Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 091043
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
443 AM MDT WED JUL 9 2014

.SHORT TERM...(TODAY THROUGH FRIDAY NIGHT)
ISSUED AT 440 AM MDT WED JUL 9 2014

PRETTY QUIET NIGHT WITH JUST SOME SCT MIDLVL CLOUDS PASSING ACROSS
THE REGION. THE MONSOONAL RIDGE IS LOCATED NEAR THE FOUR CORNERS
REGION WITH THE BEST SUBTROPICAL MOISTURE ACROSS ARIZONA AND
NEVADA. STORM CHANCES THIS AFTN WILL BE BETTER THAN YESTERDAY BUT
NOT AS GOOD AS THE FOLLOWING DAYS (THURS AND FRI). SFC WINDS WILL
BE SOUTH-TO-SOUTHEAST THIS AFTN ACROSS THE PLAINS WITH GOOD LLVL
MOISTURE...ESPECIALLY OVER THE NEBRASKA PANHANDLE WHERE DEWPOINTS
WILL BE IN THE 55-60F RANGE. THIS RESULTS IN LI VALUES AROUND -5C
ACROSS THE PANHANDLE. A WEAK SHORTWAVE MOVING OVER THE NORTHERN
PLAINS DURING THE AFTN WILL SERVE TO STRENGTHEN THE FLOW ALOFT SUCH
THAT BULK SHEAR WILL BE 40-45 KTS. WITH THESE CONVECTIVE
PARAMETERS...A BIT CONCERNED ABOUT A STRONG TO SVR STORM IN THE
PANHANDLE. SPC HAS THE DAY1 SLIGHT RISK GRAZING CHEYENNE COUNTY
BUT MAINLY TO THE SOUTHEAST OF THE CWA. THINKING THAT COVERAGE OF
STORMS WILL BE ISOLATED DUE TO RISING HEIGHTS ALOFT OVER THE
COURSE OF THE DAY.

MIDLVL RIDGE SHIFTS EASTWARD INTO NEW MEXICO ON THURS. THIS
MOVEMENT CAUSES THE MIDLVL FLOW TO HAVE A MORE WEST TO SOUTHWEST
COMPONENT WITH INCREASING SUBTROPICAL MOISTURE. IT IS THE MOISTURE
PLUME CURRENTLY OVER NEVADA THAT PUSHES ACROSS THE CWA ON THURS
AFTN. THE GFS SHOWS PW VALUES RISING TO AROUND 1 INCH EVEN FOR
AREAS TO THE WEST OF THE LARAMIE RANGE...SO HAVE MORE OF A SCT
COVERAGE OF STORMS. MIDLVL FLOW IS WEAKER ON THURS AND COMBINED
WITH LESS SFC INSTABILITY...THE SVR RISK IS QUITE SMALL. THE
MODELS CONTINUE TO INDICATE THAT FRI SHOULD SEE THE GREATEST
COVERAGE OF STORMS. PW VALUES RISE FURTHER WITH MOST LOCATIONS AT
1-1.3 INCHES. IN ADDITION...A WEAK COOL FRONT/SFC BOUNDARY WILL
MOVE OVER THE PLAINS IN THE MORNING WITH LLVL WINDS BECOMING
INCREASING EASTERLY AND UPSLOPE. HEAVY RAIN WILL PROBABLY BE THE
PRIMARY THREAT WITH THE STORMS ON FRI...ALTHOUGH SMALL HAIL WILL
BE POSSIBLE ALSO.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 440 AM MDT WED JUL 9 2014

