Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 231558
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
958 AM MDT SAT AUG 23 2014

.UPDATE...
ISSUED AT 947 AM MDT SAT AUG 23 2014

CURRENT FORECAST FOR TODAY LOOKS ON TRACK AS THE MAIN 500MB UPPER
LEVEL LOW WILL MOVES ACROSS WYOMING AND INTO MONTANA. DEEP
MOISTURE...SOME INSTABILITY...AND A 75 KNOT JET WILL AID IN THE
PRODUCTION OF ANOTHER ROUND OF SHOWERS AND ISOLATED THUNDERSTORMS.
EXPECT ACTIVITY TO BE MORE SHOWERY IN NATURE WITHIN BANDS OF
LIGHTER RAINFALL...BUT TSTORMS WILL BE PRETTY ISOLATED DUE TO THE
LACK OF DEEP INSTABILITY AND COOLER TEMPERATURES TODAY. SHOWERS
WILL ALSO MOVE PRETTY FAST ACROSS THE AREA...LIKELY EXITING THE
AREA BY EARLY THIS EVENING. ANOTHER TENTH TO QUARTER INCH OF RAIN
IS EXPECTED...MAINLY SOUTH ALONG I80. FURTHER NORTH ACROSS THE
NORTH PLATTE RIVER VALLEY...NOT AS MUCH RAINFALL IS EXPECTED DUE
TO DRIER AIR MOVING INTO THE AREA. OTHERWISE...SKIES WILL BECOME
MOSTLY CLEAR TO PARTLY CLOUDY TONIGHT WITH COOL OVERNIGHT LOWS
EXPECTED.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 418 AM MDT SAT AUG 23 2014

A BREAK IN THE ACTION TO BEGIN THE DAY AS THE CWA IS CAUGHT
BETWEEN SYSTEMS. THE FIRST SHORTWAVE THAT BROUGHT 3+ INCH RADAR
PRECIP ESTIMATES TO CHEYENNE COUNTY YESTERDAY WAS INTO THE
DAKOTAS...WHILE ITS PARENT UPPER-LOW WAS STILL SPINNING OVR SRN
IDAHO. LINGERING LIGHT SHOWER ACTIVITY FROM ALLIANCE TO CHADRON
WILL GRADUALLY MOVE OUT THRU SUNRISE. MAY ALSO SEE SOME LIGHT FOG
IN AND AROUND SIDNEY EARLY THIS MORNING. REGIONAL RADAR RETURNS
SHOW A MINIMUM IN PRECIP ACROSS THE CWFA WITH THE NEXT BAND OF
RAIN ORIENTED FROM N-S FROM AROUND BILLINGS TO GRAND JUNCTION AS
OF 09Z. WOULD EXPECT TO SEE THOSE RAIN SHOWERS SPREAD INTO THE
SNOWY/SIERRA MADRES TOWARD DAYBREAK AND INTO CARBON/ALBANY
COUNTIES DURING THE REST OF THE MORNING. THEY MAY EVEN GET INTO
LARAMIE RANGE AND LARAMIE COUNTY TOWARDS NOONISH. SUFFICIENT
DESTABILIZATION WILL OCCUR BETWEEN THE TWO SYSTEMS OVR THE ERN
PLAINS FOR CONVECTIVE INITIATION THIS AFTERNOON. AVAILABLE
INSTABILITY WILL DEPEND UPON THE AMOUNT AND THICKNESS OF CLOUD-
COVER THIS AFTERNOON. CONSERVATIVELY...WILL SEE 500-1000 J/KG OF
SBCAPE OVR THE WRN NEBRASKA PANHANDLE THIS AFTERNOON. ALTHOUGH THE
06Z NAM DATA PAINTS UPWARDS OF 1500 J/KG NR SIDNEY...WHICH WHEN
COMBINED WITH AROUND 30 KNOTS OF DEEP LAYER SHEAR MAY ENOUGH FOR A
FEW STORMS TO BECOME STRONG OVR THE FAR ERN PANHANDLE LATER THIS
AFTERNOON. TOO MUCH UNCERTAINTY EXISTS THOUGH TO INCLUDE THAT
MENTION FOR NOW. THE OTHER CONCERN WILL BE FLASH FLOOD POTENTIAL
ACROSS CHEYENNE AND SRN MORRILL COUNTIES. CONTEMPLATED A WATCH OVR
THESE AREAS...AS THE ALREADY SATURATED GROUND WOULD STRUGGLE TO
HANDLE ANY SIGNIFICANT RAINFALL RATES. WILL HOLD OFF FOR NOW AS AM
NOT CONVINCED RATES NOR CONVECTIVE COVERAGE WILL BE ENOUGH.
CONVECTION WILL EXIT EAST OF THE CWFA LATE THIS EVENING. UPPER-LOW
WILL EJECT INTO WRN DAKOTAS ON SUNDAY...PUTTING THE CWFA BENEATH
ON THE DRY SRN FLANK OF THE SYSTEM. THIS WILL YIELD A DRY
CONDITIONS TO END THE WEEKEND.

