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000
FXUS65 KCYS 080330
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
830 PM MST FRI MAR 7 2014

.UPDATE...
ISSUED AT 825 PM MST FRI MAR 7 2014

RECENT CHECK OF SNOTEL DATA AND WEB CAMS INDICATED THAT SNOW SHOWERS
HAVE DIMINISHED. THIS TREND WILL CONTINUE THIS EVENING. AN ADDITIONAL
INCH OF SNOW WILL BE POSSIBLE. THE WINTER WEATHER ADVISORY FOR THE
SNOWY AND SIERRA MADRE RANGES WAS CANCELLED.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 203 PM MST FRI MAR 7 2014

VISIBLE SATELLITE IMAGERY SHOWING ENHANCED SNOW BANDS NICELY OVER
CENTRAL AND NORTHERN COLORADO...CLOSE TO WHERE THE NAM AND GFS
CORRECTLY PREDICTED THE MORE INTENSE SNOW BANDING WOULD BE...WHILE
IN CONTRAST...OVER OUR COUNTIES...PRECIPITATION RATES ARE LESS
THAN OVER COLORADO BASED ON SATELLITE AND RADAR IMAGERY.

IN FACT...THE CHEYENNE WSR-88D REFLECTIVITY SHOWS THE BACK EDGE OF
THE PRECIPITATION ADVANCING SOUTHWARD ACROSS A MEDICINE BOW...TO
WHEATLAND TO NEAR SCOTTSBLUFF LINE.

OUR FORECAST TEAM HAS OPTED TO CONTINUE THE WINTER WEATHER ADVISORY
FOR OUR SNOWY AND SIERRA MADRE RANGES FOR NOW...BASED ON WEB CAMS...
SNOTEL CHECK...MODEL PROGNOSIS...SATELLITE IMAGERY AND TO ERR ON THE
SIDE OF CAUTION.

WILL SEE DECREASING CLOUDINESS FROM NORTH TO SOUTH OVERNIGHT. BASED
ON CURRENT TEMPERATURE AND DEWPOINT SPREADS AND NAM BOUNDARY LAYER
AND RELATIVE HUMIDITY FORECAST...HAVE ADDED AREAS OF FOG TO FAVORED
LOCATIONS.

SATURDAY...RIDGING ALOFT PREVAILS PRODUCING A DRY DAY. WARMING TREND
WILL BE TEMPERED SOMEWHAT BY NORTH FLOW ALOFT...THOUGH STILL
RELATIVELY MILD MAXIMA BASED ON PROJECTED THICKNESSES AND 700 MB
TEMPERATURES.

SATURDAY NIGHT...SNOW EATER DOWNSLOPE WINDS AND SURFACE LEE TROUGHING
WILL DEVELOP DUE TO FLOW ALOFT BECOMING NORTHWEST AND INCREASING
PRODUCING TYPICALLY LOCALIZED WARMER OVERNIGHT MINIMA ALONG THE
INTERSTATE 25 CORRIDOR DOWNWIND OF THE LARAMIE RANGE FROM WHEATLAND
TO CHEYENNE.

SUNDAY...NEAR PERFECT DAY FOR MILD WEATHER OUTDOOR ENTHUSIASTS WITH
DOMINANT RIDGE ALOFT OVER THE DESERT SOUTHWEST...AND OUR ABNORMALLY
HIGH 500 MB HEIGHTS...NEAR 5700 METERS...AIDING A SIGNIFICANT SURFACE
LEE TROUGH. STARK CONTRAST AS GFS MOS GUIDANCE SHOWS MAXIMUMS
CONSIDERABLY WARMER THAN COOLER NAM MOS...LIKELY INFLUENCED BY THE
NAM SHOWING MORE MIDDLE AND HIGH CLOUD OPACITY...THICKNESS...EXTENDING
ACROSS OUR COUNTIES DOWNWIND OF THICKER CLOUD COVER OVER OREGON AND
IDAHO. BASED ON LOCAL KNOWLEDGE OF HOW DOWNSLOPING ADDS CONSIDERABLE
WARMTH...PREFER THE WARMER GFS MOS OVER THE NAM MOS...AND BELIEVE
THE NAM IS TOO BULLISH WITH MIDDLE AND HIGH CLOUD THICKNESS OVER
OUR COUNTIES.

