Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 170453
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1053 PM MDT THU APR 16 2015

.UPDATE...
ISSUED AT 539 PM MDT THU APR 16 2015

LATEST RADAR TRENDS SHOWING PRECIP FILLING IN OVER NORTEASTERN
COLORADO. LATEST INFRARED IMAGERY SHOWING RAPIDLY COOLING CLOUD
TOPS OVER SOUTHEASTERN COLORADO...MOVING DUE NORTH...SO OUR DRY
SLOT WE HAVE BEEN LOOKING AT LATE THIS AFTERNOON IS GETTING EDGED
EASTWARD. BOTH GFS AND NAM SOUNDINGS SHOWING FAVORABLE TEMPERATURE
PROFILES LATE THIS EVENING WITH SURFACE TEMPERATURES FALLING TO
BELOW FREEZING DURING THE BEST TIME OF LOW LEVEL MOISTURE
CONVERGENCE OVER THE SOUTH LARAMIE RANGE. VERY STRONG ISENTROPIC
LIFT OVER EXTREME SOUTHEAST WYOMING THIS EVENING FROM THE 300-310K
PRESSURE SURFACES. OPTED TO UPGRADE THE CURRENT WINTERWEATHER
ADVISORY WE HAVE GOING FOR CENTRAL LARAMIE COUNTY TO A WINTER
STORM WARNING AS WELL AS INCREASING SNOW AMOUNTS ACROSS THE WARNED
AREA AS ALL GUIDANCE POINTING TOWARDS OVER AN INCH OF STORM TOTAL
QPF WITH THIS EVENT. UPDATES HAVE BEEN SENT.

NEXT CONCERN DEALS WITH POSSIBILITY OF UPGRADING ADVISORIES
FURTHER NORTH ACROSS THE CENTRAL LARAMIE RANGE AND POSSIBLY PLATTE
COUNTY. CURRENT THINKING RIGHT NOW IS THE AXIS OF HEAVIEST PRECIP
WILL MOVE INTO THIS AREA TOMORROW AFTERNOON DURING DAYLIGHT
HOURS...SO MAYBE THERE WOULD BE A LITTLE MORE MELTING. DECIDED TO
LET THE NIGHT CREW TAKE ANOTHER LOOK AT THIS BEFORE ISSUING
ANYTHING.

&&

.SHORT TERM...(TONIGHT-SATURDAY NIGHT)
ISSUED AT 248 PM MDT THU APR 16 2015

FORECAST PROBLEMS WILL BE TEMPERATURES AND PRECIPITATION AMOUNTS
AND WHERE THE HEAVIER SNOWS WILL FALL OVER THE NEXT COUPLE DAYS.

UPPER LOW SPINNING OVER THE 4 CORNERS AREA SHOULD BEGIN A SLOW ENE
DRIFT ACROSS COLORADO LATER TONIGHT BEFORE LIKELY STALLING AGAIN
OVER COLORADO. PERIODIC DISTURBANCES ROTATING AROUND THIS LOW WILL
BRING SHOTS OF RAIN AND SNOW TO MOST OF THE CWA THROUGH SATURDAY
BEFORE A SHORTWAVE DROPS OUT OF SW CANADA AND PICKS UP THE
LOW...MOVING IT EAST INTO KANSAS AND DECREASING PCPN ACROSS THE
CWA. HIGHEST SNOWFALL WILL BE OVER THE LARAMIE RANGE AND THE
SNOWYS. ONE CONCERN IS CONVECTION CURRENTLY FIRING OVER KANSAS
WHICH COULD CUT MOISTURE AVAILABILITY IN THIS AREA AND REDUCE
SNOWFALL AMOUNTS. CURRENT WINTER STORM WARNING LOOKS IN GOOD SHAPE
REGARDLESS BUT FOR AREAS SUCH AS AROUND CHEYENNE SNOWFALL COULD
TURN OUT GREATER THAN CURRENTLY ANTICIPATED...WITH THE GREATEST
RISK BEING LATER TONIGHT INTO FRIDAY MORNING. WILL STAY WITH THE
WINTER WX ADVY BUT IT WONT TAKE MUCH TO UPGRADE IT.

