Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 280941
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
341 AM MDT THU MAY 28 2015

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 225 AM MDT THU MAY 28 2015

CURRENT IR SATELLITE LOOP SHOWS SKIES BECOMING PARTLY CLOUDY
ACROSS THE REGION EARLY THIS MORNING AS AN EARLIER BAND OF
SHOWERS AND TSTORMS WEAKENS OVER THE HIGH PLAINS AND PUSHES
EASTWARD ACROSS WESTERN NEBRASKA. IR SATELLITE SHOWS A MIDLEVEL
CIRCULATION OVER IDAHO AND WESTERN MONTANA. THIS FEATURE WILL
SLOWLY MOVE EASTWARD INTO WYOMING TODAY...WITH THE TROUGH AXIS
OVERHEAD BY EARLY FRIDAY MORNING. THIS WILL RESULT IN A
CONTINUATION OF SHOWERS AND TSTORMS OVER WYOMING AND WESTERN
NEBRASKA TODAY THROUGH FRIDAY EVENING...ALONG WITH MOSTLY CLOUDY
SKIES.

FOR TODAY...MODELS INDICATE AN UPPER LEVEL JET MOVING EASTWARD
NEAR THE COLORADO BORDER. LLVL INSTABILITY AND UPPER LEVEL
DIFFLUENCE WILL BE THE PRIMARY FORCING MECHANISMS TODAY BEFORE THE
COOL FRONT...JUST ABOVE THE SURFACE...MOVES INTO THE FORECAST
AREA TONIGHT...LIKELY PROLONGING RAIN SHOWER AND TSTORM ACTIVITY.
INCREASED POP AROUND 60 TO 65 PERCENT OVER THE HIGH PLAINS TODAY
WITH BANDS OF SHOWERS AND TSTORMS DEVELOPING...PUSHING NORTHEAST
ACROSS THE HIGH PLAINS...WITH OTHER BANDS DEVELOPING FURTHER WEST
AND LIKELY TRAINING OVER THE SAME AREAS INTO THIS EVENING. A FEW
STRONGER TSTORMS ARE POSSIBLE OVER WESTERN NEBRASKA...WHICH MAY
CONTAIN HAIL...FREQUENT LIGHTNING AND VERY HEAVY RAINFALL.
ACTIVITY WILL PROBABLY LINGER THROUGH TONIGHT...ALTHOUGH IT
APPEARS THIS DEEPER CONVECTION WILL SHIFT FURTHER NORTHWARD NEAR
THE ACTUAL UPPER LEVEL TROUGH AXIS...DUE TO CONDITIONAL
INSTABILITY PRESENT ALOFT.

ALL MODELS SHOW THE TROUGH AXIS MOVING SOUTHEAST THROUGH THE AREA
ON FRIDAY...WITH THE BEST CHANCE OF MODERATE RAINFALL AMOUNTS
ACROSS THE EASTERN HIGH PLAINS. MOST AREAS WILL SEE AN ADDITIONAL
ONE QUARTER TO ONE HALF INCH OF RAIN...WITH SOME AREAS CLOSER TO
ONE INCH BY FRIDAY EVENING. WILL CONTINUE TO MONITOR RIVER LEVELS
AND FLASH FLOOD POTENTIAL EAST OF THE LARAMIE RANGE. VERY LITTLE
IF ANY IMPACTS ARE ANTICIPATED FURTHER WEST OVER ALBANY AND CARBON
COUNTIES. 700MB TEMPERATURES WILL LOWER TO AROUND 0C...SO HIGH
TEMPERATURES AT THE SURFACE WILL STRUGGLE TO BREAK 60 DEGREES AS
WINDS SHIFT INTO THE NORTHEAST.

MODEL SOUNDINGS THEN SHOW THE MIDLEVELS BECOMING DRIER INTO
SATURDAY MORNING AS SOME SUBSIDENCE DEVELOPS BEHIND THE UPPER
LEVEL TROUGH. HOWEVER...CAN NOT RULE OUT A FEW ISOLATED TSTORMS
NEAR AND JUST EAST OF THE LARAMIE RANGE SATURDAY AFTERNOON DUE TO
LLVL CONVERGENCE...AVAILABLE MOISTURE...AND DAYTIME INSTABILITY.
INCREASED POP BETWEEN 15 TO 25 PERCENT FROM CHEYENNE TO LARAMIE
AND NEAR DOUGLAS WYOMING. REGARDLESS...IT WILL BE A PLEASANT START
TO THE WEEKEND WITH PARTLY TO MOSTLY SUNNY SKIES.


.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 225 AM MDT THU MAY 28 2015

