHORTER WAVELENGTH TROUGHS WILL  
ROTATE ABOUT THE PARENT TROUGH ACROSS WYOMING. AS A RESULT, A  
FRONTAL BOUNDARY WILL SHIFT NEAR AND/OR BISECT SOUTHEAST WYOMING  
LATE FRIDAY INTO SATURDAY AS THE FIRST SHORTWAVE TROUGHS PIVOTS  
ACROSS NORTH-CENTRAL WYOMING. WITH BROAD SYNOPTIC LIFT AND  
ISENTROPIC UPGLIDE OVER-TOP THE FRONTAL ZONE, SHOWERS WILL LIKELY  
PERSIST FRIDAY NIGHT INTO EARLY SATURDAY MORNING. DEEPER H7-H5  
SOUTHWEST FLOW WILL OCCUR BY SATURDAY, BRINGING THE FRONTAL BOUNDARY  
NORTH AS A WARM FRONT WHILE ALSO ADVECTING HIGHER THETA-E AIR INTO  
THE REGION. WITH GREATER THETA-E AIR COMES GREATER INSTABILITY AND  
COVERAGE OF SHOWERS AND STORMS SHOULD INCREASE SATURDAY AFTERNOON  
WITH ADDED DAYTIME HEATING. NOT OUT OF THE QUESTION THAT SOME STORMS  
COULD BE STRONG AND ALSO HAVE HEAVY RAIN IN ISOLATED AREAS. IT  
REMAINS TO EARLY TO PINPOINT MORE FAVORED AREAS OF THIS POSSIBLE  
HEAVIER RAINFALL.  
 
MID-RANGE MODELS DIVERGE ON SUNDAY WITH GFS MUCH SLOWER ON TROUGH  
MOVEMENT WHILE ECMWF MORE PROGRESSIVE BUT HAS SLOWED VS. THE  
PREVIOUS 18/12Z RUN. LATEST OPERATIONAL GFS REMAINS QUITE BULLISH ON  
MORE RAIN/STORM CHANCES SUNDAY BUT WILL TEMPER THESE DOWN UNTIL  
GREATER MID-RANGE AGREEMENT OCCURS.  
 
FOR EARLY TO MID NEXT WEEK - WARMER AND OVERALL DRIER CONDITIONS  
LOOK TO SET UP WITH SHORTWAVE RIDGING OCCURRING OVER THE CENTRAL  
ROCKIES. WHILE SOME AFTERNOON HIGH TERRAIN SHOWERS/STORMS COULD BE  
POSSIBLE, COVERAGE COMPARED TO THE CURRENT STRETCH OF WET WEATHER  
SHOULD BE REDUCED BY A GOOD FACTOR.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)  
ISSUED AT 1132 AM MDT WED JUN 19 2019  
 
CONTINUED STRONG WINDS AND ISOLATED SHOWERS AND THUNDERSTORMS  
POSSIBLE LATER THIS AFTERNOON INTO THE EARLY EVENING. BASED OFF  
THE LATEST HRRR STRONGEST POTENTIAL WILL BE ON THE NORTHERN  
COUNTIES WITH KCDR SEEING MORE OF THE THUNDERSTORM ACTIVITY THOUGH  
LINGERING STORMS MAY PASS NEAR FROM KCYS EASTWARD. MVFR CONDITIONS  
AT THE TERMINAL MAY BE POSSIBLE WITH ANY STORMS OVER EACH SITE. MODELS  
ARE ALSO TRENDING TO STRONGER WIND FIELD ALOFT PARTICULARLY AT  
KLAR TO INTRODUCE OVERNIGHT LLWS THERE.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 320 AM MDT WED JUN 19 2019  
 
FIRE WEATHER CONCERNS REMAIN LOW THANKS TO THE VERY WET AND COOL  
PATTERN OF LATE. INCREASING WINDS AND DECREASING RH WILL FAVOR  
MARGINAL ELEVATED FIRE WEATHER CONDITIONS ACROSS THE WEST TODAY  
AND THURSDAY BUT FUELS REMAIN WET AND FIRE WEATHER IS UNLIKELY TO  
BE CRITICAL. ADDITIONAL MOISTURE WILL RETURN FOR THE WEEKEND  
ENDING ANY THREAT.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 320 AM MDT WED JUN 19 2019  
 
FLOOD WARNING FOR THE NORTH PLATTE AT SARATOGA REMAINS. THE NEXT  
UPDATE IS EXPECTED BY 10 AM THIS MORNING. 3 AM HYDROGRAPHS SHOW A  
CONTINUED STEADY RISE ABOVE ELEVATED BASE FLOWS AT THE SITE.  
RIVER STAGE IS EXPECTED TO CONTINUE ABOVE 8 FEET TODAY WITH  
EXPECTED CREST IN MINOR FLOOD STAGE AT 8.5 FEET WITHIN THE NEXT 20  
TO 24 HOURS. LITTLE CHANGE IS EXPECTED TODAY WITH LOW CHANCES FOR  
PRECIPITATION INTO THE BASIN. WARMER TEMPERATURES AND STRONG  
WINDS COULD SLIGHTLY INCREASE EVAPORATION AND LIMIT SNOW MELT RUN  
OFF TODAY SLOWING THE RISE. HOWEVER, THE FORECAST REMAINS ON  
TRACK AND MINOR FLOODING IS POSSIBLE. WET WEATHER RETURNS THIS  
WEEKEND AND COULD INCREASE FLOWS.  
 

 
   
CYS WATCHES/WARNINGS/ADVISORIES
 
 
WY...HIGH WIND WATCH FROM 3 PM MDT THIS AFTERNOON THROUGH THURSDAY  
EVENING FOR WYZ110.  
 
NE...NONE.  

 
 

 
 
UPDATE...TJT  
SHORT TERM...ALYONS  
LONG TERM...JSA  
AVIATION...WM  
FIRE WEATHER...ALYONS  
HYDROLOGY...ALYONS  
 
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