Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 020540
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1140 PM MDT WED OCT 1 2014

.UPDATE...
ISSUED AT 834 PM MDT WED OCT 1 2014

IR IMAGERY SHOWS THE COLDEST CLOUD TOPS ASSOCIATED WITH THE
SHORTWAVE MOVING QUICKLY OFF TO THE EAST ACROSS WESTERN NEBRASKA.
WILL KEEP SCATTERED SHOWERS IN THE FCST FOR THE NEXT FEW HOURS
ACROSS THE FAR EASTERN ZONES AS THE RADAR STILL INDICATES LIGHT
RAIN OVER CHEYENNE AND MORRILL COUNTIES. OUTSIDE OF THE EASTERN
CWA BOUNDARY AND THE MTNS...PRECIP CHANCES WILL BE SMALL THROUGH
THE REMAINDER OF THE NIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 325 PM MDT WED OCT 1 2014

REGIONAL RADARS HAVE BEEN FILLING IN OVER THE PAST SEVERAL
HOURS...WITH RAIN BEGINNING TO FALL ACROSS LARAMIE COUNTY. SNOW
LEVELS THUS FAR HAVE FALLEN TO AROUND 7 KFT...WITH PUMPKIN VINE
TURNING OVER AT AROUND NOON AND AREAS OVR THE I-80 SUMMIT SHORTLY
THEREAFTER. THIS ALL HAS BEEN A RESULT OF A FAST-MOVING YET SHARP
SHORTWAVE...ITS AXIS OF WHICH WILL PASS OVERHEAD THIS EVENING AND
BE EAST OF THE CWFA BY THURSDAY MORNING. AT THE SFC...THE FRONT
HAS PUSHED SOUTH OF THE WY/CO STATE LINE AS EVIDENT BY WIND SHIFT
TO THE NORTH...11 DEGREES OF COOLING AND ONSET OF RAIN BETWEEN
17-18Z. MODELS ARE CONSISTENT IN TRACKING THE AREA OF BEST H7
OMEGA AND QG ASCENT LARAMIE COUNTY...SOUTHERN GOSHEN COUNTY AND
THE SOUTHERN NEBRASKA PANHANDLE THROUGH THE EVENING HOURS. SNOW-
LEVELS WILL FALL TO AROUND 6500 FEET THIS EVENING BEFORE
PRECIPITATION FINALLY ENDS. MAY EVEN MIX BELOW BRIEFLY. HRRR
PUSHES THIS AREA OF PRECIP OUT OF WYOMING BY AROUND 02-03Z AND OUT
OF THE WESTERN NEBRASKA PANHANDLE BY AROUND 06Z...SO HAVE TRENDED
PRECIP CHANCES DOWN ACCORDINGLY. SHOULD SEE 3-5 INCHES OVER THE
SNOWY/SIERRA MADRES WITH MAYBE 1-3 INCHES OVER THE SRN LARAMIE
RANGE BY THE TIME THE SYSTEM DEPARTS. WILL BE A BRIEF BREAK IN
PRECIP BEHIND THE DEPARTING SHORTWAVE AND AHEAD OF THE NEXT FAST
MOVING CLIPPER POISED TO PUSH THROUGH LATE THURSDAY. IN THE
MEANTIME...WILL SEE A DRY...BUT BREEZY/RAW DAY TOMORROW AS
SUBSIDENCE ALLOWS FOR 25-30 KNOT 650-700MB BELOW THE INVERSION TO
SFC. SUBSIDENT INVERSION ERODES QUICKLY THOUGH...WITH THE NEXT
CLIPPER QUICKLY APPROACHING THE CWFA. LATEST MODELS HAVE BEEN
TRENDING A BIT STRONGER AND DEEPER WITH THIS SYSTEM COMPARED TO
THOSE A FEW DAYS AGO. WILL SEE PRECIP BEGIN ACROSS EAST CENTRAL
WYOMING AND THE NRN NEBRASKA PANHANDLE THURSDAY EVENING SPREADING
SOUTH INTO SOUTHEAST WYOMING AND THE REST OF THE PANHANDLE THRU
MIDNIGHT. TEMPERATURES WILL AGAIN BE TRICKY WITH THIS
SYSTEM...WITH SOME INDICATION THAT SNOW LEVELS WILL AGAIN FALL TO
AROUND 5 KFT...WHICH WOULD SUGGEST A TRANSITION TO SNOW FROM
DOUGLAS TO LUSK AND PERHAPS EVEN EAST ALONG THE PINE RIDGE. ANY
PRECIPITATION THAT FALLS THURSDAY EVENING SHOULD END BY
MIDNIGHT...WITH CLEARING CONDITIONS THEREAFTER. OVERNIGHT LOWS
WILL DROP BELOW FREEZING...WITH ROADWAYS AT LEAST HAVING THE
POTENTIAL OF BECOMING SLICK WHERE PRECIPITATION FALLS EARLIER.
WILL NEED TO CONSIDER HIGHLIGHTS IN TIME FOR THOSE AREAS THAT HAVE
NOT ALREADY RECEIVED A KILLING FREEZE...WHICH IS FROM CHADRON
SOUTH TO SIDNEY AS WELL AS IN SCOTTS BLUFF AND BANNER COUNTIES.
WILL LET FOLLOWING SHIFTS EVALUATE THAT NEED. FRIDAY WILL BE A DRY
BUT COOLER DAY AS THE POST-FRONTAL AIR MASS ERODES...WITH HIGHS
REACHING THE 50S IN WY AND 60S OVR THE PANHANDLE.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 340 PM MDT WED OCT 1 2014

