Area Forecast Discussion
Issued by NWS Cheyenne, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KCYS 200604
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1204 AM MDT SAT SEP 20 2014

.UPDATE...
ISSUED AT 913 PM MDT FRI SEP 19 2014

A NUMBER OF OUTFLOW BOUNDARIES HAVE BEEN SITUATED ACROSS EASTERN
LARAMIE COUNTY THIS EVENING...AND INTERACTED WITH WHAT APPEARS
TO BE A PREFRONTAL TROUGH MOVING EAST ACROSS THE CWA TO MAINTAIN
DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS ALONG THE
I-80 CORRIDOR. A FEW SHOWERS CONTINUE TO POP UP AT THIS HOUR FROM
EASTERN LARAMIE COUNTY AND POINTS TO THE EAST...BUT THINK THE
MAIN SFC AND MID LEVEL FORCING HAS PUSHED SOUTH AND EAST OF THE
CWA BASED ON SATELLITE IMAGERY. WILL KEEP WIDELY SCATTERED
COVERAGE FOR SHOWERS WITH MENTION OF ISO-T THROUGH 06Z FOR THIS
AREA...BUT THIS MAY BE OVERLY OPTIMISTIC BASED ON RADAR TRENDS
ALREADY TAKING A DOWNWARD TURN. THE MAIN SFC COLD FRONT LOOKS TO
BE JUST NORTH OF THE CWA AND WILL CONTINUE TO MOVE SOUTH
OVERNIGHT. FOCUSED HIGHEST CLOUD COVER ALONG THE LARAMIE RANGE
THROUGH THE EARLY MORNING HOURS AS MODELS HINT AT A SCT STRATUS
DECK ACCOMPANYING THE FRONT ALONG WITH NORTH-NORTHEAST UPSLOPE
FLOW. OTHERWISE...FORECAST IS IN GOOD SHAPE.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 350 PM MDT FRI SEP 19 2014

NEAR TERM FORECAST CONCERNS REVOLVE AROUND PCPN CHANCES FOR THE REST
OF THE AFTN AND EVE. WATER VAPOR SATELLITE SHOWS A WELL PRONOUNCED
UPPER-LEVEL SHORTWAVE MOVING ACROSS NORTHWEST WY AT 20Z. ASSOCIATED
SFC COLD FRONT HAS MADE LITTLE FORWARD PROGRESS THIS AFTN...ANALYZED
FROM SOUTHWEST TO NORTHEAST ACROSS THE STATE. THIS FEATURE COMBINED
WITH MODEST LARGER SCALE SUPPORT SHOULD SERVE AS A FOCUS FOR SHOWER
AND TSTM DEVELOPMENT IN THE NEXT FEW HOURS. HRRR HAS BEEN CONSISTENT
WITH SHOWING ISOLATED ACTIVITY FROM SOUTHEAST WY INTO THE SOUTHERN
NE PANHANDLE BETWEEN 22Z AND 02Z. LACK OF SUBSTANTIAL FORCING SHOULD
KEEP THINGS ISOLATED. GFS AND NAM BUFKIT SOUNDINGS INDICATE INVERTED
V LLVL PROFILES OVER MUCH OF THE CWA. DCAPES AROUND 1300 J/KG ON THE
LATEST SPC MESOANALYSIS SUGGESTS GUSTY OUTFLOW WINDS COULD BE A BIT
OF A PROBLEM TONIGHT. DID NOT MENTION IN THE GRIDS WITH COVERAGE NOT
HIGH ENOUGH TO WARRANT.

COLD FRONT IS PROGGED TO SWEEP ACROSS THE CWA BY LATE TONIGHT. DRIER
AIR WILL SLOWLY WORK INTO THE AREA...ENDING CHANCES FOR PCPN FROM NW
TO SE BY 06Z SAT. GFS AND NAM SHOW H7 TEMPS COOLING TO 6 TO 8 DEG C
OVER THE PLAINS BY SAT AFTN...DOWN FROM AROUND TODAY`S 13 C OVER CYS
PER A RECENT LAPS SOUNDING ANALYSIS. DRY COLUMN OVERHEAD FOR SAT AS
HIGH-AMPLITUDE UPPER RIDGING TAKES OVER...SO LOOKING AT MOSTLY SUNNY
SKIES AND A SUBSTANTIAL COOL DOWN FROM TODAY`S HIGHS. NEXT CONCERN IS
A LARGE CUTOFF LOW CURRENTLY SEEN ON WATER VAPOR SATELLITE OVER WEST
CENTRAL CALIFORNIA. THIS FEATURE WILL LIFT SLOWLY NORTHEAST ON SUN
WITH INCREASING 700-300 MILLIBAR MOISTURE OVER CARBON COUNTY BY 12Z.
MOISTURE AND QG ASCENT OVERSPREADS THE CWA THROUGH THE REMAINDER OF
THE FCST PERIOD. LLVL UPSLOPE AND SOME CLOUD COVER SUGGESTS SUN AFTN
SHOULD BE QUITE COOL. THE MAJORITY OF MOS GUIDANCE SUGGESTS HIGHS AT
70F OR BELOW AS A GENERAL RULE...SO TRENDED LOWER ON TEMPS. ISOLATED
TO SCATTERED SHOWER AND THUNDERSTORM ACTIVITY WILL INCREASE FROM SW
TO NE DURING THAT TIME FRAME.

