Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 312226
AFDCYS

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

.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 GRADEITNS 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
CANADAIN 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
IMPULESE 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 324 PM MST SAT JAN 31 2015

FAIRLY WIDESPREAD MVFR/IFR CONDITIONS DUE TO LOW CIGS EXPECTED TO
RETURN TO THE AREA TONIGHT WITH AREAS OF LIGHT SNOW AS WELL.
CONDITIONS EXPECTED TO IMPROVE SUNDAY MORNING WITH MAINLY VFR BY
MONDAY AFTERNOON.

&&

.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.
&&

$$

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



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