THE NEXT TROUGH DIGS INTO THE GREAT BASIN FOR MONDAY. EMBEDDED
SHORTWAVES WITHIN SOUTHWEST FLOW WILL RIDE ATOP LLVL ERLY UPSLOPE
FLOW. PRECIP WILL SPREAD INTO WRN SECTIONS OF THE CWFA AS EARLY AS
MONDAY MORNING...WITH PROGD SBCAPES UP AROUND 2000 J/KG OVR THE
ERN PLAINS SUPPORTING ORGANIZED CONVECTION MONDAY AFTERNOON. SOME
OF THESE THUNDERSTORMS AGAIN MAY BECOME STRONG TO LOCALLY SEVERE
OVR WRN NEBRASKA IF CURRENT MODEL PROGS HOLD.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 418 AM MDT SAT AUG 23 2014

MAIN DIFFICULTY THIS PERIOD WILL BE CONCERNING THE UPPER SYSTEM
THAT WILL BE AFFECTING THE REGION AT LEAST INTO TUESDAY EVENING
WITH AN UPPER TROF/LOW DROPPING SLOWLY SE ACROSS THE REGION FROM
THE PACIFIC NW. THIS WILL KEEP AT LEAST SCTD SHOWERS AND TSTRMS
GOING AT TIMES ACROSS MUCH OF THE CWA AS VORT ENERGY OVERRIDES
MODEST SFC UPSLOPE FLOW. MODELS DIVERGE BEGINNING WEDS WITH THE EC
HOLDING A CLOSED UPPER LOW BACK OVER THE CENTRAL ROCKIES
INITIALLY...THEN WEAKENING AND OPENING IT UP AS IT MOVES INTO THE
HIGH PLAINS THROUGH THURSDAY. GFS MAINTAINS AN OPEN TROF AND
SWINGS IT EAST OF THE CWA WEDS MORNING...ENDING PCPN AT THAT TIME.
RIGHT NOW GFS LOOKS TO BE TOO PROGRESSIVE THUS WILL LEAN TOWARDS
THE SLOWER EC BUT NOT AS SLOW AS IT DEPICTS...KEEPING POPS IN
THROUGH WEDS. TEMPS WILL REMAIN ON THE MILD SIDE OVERALL WITH THE
COOLEST TIME BEING MIDWEEK AS THE UPPER SYSTEM MOVES ACROSS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 418 AM MDT SAT AUG 23 2014

AREAS OF MVFR/IFR CIGS THIS MORNING EAST OF THE MTNS WITH SOME
SHOWERS. CIGS SHOULD LIFT TO VFR AREA-WIDE BY LATE MORNING AND
REMAIN VFR THROUGH SUNDAY AS DRIER AIR MOVES IN. WDLY SCTD SHOWERS
AND TSTMS SHOULD OCCUR AGAIN THIS AFTERNOON AND EVENING.


&&

.FIRE WEATHER...
ISSUED AT 418 AM MDT SAT AUG 23 2014

THE UNSETTLED PATTERN WILL CONTINUE INTO EARLY NEXT WEEK...WITH
SUNDAY THE ONLY DAY OF THE NEXT FOUR THAT ALL AREAS WILL BE DRY.
MINIMUM RELATIVE HUMIDITIES WILL ONLY FALL INTO THE 20 TO 30 PERCENT
RANGE ALONG WITH EXCELLENT RECOVERIES OVERNIGHT. HIGH TEMPERATURES
WILL HOLD GENERALLY IN THE 70S AND 80S THRU THE PERIOD...WITH SOME
60S TODAY AND TUESDAY FOR AREAS WEST OF THE LARAMIE RANGE.

&&

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

$$

UPDATE...TJT
SHORT TERM...HAHN
LONG TERM...RE
AVIATION...RE
FIRE WEATHER...HAHN






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