Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 230057 AAA
AFDCYS

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHEYENNE WY
657 PM MDT FRI MAY 22 2015

.UPDATE...FOR EVENING AVIATION UPDATE.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 315 PM MDT FRI MAY 22 2015

SHORTWAVE LIFTING NORTHEAST FROM NORTHEAST COLORADO INTO WESTERN
NEBRASKA NOW WITH SOME CLEARING NOTED OVER EASTERN COLORADO. RAIN
AND CLOUDS HAVE KEPT THE AIRMASS RATHER STABLE OVER THE CWA WITH
NO STORMS NOTED SO FAR. A FEW NOT OUT OF THE QUESTION OUT WEST FOR
THE REST OF THE AFTERNOON.

SHOULD SEE SHOWERS BECOME MORE SCATTERED IN NATURE TONIGHT AS THE
INITIAL WAVE LIFTS NORTHEAST AND AWAY FROM THE AREA WITH A
MINIMUM IN COVERAGE LATER TONIGHT INTO SAT MORNING. MAIN UPPER
LOW CURRENTLY SOUTH OF LAS VEGAS NV WILL LIFT SLOWLY NORTHEAST
THROUGH SATURDAY AND ARRIVE OVER NW COLORADO BY LATE SAT
AFTERNOON. EXPECT YET ANOTHER ROUND OF CONVECTION TO DEVELOP OVER
MUCH OF THE CWA SAT AFTERNOON UNDER SFC UPSLOPE FLOW OVERTOPPED BY
DIFFLUENT UPPER FLOW. BETTER INSTABILITY STILL DEPICTED BY MODELS
FOR A RELATIVELY SHORT TIME SAT AFTERNOON FROM FAR SE WY INTO THE
SRN PANHANDLE WITH CAPES FROM ABOUT 1000-1500 J/KG. THIS ALONG
WITH DECENT SHEAR MAY LEAD TO A FEW STRONGER STORMS THOUGH
CONVECTION MAY BE ELEVATED. HAIL WOULD BE THE MAIN THREAT.

FAIRLY WIDESPREAD RAIN AND SHOWERS LIKELY TO CONTINUE SAT NIGHT
INTO SUNDAY AS THE UPPER LOW TREKS SLOWLY NORTHEAST ACROSS THE
CWA. A DRIER NORTHWEST TO WESTERLY FLOW ARRIVES LATE SUNDAY WHICH
WILL DECREASE SHOWER ACTIVITY.

TEMPS REMAINING COOL TO MILD GIVEN THE CLOUDS AND PCPN WITH MAXS
BELOW SEASONAL NORMS.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 315 PM MDT FRI MAY 22 2015

THE MAIN CONCERN WITH THIS PORTION OF THE FORECAST IS THE TIMING
OF THE UPPER LEVEL WAVES MOVING THROUGH THE REGION NEXT WEEK.

MONDAY-MONDAY NIGHT:
THE MODELS ARE IN FAIRLY GOOD AGREEMENT IS SHOWING ANOTHER WEAK
POTENTIAL VORTICITY ANOMALY MOVING THROUGH THE FORECAST AREA
MONDAY MORNING. THIS FEATURE MAY TRIGGER A FEW SHOWERS AS IT
PASSES THROUGH. OTHERWISE...THIS UPPER LEVEL TROF SHOULD CONTINUE TO
LIFT NORTHEAST INTO NORTHERN PLAINS AND TAKE THE BULK OF THE SHOWERS
EAST OF THE FORECAST AREA BY MIDDAY. HOWEVER...ON ITS HEELS
ANOTHER UPPER LEVEL TROF IS EXPECTED TO SPIN INTO THE NORTHERN
ROCKIES. AHEAD OF THIS FEATURE...THERE WILL BE SOME UPPER LEVEL
DIFFLUENCE WHICH MAY BE ENOUGH TO INITIATE A FEW SHOWERS AND
THUNDERSTORMS MAINLY WEST OF THE LARAMIE RANGE. ELSEWHERE...WE MAY
SEE SOME SUNSHINE UNLESS WE SEE A STRONGER SURFACE HIGH BUILD ON
THE LEE SIDE OF THE LARAMIE RANGE. NOT REAL CONFIDENT THIS WILL
OCCUR...BUT THERE A FEW CANADIAN/GEM ENSEMBLES THAT ARE DEPICTING
A LITTLE STRONGER SURFACE HIGH THAN WHAT DEPICTED ON THE
OPERATIONAL MODELS. IF THE WEAKER HIGH DEVELOPS...WE ARE LOOKING
A LITTLE WARMER TEMPERATURES WITH HIGHS FINALLY REACHING THE 60S
FOR MUCH OF THE AREA. ON THE OTHER HAND...IF THE STRONGER SURFACE
HIGH PLUNGES INTO THE AREA...WE MAY SEE ANOTHER CLOUDY AND COOL
DAY WITH HIGHS ONLY REACHING THE 50S EAST OF THE LARAMIE RANGE.