MODELS CONTINUE TO SHOW AN UPPER LEVEL RIDGE APPROACHING FROM THE
WEST SATURDAY NIGHT AND MOVING OVERHEAD FOR SUNDAY. THIS WILL BRING
DIMINISHED CHANCES FOR SHOWERS AND STORMS THRU THE WEEKEND. TEMPS
WILL WARM TO MORE ABOVE NORMAL READINGS FOR THIS TIME OF YEAR...AND
HOPEFULLY WE WILL SEE MANY AREAS FINALLY DRY OUT A BIT. FIRST
OFF...THE LEESIDE SFC TROUGH LOOKS TO DEEPEN SATURDAY EVENING IN
RESPONSE TO A VORT MAX RIDING ATOP THE RIDGE AND ACROSS MONTANA.
SOUTHERLY SFC FLOW WILL STRENGTHEN AS RESULT ACROSS THE PLAINS...SO
CANT RULE OUT A WEAK T-STORM OVER THE SOUTHERN LARAMIE RANGE IN
THIS UPSLOPE PATTERN...WITH PERHAPS A FEW LIGHT SHOWERS OVER THE
CHEYENNE RIDGE AS WELL. MODELS SHOW WEAK ENERGY CONTINUING TO RIDE
ATOP THE RIDGE AND OVER THE NORTHERN ROCKIES ON SUNDAY WHICH
SHOULD SPARK OFF A FEW AFTERNOON SHOWER AND T-STORMS. AT THIS
POINT...THE MAIN INSTABILITY AXIS WILL REMAIN EAST OF THE AREA SO
EXPECT ANY ACTIVITY THAT DEVELOPS TO REMAIN QUITE ISOLATED AND
WEAK. THE RIDGE WILL BEGIN TO SHIFT EAST ON MONDAY WITH
SOUTHWESTERLY FLOW ALOFT TAKING OVER THE WESTERN CONUS AS AN UPPER
LOW STALLS OVER THE PAC NW THROUGH TUESDAY. A FEW WEAK PIECES OF
ENERGY WILL MOVE UP FROM THE SOUTHWEST WITH THIS FLOW PATTERN IN
PLACE...LIKELY SKIRTING WESTERN PORTIONS OF THE CWA MONDAY AND
PERHAPS MORE DIRECTLY FOR TUESDAY. VERY WARM TEMPS AT H7 OF 12 TO
14C THROUGH THIS TIME WILL LIMIT CONVECTIVE ACTIVITY...HOWEVER
CANNOT RULE OUT MORE DIURNALLY AND OROGRAPHIC DRIVEN SHOWER AND
T-STORM ACTIVITY BOTH AFTERNOONS. AS THE UPPER TROUGH SHIFTS EAST
ON WEDNESDAY...COOLER TEMPS ALOFT ALONG WITH STRONGER UPPER
FORCING WILL SET THE STAGE FOR A BETTER CHANCE FOR CONVECTION IN
THE AFTERNOON AND EVENING.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 225 AM MDT THU MAY 28 2015

SHOWERS AND T-STORMS WILL CONTINUE ACROSS THE PLAINS THROUGH ABOUT
08-09Z BEFORE DIMINISHING OVERNIGHT. LIFR CONDITIONS LOOK PROBABLE
AT KSNY AND KAIA AFTER CONVECTION DISSIPATES THROUGH AROUND
SUNRISE IN MOIST SOUTHERLY FLOW. VFR CONDITIONS WILL CONTINUE
ELSEWHERE. ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS WILL DEVELOP
ON THURSDAY STARTING IN THE MOUNTAINS AFTER 15Z AND SPREADING TO
THE EAST THROUGH THE AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 225 AM MDT THU MAY 28 2015

NO FIRE WEATHER CONCERNS IN THE IMMEDIATE FUTURE DUE TO MONTHLY
RAINFALL TOTALS BETWEEN 2 TO 5 INCHES ABOVE AVERAGE. SHOWERS AND
THUNDERSTORMS WILL CONTINUE LATE THIS WEEK EACH DAY BEFORE A
SLIGHTLY DRIER AND MORE STABLE AIRMASS MOVES OVER THE AREA FOR
THIS WEEKEND. HOWEVER...SHOWERS AND THUNDERSTORMS WILL QUICKLY
RETURN TO THE REGION BY WEDNESDAY NEXT WEEK.
&&

.HYDROLOGY...
ISSUED AT 225 AM MDT THU MAY 28 2015

MODERATE FLOODING CONTINUES ON THE LARAMIE RIVER AT FORT
LARAMIE...WITH THE RIVER NEAR BANKFULL IN LARAMIE WYOMING. RIVER
LEVELS WILL BE STEADY FURTHER UPSTREAM...BUT WILL BEGIN TO LOWER
FURTHER DOWNSTREAM NEAR FORT LARAMIE AS WATER RELEASED FROM NEARBY
RESERVOIRS EASE A BIT.

ALONG THE NORTH PLATTE RIVER...HENRY AND MITCHELL WILL REMAIN
ABOVE FLOOD STAGE TODAY...BUT SHOULD GRADUALLY LOWER BELOW FLOOD
STAGE INTO THIS WEEKEND. HOWEVER...ANOTHER ROUND OF SHOWERS AND
TSTORMS ARE EXPECTED TODAY AND FRIDAY. THESE SHOWERS WILL BE
PRETTY WIDESPREAD OVER THE HIGH PLAINS...SO WILL HAVE TO CONTINUE
TO MONITOR RAINFALL RATES OVER THE UPSTREAM BASINS INTO THIS
WEEKEND...SINCE THE POTENTIAL FOR ADDITIONAL RUNOFF IS PRETTY
HIGH. CAN NOT RULE OUT THE POSSIBILITY THAT RIVER LEVELS MAY
INCREASE THIS WEEKEND DUE TO THE MODERATE TO HEAVY RAINFALL TODAY
AND FRIDAY.

&&

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

$$

SHORT TERM...TJT
LONG TERM...RJM
AVIATION...RJM
FIRE WEATHER...TJT
HYDROLOGY...TJT


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