Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 301141
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
545 AM MDT THU OCT 30 2014

.SHORT TERM...TODAY THROUGH SATURDAY...NW FLOW PERSISTS ACROSS SE
WYOMING AND W NEBRASKA THIS MORNING WITH MID-LEVEL MOISTURE SPILLING
ACROSS THE NRN ROCKIES ALONG THE ANTICYCLONIC SIDE OF A H3 JET
STREAK. SATELLITE TRENDS DEPICT THIS MOISTURE DECREASING...SO
SUSPECT MOST AREAS WILL BEGIN THE DAY MOSTLY CLEAR. UPSTREAM RIDGE
AMPLIFICATION EVIDENT ON WV IMAGERY WILL KEEP CONDITIONS DRY INTO
THE UPCOMING WEEKEND. AT THE SFC...A 1036MB AREA OF HIGH PRESSURE
OVER CENTRAL CANADA WILL DROP SOUTHEAST INTO THE DAKOTAS THIS
EVENING TURNING WINDS FROM NW THIS MORNING TO NE THIS EVENING AND
EVENTUALLY TO SE TONIGHT. HIGH TEMPS WILL BE SEASONABLY MILD
TODAY...WITH HIGHS GENERALLY IN THE 50S...WITH SOME LOW 60S IN LOWER
ELEVATIONS.

THE PATTERN WILL BECOME FAVORABLE FOR A LOW STRATUS/FOG EVENT LATER
TONIGHT AND EARLY FRIDAY AS SOUTHEASTERLY SFC WINDS ENSUE. FOG
EVENTS ARE ALWAYS TRICKY TO PIN DOWN EVEN A DAY AHEAD OF TIME...BUT
DID OPT TO ADD PATCHY FOG MENTION TO MOST AREAS EAST OF I-25. MODELS
ARE HITTING THE SRN PANHANDLE THE STRONGEST...SO CONFIDENCE IS
HIGHEST IN FOG OCCURRENCE THERE. STRONGER WINDS OVR THE SOUTHEAST WY
PLAINS MAY BE JUST ENOUGH TO KEEP THE PBL STIRRED UP ENOUGH AND CIGS
OFF THE SFC. FOG/LOW CLOUDS WILL MIX OUT BY LATE FRIDAY MORNING.
DELAYED WARMING EAST OF THE LARAMIE RANGE WILL DELAY HEATING
RESULTING IN HIGHS ONLY REACHING THE 50S AT MOST LOCATIONS. AREAS
THAT DONT SEE AM LOW CLOUDS AND FOG (WEST OF THE LARAMIE RANGE AND
DOUGLAS) WILL BENEFIT FROM BETTER MIXING AND HIGHS THAT WILL REACH
THE 60S.

RIDGE AXIS SLIDES EAST ON SATURDAY TURNING THE PATTERN SOUTHWEST
AHEAD OF THE APPROACHING WEST COAST TROUGH. TEMPERATURES WILL WARM
WELL ABOVE NORMAL ON SATURDAY WITH HIGHS REACHING THE 60S WEST OF
THE LARAMIE RANGE WITH 60S AND LOW 70S ACROSS THE ERN PLAINS. ANY
PRECIPITATION CHANCES WILL HOLD OFF UNTIL JUST BEYOND THIS PERIOD.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 345 AM MDT THU OCT 30 2014

