Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 261749
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1149 AM MDT SUN APR 26 2015

.UPDATE...
ISSUED AT 1042 AM MDT SUN APR 26 2015

MODERATE RAIN CONTINUES THIS MORNING NEAR THE WYO/COLO/NEB
BORDERS WITH LIGHT RAIN ELSEWHERE ACROSS THE PLAINS. AREAS OF FOG
WERE ALSO OBSERVED IN STRONG UPSLOPE FLOW ALONG THE CHEYENNE
RIDGE FROM SIDNEY TO SUMMIT...WITH PATCHY FOG FURTHER NORTH AS
WELL. HAVE NOT RECEIVED ANY REPORTS OF FLOODING ISSUES WITHIN THE
AREA OF MODERATE RAIN SO FAR...BUT WILL KEEP AN EYE ON THIS AREA
AS PERIODS OF RAIN WILL CONTINUE THIS AFTERNOON. FURTHER WEST
ACROSS CARBON AND PORTIONS OF ALBANY COUNTIES...SKIES WERE MOSTLY
CLEAR/PARTLY CLOUDY THROUGH THE MORNING. CURRENT WATER VAPOR
IMAGERY SHOWS THE NEXT PIECE OF ENERGY MOVING NORTH ACROSS
COLORADO...WITH CONVECTION FIRING ALONG THE FRONT RANGE MOUNTAINS
AND POINTS TO THE SOUTHEAST. THIS WAVE WILL MOVE NORTH-NORTHWEST
THROUGH THE AFTERNOON AND SHOULD FIRE UP ADDITIONAL CONVECTION
ACROSS THE PLAINS AS THE CURRENT AREA OF ACTIVITY SHIFTS
NORTH...WITH CONVECTIVE RAIN/SNOW SHOWERS EXPECTED ALONG AND WEST
OF THE LARAMIE RANGE AS WELL WHERE MID/LLVL LAPSE RATES ARE
BETWEEN 6 AND 8 C/KM WITH SOME WEAK INSTABILITY PRESENT. WILL SEE
A FEW TSTORMS AS WELL WITHIN THESE AREAS OF CONVECTION.

BASED ON THIS MORNINGS SOUNDINGS AND 700 MB TEMPS PROGGED TO
DECREASE A DEGREE OR TWO THRU THIS AFTERNOON WITH THE INCOMING
WAVE...THINK SNOW LEVELS TODAY WILL HOVER AROUND 8000 FEET ON
AVERAGE. THEY COULD DROP TO BETWEEN 7000 AND 7500 FEET IN AREAS OF
STRONGER CONVECTION THO. THE MORE PERSISTENT SNOW SHOWERS SHOULD
SET UP ACROSS THE MOUNTAINS WITH PERHAPS A BAND OF ACTIVITY
EXTENDING FROM THE SOUTHERN LARAMIE RANGE EAST-SOUTHEAST ACROSS
THE CHEYENNE RIDGE LATER THIS AFTERNOON. LOOKING AT MODERATE TO
HEAVY SNOW RATES IN SHOWERS AND THUNDERSNOW OVER THE
MOUNTAINS...INCLUDING THE SOUTHERN LARAMIE RANGE SUMMIT...WITH
RAIN FURTHER EAST. THE WINTER WEATHER ADVISORY IS IN GOOD SHAPE
FOR NOW...WITH MOST OF THE ACCUMULATIONS EXPECTED THIS AFTERNOON
AND EVENING. DEFINITELY CAN SEE SOME CONVECTIVE SNOW REACHING THE
VALLEY FLOORS ACROSS ALBANY AND CARBON COUNTIES...WITH SOME
ACCUMULATION POSSIBLE ON GRASSY SURFACES AND ROADS NEAR
ARLINGTON/ELK MOUNTAIN TO RAWLINS IF HEAVIER SHOWERS/TSTORMS MOVE
INTO THESE AREAS. EASTERN PORTIONS OF THE LARAMIE
VALLEY...INCLUDING LARAMIE MAY SEE JUST ENOUGH DOWNSLOPE TO KEEP
PRECIP CHANCES LOWER BUT WILL KEEP AN EYE ON TRENDS AND WILL
UPDATE THE FORECAST AS NEEDED.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 236 AM MDT SUN APR 26 2015

