Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 092150
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
350 PM MDT WED APR 9 2014

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 350 PM MDT WED APR 9 2014

CURRENT OBS ACROSS SOUTHEAST WYOMING AND WESTERN NEBRASKA SHOW DRY
AND WINDY CONDITIONS THIS AFTERNOON. MAIN CONCERN HAS BEEN FIRE
WEATHER TODAY...WITH RELATIVE HUMIDITIES BETWEEN 10 TO 15 PERCENT
IN MOST AREAS. ATTENTION WILL THEN SHIFT TO THE COOL FRONT
FORECAST TO MOVE ACROSS THE AREA THIS EVENING. THIS FRONT IS
CURRENTLY NEAR THE WYOMING/MONTANA BORDER AND QUICKLY MOVING
SOUTHEAST. ALTHOUGH THE BOUNDARY LAYER IS RATHER DRY...CAN NOT
RULE OUT A THUNDER SHOWER OR TWO AHEAD OF THIS FRONT THIS EVENING.
KEPT POP BETWEEN 15 TO 25 PERCENT FOR ISOLATED TO WIDELY SCATTERED
SHOWERS AND SOME THUNDER UNTIL SUNSET. BEHIND THE FRONT DEWPOINTS
ARE INCREASING BETWEEN 35F TO 40F...SO THERE IS THE POTENTIAL FOR
FOG AS THE FRONT MOVES SOUTHWARD...STALLS ALONG THE ROCKY MOUNTAINS
AND WINDS SHIFT INTO THE NORTHEAST. LOW CLOUDS AND FOG ARE EXPECTED
TO FORM AFTER MIDNIGHT ALONG AND EAST OF THE LARAMIE RANGE. THE
CHANCES FOR FOG WILL INCREASE IF THERE ANY RAIN DOES FALL THIS
EVENING.

THIS COOL FRONT WILL RETREAT EASTWARD AS A WARM FRONT ON THURSDAY
AS A WAVE OF LOW PRESSURE DEVELOPS ALONG THE BOUNDARY. IT WILL BE
SLIGHTLY COOLER THURSDAY AFTERNOON...BUT HIGHS WILL STILL BE ABOVE
NORMAL AND IN THE 60S TO NEAR 70...WARMEST ACROSS THE LOWER NORTH
PLATTE RIVER VALLEY. THERE IS A BETTER CHANCE FOR AFTERNOON
SHOWERS AND THUNDERSTORMS AS AN UPPER LEVEL DISTURBANCE MOVES
ACROSS THE AREA IN THE AFTERNOON. MODELS SHOW TEMPERATURES ALOFT
LOWERING SLIGHTLY AS THE DISTURBANCE PUSHES THROUGH THE
AREA...RESULTING IN MORE INSTABILITY IN THE AFTERNOON. HOWEVER...A
DRY LAYER ALOFT MAY SUPPRESS ANY DEEPER CONVECTION FROM DEVELOPING.
KEPT POP BETWEEN 20 TO 30 PERCENT IN THE MOUNTAINS AND EAST OF THE
LARAMIE RANGE. FURTHER WEST...GUSTY WINDS WILL BE THE PRIMARY
FOCUS WITH GUSTS BETWEEN 45 TO 50 MPH. CONVECTION AND WINDS WILL
GRADUALLY DIMINISH AROUND SUNSET.

FOR FRIDAY AND FRIDAY NIGHT...UPPER LEVEL FLOW WILL START TO SHIFT
INTO THE WEST AHEAD OF A POTENTIAL WINTER WEATHER EVENT FOR THIS
WEEKEND. AHEAD OF THIS STORM...TEMPERATURES WILL INCREASE INTO THE
MID 60S (WEST) TO MID 70 (EAST) IN THE AFTERNOON. CONDITIONS WILL
REMAIN DRY WITH POP NEAR ZERO.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 350 PM MDT WED APR 9 2014

