Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 300924
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
324 AM MDT WED JUL 30 2014

.SHORT TERM...(TODAY THROUGH FRIDAY NIGHT)
ISSUED AT 234 AM MDT WED JUL 30 2014

A LARGE AREA OF STRATIFORM RAIN PERSISTS ACROSS MUCH OF THE CWA
THIS AM WITH GOOD LLVL UPSLOPE FLOW ALONG AND EAST OF THE LARAMIE
RANGE. LATEST WATER VAPOR LOOP SHOWS AN UPPER LOW MOVING TOWARD
THE CENTRAL PLAINS FROM NORTHEAST CO...WITH ABUNDANT MID AND HIGH
LEVEL MOISTURE IN PLACE FROM SOUTHEAST WY INTO PORTIONS OF THE
SOUTHERN PANHANDLE. THIS SHOULD KEEP LIGHT TO MODERATE RAIN GOING
FOR SEVERAL MORE HOURS. RAINFALL RATES THROUGH THE OVERNIGHT HAVE
BEEN BETWEEN ONE AND TWO TENTHS OF AN INCH PER HOUR...SO HAVE NOT
BEEN SEEING ANYTHING PARTICULARLY HEAVY. MODELED SOUNDINGS FOR CYS
HAVE SHOWN A GRADUAL DECREASE IN HEAVY RAIN PARAMETERS WITH PWAT
VALUES CLOSER TO 1 INCH AND THE K-INDEX UNDER 30 AS OF 08Z. MOST
IMPORTANTLY...AIR MASS IS NOW MUCH MORE STABLE THAN IT WAS ON TUE
AFTN AND EVE. THE THREAT FOR FLASH FLOODING HAS DIMINISHED...SO
WILL DROP THE FLASH FLOOD WATCH PRIOR TO ITS SCHEDULED EXPIRATION
AT 12Z THIS AM. UPSLOPE WILL WEAKEN THROUGH EARLY AFTN AND UPPER
LEVEL SUPPORT WILL BE LOST AS FAVORABLE JET DYNAMICS SHIFT ACROSS
THE MIDWEST STATES AND MIDLVL PVA SPREADS INTO CO. SHOULD SEE THE
MAIN AREA OF PCPN GRADUALLY SHIFT SOUTH AND DIMINISH IN COVERAGE
THROUGH THE DAY. REMOVED MENTION OF THUNDER FROM THE GRIDS AS BOTH
THE GFS AND NAM SHOW VIRTUALLY NO CAPE THROUGH THE PERIOD. IT WILL
BE QUITE COOL TODAY...PARTICULARLY ALONG AND JUST E OF THE LARAMIE
RANGE WITH PERSISTENT UPSLOPE KEEPING IT CLOUDY AND WET THROUGH AT
LEAST PEAK HEATING. HIGHS AROUND 60 FOR CYS WOULD PUT US CLOSE TO
A RECORD LOW MAXIMUM OF 59 F FOR THIS DATE.

UPPER-LEVEL RIDGING WILL SHIFT EASTWARD ACROSS THE CENTRAL ROCKIES
THROUGH THE REMAINDER OF THE PERIOD. H7 TEMPS INCREASE ANOTHER 5
TO 8 DEG C THROUGH FRI AFTN PER BOTH THE GFS AND NAM...AND MODEST
MOISTURE ABOVE 700 MILLIBARS SHOULD YIELD PLENTY OF SUNSHINE ON
THU AND FRI WITH UPPER 80S RETURNING TO THE PANHANDLE. NO FURTHER
SIGNIFICANT PCPN EXPECTED AS THE OVERALL PATTERN WOULD FAVOR ANY
ACTIVITY TO BE OVER THE MOUNTAINS. MOST OF THE MODELS SHOW A BIT
OF MIDLVL MOISTURE SPREADING ALONG THE NORTHERN EDGE OF THE RIDGE
ON FRI AFTN...SO CANNOT RULE OUT A FEW SHOWERS OR TSTMS ASSOCIATED
WITH THAT. BELIEVE IT WILL REMAIN ISOLATED THOUGH GIVEN THE LACK
OF ANY SUBSTANTIAL FORCING MECHANISM...SO WENT AHEAD AND BROUGHT
POPS DOWN SLIGHTLY FROM THE PREVIOUS FCST.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 234 AM MDT WED JUL 30 2014

