Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 222143
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
343 PM MDT SUN MAR 22 2015

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 339 PM MDT SUN MAR 22 2015

TONIGHT...RELATIVELY MILD...YET BREEZY SUNDAY AFTERNOON ONGOING.
STILL NOT MUCH EVIDENCE OF OUR EXPECTED SHOWER DEVELOPMENT VIA RADAR
OR VIA VISIBLE SATELLITE IMAGERY. LOOKS LIKE SOME SHOWERS DEVELOPING
OVER THE COLORADO FRONT RANGE. WITH MID AFTERNOON TEMPERATURE AND
DEWPOINT SPREADS SOME 40 TO 50 DEGREES ACROSS SOUTHEAST
WYOMING...EVEN IF SHOWERS CAN DEVELOP...LITTLE IF ANY CHANCE SHOWERS
WILL REACH THE GROUND...THUS HAVE REDUCED OUR RAIN CHANCES THIS
EVENING TO NEAR ZERO...DESPITE WHAT THE GFS INDICATES.

FOR AFTER MIDNIGHT...RIDGE AXIS ALOFT MOVES JUST TO OUR EAST WITH
SOUTHWEST FLOW ALOFT DEVELOPING. LOOKS LIKE PERHAPS A WEAK SHORTWAVE
TROUGH ALOFT AND SOME WARM AIR ADVECTION ALOFT WILL HELP AID IN
PRODUCING ISOLATED TO SCATTERED SHOWERS...WELL DEPICTED BY THE GFS
QPF FIELD...THUS HAVE PAINTED THESE POPS FROM RAWLINS TO WHEATLAND
TO ALLIANCE.

MONDAY...NEGATIVELY TILTED SHORTWAVE TROUGH ALOFT MOVES NORTHEAST
ACROSS EASTERN WYOMING...WITH ITS ASSOCIATED SURFACE TROUGH
STRETCHING NORTH TO SOUTH ALONG INTERSTATE 25 IN THE AFTERNOON.
DECENT 850/700 MB THETA-E RIDGE AXIS STRETCHES NORTH TO SOUTH ACROSS
SOUTHEAST WYOMING...AND COMBINED WITH DIFFERENTIAL HEATING AND
CONVERGENCE ALONG THE SURFACE TROUGH...EXPECT ISOLATED TO SCATTERED
AFTERNOON SHOWERS AND ISOLATED THUNDERSTORMS TO DEVELOP...MOST
NUMEROUS OVER THE SNOWY AND SIERRA MADRE RANGES DUE TO OROGRAPHICS
COMBINED WITH SYNOPTIC AND MESOSCALE LIFT.

MONDAY NIGHT...RELATIVELY POTENT PACIFIC ORIGIN COLD FRONT MOVES
ACROSS OUR COUNTIES AND WITH ITS ASSOCIATED BAROCLINIC BAND AND
SHORTWAVE TROUGH ALOFT...WE EXPECT SCATTERED TO NUMEROUS SHOWERS...
MOST NUMEROUS OVER THE SNOWY AND SIERRA MADRE RANGES. ALSO QUITE
WINDY BASED ON PROGGED SURFACE THROUGH MID LEVEL GRADIENTS AND
ISOTACHS.

TUESDAY...RIGHT ON THE HEELS OF THE INITIAL SHORTWAVE TROUGH
ALOFT...WILL BE ANOTHER SHORTWAVE TROUGH MOVING ACROSS WESTERN
WYOMING...AND WITH OROGRAPHICS...COMBINED WITH DYNAMICS AND
DIFFERENTIAL HEATING OVER OUR WESTERN MOUNTAINS...AND DIFFLUENT FLOW
ALOFT...WE EXPECT SCATTERED TO NUMEROUS AFTERNOON SHOWERS WEST OF
INTERSTATE 25...WITH MORE ISOLATED COVERAGE EAST OF THE MOUNTAINS
AND EAST OF INTERSTATE 25 DUE TO RAIN SHADOWING EFFECTS OF DOWNSLOPE
WEST WINDS IN THE LOW AND MID LEVELS. WE WILL NEED TO WATCH FOR
POSSIBLE HIGH WIND CRITERIA IN OUR WIND PRONE LOCATIONS SUCH AS
VEDAUWOO...ARLINGTON AND BORDEAUX BASED ON PROGGED LOW AND MID LEVEL
GRADIENTS...WITH APPROACHING HIGH WIND CRITERIA ACROSS THE REST OF
SOUTHEAST WYOMING SOUTH OF A RAWLINS TO TORRINGTON LINE...AND OVER
THE SOUTHERN NEBRASKA PANHANDLE...THOUGH BELIEVE THE UPWARD VERTICAL
MOTION INDICATED BY THE 500-300 MB AND 700-500 MB LAYERS
QUASIGEOSTROPHIC FORCING WILL LIMIT THE WIND POTENTIAL SOMEWHAT.

