Area Forecast Discussion
Issued by NWS Cheyenne, WY

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

000
FXUS65 KCYS 120445
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1045 PM MDT FRI APR 11 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 300 PM MDT FRI APR 11 2014

MAIN FORECAST FOCUS CONTINUES TO CENTER AROUND THE POTENTIAL FOR
A SPRING SNOWSTORM SATURDAY NIGHT AND SUNDAY. BEFORE THAT
HAPPENS...AFTERNOON SATELLITE PIX SHOW TWO SEPARATE SHORTWAVES...
ONE SPINNING THRU THE PACNW AND THE OTHER JUST BEGINNING TO MOVE
INTO SOCAL. NRN AND CENTRAL ROCKIES STILL UNDER THE INFLUENCE OF
THE NRN STREAM WITH WNW MID/UPPER-LEVEL FLOW ADVECTING A THIN
CIRRUS CANOPY ACROSS THE NRN HALF OF THE CWA. THIS PATTERN WILL
CONTINUE THRU THE OVERNIGHT HOURS...WITH DRY CONDITIONS PREVAILING.
THE FLOW WILL BACK ON SATURDAY AS THE PACNW SHORTWAVE AMPLIFIES
AND THE SRN STREAM SHORTWAVE ENERGY APPROACHES THE FOUR CORNERS.
FALLING PRESSURES IN THE LEE WILL SPIN UP A SFC LOW OVR SOUTHEAST
COLORADO AND INVERTED SFC TROF EXTENDING NORTH ALONG THE FRONT
RANGE. THIS WILL PROVIDE A FAVORABLE AREA OF CONVERGENCE FOR
CONVECTIVE INITIATION ON SATURDAY AFTERNOON. LIFTED INDICES WILL
FALL SLIGHTLY NEGATIVE TO AROUND -1C SOUTH OF THE NORTH PLATTE
RIVER VALLEY. EVEN THOUGH LLVLS WILL BE FAIRLY DRY...EXPECT AT
LEAST ISOLATED SHOWERS AND THUNDERSTORMS DEVELOP BY LATER SATURDAY
AFTERNOON. THIS INVERTED SFC TROF WILL SLIDE EAST INTO THE SRN
PANHANDLE AS WELL LATE SATURDAY AFTERNOON...SO ISOLATED THUNDER
LOOKS A SAFE BET THERE. OTHERWISE...ONE MORE WARM DAY IN STORE ON
SATURDAY AS H7 TEMPERATURES OF AROUND 0C RESULTING IN HIGHS IN THE
60S...WITH EVEN SOME LOW 70S OVR LOWER ELEVATIONS OF THE WRN
NEBRASKA PANHANDLE.

12Z MODEL DATA HAS NO LONGER TRENDED AS FAR WEST WITH THE
SHORTWAVE AS PREVIOUS OUTPUT HAD. COLD FRONT STILL LOOKS TO SLIDE
FROM N TO S SATURDAY EVENING...WITH THE BULK OF THE COLD AIR
HOLDING OFF UNTIL LATE SATURDAY NIGHT. PRECIPITATION WILL START
OUT AS RAIN SATURDAY EVENING BEFORE TRANSITIONING TO SNOW FROM
NORTH TO SOUTH BY LATE IN THE EVENING AND MORE SO DURING THE
OVERNIGHT HOURS. THERE WILL STILL BE NO SHORTAGE OF LIFT...WITH
UPSLOPE...OVERRUNNING ATOP THE SFC FRONT...JET COUPLETING AND
ASCENT AHEAD OF THE SHORTWAVE. TEMPERATURES WILL BE COLD ENOUGH
FOR SNOW EVERYWHERE BY EARLY MORNING SUNDAY. SNOW WILL BE HEAVY AT
TIMES DURING THE DAY ON SUNDAY...WITH RATES POTENTIALLY
APPROACHING 1 INCH PER HOUR AT TIMES. THE NAM LINGERS SNOW INTO
SUNDAY EVENING AS WELL. FOR NOW HAVE CONSIDERED THIS SLOWER
DEPARTURE AS AN OUTLIER AND CONTINUED THE IDEA SUPPORTED BY THE
GFS/ECMWF AS WELL AS EARLIER RUNS WITH SNOW COMING TO AN END
LATE SUNDAY AFTERNOON. ADDITIONALLY...NORTHEAST WIND GUSTS OF 25
TO 35 MPH WILL PRODUCE PATCHY/AREAS OF BLOWING AND DRIFTING SNOW
MAINLY ON SUNDAY. AS FOR ACCUMULATIONS...LOOKING AT GENERALLY 8-14
INCHES POTENTIAL ABOVE 8 KFT...4-8 INCH POTENTIAL BETWEEN 5-8 KFT
AND LESSER AMOUNTS BELOW. HAVE OPTED TO HOIST A WINTER STORM WATCH
GENERALLY FOR AREAS ABOVE 5000 FEET EFFECT 9 PM SATURDAY THROUGH 6
PM SUNDAY. AM CONCERNED THAT A FEW AREAS...SPECIFICALLY LOWER
ELEVATIONS OF CONVERSE AND PLATTE COUNTIES MAY END UP BEING AN
ADVISORY...HOWEVER WITH GUSTY WINDS AND THE POTENTIAL REMAINING
FOR PRECIP TO BE SNOW THRU THE DURATION...HAVE INCLUDED FOR NOW.
AM ALSO CONCERNED A BIT WITH AMOUNTS IN THE SIERRA MADRE RANGE AS
STRONG NORTHEASTERLY FLOW TYPICALLY SHADOWS THAT AREA. OVERNIGHT
LOW TEMPERATURES ON SUNDAY NIGHT WILL BE RELY ON THE AMOUNT OF
CLEARING. IF IT DOES CLEAR OUT LATE SUNDAY NIGHT...SINGLE DIGITS
AND TEENS WILL BE A REAL POSSIBILITY FOR LOWER ELEVATIONS WEST OF
THE LARAMIE RANGE.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 400 PM MDT FRI APR 11 2014