SUNDAY NIGHT...ANOTHER RELATIVELY MILD NIGHT WITH ZONAL...WEST TO
EAST...FLOW ALOFT AND DECENT LOW LEVEL MIXING...WINDS...AIDING THE
RELATIVELY MILD OVERNIGHT MINIMUM TEMPERATURES...LOCALLY WARMER
ALONG THE SPINE OF THE LARAMIE RANGE FROM WHEATLAND TO CHEYENNE.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 305 PM MST FRI MAR 7 2014

MAIN FORECAST CONCERN FOR THE LONG RANGE IS A PACIFIC UPPER LEVEL
TROUGH AND ASSOCIATED COLD FRONT FORECAST TO MOVE ACROSS THE
NORTHERN AND CENTRAL ROCKIES ON TUESDAY. EARLIER IN THE WEEK...VERY
MILD TEMPERATURES AND A PLEASANT SPRINGLIKE DAY WILL CONTINUE ON
MONDAY WITH HIGHS IN THE MID 50S TO MID 60S. A FEW LOCATIONS
ACROSS WESTERN NEBRASKA OR ALONG THE WYOMING BORDER MAY REACH 70
DEGREES BEFORE THE COLD FRONT BEGINS TO PUSH INTO THE FORECAST
AREA.

MODELS IN GOOD AGREEMENT REGARDING TIMING AND EVOLUTION...AS THE
COLD FRONT PUSHES SOUTHEAST ACROSS THE AREA EARLY TUESDAY MORNING
AND SNOWFALL DEVELOPS FROM NORTHWEST TO SOUTHEAST. THIS SYSTEM IS
SIMILAR THAN THE ONE THAT WENT THROUGH TODAY...BUT THIS ONE WILL
BE COLDER AND NOT AS PROGRESSIVE...ALLOWING THE A GREATER POTENTIAL
OF ACCUMULATING SNOW. ALL MODELS INDICATE THE BEST AREA FOR MODERATE
OR HEAVY SNOW ACCUMULATIONS WILL BE ALONG AND WEST OF THE LARAMIE
RANGE...ESPECIALLY IN THE MOUNTAINS. THE HIGH PLAINS WILL SEE SOME
SNOW...BUT MODELS SHOW THE JET ENERGY SPLITTING AS THE TROUGH DIGS
SOUTHWARD. MOST OF THE ENERGY WILL TRANSLATE SOUTHWARD RESULTING
IN THE START OF SPLIT FLOW FURTHER NORTH AND EAST. PLACES SUCH AS
CHADRON AND TH EAST CENTRAL WYOMING PLAINS MAY NOT GET MUCH OUT OF
THIS SYSTEM...ALTHOUGH SOME SNOW IS STILL EXPECTED AS THE FRONT
SWINGS THROUGH. INCREASED POP BETWEEN 40 TO 70 PERCENT ALONG THE
I-25 AND I-80 CORRIDORS...HIGHEST IN THE MOUNTAINS WHICH WILL LIKELY
SEE ACCUMULATIONS OVER 6 INCHES. HIGH TEMPERATURES ON TUESDAY WILL
LIKELY BE EARLY IN THE MORNING...AND ABOUT 20 TO 25 DEGREES LOWER
COMPARED TO MONDAY. TEMPERATURES ON TUESDAY AFTERNOON ARE EXPECTED
TO LOWER INTO THE 20S BEFORE THE PRECIPITATION COMES TO AND END
TUESDAY NIGHT.