THE MEDIUM RANGE MODELS REMAIN CONSISTENT WITH THE DRY AND MILD
WEATHER PATTERN UNDER PERSISTENT NORTHWEST FLOW ALOFT. THE UPPER
JET AXIS WILL BE POSITIONED FROM SOUTHWEST CANADA THROUGH THE
CENTRAL GREAT PLAINS AND OHIO VALLEY...WITH A RATHER DEEP LONG
WAVE TROUGH OVER THE EASTERN CONUS AND A HIGH AMPLITUDE RIDGE OVER
THE WESTERN CONUS. POTENTIAL ALBERTA CLIPPER SYSTEMS WILL REMAIN
TO THE EAST OF THE CWA. THE ECMWF PROGS A STRONG SHORT WAVE MOVING
THROUGH THE NORTHWEST FLOW ALOFT SUNDAY AFTERNOON WHICH COULD
BRING SOME MOISTURE AND LIFT FOR SHOWER ACTIVITY OVER THE HIGH
PLAINS. THE GFS KEEPS SHORT WAVE ENERGY FURTHER EAST WITH NO
PRECIPITATION. FOR CONSISTENCY SAKE...KEPT SUNDAY DRY WITH
INCREASING CLOUDINESS DURING THE AFTERNOON. TEMPERATURES DURING
THE LONG TERM WILL REMAIN AT OR SLIGHTLY ABOVE SEASONAL NORMALS...
WITH HIGHS IN THE MID 60S TO MID 70S AND MID 50S TO MID 60S FOR
THE HIGH VALLEYS AND MOUNTAINS. BREEZY WEST TO NORTHWEST WINDS
WILL DEVELOP EACH AFTERNOON AND EVENING...MAINLY FOR SOUTHEAST
WYOMING.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY EVENING)
ISSUED AT 1135 PM MDT WED OCT 1 2014

BRIEF MVFR TO IFR CIGS WILL BE POSSIBLE OVER THE PANHANDLE SITES
AND KCYS THROUGH 09Z THU. CONDITIONS WILL IMPROVE ACROSS THE AREA
BEYOND THAT TIME WITH VFR PREVAILING THROUGH THE REMAINDER OF THE
TAF PERIOD. GUSTY WINDS EXPECTED FOR THU AFTN AS A COLD FRONT
MOVES ACROSS THE REGION.

&&

.FIRE WEATHER...
ISSUED AT 325 PM MDT WED OCT 1 2014

A FAST MOVING WEATHER DISTURBANCE TO BRING ANOTHER ROUND OF
PRECIPITATION TO A PORTION OF THE DISTRICTS THROUGH THE REST OF THE
EVENING. SNOW LEVELS HAVE RECENTLY FELL TO AROUND 8 KFT WITH AREAS
ALONG HWY 287 SOUTH OF LARAMIE TURNING OVER. BEST CHANCES FOR
PRECIPITATION WILL BE BETWEEN LARAMIE AND SIDNEY ALONG THE SOUTHERN
TIER OF COUNTIES. THE SYSTEM WILL DEPART TONIGHT AS QUICKLY AS IT
MOVED IN...LEAVING IMPROVING BUT BREEZY AND COOL CONDITIONS FOR
THURSDAY. ANOTHER FAST MOVING CLIPPER SYSTEM WILL "CLIP" THE REGION
THURSDAY NIGHT. ANOTHER ROUND OF LIGHT PRECIP WILL BE POSSIBLE
THURSDAY EVENING WITH RAIN MIXING WITH SNOW POSSIBLY DOWN TO 6000
FEET OR SO. DRY AND WARMING CONDITIONS ARE ANTICIPATED INTO THE
WEEKEND.

&&

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

$$

UPDATE...FINCH
SHORT TERM...HAHN
LONG TERM...JAMSKI
AVIATION...HAMMER
FIRE WEATHER...HAHN





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