Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 111125
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
525 AM MDT FRI APR 11 2014

.SHORT TERM...(TODAY THROUGH SATURDAY NIGHT)
ISSUED AT 518 AM MDT FRI APR 11 2014

WARM AND DRY CONDITIONS WILL PREVAIL TODAY UNDER DRY WEST-NORTHWEST
FLOW. HIGH CIRRUS EVIDENT ON WATER VAPOR UPSTREAM OF THE CWA WILL
MOVE OVERHEAD TODAY...AND SHOULD KEEP TEMPS DOWN A FEW DEGREES FROM
WHAT THEY COULD BE WITH A 3 TO 5 C INCREASE AT 700 MB. HUMIDITIES
WILL DROP TO THE UPPER TEENS ACROSS THE PLAINS WITH TEENS AND 20S
EXPECTED OUT WEST. THE LEE SIDE PRESSURE TROUGH WILL BEGIN TO DEEPEN
TODAY AHEAD OF THE STRONG SHORTWAVE THAT WILL BEGIN TO MOVE ACROSS
THE PACIFIC NW...WITH THE STRONGEST SURFACE PRESSURE GRADIENT
DEVELOPING LATE THIS AFTERNOON AS THE TROUGH DEEPENS AND SHIFTS
SOUTHEAST ACROSS THE AREA. SURFACE WINDS WILL INITIALLY GENERALLY
BE AT A MORE SOUTHERN COMPONENT ACROSS THE EASTERN PLAINS...VEERING
TO THE WEST-NORTHWEST WITH THE MOVEMENT OF THE SURFACE TROUGH
AXIS. TIMING LOOKS TO BE SUCH THAT THE STRONGEST WINDS ACROSS THE
PLAINS WILL NOT DEVELOP UNTIL AFTER NOON...WITH GUSTS OF 25 TO 30
MPH POSSIBLE ACROSS SOUTHEAST WYOMING AND LIGHTER SPEEDS FURTHER
EAST. THEREFORE...WILL CONTINUE THE IDEA OF ELEVATED FIRE WEATHER
THREAT FOR THE PLAINS. A RATHER WARM NIGHT IS ON TAP FOR TONIGHT
WITH WINDS EASING OVERNIGHT AND VEERING TO THE NORTH-NORTHWEST AS
THE SURFACE TROUGH SHIFTS EAST AWAY FROM THE FORECAST AREA.

FOR SATURDAY...FLOW ALOFT WILL BEGIN TO BACK TO THE SOUTHWEST AHEAD
OF THE SHORTWAVE MOVING THROUGH THE PACIFIC NW WHILE A SECOND SHORTWAVE
TREKS ACROSS THE DESERT SOUTHWEST. ENERGY BREAKING OFF FROM THE MAIN
WAVE WILL MOVE UP TOWARD THE FORECAST AREA IN SOUTHWEST FLOW ALOFT...
ALONG WITH A FETCH OF PACIFIC MOISTURE. WINDS AT THE SURFACE LOOK
TO VEER TO THE EAST SOUTHEAST THROUGH THE MORNING ACROSS THE PLAINS...
WHICH WILL AID IN THE INITIATION OF CONVECTION OFF THE MOUNTAINS.
DURING THIS TIME...THE LEFT EXIT REGION OF THE SOUTHERN STREAM JET
WILL MOVE OVERHEAD SATURDAY MORNING WITH LI`S DROPPING TO BETWEEN
0 AND MINUS 2. THE COMBINATION OF UPPER LEVEL DYNAMICS...INSTABILITY
AND SURFACE FORCING WILL BRING A CHANCE FOR SHOWERS AND THUNDERSTORMS
BEGINNING LATE MORNING AND CONTINUING THROUGH THE AFTERNOON...WITH
THE BEST CHANCE FOR STORM ACTIVITY IN THE MOUNTAINS AND SOUTHERN
PLAINS. WITH THE PACIFIC FETCH IN PLACE...COULD SEE A FAIR BIT
OF QPF WITH THIS ACTIVITY. THE MAIN CANADIAN COLD FRONT ASSOCIATED
WITH THE NORTHERN SHORTWAVE WILL BEGIN TO TREK SOUTH THROUGH THE
AREA SATURDAY AFTERNOON...BUT THE STRONGEST CAA IS PROGGED TO HOLD
OFF UNTIL LATE SUNDAY NIGHT. SOUNDINGS SHOW MUCH OF THE AREA
REMAINING ABOVE FREEZING UNTIL AFTER 06Z SUNDAY...WITH THE
EXCEPTION BEING THE NORTHERN ZONES WHICH MAY DIP BELOW FREEZING
AFTER 03Z. SO PRECIP TYPE WILL INITIALLY BE QUITE TRICKY
ESPECIALLY WITH THE TRANSITION FROM RAIN TO SNOW. STRONG JET
DYNAMICS WILL BE OVERHEAD THROUGH THIS TIME AND FRONTOGENESIS WILL
STRENGTHEN OVERNIGHT FROM NORTH TO SOUTH. CONFIDENT WIDESPREAD
LIGHT TO MODERATE RAIN WILL OCCUR SATURDAY EVENING...WITH A SLOW
TRANSITION FROM RAIN TO SNOW SATURDAY NIGHT. TIMING WILL BE TRICKY
DEPENDING ON HOW MUCH THE SOUTHWEST FLOW ALOFT WILL SLOW THE
SOUTHERN TREK OF THE SURFACE COLD FRONT AND SUBSEQUENT LLVL CAA.
WITH THAT SAID...THE HEAVIEST SNOWS MAY NOT DEVELOP UNTIL LATE
SATURDAY NIGHT INTO SUNDAY MORNING WHEN STRONGEST CAA WILL
OCCUR...SO STILL THINK IT IS TOO EARLY TO ISSUE ANY WINTER
HIGHLIGHTS AT THIS TIME. ONCE RAIN DOES TRANSITION TO SNOW...CAN
EXPECT MODERATE TO HEAVY RATES THROUGH EARLY SUNDAY MORNING WHICH
COULD ACCUMULATE QUICK.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 500 AM MDT FRI APR 11 2014

