Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 121744
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1144 AM MDT SAT JUL 12 2014

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 330 AM MDT SAT JUL 12 2014

CURRENT PREDAWN WATER VAPOR/H5 COMPOSITE ANALYSIS DEPICTED A MID/UPPER
LEVEL RIDGE FROM THE SOUTH CENTRAL CONUS TO THE PACIFIC NORTHWEST. POLAR
VORTEX RESIDED OVER NORTH CENTRAL CANADA. CLOCKWISE FLOW ALOFT WAS
ADVECTING SUBTROPICAL MOISTURE NORTHEASTWARD FROM THE CENTRAL AND
SOUTHERN ROCKIES INTO THE CENTRAL GREAT PLAINS. THE SHORTWAVE RESPONSIBLE
FOR THE STRONG CONVECTION FRIDAY EVENING MOVED INTO NEBRASKA AND IOWA
OVERNIGHT. RESIDUAL OUTFLOW BOUNDARIES COLLIDING IN THE WAKE OF THE
DISTURBANCE WAS PRODUCING ISOLATED SHOWERS ALONG THE COLORADO-WYOMING
BORDER. A COOL FRONT PUSHED SOUTH INTO NORTHEAST COLORADO AND EXTENDED
INTO CENTRAL WYOMING. NORTHERLY SURFACE WINDS PREVAILED BEHIND THE
FRONT. TEMPERATURES RANGED FROM THE MID 5OS TO MID 60S. POST-FRONTAL
UPSLOPE PRODUCED AREAS OF LOW CEILINGS.

00Z SHORT RANGE MODEL GUIDANCE IS CONSISTENT DEPICTING A PREVAILING
NORTHWEST FLOW ALOFT OVER THE CWA AS AN EXTENSION OF THE CANADIAN
POLAR VORTEX PROGRESSES SOUTHEAST INTO THE MIDWEST AND UPPER RIDGE
AMPLIFIES OVER THE INTERMOUNTAIN WEST. SUBTROPICAL MOISTURE COMBINED
WITH PASSING DISTURBANCES IN THE NORTHWEST FLOW WILL PRODUCE SCATTERED
MAINLY AFTERNOON AND EVENING SHOWERS/TSTORMS DURING THE PERIOD. MODEL
SOUNDINGS INDICATE PRECIPITABLE WATER VALUES OF ONE TO TWO STANDARD
DEVIATIONS ABOVE NORMAL /1.0 TO 1.25 INCHES/ TODAY. MUCAPES GENERALLY
RANGE FROM 500-1000 J/KG HOWEVER 0-6KM SHEAR PROFILES ARE NOT THAT
IMPRESSIVE /15-25 KT/. THE STRONGER TSTORMS WILL BE CAPABLE OF PRODUCING
HEAVY RAINFALL /0.5-1.O INCHES PER HR/...SMALL HAIL AND WIND GUSTS TO
40 KT. IT WILL BE COOLER TODAY WITH 700MB TEMPERATURES NEAR 10C.

SUNDAY WILL NOT BE AS CONVECTIVELY ACTIVE AS TODAY WITH PRECIPITABLE
WATER VALUES BETWEEN 0.75 AND 1.0 INCHES. MUCAPES ARE A BIT HIGHER
BUT SHEAR VALUES REMAIN LOW. TSTORMS WILL NOT BE AS EFFICIENT RAIN
PRODUCERS AS THEY WILL BE TODAY BUT STILL COULD PRODUCE BRIEF HEAVY
RAIN. 700MB TEMPERATURES ARE SIMILAR TO TODAY WITH HIGHS NEAR SEASONAL
NORMALS.

AS THE UPPER TROUGH DEEPENS TO THE EAST...IT WILL PUSH A FAIRLY STRONG
COLD FRONT SOUTHWARD THROUGH THE REGION MONDAY AFTERNOON WITH A SURGE
OF COOLER AND DRIER AIR ACROSS THE PLAINS. CONVERGENCE AND MOISTURE
ALONG AND AHEAD OF THE FRONT WILL GENERATE WIDELY SCATTERED AFTERNOON
CONVECTION FROM THE SOUTHERN NEBRASKA PANHANDLE INTO SOUTHEAST AND
SOUTH CENTRAL WYOMING. 700MB TEMPERATURES LOWER TO NEAR 6C EAST OF
THE LARAMIE RANGE.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY NIGHT)
ISSUED AT 315 AM MDT SAT JUL 12 2014