.LONG TERM...(MONDAY THROUGH THURSDAY)
ISSUED AT 350 PM MDT FRI SEP 19 2014

MODELS ARE IN GOOD AGREEMENT AT SHOWING THE UPPER LOW OVER THE
GREAT BASIN MOVING EASTWARD ON MON AND LOCATED OVER NORTHERN WY BY
THE AFTN. GOOD UPPER LEVEL DIFFLUENCE WILL DEVELOP DURING THE
DAY...ESPECIALLY ACROSS THE PLAINS. SCATTERED SHOWERS AND TSTMS
WILL BE POSSIBLE THROUGH THE DAY. LOOKING AT SOUNDINGS AND
CONVECTIVE PARAMETERS OVER THE NEBRASKA PANHANDLE...COULD SEE A
FEW STRONGER STORMS WITH SMALL HAIL. MID LEVEL LOW CONTINUES EASTWARD
INTO SOUTH DAKOTA ON MON NIGHT AND TUES WITH LARGE SCALE
SUBSIDENCE FOLLOWING. PRECIP CHANCES COME DOWN ON TUES AS THE BEST LIFT
AND MOISTURE IS WELL EAST...HOWEVER KEPT SLIGHT CHANCE POPS DURING
TH AFTN WITH WEAK INSTABILITY COMBINED WITH MODEST MID LEVEL
MOISTURE ON THE BACKSIDE OF THE LOW. IT WILL BE BREEZY ON TUES
WITH ENHANCED NORTHWEST FLOW ALOFT AND GOOD MIXING. THE REMAINDER
OF THE LONG TERM WILL FEATURE INCREASING HEIGHTS AS A RIDGE BUILDS
OVER THE INTERMOUNTAIN WEST IN ADVANCE OF A LARGE SCALE TROUGH OFF
THE WEST COAST. TEMPS WILL BE SLIGHTLY ABOVE SEASONAL NORMS AND
WINDS WILL BE RELATIVELY WEAK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1200 AM MDT SAT SEP 20 2014

WINDS WILL SHIFT TO NORTH AND NORTHEAST WITH THE PASSAGE OF A WEAK
COLD FRONT. UPSLOPE MAY LEAD TO SCATTERED LOW STRATUS ALONG THE
LARAMIE RANGE BY SATURDAY MORNING. OTHERWISE...VFR WILL PREVAIL.
EAST TO NORTHEAST WINDS WILL BE BREEZY AT TIMES FOR THE PLAINS
SATURDAY.

&&

.FIRE WEATHER...
ISSUED AT 350 PM MDT FRI SEP 19 2014

A WEAK COLD FRONT WILL MOVE ACROSS SOUTHEAST WY AND THE WESTERN NE
PANHANDLE TONIGHT. ISOLATED TO WIDELY SCATTERED SHOWERS AND STORMS
WILL BE POSSIBLE THROUGH THE AFTN AND EVE WITH GUSTY OUTFLOW WINDS
THE PRIMARY HAZARD. COOLER AND DRIER FOR SAT IN THE POST-FRONTAL AIR
MASS WITH LITTLE OR NO CHANCE FOR PCPN. THE NEXT CHANCE FOR WETTING
RAINS WILL BE FROM SUN NIGHT THROUGH TUE AS A POTENT WEATHER SYSTEM
MOVES SLOWLY NORTHEAST ACROSS THE REGION. CRITICAL FIRE WEATHER IS
NOT EXPECTED IN THE FORESEEABLE FUTURE.

&&

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

$$

UPDATE...RJM
SHORT TERM...HAMMER
LONG TERM...FINCH
AVIATION...JAMSKI
FIRE WEATHER...HAMMER





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.