THE ACTIVE NRN STREAM WILL TAKE OVER ONCE AGAIN FOR THE SECOND HALF
OF THE WEEKEND. BEFORE THEN...ONE MORE RELATIVELY MILD DAY AHEAD FOR
SATURDAY. H7 TEMPERATURES WILL STILL BE HOVERING AROUND 0C...WHICH
WILL PRODUCE 60S ACROSS MOST OF THE AREA WITH LOWS 70S OVER THE
SRN NEBRASKA PANHANDLE. CLOUDS WILL BE ON THE INCREASE THRU THE
DAY COURTESY OF MOISTURE ADVECTION AHEAD OF SYSTEMS OVR THE PACNW
AND DESERT SW. MEANWHILE...AT THE SFC A COLD FRONT WILL PUSH SOUTH
THROUGH THE AREA DURING THE DAY ON SATURDAY. WOULD SUSPECT MANY
LOCATIONS WILL REACH THEIR HIGH TEMPERATURES AROUND MIDDAY
SATURDAY...WITH TEMPS FALLING AS CLOUD CANOPY THICKENS AND FRONT
DROPS THRU THE AREA. SHOWER CHANCES WILL BE ON THE INCREASE AS
UPSLOPE FLOW COMBINES WITH GOOD PACIFIC MOISTURE FETCH...SETTING
THE STAGE FOR A GOOD OVERRUNNING SET-UP. THIS WILL ESPECIALLY BE
THE CASE OVER THE HIER TERRAIN SATURDAY AFTERNOON. FREEZING LEVELS
WILL STILL BE UP AROUND 11 KFT SATURDAY AFTERNOON...SO EXPECT
MOSTLY RAIN THRU SUNSET. SNOW-LEVELS WILL DESCEND THRU 7 KFT BY
06Z SUNDAY AND TO 5 KFT BY SUNRISE SUNDAY. RAIN WILL TURN-OVER TO
SNOW LATE SATURDAY NIGHT MOST PLACES. THE BEST QG VERTICAL VELOCITIES
WILL BE THE HIGHEST AROUND THIS TIME AS WELL...SO EXPECT SOME AT
LEAST LIGHT/MODERATE ACCUMULATIONS LATE SATURDAY NIGHT. THE NRN
STREAM SHORTWAVE WILL DIVE SOUTHEAST FROM IDAHO TO WRN COLORADO ON
SUNDAY. THIS WILL CONTINUE TO PRODUCE WIDESPREAD LIGHT/MODERATE
SNOWFALL AT LEAST ON MONDAY MORNING...WITH A GRADUAL DECREASE
DURING THE AFTERNOON. HAVE BOOSTED PRECIPITATION CHANCES INTO
LIKELY MOST PLACES SATURDAY NIGHT/SUNDAY. SUNDAY WILL BE THE
COLDEST DAY OF THE PERIOD WITH HIGHS ONLY REACHING THE 30S.

A FLATTENING RIDGE WILL WORK IN EARLY NEXT WEEK...RESULTING IN DRY
CONDITIONS AND MODERATING TEMPERATURES. NEXT WEAK SYSTEM MAY BE IN
AS EARLY AS WEDNESDAY...SO HAVE INTRODUCED JUST SOME VERY LIGHT
PRECIP CHANCES THEN. OTHERWISE...TEMPERATURES WILL RETURN BACK TO
SEASONAL NORMS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY MORNING)
ISSUED AT 1147 AM MDT WED APR 9 2014

IN ADDITION TO THE BREEZY AFTERNOON WINDS...THE MAIN AVIATION
IMPACT WILL FOCUS ON THE POTENTIAL FOR LOW STRATUS/FOG BEHIND THE
COLD FRONTAL PASSAGE LATE TONIGHT/EARLY THURSDAY. BEFORE THE
FRONT...WINDS WILL GUST TO BETWEEN 25 AND 35 KNOTS AT ALL SITES
THIS AFTERNOON. THE FRONTAL PASSAGE WILL OCCUR BETWEEN
00-06Z...TURNING WEST WINDS NORTHERLY IN ITS WAKE. COOLER...MORE
MOISTURE AND UPSLOPE FLOW BEHIND THE FRONT WILL SET THE STAGE FOR
AT LEAST THE POSSIBILITY OF MVFR CIGS/VSBYS BETWEEN 09-14Z.


&&

.FIRE WEATHER...
ISSUED AT 350 PM MDT WED APR 9 2014

A RED FLAG WARNING REMAINS IN EFFECT EAST OF INTERSTATE 25
INCLUDING THE WESTERN NEBRASKA PANHANDLE UNTIL 7 PM. AFTERNOON
RELATIVE HUMIDITIES WILL REMAIN AROUND 15 PERCENT WITH WINDS
GUSTING BETWEEN 30 TO 40 MPH AT TIMES. A WEAK COOL FRONT WILL THEN
PUSH SOUTH ACROSS THE REGION TONIGHT...AND THEN EASTWARD AS A WARM
FRONT BY THURSDAY AFTERNOON...RESULTING IN A SLIGHT CHANCE OF
THUNDERSTORMS.RELATIVE HUMIDITIES WILL THEN TREND HIGHER LATE THIS
WEEK AND THIS WEEKEND WITH LIGHTER WINDS. THERE IS A CHANCE OF
SIGNIFICANT SNOW ACCUMULATIONS ACROSS PORTIONS OF SOUTHEAST
WYOMING ON SUNDAY AS A STRONG COLD FRONT MOVES SOUTHWARD OUT OF
CANADA.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING UNTIL 7 PM MDT THIS EVENING FOR WYZ310.

NE...RED FLAG WARNING UNTIL 7 PM MDT THIS EVENING FOR NEZ311>313.

&&

$$

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





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