AN INCREASINGLY ACTIVE PERIOD TAKING SHAPE FOR THE UPCOMING WEEKEND
AND INTO EARLY NEXT WEEK. THE SRN PLAINS HIGH PRESSURE WILL
RETROGRADE WEST TOWARDS THE FOUR CORNERS/GREAT BASIN BY EARLY NEXT
WEEK. A SERIES OF SHORTWAVES WILL ROTATE AROUND ITS PERIPHERY AND
INTERACT WITH A FAIRLY PERSISTENT INSTABILITY AXIS THAT WILL EXIST
ALONG THE FRONT RANGE. MEDIUM RANGE GUIDANCE ARE CONSISTENT IN
MOVING THE FIRST SHORTWAVE AND ASSOCIATED WK FRONT THRU THE REGION
ON SATURDAY. NORTHEASTERLY UPSLOPE FLOW WILL FOLLOW IN THE LLVLS
AIDING CONVECTIVE COVERAGE. MODELS ALSO SHOW THE RRQ OF A H3 JET
STREAK SAGGING SOUTH LATE IN THE DAY...WHICH WILL ELEVATE DEEP LAYER
SHEAR TO AROUND 40 KNOTS. WOULD SUSPECT AT A MINIMUM A FEW STRONG
STORMS ON SATURDAY...WHICH PERHAPS SOME MARGINALLY SEVERE ACTIVITY.
CONVECTION WILL LIKELY BECOME ELEVATED AND LINGER SATURDAY NIGHT AND
SUNDAY MORNING AS WELL. CONVECTIVE COVERAGE LOOKS A BIT LESS ON
SUNDAY...BUT STILL CANT RULE IT OUT GIVEN ACTIVE NORTHWEST FLOW.
HIGH PRESSURE CENTER WILL RE-ESTABLISH ITSELF NR THE FOUR
CORNERS/GREAT BASIN MON-TUE. NORTHWEST FLOW WILL BE THE
RESULT...ALLOWING FOR A STRONGER FROPA SOMETIME ON MONDAY. THE ECMWF
IS THE QUICKEST IN DRIVING IT THRU DURING THE DAYTIME HOURS...WHILE
THE GFS HOLDS IT BACK UNTIL MONDAY NIGHT. IN EITHER
CASE...CONVECTIVE CHANCES WILL INCREASE AGAIN FOR BOTH
MONDAY/TUESDAY. SHOWER/THUNDERSTORM COVERAGE AND ORGANIZATION WILL
AGAIN BE AIDED BY THE RRQ OF A H3 JET STREAK DIVING INTO THE CENTER
OF THE COUNTRY. HAVE COOLED TEMPERATURES SOME FOR TUE AND WED...BUT
STILL LIKELY NOT ENOUGH IF THE STRONGER FROPA IS REALIZED. WEDNESDAY
LOOKS TO TURN A BIT DRIER...BUT STEERED THE FORECAST TOWARD
CLIMATOLOGY GIVEN TIMING UNCERTAINTIES AT THE FAR RANGES OF THE
PERIOD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY EVENING)
ISSUED AT 1106 PM MDT TUE JUL 8 2014

NO SIGNIFICANT AVIATION CONCERNS WITH VFR CONDITIONS EXPECTED FOR
ALL TERMINALS ACROSS THE AREA. LIGHT AND VARIABLE WINDS ARE LIKELY
THROUGH TONIGHT AS HIGH PRESSURE ALOFT REMAINS IN PLACE OVER THE
AREA. CLOUDS WILL INCREASE TONIGHT WITH A MIDLVL SCT-BKN CLOUD DECK
DEVELOPING ACROSS WYOMING. INCLUDED VCSH FOR CDR AND AIA AFTER 09Z
WED WITH A WEAK DISTURBANCE AFFECTING THE AREA...BUT OVERALL
CONFIDENCE IN SHOWER DEVELOPMENT IS LOW. THERE IS A RISK FOR A FEW
SHOWERS AND THUNDERSTORMS ON WED AFTN AND EVE...SOME OF WHICH COULD
BE STRONG TO SEVERE WITH HAIL AND GUSTY WINDS. GREATEST COVERAGE
WILL BE NEAR THE MOUNTAINS...SO ADDED VCTS TO CYS AND LAR.

&&

.FIRE WEATHER...
ISSUED AT 440 AM MDT WED JUL 9 2014

MINIMAL FIRE WEATHER CONCERNS THROUGH FRIDAY. HUMIDITY VALUES THIS
AFTERNOON WILL BE IN THE 15-20 PERCENT RANGE FOR AREAS TO THE WEST
OF THE LARAMIE RANGE...HOWEVER WIND GUSTS WILL GENERALLY BE BELOW
20 MPH. ISOLATED THUNDERSTORMS WILL BE POSSIBLE DURING THE
AFTERNOON AND EVENING. MOISTURE WILL INCREASE ON THURSDAY AND
FRIDAY AND MINIMUM HUMIDITY VALUES WILL RISE TO ABOVE 25 PERCENT.
THE INCREASE IN MOISTURE WILL RESULT IN A MORE WIDESPREAD COVERAGE
OF SHOWERS AND THUNDERSTORMS ON THESE DAYS.

&&

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

$$

SHORT TERM...FINCH
LONG TERM...HAHN
AVIATION...HAMMER
FIRE WEATHER...FINCH



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