QUIET WEATHER EXPECTED FOR THE REST OF THE WEEK AFTER THE UPPER
LEVEL TROUGH WEAKENS AND MOVES SOUTHEAST. WEDNESDAY MAY BE MUCH
COLDER THAN MODEL GUIDANCE SUGGESTS AS THE 12Z GFS SHOWS A WEAK
UPPER LEVEL LOW NEAR UTAH/COLORADO/WYOMING BORDER...PRODUCING
UPSLOPE FLOW ACROSS MOST OF THE HIGH PLAINS AND MUCH COOLER TEMPERATURES
NEAR 30 FOR DAYTIME HIGHS. THE ECMWF AND GEM SHOW THIS WEAK LOW MUCH
FURTHER SOUTHWEST AND NOT IMPACTING THE FORECAST AREA TOO MUCH WITH
NORTHWEST FLOW AND SLIGHTLY WARMER TEMPERATURES. TEMPERATURES WILL
INCREASE TO NEAR OR SLIGHTLY ABOVE NORMAL FOR THURSDAY AND FRIDAY
AS A PROGRESSIVE RIDGE OF HIGH PRESSURE ALOFT MOVES OVER THE AREA.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY AFTERNOON)
ISSUED AT 425 PM MST FRI MAR 7 2014

OCCASIONAL LIGHT SNOW OR SHOWERS WILL CONTINUE THROUGH EARLY EVENING
BEFORE ENDING FROM NORTH TO SOUTH. PERIODS OF IFR TO LIFR CONDITIONS
WILL PERSIST THROUGH TONIGHT...MAINLY ALONG AND EAST OF THE LARAMIE
RANGE DUE TO MOIST BOUNDARY LAYER. NORTH TO NORTHEAST SURFACE WINDS
WILL BECOME LIGHT VARIABLE TO NORTHWESTERLY. VFR CONDITIONS ARE
EXPECTED TO RETURN BY SUNRISE SATURDAY.

&&

.FIRE WEATHER...
ISSUED AT 203 PM MST FRI MAR 7 2014

MINIMAL ISSUES...THOUGH WE WILL NEED TO KEEP AN EYE ON SUNDAY AND
MONDAY AFTERNOONS AS WINDS AND HUMIDITIES APPROACH CRITICAL
THRESHOLDS.

&&

.HYDROLOGY...
ISSUED AT 1101 AM MST FRI MAR 7 2014

MELTING SNOW CAUSING SOME FLOODING PROBLEMS OVER PORTIONS OF THE
FORECAST AREA. SEVERAL STREETS CURRENTLY UNDER WATER IN LUSK
WYOMING AS THE NIOBRARA RIVER OVERFLOWS ITS BANKS. SHERIFFS OFFICE
THERE REPORTED FLOODING WAS SLIGHTLY WORSE THIS MORNING...COMPARED
TO LAST NIGHT.

INTO KIMBALL COUNTY NEBRASKA...MANY ROADS UNDERWATER DUE LARGELY
TO OVERLAND FLOODING. THE FLOODING IS OCCURRING EVEN THOUGH THERE
IS NOT ALL THAT MUCH SNOW TO MELT. THE BIGGEST FACTOR IS LIKELY
THE FROZEN GROUND. VERY COLD TEMPERATURES OVER THE LAST FEW MONTHS
HAVE FROZE THE GROUND AND IS LIKELY NOT LETTING SNOW MELT SOAK
INTO THE GROUND. ALSO LAST FALL WAS VERY WET WHICH PROBABLY IS NOT
HELPING ANY. THE FROST DEPTH A FEW DAYS AGO WAS 4 INCHES IN
CHEYENNE BUT WITH MILD TEMPERATURES...IS NOW COMPLETELY THAWED.
THESE FLOODING AREAS SHOULD NOT BE FAR BEHIND IN LOSING THEIR
FROZEN GROUND LAYER. SHOULD START TO SEE RELIEF OVER THE NEXT DAY
OR TWO AS RUNOFF PUSHES OUT OF THE AREA AND WATER STARTS TO SOAK
INTO THE GROUND.

&&

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

$$

UPDATE...JAMSKI
SHORT TERM...RUBIN
LONG TERM...TJT
AVIATION...JAMSKI
FIRE WEATHER...RUBIN
HYDROLOGY...RUBIN/SML