Area Forecast Discussion
Issued by NWS Cheyenne, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 062354
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
554 PM MDT WED MAY 6 2015

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 300 PM MDT WED MAY 6 2015

AFTERNOON WATER VAPOR LOOP PORTRAYED A HIGHLY AMPLIFIED LARGE
SCALE PATTERN ACROSS THE LOWER 48. PESKY UPPER TROUGH OVER THE
WESTERN HIGH PLAINS CONTINUES TO PRODUCE A WIDE VARIETY OF
INCLEMENT WEATHER FROM THE CENTRAL ROCKIES TO NORTHERN AND
CENTRAL PLAINS. A MORE SIGNIFICANT UPPER TROUGH WAS DIGGING
SOUTH THROUGH THE PACIFIC NORTHWEST. MOST OF THE TSTORM ACTIVITY
HAS BEEN WELL SOUTH AND EAST OF THE CWA TODAY...WITH GENERALLY
COOL AND SHOWERY CONDITIONS. THE SURFACE ANALYSIS SHOWED A QUASI-
STATIONARY FRONT FROM SOUTHERN WY ACROSS SD AND NORTHERN IA. AN
INVERTED SURFACE TROUGH EXTENDED NORTH FROM A LOW OVER NORTHEAST
CO INTO THE WESTERN DAKOTAS.

THE 12Z DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT PROGGING
THE UPPER TROUGH OVER THE CENTRAL PLAINS TO WEAKEN AS IT LIFTS
NORTHEAST ACROSS THE EASTERN DAKOTAS AND UPPER MIDWEST THROUGH
THURSDAY NIGHT. MEANWHILE...THE UPPER TROUGH OVER THE NORTHWEST
INTENSIFIES AS IT DIGS FURTHER SOUTH INTO CA DURING THE NEXT 24
HOURS...THEN GRADUALLY MOVES EAST TOWARD THE FOUR CORNERS FRIDAY
NIGHT. THE FLOW ALOFT WILL CONTINUE FROM THE SOUTHWEST...TRANSPORTING
SUBTROPICAL MOISTURE INTO THE CWA. A SERIES OF WEAK UPPER LEVEL
DISTURBANCES WILL INTERACT WITH THE MOISTURE TO KEEP SHOWER
CHANCES GOING THROUGH THE SHORT TERM...WITH QPF AMOUNTS AVERAGING
BETWEEN 0.25" AND 0.75". AFTERNOON/EARLY EVENING TSTORM ACTIVITY
WILL REMAIN ISOLATED AND GENERALLY CONFINED TO THE SOUTHERN
PORTION OF THE CWA THURSDAY...AND MAINLY WEST OF THE LARAMIE RANGE
FRIDAY. FOG POTENTIAL WILL BE MINIMIZED BY A MIXED BOUNDARY LAYER
TONIGHT...BUT MENTIONED PATCHY FOG FROM THE SUMMIT ACROSS THE
SOUTHEAST WY PLAINS AND SOUTHERN NE PANHANDLE. NEAR SEASONAL
TEMPERATURES WILL PREVAIL THROUGH THURSDAY...THEN COOL BELOW
NORMAL THURSDAY NIGHT AND FRIDAY WITH NORTHEASTERLY FLOW.
PRECIPITATION WILL BEGIN TO TRANSITION TO A RAIN/SNOW MIX FRIDAY
NIGHT ALONG AND WEST OF THE LARAMIE RANGE AS SNOW LEVELS DROP TO
AROUND 8000 FEET.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 300 PM MDT WED MAY 6 2015

ATTENTION WILL BE FOCUSED ON THE UPPER LOW THAT WILL EJECT
NORTHEAST FROM THE FOUR CORNERS AREA SATURDAY INTO THE CENTRAL AND
NORTHERN PLAINS ON SUNDAY. BY FAR MAIN PROBLEMS WILL BE QPF AND
SNOWFALL AMOUNTS...AND THE SNOW LEVELS.

