Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 230031
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
631 PM MDT MON SEP 22 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 345 PM MDT MON SEP 22 2014

MOST ACTIVE WEATHER IN THE SHORT TERM WILL BE THROUGH THIS EVENING.
WATER VAPOR IMAGERY SHOWS THE MIDLEVEL LOW CENTER ACROSS CENTRAL WY
WITH LIFT AND MOISTURE OFF TO THE EAST.  THE MOST POTENT AND
WIDESPREAD AREA OF SHOWERS AND EMBEDDED TSTMS IS CURRENTLY ACROSS
THE NEBRASKA PANHANDLE.  CLOUD COVER HAS LIMITED SOME HEATING
THROUGH THE EARLY AFTN AND THE SPC MESOANALYSIS ONLY SHOWS SFC BASED
CAPE OF AROUND 500 J/KG OVER THE PANHANDLE.  WITH LIMITED
INSTABILITY AND ONLY MODEST DEEP LAYER SHEAR OF AROUND 30 KTS...NOT
TOO CONFIDENT WE WILL SEE SMALL HAIL OUT OF THE STRONGER STORMS.
HOWEVER...KEPT THE MENTION OF SMALL HAIL IN THE GRIDS WITH THE SMALL
POTENTIAL.  ANOTHER AREA OF SHOWERS EXISTS OVER CARBON COUNTY AND
WILL CONTINUE TO MOVE EASTWARD THROUGH THE EVENING.  UPPER TROUGH
AXIS WILL PASS OVER THE CWA THIS EVENING AND EARLY TONIGHT WITH
LARGE SCALE SUBSIDENCE ENSUING AND SHOWERS ENDING BY LATER TONIGHT.

TUESDAY WILL FEATURE DRY NORTHWESTERLY FLOW ON THE BACKSIDE OF THE
UPPER TROUGH THAT WILL BE OVER SOUTH DAKOTA.  IT WILL BE BREEZY FROM
THE MORNING THROUGH THE EARLY AFTN...MAINLY ACROSS SOUTHEAST WY.
SOUNDINGS SHOW 25-30 KTS AT THE TOP OF THE MIXED LAYER SO WINDS WILL
DEFINITELY BE ELEVATED COMPARED TO RECENTLY.  KEPT SLIGHT CHANCE
AFTN POPS IN FOR THE FAR EASTERN ZONES IN THE PANHANDLE WITH SOME
MIDLEVEL MOISTURE ON THE BACKSIDE OF THE SYSTEM...OTHERWISE IT WILL BE
DRY.  RIDGE ALOFT AMPLIFIES OVER COLORADO AND WYOMING ON WED.  TUES
WILL SEE HIGHS ABOUT 5 DEGREES WARMER THAN TODAY AND THEN ANOTHER 5
DEGREES OF WARMING WILL FOLLOW ON WED.  WEATHER WILL BE TRANQUIL ON
WED WITH A STABLE AIRMASS AND MOSTLY CLEAR SKIES ALONG WITH LIGHT
WINDS.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 345 PM MDT MON SEP 22 2014

AN AMPLIFIED PATTERN WILL PREVAIL THROUGH THIS PERIOD...INITIALLY
WITH A LARGE SCALE RIDGE OF HIGH PRESSURE CENTERED ACROSS THE
INTERMOUNTAIN WEST FOLLOWED BY A LONGWAVE TROUGH THAT WILL MOVE
ONTO THE PACIFIC COAST LATER THIS WEEKEND. DRY AND MUCH ABOVE
AVERAGE TEMPERATURES CAN BE EXPECTED AT LEAST FOR THU AND FRI AS
PROGD LLVL THERMAL RIDGE BOOSTS H7 TEMPS TO AROUND 14C. THIS WILL
YIELD HIGH TEMPS THAT WILL CLIMB WELL INTO THE 80S AND 90S FOR ALL
LOWER ELEVATIONS. MEDIUM RANGE GUIDANCE BEGIN TO PAINT SOME
QUESTION MARKS WITH THE TIMING OF LONGWAVE TROUGH THAT WILL MOVE
THROUGH AT SOME POINT THIS WEEKEND. 12Z GFS IS THE
QUICKEST...MOVING THIS TROUGH INTO THE GREAT BASIN ON
SATURDAY...WHICH WOULD SPREAD PRECIP INTO THE AREA AS EARLY AS
SATURDAY AFTERNOON. IN COMPARISON...THE 12Z ECMWF IS SIGNIFICANTLY
SLOWER WITH THE PATTERN PROGRESSION...NOT MOVING PRECIP INTO SE WY
AND W NE UNTIL SOMETIME DURING THE DAY ON SUNDAY. THE SLOWER
SOLUTION OFTEN IS MORE CORRECT IN THESE SITUATIONS. HOWEVER...HAVE
GIVEN THE GFS WHICH HAS BEEN FAIRLY CONSISTENT OVR RECENT RUNS
SOME RESPECT...BY AT LEAST KEEPING SMALL PRECIPITATION CHANCES
GOING FOR LATE SATURDAY AND SATURDAY NIGHT. THE BEST CHANCE FOR
PRECIP IN BOTH SCENARIOS LOOKS TO COME ON SUNDAY AND PERHAPS
LINGERING INTO MONDAY. SATURDAYS TEMPS WILL DEPEND UPON THE TIMING
OF THE SYSTEM. THE SLOWER ECMWF WOULD OFFER ANOTHER DAY OF MUCH
ABOVE AVERAGE TEMPS...WHILE THE QUICKER GFS WOULD SUGGEST A COOLER
DAY ON SATURDAY. TEMPERATURES WILL FALL BACK TO MORE SEASONAL
NORMS FOR SUNDAY AND MONDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY AFTERNOON)
ISSUED AT 607 PM MDT MON SEP 22 2014

ISOLATED SHOWERS WILL OCCUR OVER SOUTHEAST WYOMING AND THE
NEBRASKA PANHANDLE THIS EVENING AS AN UPPER LEVEL LOW MOVES EAST
ACROSS THIS AREA. AVIATION CONCERNS ARE MINIMAL AS HEAVIER SHOWERS
MAY PRODUCE MVFR BUT MAINLY LOOKING AT VFR THROUGH THE TAF PERIOD.

&&

.FIRE WEATHER...
ISSUED AT 336 PM MDT MON SEP 22 2014

MINIMAL FIRE WEATHER CONCERNS THROUGH MIDWEEK. SCATTERED SHOWERS
AND THUNDERSTORMS WILL BE POSSIBLE THROUGH THIS EVENING OVER MUCH
OF THE AREA. A DRIER AIRMASS WILL RETURN ON TUESDAY AND CONTINUE
THROUGH FRIDAY. MINIMUM HUMIDITY VALUES ACROSS SOUTHEAST WYOMING
WILL DROP TO 25-30 PERCENT ON TUESDAY AFTERNOON AND TO 15-25
PERCENT EACH AFTERNOON FROM WEDNESDAY TO FRIDAY. NORTHWEST WINDS
WILL BE BREEZY ON TUESDAY AND THEN WILL BE GENERALLY LESS THAN 15
MPH THROUGH THE REMAINDER OF THE PERIOD.

&&

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

$$

SHORT TERM...FINCH
LONG TERM...HAHN
AVIATION...SML
FIRE WEATHER...FINCH






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