LONG RANGE MODELS ARE IN BETTER AGREEMENT TONIGHT COMPARED TO
YESTERDAY. THE MAIN FORECAST CHALLENGE IS SPLIT FLOW OVER THE
AREA AS PACIFIC STORM SYSTEMS INTERACT WITH THE RELATIVELY STRONG
UPPER LEVEL RIDGE OVER THE GREAT PLAINS. MODELS AND CURRENT
ENSEMBLE RUNS NOW SHOW THE SOUTHERN BRANCH OF THE JET BECOMING
MORE DOMINANT BY LATE THIS WEEKEND AND INTO EARLY MONDAY
MORNING...WITH THE POTENTIAL FOR RAIN/SNOW ALONG I80. ALL MODELS
INDICATE THE NORTHERN SHORTWAVE AND ASSOCIATED JET PUSHING WELL
NORTH OF THE AREA INTO MONTANA AS IT WEAKENS. GFS AND ECMWF IN
RELATIVELY GOOD AGREEMENT...BUT THE GEM IS NO WHERE NEAR WHAT THE
00Z RUN WAS SHOWING 24 HOURS AGO...SO WILL CONTINUE TO CONSIDER IT
AN OUTLIER. INCREASED POP UP TO 35 PERCENT ALONG THE I80 CORRIDOR
INTO WESTERN NEBRASKA FOR SUNDAY NIGHT AND INTO EARLY MONDAY
MORNING. 700MB TEMPERATURES WILL LOWER TO -8C WEST OF THE LARAMIE
RANGE...SO SOME SNOWFALL CAN NOT BE RULED OUT DOWN TO ELEVATIONS
OF 5500 FEET. HIGH CONFIDENCE THAT MUCH COLDER AIR WILL PUSH INTO
THE AREA BY LATE SUNDAY AS HIGHS STRUGGLE TO REACH THE MID TO
UPPER 40S ON MONDAY. LOW TEMPERATURES IN THE TEENS TO MID 20S ARE
EXPECTED BY LATE MONDAY NIGHT AS THE COOLER AIR SETTLES OVER THE
REGION. ANY PRECIPITATION WILL BE PRETTY LIGHT AND GENERALLY BELOW
0.25 OF AN INCH SUNDAY NIGHT...WITH A TRACE TO TENTH OF AN INCH
ALONG AND NORTH OF THE PLATTE RIVER VALLEY. GUSTY WINDS ARE
EXPECTED BEGINNING LATE SATURDAY NIGHT AND CONTINUING THROUGH
MOST OF SUNDAY MORNING AHEAD OF THE FRONT. HIGH WIND CRITERIA
APPEARS UNLIKELY AT THIS TIME...EVEN IN THE WIND PRONE AREAS.

THE UPPER LEVEL TROUGH WILL PUSH EAST OF THE REGION EARLY NEXT
WEEK RESULTING IN BROAD NORTHWEST FLOW AND COOL TEMPERATURES.
MODELS DO SHOW A WEAK SECONDARY SHORTWAVE DIGGING SOUTH ACROSS THE
AREA ON MONDAY...WITH SOME RAIN/SNOW SHOWER ACTIVITY LINGERING
ALONG THE I80 CORRIDOR. INCREASED POP ACROSS THE AREA BETWEEN 15
TO 25 PERCENT. OTHERWISE...DRY CONDITIONS ARE EXPECTED INTO THIS
MIDDLE OF NEXT WEEK WITH HIGH TEMPERATURES INCREASING TO NEAR
NORMAL...AND GENERALLY IN THE 50S AND LOW 60S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH THURSDAY NIGHT)

WINDS WILL SHIFT INTO THE NORTH TODAY AS A COLD FRONT MOVES ACROSS
THE REGION. HOWEVER...WINDS SHOULD REMAIN LIGHT INTO TONIGHT. VFR
CONDITIONS ARE EXPECTED AT LEAST THROUGH THIS EVENING...BUT WILL
HAVE TO MONITOR THE WESTERN NEBRASKA PANHANDLE FOR FOG LATER
TONIGHT...ESPECIALLY AFTER 06Z. THERE IS A SLIGHT CHANCE FOR IFR VIS
AND CIGS BY EARLY FRIDAY MORNING.

&&

.FIRE WEATHER... ANOTHER DRY DAY IN STORE...WITH MUCH LESS WIND
COMPARED TO YESTERDAY. TEMPERATURES WILL REMAIN SEASONABLY MILD FOR
BOTH TODAY AND TOMORROW WITH HIGHS REACHING THE 50S TO LOW 60S.
HUMIDITY RECOVERIES WILL BE EXCELLENT IN AREAS EAST OF THE LARAMIE
RANGE TONIGHT AS LOW CLOUDS AND FOG DEVELOP. FRIDAY WILL BE A
TRANSITION DAY WITH FAIRLY MILD CONDITIONS WEST WITH CONTINUED COOL
TEMPS EAST. DRY AND VERY MILD CONDITIONS WILL OVERSPREAD THE ENTIRE
AREA ON SATURDAY...WITH THE NEXT SYSTEM BRINGING THE NEXT CHANCE OF
PRECIPITATION AND A RETURN TO COOLER TEMPERATURES ON SUNDAY AND
MONDAY.

&&

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

$$

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



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