MODELS IN GOOD AGREEMENT THROUGH THE MIDDLE OF NEXT WEEK...SHOWING
A DEEP UPPER LEVEL TROUGH REMAINING OVER THE EASTERN HALF OF THE
UNITED STATES AND AN UPPER LEVEL RIDGE RETROGRADING SLIGHTLY
WESTWARD OVER THE EASTERN PACIFIC. THIS PATTERN WILL CHANGE VERY
LITTLE FROM THIS WEEKEND THROUGH AT LEAST WEDNESDAY OF NEXT WEEK.
THEREFORE...EXPECT SHOWERS AND TSTORMS TO CONTINUE EACH DAY WITH
GOOD UPSLOPE FLOW EXPECTED ALONG WITH DEEP MOISTURE AND DAYTIME
INSTABILITY. IN ADDITION...SEVERAL UPPER LEVEL DISTURBANCES AND AN
ACTIVE JET STREAM WILL PROVIDE THE NORTHERN AND CENTRAL ROCKY
MOUNTAINS AND ADJACENT PLAINS WITH FAVORABLE DYNAMICS TO PRODUCE
STRONG TSTORMS AND VERY HEAVY RAINFALL AT TIMES. SOME OF THIS
CONVECTIVE ACTIVITY WILL LINGER WELL INTO THE NIGHT THROUGH THE
MIDDLE OF THE WEEK. MODELS SHOW THE MAIN UPPER LEVEL DISTURBANCE
PUSHING SOUTHEAST ACROSS WYOMING SOMETIME BETWEEN TUESDAY NIGHT AND
WEDNESDAY AFTERNOON...PRODUCING WIDESPREAD RAIN SHOWERS AND
THUNDERSTORMS. WILL HAVE TO MONITOR THIS TIME PERIOD OVER THE NEXT
FEW DAYS DUE TO THE POTENTIAL FOR FLASH FLOODING IN ADDITION TO
STRONG TSTORMS. WITH NORTHWEST FLOW ALOFT...TEMPERATURES WILL BE 10
TO 15 DEGREES BELOW NORMAL FOR THIS TIME OF THE YEAR AND GENERALLY
IN THE 70S TO LOW 80S ACROSS THE HIGH VALLEYS AND HIGH PLAINS EAST
OF THE LARAMIE RANGE.

BY THURSDAY AND FRIDAY NEXT WEEK...MODELS DO INDICATE SLIGHTLY DRIER
AIR MOVING INTO WYOMING AS THE LOW TO MID LEVEL FLOW VEERS INTO THE
SOUTH...AND THEN WEST. LOWERED POP BETWEEN 15 TO 20 PERCENT ACROSS
SOUTHEAST WYOMING WITH JUST A SLIGHT CHANCE OF MOUNTAIN SHOWERS/TSTORMS.
HOWEVER...THIS BREAK IN THE ACTION MAY BE SHORT LIVED AS MODELS SHOW
ANOTHER COOL FRONT MOVING ACROSS THE AREA WITH A RETURN TO NORTHERLY
FLOW ALOFT BY NEXT WEEKEND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY MORNING)
ISSUED AT 1140 AM MDT SAT JUL 12 2014

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ACROSS SOUTHEAST
WYOMING TODAY WITH A FEW SHOWERS AND THUNDERSTORMS NOT OUT OF THE
QUESTION INTO THE NEBRASKA PANHANDLE. NOT EXPECTING SEVERE
THUNDERSTORMS...SO LOW CHANCES FOR HAIL AND STRONG WINDS HOWEVER
HEAVY RAIN AND LOW VISIBILITIES POSSIBLE WITH ANY OF THE STRONGER
THUNDERSTORMS. SHOWERS AND THUNDERSTORMS WILL LINGER INTO LATE
EVENING BEFORE DISSIPATING COMPLETELY. FOG NOT OUT OF THE
QUESTION LATE SATURDAY NIGHT...MAINLY ALONG AND WEST OF THE
LARAMIE RANGE.

&&

.FIRE WEATHER...
ISSUED AT 230 AM MDT SAT JUL 12 2014

NON-CRITICAL CONDITIONS WILL CONTINUE FOR THE NEXT SEVERAL DAYS AS
MONSOONAL MOISTURE KEEPS GOOD CHANCES FOR MAINLY AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS IN THE FORECAST. LOCALLY HEAVY RAINFALL AND
GUSTY WINDS WILL BE THE PRIMARY THREATS FROM THUNDERSTORMS TODAY.
TEMPERATURES WILL GRADUALLY COOL TO BELOW SEASONAL NORMALS THROUGH
THE MIDDLE OF NEXT WEEK AS A FEW COLD FRONTS PUSH SOUTH ACROSS THE
DISTRICTS. WARMER AND DRIER CONDITIONS WILL RETURN LATE NEXT WEEK.

&&

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

$$

SHORT TERM...JAMSKI
LONG TERM...TJT
AVIATION...SML
FIRE WEATHER...JAMSKI






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