ALL MODELS SHOW THE LATE SEASON WINTER STORM MOVING SOUTH AND
EAST OF THE FORECAST AREA INTO THE SOUTHERN GREAT PLAINS ON
MONDAY. ALTHOUGH SUNSHINE IS EXPECTED DURING THE DAY. A
COMBINATION OF NORTHERLY FLOW AND THE POTENTIAL FOR A SOLID
SNOWPACK...ESPECIALLY ACROSS SOUTHEAST WYOMING...WILL LIKELY
RESULT IN MUCH COOLER TEMPERATURES THAN GUIDANCE IS SHOWING FOR
MONDAY. LOWERED MAX TEMPERATURES ANOTHER 5 TO 10 DEGREES WITH
HIGHS GENERALLY IN THE 40S ACROSS MOST OF THE AREA AND NEAR 50
OVER THE LOWEST ELEVATIONS OF WESTERN NEBRASKA. A WEAK RIDGE WILL
THEN PUSH ACROSS THE FORECAST AREA IN NORTHWEST FLOW FOR TUESDAY
RESULTING IN TEMPERATURES MODIFYING TO NEAR NORMAL ON TUESDAY.
ONE FORECAST CONCERN WILL BE FOG DEVELOPMENT EARLY MONDAY AS WELL
AS EARLY TUESDAY AS THE SNOW MELTS AND MOISTURE IS TRAPPED IN THE
RESIDUAL BOUNDARY LAYER.

MODELS SHOW THE NEXT POTENTIAL STORM SYSTEM MOVING INTO THE
NORTHERN AND CENTRAL ROCKY MOUNTAINS TUESDAY NIGHT...AND
POTENTIALLY LINGERING INTO EARLY THURSDAY MORNING AS ANOTHER COLD
FRONT MOVES SOUTH AND STALLS AGAINST THE MOUNTAINS. THIS SYSTEM IS
LOOKING SIMILAR TO THE WEEKEND STORM THIS FAR OUT IN THE LONG
RANGE...SO WILL HAVE TO MONITOR THIS ONE AS WELL. THE GEM IS
ALREADY HINTING TO ANOTHER WIDESPREAD SNOWFALL EVENT...ESPECIALLY
ALONG THE I80 CORRIDOR. INCREASED POP BETWEEN 20 TO 30 PERCENT
THROUGH THURSDAY. COOLER TEMPERATURES ARE EXPECTED...WITH HIGHS IN
THE 40S ACROSS MOST OF THE AREA THURSDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY EVENING)
ISSUED AT 1042 PM MDT FRI APR 11 2014

VFR CONDITIONS THROUGH 00Z SUNDAY. A COLD FRONT CONTINUES TO BE
FORECAST TO DROP SOUTH OUT OF MONTANA. EXPECTING INSTABILITY AHEAD
OF THE FRONT SATURDAY AFTERNOON TO PRODUCE INCREASING CHANCES FOR
SHOWERS AND ISOLATED THUNDERSTORMS. BEHIND THE FRONT...MUCH COLDER
AIR TO USHER IN WIDESPREAD SNOW THAT SHOULD REDUCE FLIGHT
CONDITIONS TO IFR/LIFR THROUGH SUNDAY AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 300 PM MDT FRI APR 11 2014

HUMIDITIES WILL TURN HIGHER THIS WEEKEND AS A STRONG STORM SYSTEM
PUSHES ACROSS THE DISTRICT. THERE IS A GOOD CHANCE FOR RAIN AND
THUNDERSTORMS ON SATURDAY...WITH SIGNIFICANT SNOW ACCUMULATIONS
ACROSS PORTIONS OF SOUTHEAST WYOMING LATE SATURDAY NIGHT AND
SUNDAY AS A STRONG COLD FRONT MOVES SOUTHWARD OUT OF CANADA. HIGH
TEMPERATURES ON SUNDAY WILL STRUGGLE TO GET OUT OF THE 20S.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
     AFTERNOON FOR WYZ101-103>107-110-112-114>118.

NE...NONE.
&&

$$

SHORT TERM...HAHN
LONG TERM...TJT
AVIATION...CLAYCOMB
FIRE WEATHER...HAHN






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