Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 101028
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
428 AM MDT THU APR 10 2014

.SHORT TERM...(TODAY THROUGH FRIDAY NIGHT)
ISSUED AT 425 AM MDT THU APR 10 2014

THE COLD FRONT HAS PASSED THROUGH THE EASTERN PLAINS OVERNIGHT AND
HAS ESSENTIALLY STALLED ALONG THE LARAMIE RANGE. LIGHT RAIN SHOWERS
ARE EXPANDING IN COVERAGE ACROSS CONVERSE AND NIOBRARA COUNTIES INTO
THE NORTHERN NEBRASKA PANHANDLE AS A SHORTWAVE AND MID LEVEL
BAROCLINIC BAND MOVE OVER THIS AREA. WILL SEE SHOWERS CONTINUE
THROUGH THE MORNING WITH GENERALLY A FEW HUNDREDTHS UP TO ONE-TENTH
AN INCH OF QPF PROGGED FOR THIS AREA. PATCHY FOG REMAINS A
POSSIBILITY EARLY THIS MORNING ACROSS THE EASTERN PLAINS AS WELL AS
THE POST FRONTAL AIRMASS SETTLES. FURTHER WEST...WINDS WILL CONTINUE
TO BE BREEZY THROUGH THE MORNING WITH A FEW SPRINKLES POSSIBLE AS
THE WAVE MOVES OVERHEAD...BUT NOT EXPECTING MUCH ELSE WITH A DRY
BOUNDARY LAYER REMAINING IN PLACE.

THE NEXT SHORTWAVE FEATURE IN THIS NORTHWEST FLOW PATTERN WILL MOVE
OVER THE FORECAST AREA THIS AFTERNOON. THE STALLED FRONT WILL BEGIN
AN EASTWARD TREK ACROSS THE PLAINS LATE THIS MORNING WITH WESTERLY
WINDS INCREASING ALONG AND WEST OF INTERSTATE 25 AS THE W-E LOW LEVEL
PRESSURE GRADIENT STRENGTHENS WITH THE DEPARTING FRONT. AHEAD OF THE
FRONT...WINDS LOOK TO BE RELATIVELY WEAK AND OUT OF THE SOUTHEAST.
RESULTANT CONVERGENCE ALONG THE FRONT ALONG WITH WEAK INSTABILITY
PROGGED THIS AFTERNOON WILL INITIATE SHOWERS AND ISOLATED
THUNDERSTORMS THROUGH THE EARLY AFTERNOON MAINLY EAST OF A LUSK TO
KIMBALL LINE...WITH A FEW OROGRAPHIC SHOWERS POSSIBLE OUT WEST IN
THE LATE AFTERNOON AS THE UPPER WAVE MOVES THROUGH. TEMPERATURES
WILL BE ROUGHLY 5 TO 10F COOLER TODAY THAN YESTERDAY SO INSTABILITY
WILL BE QUITE WEAK OVERALL. HOWEVER...ROUGHLY 50 KT OF DEEP LAYER
SHEAR WILL BE IN PLACE THROUGH THE EARLY EVENING WITH UP TO 200 J/KG
OF CAPE PROGGED NEAR THE COLORADO BORDER AS THE FRONT MOVES THROUGH.
SO THERE IS A POSSIBILITY FOR SOME OF THIS ACTIVITY TO PRODUCE SMALL
HAIL AND GUSTY WINDS IF THE UPDRAFTS CAN SUSTAIN WITH THE STRONG
SHEAR AND WEAK INSTABILITY IN PLACE.

THE SHORTWAVE WILL MOVE OFF TO THE EAST TONIGHT...WITH DRY AND
WARMER CONDITIONS MOVING IN FOR FRIDAY. FORECAST SOUNDINGS ACROSS
THE EASTERN PLAINS WHERE FUELS ARE CURED DO NOT LOOK AS DRY FRIDAY
AFTERNOON AS THEY DID YESTERDAY...WITH HUMIDITIES LOOKING TO DROP
INTO THE UPPER TEENS. TEMPS WILL PEAK IN THE MID 60S TO MID
70S...AND WINDS ARE PROGGED TO BE MUCH WEAKER OVERALL DUE TO A
WEAKER W-E SURFACE PRESSURE GRADIENT. THEREFORE...THINK THE FIRE
WEATHER THREAT WILL BE ELEVATED BUT SHOULD NOT BREACH CRITICAL
THRESHOLDS.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 400 AM MDT THU APR 10 2014

MAIN FORECAST CONCERNS WILL FOCUS ON THE POTENTIAL FOR ACCUMULATING
SNOW AND COLDER TEMPERATURES THIS WEEKEND. THE LATEST MEDIUM RANGE
MODEL GUIDANCE CONTINUES TO INDICATE A DEEPENING UPPER TROUGH OVER
THE NORTH CENTRAL CONUS THIS WEEKEND. THE BULK OF THE SHORTWAVE
ENERGY WITH THIS FEATURE WILL DIG SOUTH FROM THE NORTHERN ROCKIES
TOWARD THE EASTERN GREAT BASIN AS PROGGED BY THE NAM...GEM AND ECMWF.
COLDER AIR FROM CANADA WILL SURGE SOUTH ACROSS THE CWA SATURDAY NIGHT.
ABUNDANT PACIFIC MOISTURE WILL OVERRUN THE SHALLOW COLD AIRMASS SETTING
THE STAGE FOR WIDESPREAD PRECIPITATION. QG FORCING MAXIMIZES SATURDAY
NIGHT AND SUNDAY MORNING. MODEL QPFS DIFFER WIDELY WITH THE ECMWF THE
WETTER BIAS. TRENDED TOWARD HPC/S QPF PREDICTION OF 0.25 TO 0.50 INCH
LIQUID EQUIVALENT. THERE WILL BE SUFFICIENT COLD AIR IN THE LOW LEVELS
TO PRODUCE SNOW. QUESTION IS HOW MUCH? STILL TOO EARLY TO PREDICT EXACT
ACCUMULATIONS BUT THE POTENTIAL EXISTS FOR SIGNIFICANT SNOWFALL FOR
THE HIGHER ELEVATIONS OF EAST CENTRAL AND SOUTHEAST WY. AFTER HIGHS
IN THE 60S TO LOWER 70S ON THE PLAINS SATURDAY...THE BOTTOM WILL FALL
OUT OF THE THERMOMETER SUNDAY WITH TEMPERATURES 25 TO 35 DEGREES COLDER.
700MB TEMPERATURES SUNDAY ARE PROGGED TO BE -10 TO -12C. BRISK NORTHEAST
WINDS WILL PRODUCE WIND CHILL TEMPERATURES IN THE 20S.