MODELS CONTINUE TO BE IN FAIRLY GOOD AGREEMENT WITH THE EVOLUTION
OF THIS SYSTEM. LATEST RUNS HAVE NUDGED THE SYSTEM A BIT FASTER
ACROSS THE AREA BUT STILL VERY HIGH QPF FORECASTED FOR MUCH OF THE
CWA. LEE CYCLONE WILL BE DEEPENING SOMEWHERE OVER EASTERN COLORADO
SATURDAY WITH GFS FARTHER NORTH THAT THE EC. REGARDLESS...COLDER
AIR WILL BE PULLED SOUTH ACROSS THE CWA SATURDAY WITH RAIN LIKELY
CHANGING TO SNOW AT INCREASINGLY LOWER ELEVATIONS DURING THE DAY
AS MID LEVEL TEMPS FALL WITH THE APPROACH OF THE UPPER LOW.
PRECIPITATION SHOULD BE ALL SNOW OVER MUCH OF SE WY SAT NIGHT
INTO SUNDAY AS 700MB TEMPS FALL TO -5 TO -10C BY SUNDAY MORNING...
WITH THE PANHANDLE SOMEWHAT MORE DELAYED IN CHANGEOVER SAT NIGHT
AS 700MB TEMPS COOL LATER. GUSTY SFC WINDS WILL LIKELY ADD TO
PROBLEMS SAT NIGHT AND SUNDAY. SNOWFALL AMOUNTS HARD TO PROJECT AT
THIS TIME DUE TO UNCERTAINTY OF THE TRACK OF THE SYSTEM AND HOW
MUCH QPF WILL OCCUR, BUT AMOUNTS OVER A FOOT LOOK A DECENT BET
OVER THE MTNS/LARAMIE RANGES WITH EVEN HIGHER AMOUNTS QUITE
POSSIBLE. COULD VERY WELL BE THE MOST SIGNIFICANT WINTER STORM OF
THE SEASON...IN MAY! DEFINITELY LOOKING LIKE ANOTHER WHITE MOTHERS
DAY FOR AT LEAST PARTS OF THE CWA.

SNOW LIKELY TO CONTINUE ACROSS THE CWA THROUGH MUCH OF SUNDAY AS
THE SFC/UPPER LOWS EDGE SLOWLY NE ACROSS NEBRASKA WITH PCPN
EXPECTED TO END LATE SUNDAY AS THE SYSTEM MOVES EVEN FARTHER AWAY.
MAINLY DRY AND COOL MONDAY THEN MODERATING TEMPS TUESDAY AND WEDS
WITH SOME MAINLY MTN SHOWERS POSSIBLE IN ASSOCIATION WITH A COUPLE
WEAK IMPULSES RIDING ACROSS THE AREA.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 541 PM MDT WED MAY 6 2015

THE MAIN CONCERN WITH THIS TAF ISSUANCE IS THE POTENTIAL FOR MVFR
CEILINGS TONIGHT.

LATEST WATER VAPOR LOOP WAS SHOWING THE UPPER LEVEL LOW SPINNING
ACROSS NEBRASKA WITH THE SURFACE LOW OVER THE NEBRASKA PANHANDLE.
MEANWHILE...HIGH PRESSURE HAS BEEN TRYING TO NOSE INTO SOUTHEAST
WYOMING. THIS HIGH PRESSURE IS INDUCING DECENT PRESSURE RISES
ACROSS THIS REGION AS WELL. LATEST RADAR LOOP WAS SHOWING A
CLUSTER OF SHOWERS MOVING IN FROM THE LARAMIE RANGE. THIS ACTIVITY
SHOULD CONTINUE TO SPREAD EAST DURING THE NEXT COUPLE OF HOURS AND
BRING SOME RAINFALL AND LOWER MVFR CEILINGS FOR THE CYS TAF SITE
DURING THE NEXT 2 TO 3 HOURS. MEANWHILE...THE LAR/RWL TAF SITES
SHOULD SEE THE CEILINGS CLIMB TO VFR THROUGH THE REMAINDER OF THE
EVENING. MEANWHILE...THE PANHANDLE TAF SITES WILL SEE THE
SCATTERED SHOWERS PERSIST THROUGH THE EVENING WITH THE CEILINGS
FLUCTUATING BETWEEN MVFR AND VFR. THIS SHOWER ACTIVITY SHOULD
BEGIN TO CLEAR OUT THURSDAY MORNING BEFORE MORE SHOWER ACTIVITY
DEVELOPS DURING THE AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 300 PM MDT WED MAY 6 2015

THE COOL AND SET WEATHER PATTERN WILL CONTINUE THROUGH THE END OF
THE WEEK...WITH GOOD CHANCES FOR MEASURABLE RAINFALL. A STRONG
STORM SYSTEM WILL IMPACT THE DISTRICTS THIS WEEKEND WITH POTENTIALLY
WIDESPREAD AND HEAVY PRECIPITATION AMOUNTS...AS WELL AS GUSTY
NORTHERLY WINDS. THIS SYSTEM WILL BE COLD ENOUGH...WITH SNOW LEVELS
DROPPING TO AROUND 5500 FEET. MINIMUM RELATIVE HUMIDITY VALUES WILL
REMAIN WELL ABOVE CRITICAL THRESHOLDS THROUGH THE FORECAST PERIOD.
A TREND TOWARD WARMER AND DRIER CONDITIONS WILL COMMENCE NEXT WEEK.

&&

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

$$

SHORT TERM...MJ
LONG TERM...RE
AVIATION...REC
FIRE WEATHER...MJ



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