Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 231802
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1102 AM MST MON FEB 23 2015

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 607 AM MST MON FEB 23 2015

TEMPERATURES HAVE PLUMMETED BELOW ZERO EARLY THIS MORNING FOR MUCH
OF SOUTHEAST WYOMING IN ADDITION TO A FEW LOCATIONS ACROSS THE
NEBRASKA PLAINS AS SKIES HAVE BECOME MOSTLY CLEAR EXCEPT ALONG THE
CHEYENNE RIDGE. WINDS ARE FAIRLY LIGHT WITH A FEW LOCATIONS IN THE 5
TO 10 MPH RANGE...AND ONE OR TWO SPOTS EXPERIENCING SLIGHTLY
HIGHER SPEEDS. RESULTANT WIND CHILLS ARE AVERAGING IN THE MINUS
SINGLE DIGITS TO MINUS TEENS WITH A FEW SPOTS IN THE MINUS 20S.
WINDS SHOULD CONTINUE TO DECREASE THROUGH THE NEXT FEW HOURS SO
THESE VALUES WILL BE ON THE RISE. FLURRIES AND PATCHY AREAS OF FOG
PERSIST THIS MORNING MAINLY ACROSS LARAMIE AND KIMBALL COUNTIES
THIS MORNING WITH SOUTHERLY UPSLOPE WINDS OVER THE CHEYENNE RIDGE.
THESE WINDS WILL GRADUALLY TURN MORE TO THE SOUTHWEST THROUGH THE
MORNING WHICH SHOULD ALLOW CIGS/VSBYS TO LIFT. WILL LIKELY TAKE A
FEW HOURS THO AS THIS PATTERN LENDS TOWARD A SLOW BREAK UP OF THE
STRATUS DECK.

THE UPPER LOW THAT WAS RESPONSIBLE FOR THE RECENT SNOW AND COLD WILL
REMAIN OVER THE DESERT SOUTHWEST TODAY AND WILL SHIFT TO THE EAST ON
TUESDAY. SHORTWAVE RIDGING WILL MOVE OVER THE FORECAST AREA AS THIS
OCCURS...ALLOWING TEMPS TO MODERATE BACK INTO THE 20S/30S TODAY AND
30S/40S TOMORROW. DRIER AIR AND SUBSIDENCE WILL MOVE OVERHEAD AS
WELL AND WILL KEEP CONDITIONS DRY. MODELS CONTINUE TO BRING THE NEXT
SHORTWAVE TROUGH ACROSS THE PAC NW AND DOWN ALONG THE ROCKIES
TUESDAY NIGHT AND WEDNESDAY WITH LEESIDE CYCLOGENESIS OCCURRING
AHEAD OF THE WAVE OVER THE HIGH PLAINS TUESDAY NIGHT. WINDS WILL
BECOME BREEZY IN THE WIND PRONE AREAS TUESDAY NIGHT AS THE
GRADIENT INCREASES DUE TO LEESIDE CYCLOGENESIS...BUT LIKELY GUSTS
WILL PEAK ONLY 45 MPH OR SO. SNOW SHOWERS WILL DEVELOP FROM NORTH
TO SOUTH LATE TUESDAY EVENING AND OVERNIGHT AS THE UPPER TROUGH
APPROACHES AND SFC LOW DEVELOPS...WITH THE MAIN COLD FRONT MOVING
THROUGH WEDNESDAY MORNING. WEAK FRONTOGENESIS AND NEGATIVE EPV ARE
PROGGED BY THE NAM EARLY WEDNESDAY AFTERNOON AS THE FRONT SLOWS
UP AGAINST THE TERRAIN AND LLVL MOISTURE INCREASES IN ITS WAKE.
THEREFORE...WILL LIKELY SEE A QUICK SHOT OF WIDESPREAD LIGHT TO
MODERATE SNOWFALL AS THE UPPER TROUGH MOVES OVERHEAD ON WEDNESDAY
WITH CONVECTIVE BANDING A POSSIBILITY IN THE AFTERNOON AS
FRONTOGENESIS AND NEGATIVE EPV DEVELOP. CONFIDENCE IS INCREASING
THAT MUCH OF THE AREA WILL RECEIVE SOME ACCUMULATING SNOW...SO
BUMPED UP POPS TO BE IN THE CHANCE-LIKELY CATEGORIES.
ACCUMULATIONS SHOULD REMAIN LIGHT- MODERATE THO WITH NO REAL
STRONG FORCING MECHANISMS IN PLACE. LOOKING LIKE 1-2 INCHES FOR
THE LOWER ELEVATIONS AND HIGH VALLEYS AND 3-5 INCHES FOR THE
MOUNTAINS THROUGH WEDNESDAY AFTERNOON. LOCALLY HIGHER AMOUNTS ARE
POSSIBLE FOR ANY STRONGER SNOW BANDS THAT DEVELOP.