CURRENT FORECAST APPEARS ON TRACK WITH CURRENT KCYS RADAR LOOP
SHOWING MODERATE TO LOCALLY HEAVY RAIN ACROSS THE HIGH PLAINS...AND
SCATTERED RAIN/SNOW WEST OF THE I25 CORRIDOR. THE MAIN FORECAST
CONCERN NOW APPEARS TO BE SNOWLEVELS...WHICH HAVE BEEN LOWER THAN
ANTICIPATED FOR EARLY THIS MORNING. THE I80 SUMMIT HAS BEEN
REPORTING SNOW AND LOW VISIBILITIES IN HEAVY SNOW FOR THE LAST
SEVERAL HOURS. EVEN LARAMIE AIRPORT IS DOWN TO 35 DEGREES AND
HEAVY RAIN...SO SNOWLEVELS ARE LIKELY BETWEEN 7500 TO 8000 FEET BY
NOW. MODELS CONTINUE TO SHOW THE LARGE AREA OF STRONG UPPER LEVEL
DIVERGENCE THROUGH NOON SUNDAY OVER MOST OF THE HIGH PLAINS ACROSS
SOUTHEAST WYOMING AND INTO WESTERN NEBRASKA. BELIEVE THIS AREA OF
PRECIPITATION CURRENTLY STRETCHING FROM DENVER TO THE SOUTHERN
NEBRASKA PANHANDLE WILL EXPAND NORTH AND WEST TODAY. WITH SNOW
STARTING TO ACCUMULATE ACROSS THE I80 SUMMIT...ISSUED A WINTER
WEATHER ADVISORY FOR THE SOUTHERN LARAMIE RANGE AND SNOWY RANGES
THROUGH EARLY MONDAY MORNING. EXPECT 5 TO 10 INCHES OF WET SNOW
ACROSS THESE AREAS. ALTHOUGH SNOW ACCUMULATION ON THE ROADS MAY BE
LIMITED...BELIEVE THE COMBINATION OF REDUCED VISIBILITIES DUE TO
SNOW AND FOG WILL MAKE TRAVEL HAZARDOUS OVER THE I80 SUMMIT. IN
ADDITION...ANY ADDITIONAL COOLING AND HEAVY SNOW MAY CREATE SLICK
CONDITIONS ABOVE 7500 FEET. DO NOT EXPECT IT TO BE SNOWING ALL THE
TIME...WITH PATCHY DENSE FOG IN BETWEEN PERIODS OF SNOWFALL DUE TO
MOIST EAST TO SOUTHEAST FLOW.

TONIGHT AND MONDAY...MODELS SHOW THE DEFORMATION BAND REMAINING
OVER AND JUST EAST OF THE LARAMIE RANGE THROUGH THE NIGHT WITH A
CONTINUATION OF LIGHT RAIN AND SNOW. WOULD NOT BE SURPRISED IF
SNOWLEVELS LOWER TO AROUND 6000 FEET BY EARLY MONDAY MORNING.
THANKFULLY...PRECIP RATES DO NOT APPEAR VERY HIGH WITH THE
DEFORMATION BAND...SO EXPECT MINIMAL ACCUMULATIONS BETWEEN 6000 TO
7500 FEET. NOT COMPLETELY CONVINCED THAT THIS STORM WILL SLIP BY
TO THE SOUTH AND EAST BY MONDAY DUE TO THE STRONG RIDGE OF HIGH
PRESSURE TO OUR EAST. WILL NEED TO CLOSELY MONITOR THIS SYSTEM TO
SEE IF IT EVENTUALLY DRIFTS EASTWARD INTO TEXAS. DID NOTE THAT THE
NEW GFS RUN HAS THE CENTER OF THE UPPER LOW A BIT FURTHER
NORTH...AND ANY NORTHEAST DRIFT WILL RESULT IN MORE PRECIP THROUGH
MONDAY. GRADUALLY LOWERED POP THROUGH MONDAY...BUT KEPT A MENTION
OF SCATTERED RAIN/SNOW SHOWERS.

EXPECT CONDITIONS TO GRADUALLY IMPROVE LATE MONDAY NIGHT AND INTO
EARLY TUESDAY MORNING AS THE UPPER LEVEL LOW MOVES INTO THE
SOUTHERN PLAINS AND WEAKENS. MODELS INDICATE A HIGH AMPLITUDE RIDGE
AXIS MOVING INTO THE ROCKY MOUNTAIN REGION FOR TUESDAY...RESULTING
IN TEMPERATURES CLIMBING TO NEAR AVERAGE LEVELS FOR THIS TIME OF
THE YEAR. KEPT POP BELOW 10 PERCENT ON TUESDAY WITH HIGHS 60S.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 259 AM MDT SUN APR 26 2015

AFTER SEVERAL DAYS OF UNSETTLED WEATHER...THE EXTENDED FORECAST
PERIOD WILL BE WARM AND ON THE DRY SIDE. UPPER RIDGE WILL SHIFT
FROM THE PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES BY MID WEEK.
WEDNESDAY WILL BE VERY NICE WITH HIGH TEMPERATURES IN THE 60S WEST
AND 70S INTO THE PLAINS. WINDS WILL BE LIGHT ALONG WITH MOSTLY
CLEAR SKIES.