UPPER-LEVEL RIDGE AXIS LOCATED ACROSS THE INTERMOUNTAIN WEST WILL
AMPLIFY THROUGH THE UPCOMING WEEKEND BEFORE BEING FLATTENED AS THE
PATTERN TURNS MORE ACTIVE EARLY NEXT WEEK. LATEST MEDIUM RANGE
MODELS HAVE TRENDED DRIER WITH THE AVAILABLE MONSOONAL MOISTURE OVR
THE WEEKEND. AS SUCH...HAVE REMOVED MENTION OF SHOWERS/THUNDERSTORM
FROM LOWER ELEVATIONS...INSTEAD CONFINING ANY PRECIPITATION CHANCES
TO THE AFTERNOON/EVENING ABOVE 7000 FEET OVR THE SNOWY/SIERRA
MADRE/SOUTHERN LARAMIE RANGES. TEMPERATURES WILL RETURN TO
SUMMERTIME NORMS OVR THE WEEKEND AS THE RIDGE AXIS AND REFLECTED
THERMAL RIDGE BUILDS OVR THE CWA. H7 TEMPERATURE PROGS CLIMB TO
AROUND 12C ON SATURDAY...AND TO AROUND 14C FOR SUNDAY. HIGHER VALUES
WILL BE FOUND OVR THE WRN CWA...WITH SLIGHTLY COOLER VALUES EAST.
THE RESULT WILL BE FOR HIGH TEMPS TO REACH THE 70S AND 80S SATURDAY
AND 80S AND 90S FOR SUNDAY.

THE RIDGE AXIS SHIFTS TO NR THE FRONT RANGE EARLY NEXT WEEK AS
SHORTWAVE ENERGY ROTATES NORTHEAST TOWARDS THE CWFA FROM THE FOUR
CORNERS. MODELS DIFFER SOMEWHAT ON THE TIMING AND STRENGTH OF THIS
FTR WITH THE ECMWF QUICKER AND STRONGER COMPARED TO THE GFS. HAVE
BOOSTED SHOWER/THUNDERSTORM CHANCES AS A RESULT MONDAY AFTERNOON
THRU TUESDAY NIGHT. PWAT VALUES RETURN TO VALUES SIMILAR THOSE SEEN
YESTERDAY. IF THIS PATTERN MATERIALIZES...THE COMBINATION OF THE
ABUNDANCE OF MOISTURE AND SLOW STEERING FLOW WILL AGAIN HEIGHTEN AT
LEAST THE POSSIBILITY OF FLOODING LATE MONDAY THRU TUESDAY.
TEMPERATURES WILL COOL SOMEWHAT AS THE UNSETTLED CONDITIONS RETURN.
SHOULD SEE CONDITIONS DRY TOWARDS THE MIDDLE OF NEXT WEEK BEHIND THE
DEPARTING SHORTWAVE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 322 AM MDT WED JUL 30 2014

POOR AVIATION CONDITIONS WILL CONTINUE THIS MORNING FOR MOST
TERMINALS AS LOW STRATUS AND -RA CONTINUES ACROSS THE AREA. THE
EXCEPTION WILL BE OVR THE WRN NEBRASKA LOCATIONS WHERE RAINS HAVE
BEEN MORE SPOTTY AND LIGHTER. ALTHOUGH LIFR/IFR CONDITIONS WILL
CONTINUE THROUGH THE MORNING...EXPECT SOME SLIGHT IMPROVEMENT BY
AROUND MIDDAY...THOUGH MVFR CIGS ARE STILL EXPECTED. THIS LOW
STRATUS WILL OBSCURE SOUTHEAST WYOMING MOUNTAINS TODAY. CONDITIONS
WILL CONTINUE TO SLOWLY IMPROVE THROUGH THE AFTERNOON...WITH A
RETURN TO VFR ANTICIPATED BY THIS EVENING.

&&

.FIRE WEATHER...
ISSUED AT 234 AM MDT WED JUL 30 2014

MINIMAL FIRE WEATHER CONCERNS. RAIN WILL GRADUALLY DECREASE IN
COVERAGE AND INTENSITY TODAY ACROSS SOUTHEAST WY AND THE WESTERN
NE PANHANDLE. ANOTHER HALF TO ONE INCH OF RAIN WILL BE POSSIBLE
ALONG AND ON EITHER SIDE OF THE LARAMIE RANGE THROUGH WEDNESDAY
AFTERNOON. VERY COOL TODAY WITH HIGHS STRUGGLING TO REACH THE
LOWER TO MIDDLE 60S AT CHEYENNE AND RAWLINS. COOLER CONDITIONS
COMBINED WITH NEW MOISTURE WILL MITIGATE ANY NOTABLE FIRE WEATHER
HAZARDS. A GRADUAL WARMING TREND IS EXPECTED THROUGH THE END OF
THE WEEK...BUT AFTERNOON RELATIVE HUMIDITY VALUES ARE EXPECTED
TO REMAIN ABOVE 20 PERCENT THROUGH THE PERIOD.

&&

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

NE...NONE.
&&

$$

SHORT TERM...HAMMER
LONG TERM...HAHN
AVIATION...HAHN
FIRE WEATHER...HAMMER



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