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 607 AM MST MON FEB 23 2015

THE EXTENDED PERIOD WILL BE DOMINATED BY COLD...CLOUDY...AND
OCCASIONALLY SNOWY CONDITIONS.  SNOWFALL RATES WILL DECREASE ON
WED NIGHT WITH MAINLY LIGHT SNOW/FLURRIES ACROSS SOUTHEAST WY AS
LLVL UPSLOPE IS THE PRIMARY FORCING MECHANISM. A SFC HIGH OVER THE
NORTHERN PLAINS WILL KEEP EAST TO SOUTHEAST WINDS GOING ACROSS THE
PLAINS ON THURS. THE BEST CHANCE OF MAINLY LIGHT SNOW WILL OCCUR
ALONG THE LARAMIE RANGE AND ADJACENT FOOTHILLS ON THURS. PRECIP
CHANCES DECREASE ON FRI AS AN UPPER LEVEL TROUGH DIGS INTO THE
GREAT BASIN. THE NEXT SNOW EVENT MAY TAKE PLACE ON SAT NIGHT INTO
SUN MORNING AS UPPER LEVEL DIFFLUENCE AND LARGE SCALE ASCENT
INCREASES ACROSS THE CWA. THE GFS IS MORE BULLISH THAN THE EURO ON
QPF AMOUNTS (WITH WIDESPREAD 0.25-0.5 INCHES). WILL KEEP POPS
AROUND 30 PERCENT FOR NOW AT ALMOST SIX DAYS AWAY. HIGH TEMPS WILL
STRUGGLE TO GET ABOVE THE MID TO UPPER 20S THROUGH THIS WEEKEND
WITH LOWS IN THE SINGLE DIGITS TO LOW TEENS. IT IS DEFINITELY
LOOKING LIKE A COLD AND SOMEWHAT UNSETTLED END TO FEBRUARY. WITH
PREDOMINANTLY HIGHER PRESSURES TO THE EAST OF THE LARAMIE
RANGE...STRONG WINDS WILL NOT BE AN ISSUE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1045 AM MST MON FEB 23 2015

VFR. CLEAR THROUGH SUNSET...THEN INCREASING CLOUDS AT OR ABOVE
10000 FEET ABOVE GROUND LEVEL...AGL...WITH SCATTERED TO BROKEN
CEILINGS. AT ALL TAF SITES...WINDS GUSTING TO 25 KNOTS AT TIMES
THROUGH SUNSET TONIGHT...AND AGAIN AFTER SUNRISE TUESDAY...WITH
WIND GUSTS TO 25 KNOTS AT TIMES AT CHEYENNE AFTER 05Z...
11 PM...TONIGHT.

&&

.FIRE WEATHER...
ISSUED AT 607 AM MST MON FEB 23 2015

THE ARCTIC AIR MASS WILL REMAIN IN PLACE TODAY ALONG WITH LIGHT
WINDS AND CLEARING SKIES BEFORE PUSHING TO THE EAST ON TUESDAY.
WILL SEE DRY AND WARMER CONDITIONS FOR TUESDAY BEFORE YET ANOTHER
ARCTIC SYSTEM INVADES THE AREA ON WEDNESDAY. VERY COLD
TEMPERATURES AND A CHANCE FOR LIGHT TO MODERATE SNOW WILL OCCUR
WEDNESDAY INTO THURSDAY WITH BELOW NORMAL TEMPERATURES EXPECTED TO
PERSIST THROUGH THE WEEKEND.

&&

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

$$

SHORT TERM...RJM
LONG TERM...ZF
AVIATION...RUBIN
FIRE WEATHER...RJM


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