TEMPERATURES TRICKY THROUGH FRIDAY ESPECIALLY ADJACENT TO THE LAR
RANGE WHERE EXPECTED WARMING TODAY DID NOT OCCUR DUE TO SOME COLD
AIR DAMMING. SFC WINDS LIKELY TO REMAIN NORTH TO NORTHEASTERLY
THUS WAA WILL BE LIMITED IF AT ALL IN THIS AREA. THUS EXPECT PCPN
TO REMAIN ALL SNOW THUS HAVE UPPED SNOWFALL AMOUNTS THERE. SHOULD
SEE IMPROVEMENT FRIDAY AFTERNOON OVER THE HIGH PLAINS WITH THE
NEXT EXPECTED LULL. PCPN SHOULD BECOME MORE SHOWERY IN NATURE
FRIDAY NIGHT AND SATURDAY WITH SNOW LEVEL RISING SLOWLY AS SOME
WARMING OCCURS.

.LONG TERM...(SUNDAY-WEDNESDAY)
ISSUED AT 248 PM MDT THU APR 16 2015

OUR PROBLEM CHILD UPPER-LOW WILL FINALLY LOOSEN ITS GRIP ON SUN AS A
STRONG KICKER SYSTEM DIVES SOUTHEAST ACROSS THE DAKOTAS. THE PATTERN
WILL REMAIN UNSETTLED THOUGH AS CYCLONIC MID LEVEL FLOW WILL REMAIN
INTACT OVER THE NORTHERN/CENTRAL ROCKIES. EXPECT INSTABILITY SHOWERS
TO CONTINUE FOR MOST OF THE CWA LATE IN THE WEEKEND. GFS/ECMWF SHOW
H7 TEMPS FALLING TO AROUND -8 TO -10 DEG C ON SUN AM BEHIND A STRONG
COLD FROPA...SO EXPECT THE PTYPE TO BE SNOW. THIS SHOULD NOT AMOUNT
TO MUCH OUTSIDE OF THE MOUNTAINS THOUGH. MOST MEDIUM RANGE GUIDANCE
SHOWS THE COOL/MOIST CYCLONIC FLOW PERSISTING THROUGH THE MIDDLE OF
NEXT WEEK...SO EXPECT CONTINUED DAILY CHANCES FOR RAIN/SNOW SHOWERS
WITH LITTLE OR NO ACCUMULATIONS. A WARMING TREND SHOULD BEGIN BY WED
AS RIDGING FINALLY TRANSLATES EASTWARD...ALLOWING H7 TEMPS TO CLIMB
BACK ABOVE FREEZING.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1049 PM MDT THU APR 16 2015

HRRR GUIDANCE USED FOR THE 06Z TAFS. IFR.LIFR CONDITIONS INITIALLY
CONFINED TO KLAR AND KCYS WITH WRAP AROUND MOISTURE AND SNOW.
LATEST IR IMAGERY SHOWS COOLING CLOUD TOPS THAT INDICATES MOE
WIDESPREAD PRECIP LATER THIS MORNING. HRRR SHOWS IFR/LIFR
SPREADING EAST INTO THE SOUTHERN NEBRASKA PANHANDLE DURING THE
09-10Z TIMEFRAME AND CONTINUING THROUGH THE DAY FRIDAY. COULD
PERSIST THROUGH FRIDAY NIGHT.

&&

.FIRE WEATHER...
ISSUED AT 248 PM MDT THU APR 16 2015

MINIMAL CONCERNS SEEN THROUGH THE WEEKEND WITH GENEROUS RAIN AN/OR
SNOWS FALLING OVER MUCH OF THE AREA. TEMPERATURES WILL BE COOL TO
MILD WITH WEATHER CONDITIONS NON-CRITICAL.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER STORM WARNING UNTIL NOON MDT FRIDAY FOR WYZ114>118.

     WINTER WEATHER ADVISORY UNTIL NOON MDT FRIDAY FOR WYZ103-105-106-
     110-112.

NE...NONE.
&&

$$

UPDATE...GCC
SHORT TERM...RE
LONG TERM...CLH
AVIATION...GCC
FIRE WEATHER...RE



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