Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 010257
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
757 PM MST SAT JAN 31 2015

.UPDATE...
ISSUED AT 756 PM MST SAT JAN 31 2015

SOUTHERN STREAM DISTURBANCE CONTINUES TO PUSH NORTHEAST AND
OUT OF THE AREA. SNOW HAS GENERALLY ENDED ACROSS THE NEBRASKA
PANHANDLE A SUBSIDENCE SETS IN BEHIND THIS DISTURBANCE...HOWEVER A
COLD FRONT AND NORTHERN STREAM DISTURBANCE IS QUICKLY FOLLOWING
AS IS MOVES INTO THE FORECAST AREA. SNOW SHOWERS ALREADY
DEVELOPING OVER SOUTHEAST WYOMING AND WILL QUICKLY SPREAD INTO THE
PANHANDLE THIS EVENING. MAINLY LOOKING FOR SCATTERED SNOW SHOWERS
TONIGHT WITH VERY LITTLE IN THE WAY OF SNOW ACCUMULATION. COULD
SEE AN INCH OR SO OF SNOW IN A FEW LOCATIONS BUT WILL BE ABOUT IT.
SNOW WILL MOSTLY END BY SUNRISE SUNDAY AS THE DISTURBANCE QUICKLY
MOVES SOUTHEAST INTO THE PLAINS.


&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 324 PM MST SAT JAN 31 2015

DISORGANIZED SPLIT FLOW PATTERN UNDERWAY ACROSS THE INTERMOUNTAIN
WEST AS UPPER-LOW CUTS OFF NR THE BAJA OF CALIFORNIA. TWO SHORTWAVES
EMBEDDED WITHIN NRN STREAM NORTHWEST FLOW HAVE BEEN THE DOMINANT
FEATURES TODAY AND WILL BE AGAIN TONIGHT. FIRST SHORTWAVE TROF THAT
WAS AT LEAST IN PART THE REASON FOR -SN LAST NT AND EARLIER TODAY
WAS SLOWLY DEPARTING THIS AFTERNOON. WELL DEFINED TROF AXIS EVIDENT
ON SATELLITE IMAGERY BY SHARP BACK EDGE OF CLOUD COVER THAT AT 20Z
EXTENDED FROM AROUND LUSK TO LARAMIE/CHEYENNE. POCKETS OF -SN WERE
STILL FALLING AHEAD OF THIS FTR OVR THE CENTRAL AND SRN NEBRASKA
PANHANDLE. MOST AREAS HAD RECEIVED AROUND AN INCH OF NEW SNOW TODAY
WITH LOCALLY UP TO A COUPLE OF INCHES IN THE WILDCAT HILLS AND NR
ALLIANCE. WILL SEE A GRADUALLY DECREASE W-E IN BOTH COVERAGE AND
INTENSITY AS THE TROF AXIS MARCHES EAST THRU THE REST OF THE
AFTERNOON. PERHAPS UP TO ANOTHER INCH WILL FALL IN THESE AREAS
THIS AFTERNOON. THE 2ND SHORTWAVE TROF QUICK ON THE HEELS OF THE
DEPARTING 1ST ONE...WILL DIVE SOUTHEAST TONIGHT AND COMBINE WITH
DEEPENING OF THE COLDER AIR MASS TO BOOST SNOW CHANCES AGAIN
TONIGHT. MOST AREAS WILL SEE AN ADDITIONAL SHOT OF LIGHT SNOW
TONIGHT AS A RESULT...WITH PERHAPS LOCALLY ANOTHER INCH OR TWO
TONIGHT. SNOWFALL RATES WILL JUST NOT BE HIGH ENOUGH TO PRODUCE
MUCH OF AN IMPACT...THOUGH SOME SLICK ROADS WILL BE A POSSIBILITY
LATER TONIGHT. THIS 2ND SHORTWAVE WILL DEPART INTO THE PLAINS
QUICKLY SUNDAY BRINGING AN END TO SNOW CHANCES EARLY. CLOUDS WILL
DECREASE ON SUNDAY ALLOWING MORE SUNSHINE THAN RECENT DAYS. MORE
SUN WILL DO LITTLE TO HELP TEMPS RECOVER HOWEVER AS THE COLDER
AIR MASS HOLDS HIGH TEMPERATURES IN THE 20S TO MAYBE AROUND 30F.