UPPER RIDGE WILL FOLD OVER INTO THE PLAINS BY THURSDAY WITH A
SHORT WAVE TROUGH SKIRTING NORTH OF THE FORECAST AREA LATE
THURSDAY INTO THURSDAY NIGHT. THE GFS HAS TRENDED TOWARD THE ECMWF
WITH THE PASSAGE OF THIS WAVE. A FEW SHOWERS AND THUNDERSTORMS
ARE A REMOTE POSSIBILITY OVER HIGHER ELEVATIONS LATE THURSDAY INTO
FRIDAY...BUT CURRENTLY THINKING THE MODELS ARE A BIT TOO
AGGRESSIVE WITH THE STRENGTH OF THE SHORTWAVE...AS IT WILL LIKELY
SHEAR APART AS IT MOVES INTO THE RIDGE. AT ANY RATE...MOST PLACES
WILL STAY DRY THURSDAY AND FRIDAY. THURSDAY WILL LIKELY BE THE
WARMEST DAY OF THE WEEK WITH BREEZY WEST FLOW SETTING UP OVER THE
AREA. DOWNSLOPING WILL CONTRIBUTE TO WARMING ACROSS EASTERN
PORTIONS OF THE FORECAST AREA. A BIT COOLER FRIDAY FOLLOWING THE
PASSAGE OF A COLD FRONT BUT CURRENTLY EXPECTING THE FRONT TO BE
WEAKER THAN THE MODELS ARE DEPICTING SO KEPT HIGH TEMPERATURES ON
THE WARM SIDE OF GUIDANCE VALUES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY)
ISSUED AT 1150 AM MDT SUN APR 26 2015

IFR TO MVFR ACROSS SOUTHEAST WYOMING AND NEBRASKA PANHANDLE
THROUGH THE TAF PERIOD. HRRR GUIDANCE USED FOR THE 18Z TAFS WHICH
SHOWS AREAS EAST OF THE LARAMIE RANGE STAYING IFR THROUGH THE LATE
AFTERNOON. COULD SEE A LIFT TO MVFR OUT IN THE PANHANDLE FOR KAIA
AND KCDR AS THE AFTERNOON PROGRESSES. SHOULD SEE A FAIRLY RAPID
DETERIORATION AFTER SUNSET WITH DENSE FOG DEVELOPING IN THE
PANHANDLE...PERSISTING INTO MONDAY LATE MORNING.

FOG AND LOW CEILINGS WITH RAIN WILL BE PREVALENT EAST OF THE
LARAMIE RANGE INTO THE PLAINS OF WESTERN NEBRASKA PANHANDLE WITH
DENSE FOG POSSIBLY DEVELOPING LATE TODAY INTO TONIGHT AS
PRECIPITATION BECOME LIGHT. LOW CEILINGS AND FOG MAY PERSIST WELL
INTO MONDAY FOR SOME AREAS.


&&

.FIRE WEATHER...
ISSUED AT 236 AM MDT SUN APR 26 2015

NO FIRE WEATHER CONCERNS THROUGH THE MIDDLE OF NEXT WEEK AS A
PERIOD OF UNSETTLED WEATHER WILL CONTINUE ACROSS SOUTHEAST
WYOMING AND WESTERN NEBRASKA. PERIODS OF RAIN SHOWERS AND HIGH
ELEVATION SNOW ARE EXPECTED INTO MONDAY WITH ISOLATED
THUNDERSTORMS POSSIBLE ON SUNDAY. HUMIDITIES WILL TREND MUCH
HIGHER THIS WEEKEND WITH RECOVERIES NEAR 90 PERCENT...AND DAYTIME
HUMIDITIES BETWEEN 60 TO 80 PERCENT. DAYTIME RELATIVE HUMIDITIES
WILL TREND LOWER LATER NEXT WEEK...RANGING BETWEEN 25 TO 35
PERCENT BY THURSDAY AFTERNOON.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY UNTIL 6 AM MDT MONDAY FOR WYZ114-116.

NE...NONE.
&&

$$

UPDATE...RJM
SHORT TERM...TJT
LONG TERM...SML
AVIATION...CLH
FIRE WEATHER...TJT


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