THE LATEST MEDIUM RANGE MODEL GUIDANCE HAS TRENDED A BIT FURTHER
WEST WITH TRACK OF THE SHORTWAVE TROUGH INTO UTAH SUNDAY. A
INTENSIFYING SURFACE LOW TO THE SOUTHEAST OF COLORADO WILL DEEPEN
THE COLD AIR MASS. SNOW LEVELS WILL DROP TO 5000 FT SUNDAY MORNING.
COLD NORTHEAST UPSLOPE FLOW IN THE LOW LEVELS AND MOIST SOUTHWEST
FLOW IN THE MID LEVELS WILL RESULT IN A FAVORABLE OVERRUNNING
SITUATION. JET COUPLETING IN THE UPPER LEVELS WILL FURTHER ENHANCE
LIFT. SNOWFALL RATES WILL INCREASE TO AN INCH PER HOUR...WITH THE
THE POSSIBILITY FOR MODERATE TO HEAVY SNOWFALL. AS FOR SNOWFALL
ACCUMULATIONS SUNDAY...6 TO 8 INCHES WILL BE POSSIBLE ABOVE 8000
FT WITH 4 TO 6 INCHES BETWEEN 5000 AND 8000 FT. WARMER TEMPERATURES
WILL DELAY THE TRANSITION TO SNOW AT LOWER ELEVATIONS...LIMITING
SNOWFALL ACCUMULATIONS TO 3 INCHES OR LESS. PRECIPITATION WILL
DIMINISH FROM NORTH TO SOUTH SUNDAY EVENING. SNOW MAY BRIEFLY MIX
WITH RAIN SUNDAY AFTERNOON AT LOWER ELEVATIONS. ANOTHER PACIFIC
FROM THIS SPRING SNOWSTORM WILL BE GUSTY NORTHEAST WINDS OF 30 TO
40 MPH SUNDAY AND THE BLOWING AND DRIFTING SNOW. WINTER WEATHER
HIGHLIGHTS WILL BE DEFFERED TO LATER SHIFTS DUE TO UNCERTAINTY AND
POTENTIAL IMPACT OF WARMER TEMPERATURES ON SNOW AMOUNTS.
TEMPERATURES WILL BE SHARPLY COLDER SUNDAY...REMAINING IN THE 30S
THROUGHOUT THE DAY.

A RIDGE PATTERN EARLY NEXT WEEK WILL PROMOTE DRY CONDITIONS WITH
WARMER TEMPERATURES. HIGHS WILL REBOUND INTO THE 40S MONDAY AND
50S TO LOWER 60S TUESDAY. THE NEXT PACIFIC TROUGH WILL IMPACT
THE WEATHER DURING THE MID TO LATE WEEK PERIOD WITH CHANCES FOR
LIGHT RAIN AND SNOW SHOWERS. BREEZY WESTERLY WINDS WILL CONFINED
TO THE WEST OF THE LARAMIE RANGE...WITH BREEZY SOUTHERLY WINDS
TO THE EAST.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 430 AM MDT FRI APR 11 2014

ASIDE FROM A PERIOD OF IFR CIG/VSBY EARLY THIS MORNING AT ALLIANCE...
VFR WILL PREVAIL THROUGH TONIGHT WITH OCCASIONAL MID AND HIGH CLOUDS.
LIGHT WINDS EARLY THIS MORNING WILL BECOME SOUTHWESTERLY AND INCREASE
LATER THIS MORNING. GUSTS OF 25 TO 40 KT WILL BE COMMON ACROSS MUCH
OF SOUTHEAST WY...WITH GUSTS TO 25 KT FOR WESTERN NE PANHANDLE IN THE
AFTERNOON. WINDS WILL DIMINISH TO 10 TO 15 KT THIS EVENING AT THE
WESTERN PANHANDLE TERMINALS BUT REMAIN BREEZY FOR THE SOUTHEAST WY
TERMINALS.

&&

.FIRE WEATHER...
ISSUED AT 500 AM MDT FRI APR 11 2014

MODERATE FIRE WEATHER CONCERNS EXPECTED TODAY WITH MINIMUM HUMIDITIES
DROPPING TO BETWEEN 15 TO 20 PERCENT ALONG WITH BREEZY CONDITIONS AT
TIMES. THE HIGHEST THREAT WILL BE FOR THE SOUTHEAST WYOMING PLAINS.
HUMIDITIES WILL THEN TREND HIGHER THIS WEEKEND AS A STRONG STORM SYSTEM
PUSHES ACROSS THE AREA. THERE IS A GOOD CHANCE FOR RAIN AND THUNDERSTORMS
SATURDAY...WITH SIGNIFICANT SNOW ACCUMULATIONS ACROSS MUCH OF SOUTHEAST
WYOMING LATE SATURDAY NIGHT AND SUNDAY AS A STRONG COLD FRONT MOVES
SOUTHWARD OUT OF CANADA.

&&

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

$$

SHORT TERM...MAZUR
LONG TERM...JAMSKI
AVIATION...JAMSKI
FIRE WEATHER...MAZUR






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