FOCUS SHIFTS TO HIGH WIND POTENTIAL FOR SUNDAY NT AND AGAIN ON
MONDAY NT AS A SERIES OF SHORTWAVES TRAVERSE THE NORTHWEST FLOW. THE
SUNDAY NT EVENT LOOKS FAIRLY MARGINAL AT THIS POINT...AS LLVL KCAG-
KCPR HEIGHTS INCREASE TO AROUND 55 METERS. IN FACT...12Z MODEL DATA
HAS BACKED OFF SOMEWHAT ON LLVL GRADIENTS COMPARED TO THE 00Z
RUN. THE BIGGER EVENT LOOKS TO BE MONDAY NT WHERE LLVL KCAG-KCPR
GRADIENTS CLIMB TO AROUND 70 METERS AT THE SAME TIME THAT THE NOSE
OF AN ANTICYCLONIC 115 KNOT H3 JET STREAK MOVES IN. FOR NOW WILL
HOLD OFF ON A WIND HIGHLIGHT AND WILL LET NEXT SHIFT GIVE 00Z DATA
ANOTHER LOOK. CONFIDENCE IS GREATEST ON THE MONDAY NT EVENT.
OTHERWISE...THE SNOWY/SIERRA MADRE RANGE CAN EXPECT FAIRLY
PERSISTENT LIGHT SNOW AS FAVORABLE OROGRAPHIC FLOW COMBINES WITH
PERIODIC BOUTS OF MID-LEVEL MOISTURE ASSOCIATED WITH THE SERIES OF
SHORTWAVES. DRY...BREEZY AND WARMER CONDITIONS WILL RETURN FOR
LOWER ELEVATIONS MONDAY WITH HIGHS RISING INTO THE 40S TO NR 50
EAST.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 324 PM MST SAT JAN 31 2015

MODELS IN GENERAL AGREEMENT WITH THE OVERALL PATTERN FEATURING A
GENERALLY WNW FLOW ALOFT THIS PERIOD. A MINOR SHORTWAVE WILL PASS
ACROSS TUESDAY BRINGING A FEW SNOW SHOWERS TO MAINLY THE MTNS WITH
OTHERWISE MILD TEMPS THAT DAY. IN THE MEANTIME A PUSH OF COLDER
CANADIAN AIR WILL SINK SOUTH OUT OF CANADA AND SHOULD BEGIN
MOVING INTO THE CWA LATE TUESDAY...BACKING UP AGAINST THE MTNS
TUESDAY NIGHT AND WEDS. CORE OF THIS COLD AIR WILL PASS EAST OF
THE CWA BUT STILL A GLANCING SHOT. FAVORABLE OVERRUNNING PATTERN
AND WEAK IMPULSE SHOULD ALLOW FOR SOME LIGHT SNOW ACROSS MUCH OF
THE CWA LATER TUESDAY NIGHT INTO WEDS BEFORE THE UPSLOPE FLOW ENDS
BY LATE WEDS. UNDERCUT GUIDANCE TEMPS FOR WEDS ESPECIALLY EAST OF
THE MTNS. THURSDAY AND FRIDAY LOOKING WARMER AND MAINLY DRY AS
RIDGING TO THE WEST SHIFTS SLOWLY EAST TOWARDS THE AREA WHILE
SLOWLY DEAMPLIFYING. A MORE ZONAL FLOW SETTING UP FOR NEXT WEEKEND
KEEPING MILD TEMPS IN PLACE BUT SHOULD SEE AN UPTICK IN WIND.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 514 PM MST SAT JAN 31 2015

TWO UPPER LEVEL DISTURBANCES AFFECTING THE AREA THIS EVENING. THE
FIRST UPPER DISTURBANCE IS NO EXITING THE NEBRASKA PANHANDLE. SNOW
WILL QUICKLY END EARLY THIS EVENING AS THIS DISTURBANCE EXITS BUT
THE NEXT NORTHERN STREAM DISTURBANCE WILL QUICKLY MOVE FROM NORTH
CENTRAL WYOMING EARLY THIS EVENING INTO SOUTHEAST WYOMING BY LATE
THIS EVENING. SNOW SHOWERS WILL DEVELOP ACROSS SOUTHEAST WYOMING
AND NEBRASKA PANHANDLE THIS EVENING WITH SNOW SHOWERS ENDING LATE
TONIGHT AS THE DISTURBANCE RAPIDLY MOVES THROUGH THE AREA. IFR TO
MVFR IS EXPECTED TONIGHT DUE TO LOW CLOUDS AND SNOW SHOWERS.
MOUNTAIN TOPS WILL BE OBSCURED AND MOUNTAINS MAY BE OBSCURED AT
TIMES.


&&

.FIRE WEATHER...
ISSUED AT 324 PM MST SAT JAN 31 2015

NO FIRE WEATHER CONCERNS INTO EARLY NEXT WEEK.
AFTER A COOLER DAY ON SUNDAY...HIGH TEMPERATURES WILL RETURN TO THE
40S AND 50S FOR MONDAY AND TUESDAY. MOUNTAIN SNOW ALONG WITH BREEZY
TO LOCALLY WINDY CONDITIONS WILL RETURN EARLY NEXT WEEK AS WELL.
MINIMUM RELATIVE HUMIDITIES WILL NOT DROP BELOW 30 PERCENT DURING
THIS PERIOD.

&&

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

$$

UPDATE...SML
SHORT TERM...CAH
LONG TERM...RE
AVIATION...SML
FIRE WEATHER...CAH



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