RAIN AND SNOW WILL END NORTH TO SOUTH SUNDAY NIGHT AS THE UPPER TROUGH
AND FORCING MOVE SOUTHEAST OF THE REGION. ADDITIONAL SNOW ACCUMULATIONS
SHOULD BE LIGHT. LOWS SUNDAY NIGHT WILL RANGE FROM THE TEENS MOUNTAINS
TO THE 20S ELSEWHERE. WINDS WILL BE DECREASING SUNDAY NIGHT WITH THE
RELAXATION OF THE PRESSURE GRADIENT.

MONDAY AND MONDAY NIGHT WILL BE DRY AND MILDER UNDER THE INFLUENCE OF
A PASSING UPPER RIDGE. HIGH TEMPERATURES MONDAY WILL REBOUND INTO THE
50S. IT WILL BECOME BREEZY WITH WEST TO SOUTHWEST WINDS GUSTING TO 35
MPH ALONG AND WEST OF THE LARAMIE RANGE.

ANOTHER PACIFIC TROUGH WILL BE MOVING ACROSS THE GREAT BASIN TUESDAY.
MODEL DIFFERENCES APPEAR AT THIS TIME WITH THE GFS INDICATING A
SOUTHWEST FLOW ALOFT WITH SHORTWAVE ENERGY LIFTING NORTHEAST ACROSS
WY WHEREAS THE ECMWF HOLDS THE ENERGY OVER THE SOUTHERN GREAT BASIN
WITH ZONAL FLOW ALOFT. IN EITHER CASE...SOME PACIFIC MOISTURE MAKES
IT AS FAR EAST AS THE LARAMIE RANGE IN THE FORM OF SCATTERED SHOWERS.
TRENDED CLOSER TO THE GFS WITH PRECIPITATION BECOMING MORE WIDESPREAD
TUESDAY NIGHT. TEMPERATURES WILL BE WARM ENOUGH WITH THIS PACIFIC
SYSTEM TO KEEP SNOW AMOUNTS LIGHT AND CONFINED TO THE HIGHER TERRAIN.
IT WILL BE ABOUT 5 TO 10 DEGREES COOLER ACROSS THE PLAINS WEDNESDAY
UNDER THE INFLUENCE OF EASTERLY LOW LEVEL FLOW.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 415 AM MDT THU APR 10 2014

COLD FRONT MOVED SOUTHWARD ACROSS THE PLAINS. A BRIEF PERIOD OF
MVFR CIGS IN PATCHY FOG WILL BE POSSIBLE EARLY THIS MORNING EAST
OF THE LARAMIE RANGE...OTHERWISE VFR CIGS. NORTHERLY WINDS EARLY
THIS MORNING ACROSS THE PLAINS WILL BACK TO THE SOUTHWEST LATER
THIS MORNING AS THE FRONT SHIFTS EASTWARD AS A WARM FRONT. WINDS
WILL BE GUSTY THROUGH MUCH OF THE DAYLIGHT HOURS TODAY OVER
SOUTHEAST WY. THERE WILL BE ISOLATED SHOWERS EARLY THIS MORNING
NORTH OF A DOUGLAS TO ALLIANCE LINE...AND THIS AFTERNOON ALONG AND
EAST OF THE MOUNTAINS. ISOLATED WEAK TSTORMS ARE POSSIBLE...BUT
CONFIDENCE IS NOT HIGH FOR INCLUSION IN THE TAFS.

&&

.FIRE WEATHER...
ISSUED AT 425 AM MDT THU APR 10 2014

LIGHT RAIN SHOWERS WILL CONTINUE EARLY THIS MORNING ACROSS NORTHERN
PORTIONS OF THE DISTRICT AS AN UPPER LEVEL DISTURBANCE MOVES OVERHEAD.
A SECOND DISTURBANCE WILL MOVE OVERHEAD THIS AFTERNOON AND WILL PUSH
A WARM FRONT EAST ACROSS THE PLAINS. THIS WILL RESULT IN A CHANCE
FOR RAIN SHOWERS WITH ISOLATED THUNDERSTORMS...ESPECIALLY EAST OF
A LINE FROM LUSK TO KIMBALL. FOR FRIDAY AFTERNOON...ELEVATED FIRE
WEATHER CONCERNS ARE ANTICIPATED FOR THE EASTERN PLAINS AS RELATIVE
HUMIDITIES WILL DROP INTO THE UPPER TEENS WITH BREEZY WESTERLY WINDS
IN PLACE. HUMIDITIES WILL THEN TREND HIGHER 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...NONE.
NE...NONE.
&&

$$

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





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