TUESDAY NIGHT...SHORTWAVE TROUGH ALOFT AND CYCLONIC FLOW ALOFT
PERSIST OVER OUR COUNTIES...AND COMBINED WITH ADEQUATE LOW AND MID
LEVEL MOISTURE...WE EXPECT SCATTERED TO NUMEROUS SHOWERS ALONG AND
WEST OF INTERSTATE 25...WITH RAIN SHADOW EFFECT SEVERELY LIMITING
SHOWER COVERAGE EAST OF THE LARAMIE RANGE AND INTERSTATE 25 CORRIDOR
DUE TO NORTHWEST DOWNSLOPE WINDS.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 339 PM MDT SUN MAR 22 2015

ACTIVE NORTHWEST FLOW WED-FRI WILL GIVE WAY TO BUILDING HEIGHTS NEXT
WEEKEND AS THE WRN CONUS RIDGE OF HIGH PRESSURE AMPLIFIES. WEDNESDAY
WILL BE THE COOLEST AND MOST UNSETTLED DAY OF THE WEEK AS A COLD AIR
MASS SLIDES IN BEHIND A COLD FROPA TUESDAY NIGHT. THE COMBINATION OF
THE SHORTWAVE PASSING DIRECTLY OVERHEAD...THE APPROACH OF UPPER JET
ENERGY AND DAYTIME INSTABILITY WILL PRODUCE A GOOD SHOT FOR
RELATIVELY WIDESPREAD MOISTURE. IT DOESNT LOOK LIKE A BIG
EVENT...BUT A FEW TENTHS OF LIQUID LOOK POSSIBLE ESPECIALLY IN AND
AROUND THE SE WY MOUNTAINS. TEMPERATURES WILL BE COLD ENOUGH FOR
SNOW ABOVE AROUND 6 KFT WEDNESDAY...WITH A MIX BELOW. THE
SNOWY/SIERRA MADRES MAY PICK UP A QUICK 2-5 INCHES WITH THIS
SYSTEM...WITH PERHAPS UP TO AN INCH IN LOWER ELEVATIONS WEST OF
THE LARAMIE RANGE. A SECONDARY SHORTWAVE WILL DROP SOUTHEAST IN
NORTHWEST FLOW THURSDAY REINFORCING THE POTENTIAL FOR INSTABILITY
ENHANCED SHOWER ACTIVITY. TEMPERATURES WOULD BE COLD ENOUGH FOR
LIGHT SNOW THURSDAY MORNING...BUT THERE SHOULD BE ENOUGH WARMING
FOR PRECIP PHASE TO TRANSITION TO RAIN BY AFTERNOON.

HEIGHTS WILL BUILD ON FRIDAY WHICH WILL END THE THREAT OF
PRECIPITATION THAT WILL CONTINUE THRU NEXT WEEKEND. HIGH TEMPS
WILL REBOUND INTO THE 50S TO NR 60 BY FRIDAY. HEIGHTS BUILD
FURTHER FOR SATURDAY WITH BREEZY CONDITIONS WEST WINDS RETURNING.
TEMPS WILL BOUNCE BACK INTO THE 60S WEST WITH 60S/LOW 70S EAST OF
THE MOUNTAINS. DRY NORTHWEST FLOW WILL KEEP DRY CONDITIONS IN
PLACE SUNDAY AS WELL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY)
ISSUED AT 1215 PM MDT SUN MAR 22 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD. THERE IS THE
POTENTIAL FOR WEAK SHOWER ACTIVITY ASSOCIATED WITH A WEAK UPPER
LEVEL DISTURBANCE AFTER AFTER 22Z AT SE WYOMING TERMINALS AND AFTER
08Z AT KBFF. AM NOT CONFIDENT IN PLACEMENT OF THESE SHOWERS NOR
COMFORTABLE TO FORECAST ANYTHING MORE THAN VCSH OR BELOW VFR AT THIS
POINT. SHOWER CHANCES FADES MONDAY MORNING...BUT WILL RETURN AGAIN
JUST BEYOND THIS TAF CYCLE.

&&

.FIRE WEATHER...
ISSUED AT 339 PM MDT SUN MAR 22 2015

MINIMAL ISSUES ON MONDAY BASED ON PROJECTED HUMIDITIES AND
WINDS...THOUGH WILL NEED TO KEEP AN EYE ON LIGHTNING STRIKES FROM
ISOLATED AFTERNOON AND EVENING THUNDERSTORMS.

FOR TUESDAY...EXPECT LOWEST AFTERNOON HUMIDITIES OF 15 TO 20 PERCENT
EAST OF INTERSTATE 25...AND SOUTH OF A WHEATLAND TO SCOTTSBLUFF
LINE...AND COMBINED WITH WIND GUSTS OVER 40 MPH...EXPECTED ELEVATED
FIRE WEATHER CONCERNS.

MINIMAL FIRE WEATHER CONCERNS FOR WEDNESDAY THROUGH FRIDAY BASED ON
HUMIDITIES AND WINDS...THEN LOWER AFTERNOON HUMIDITIES EXPECTED FOR
SATURDAY TO HEIGHTEN CONCERNS.

&&

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

&&

$$

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



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