Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 150520
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1120 PM MDT SUN SEP 14 2014

.UPDATE...
ISSUED AT 830 PM MDT SUN SEP 14 2014

EVENING REGIONAL SURFACE ANALYSIS SHOWED THAT A WEAK COLD FRONT
HAD PUSHED SOUTH ACROSS THE PLAINS INTO NORTHEAST COLORADO. DEW
POINTS ROSE ABOUT 10-15 DEGREES AND WINDS SHIFTED TO NORTHEASTERLY
IN THE WAKE OF THE FROPA. MOST OF THE MODELS CONTINUE TO SHOW AMPLE
LOW LEVEL MOISTURE POOLING EAST OF THE LARAMIE RANGE OVERNIGHT AND
MONDAY MORNING. IN A RECENT FORECAST UPDATE...EXPANDED THE LOW
CLOUDS AND PATCHY FOG FURTHER WEST TOWARD THE LARAMIE RANGE.

&&

.SHORT TERM...THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 300 PM MDT SUN SEP 14 2014

A FEW SHOWERS ALONG WITH A WEAK TSTM OR TWO MOVING EAST NEAR THE
COLORADO BORDER THIS AFTERNOON. THESE SHOULD DISSIPATE BY EVENING
WITH LOSS OF HEATING AND THE PASSAGE OF A MINOR DISTURBANCE.

MAIN DIFFICULTY WILL BE HOW MUCH LOW CLOUDINESS REDEVELOPS OVER
THE PLAINS OVERNIGHT. A REINFORCING SHOT OF COOLER AIR WILL SAG
SOUTH ACROSS THE PLAINS IN RESPONSE TO A SHORTWAVE THAT WILL MOVE
ACROSS THE NORTHERN PLAINS OVERNIGHT. NO PRECIPITATION EXPECTED
BUT SOME FOG SHOULD OCCUR LATER TONIGHT INTO EARLY MONDAY. 850MB
RHS BECOME VERY HIGH AND SHOULD SEE A FAIRLY EXPANSIVE AREA OF LOW
CLOUDS MAINLY OVER THE PANHANDLE BY LATE TONIGHT.

A MILD DAY EXPECTED ACROSS THE CWA MONDAY ESPECIALLY OVER THE
PLAINS WHERE CLOUDS WILL BE SLOW TO ERODE. DRIER AIR WILL SPREAD
GRADUALLY ACROSS THE CWA LATER MONDAY AND CONTINUE THROUGH TUESDAY
SO EXPECT MAINLY CLEAR SKIES THEN. WARMER AS WELL TUESDAY AS THE
COOL SFC AIRMASS CONTINUES RETREATING TO THE SOUTHEAST OF THE CWA.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 300 PM MDT SUN SEP 14 2014

NOT MANY CHANGES TO THE PREVIOUS LONG TERM FORECAST. UPPER RIDGE
STILL LOOKS TO BE THE DOMINATE FEATURE MIDWEEK WITH DRY CONDITIONS
AND ABOVE NORMAL TEMPERATURES. CONTINUED WITH HIGH TEMPERATURES
A FEW DEGREES ABOVE WARMEST GUIDANCE AND LOWS NEAR TO SLIGHTLY
BELOW GUIDANCE CONSENSUS AS A DRY ATMOSPHERE AND LIGHT WINDS
ALLOW FOR LARGER DIURNAL TEMPERATURE RANGES. MAIN CHANCE FOR
PRECIPITATION THROUGH THE PERIOD WILL BE FRIDAY AS A SHORTWAVE
MOVES THROUGH THE BACKSIDE OF THE UPPER LEVEL TROUGH. TODAY`S MODEL
SOLUTION TREND IS DRIER WITH THIS FEATURE THAN THE MODELS SHOWED
YESTERDAY...WHICH IS THE CASE FOR BOTH THE ECMWF AND GFS.
TYPICALLY THE MODELS OVERDO THE STRENGTH OF THE FIRST SHORTWAVE
CRASHING INTO AN UPPER LEVEL RIDGE SO WOULD NOT BE SURPRISED TO
SEE MODELS BACK OFF ON PRECIPITATION CHANCES FURTHER IN THE NEXT
SEVERAL RUNS FOR LATE THIS WEEK. EITHER WAY EXPECTING SOME
COOLING FROM A COLD FRONT LATE IN THE WEEK...THE QUESTION IS HOW
MUCH COOLER.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY EVENING)
ISSUED AT 1120 PM MDT SUN SEP 14 2014

INCREASING BOUNDARY LAYER MOISTURE AND NORTHEASTERLY UPSLOPE WILL
FAVOR LOW CLOUD AND PATCHY FOG FORMATION EAST OF THE LARAMIE RANGE
OVERNIGHT INTO MONDAY MORNING. HRRR/SREF/NAM MODEL GUIDANCE DEVELOPS
MVFR TO LIFR CIGS AFTER 06Z...WITH MVFR VSBYS AT BFF AND CYS AND
IFR AT SNY. SNY MAY MAINTAIN THE LOW CIGS/VSBYS UNTIL 20Z...WITH
CYS...BFF AND AIA IMPROVING TO VFR FROM 16Z TO 18Z MONDAY. VFR
CONDITIONS WILL PREVAIL WEST OF THE LARAMIE RANGE AT LAR AND RWL
WHERE WINDS WILL BE SOUTHWESTERLY.

&&

.FIRE WEATHER...
ISSUED AT 300 PM MDT SUN SEP 14 2014

NO CONCERNS EXPECTED FOR MUCH OF THE UPCOMING WEEK WITH WEATHER
CONDITIONS EXPECTED TO REMAIN ABOVE CRITICAL THRESHOLDS. A MINOR
PUSH OF COOLER AIR WILL ALLOW FOR A MILD DAY OVER THE PLAINS
MONDAY THEN WARMER TEMPERATURES RETURN TUESDAY.

&&

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

$$

UPDATE...JAMSKI
SHORT TERM...RE
LONG TERM...LIEBL
AVIATION...JAMSKI
FIRE WEATHER...RE







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