TUESDAY-FRIDAY:
THE MODELS ARE IN FAIRLY GOOD AGREEMENT IN SHOWING THE NEXT UPPER
LEVEL TROF DEVELOPING OVER THE NORTHERN ROCKIES AND SLOWLY
SHIFTING EASTWARD THROUGH THE WEEK. THIS FEATURE WILL KEEP OUR
PATTERN PRETTY UNSETTLED THROUGH MUCH OF THE WEEK. AS A
RESULT...WE WILL HAVE A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS
EACH DAY. HOWEVER...THE GOOD NEWS IS THAT THIS PATTERN SHOULD
FAVOR A BIT WARMER TEMPERATURES COMPARED TO WHAT WE HAVE SEEN THIS
PAST WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 657 PM MDT FRI MAY 22 2015

RAIN ACTIVITY CONTINUE TO DIMINISH ACROSS THE AREA...BUT
SOUTHEASTERLY UPSLOPE FLOW FROM LARAMIE EAST WILL KEEP LOW CLOUDS
IN THE FORECAST THROUGH MID-DAY TOMORROW FOR MOST SITES EXCEPT
FOR RAWLINS. BROUGHT LIFR VISIBILITIES/CEILINGS IN FOR CHEYENNE
AND SIDNEY LATE THIS EVENING THROUGH MID MORNING...AND LIFR
CEILINGS IN FOR ALL OTHER SITES EXCEPT RAWLINS. MODELS INSISTING
MOST OF THE LOW CLOUDS WILL STICK AROUND THROUGH EARLY
AFTERNOON...THEN AS BREAKS START OCCURRING WE SHOULD SEE SCATTERED
THUNDERSTORMS DEVELOP IN THE LATE AFTERNOON HOURS ACROSS SOUTHEAST
WYOMING AND THE SOUTHERN NEBRASKA PANHANDLE.

&&

.FIRE WEATHER...
ISSUED AT 315 PM MDT FRI MAY 22 2015

WIDESPREAD WETTING RAINS EXPECTED THROUGH SATURDAY EVENING BEFORE
PRECIPITATION DECREASES AND BECOMES MORE SCATTERED INTO EARLY NEXT
WEEK. NO CONCERNS SEEN INTO EARLY NEXT WEEK WITH FUELS MOIST AND
WEATHER CONDITIONS NON-CRITICAL.

&&

.HYDROLOGY...
ISSUED AT 315 PM MDT FRI MAY 22 2015

RELEASES FROM GRAYROCKS AND CONTINUED RUNOFF FROM AREA RAINFALL
WILL KEEP THE LARAMIE RIVER NEAR FORT LARAMIE AT MINOR FLOOD STAGE
THROUGH THE WEEKEND. RAIN LIKELY TO CONTINUE THROUGH LATE SATURDAY
THEN ACTIVITY SHOULD DECREASE AND BE MORE SCATTERED IN NATURE INTO
EARLY NEXT WEEK.

&&

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

$$

SHORT TERM...RE
LONG TERM...REC
AVIATION...JG
FIRE WEATHER...RE
HYDROLOGY...RE


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