Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 041146
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
546 AM MDT TUE AUG 4 2015

.SHORT TERM...(TODAY THROUGH WEDNESDAY NIGHT)
ISSUED AT 300 AM MDT TUE AUG 4 2015

WATER VAPOR IMAGERY SHOWING MONSOON PLUME BEING ADVECTED EAST INTO
THE EASTERN CWFA THIS MORNING AHEAD OF AN UPPER LOW CURRENTLY
TRACKING INTO SOUTHERN WYOMING NEAR RAWLINS. DRY SLOT MOVING INTO
CARBON COUNTY AT THIS TIME. STILL SEEING SOME SHOWERS OVER THE
LARAMIE RANGE AT 2 AM THIS MORNING. LATEST MESOWEST OBSERVATIONS
SHOWING THAT FAIRLY WIDESPREAD ACCUMULATING RAIN DID FALL ACROSS
CARBON AND ALBANY COUNTIES YESTERDAY UNDER THE MOISTURE PLUME.
AREAS EAST OF THE LARAMIE RANGE SHOULD SEE THIS PLUME TODAY.

DO BELIEVE MOST SEVERE THUNDERSTORM ACTIVITY WILL BE EAST OF THE
PANHANDLE TODAY...THOUGH LATEST HRRR SIMULATED RADAR DOES SHOW
SOME EARLY DEVELOPMENT LATER THIS MORNING. LATEST NAM SOUNDINGS
SHOWING LITTLE TO NO SHEAR AND CAPE VALUES OF 1000-1300J/KG OUT IN
THE NORTHERN PANHANDLE THIS AFTERNOON. PRECIPITABLE WATER VALUES
NEAR 1.3 INCHES THIS AFTERNOON OUT IN THE PANHANDLE MAKES ME THINK
THAT HEAVY RAIN WOULD BE THE PRIMARY HAZARD ASSOCIATED WITH ANY
THUNDERSTORMS TODAY. DID INCLUDE HEAVY RAINFALL IN THE NORTHERN
PANHANDLE ZONES AND NIOBRARA/NORTHERN GOSHEN COUNTIES IN SOUTHEAST
WYOMING. WEAK STEERING FLOW COULD CREATE SLOW MOVING STORMS...SO
DAY CREW WOULD NEED TO BE ON THE LOOKOUT FOR POSSIBLE FLASH
FLOODING FOR SOME AREAS.

UPPER LOW MOVES EAST INTO CENTRAL NEBRASKA AFTER 06Z THIS EVENING
WITH MOST SHOWERS AND THUNDERSTORMS COMING TO AN END AFTER THAT
TIME. UPPER RIDGE BUILDS BACK OVER THE AREA FOR WEDNESDAY WITH
MAINLY DRY CONDITIONS ACROSS THE CWFA. WINDS ON THE INCREASE
WEDNESDAY NIGHT INTO THURSDAY AS AN UPPER LOW TRACKS ACROSS
NORTHERN MONTANA. GFS 700MB WINDS BEGIN TO INCREASE AFTER 00Z
THURSDAY...SETTING THE STAGE FOR POSSIBLE ELEVATED TO CRITICAL
FIRE WEATHER CONDITIONS THURSDAY.

.LONG TERM...(THURSDAY THROUGH MONDAY)

ISSUED AT 151 AM MDT TUE AUG 4 2015

THE MAIN CONCERN WITH THIS PORTION OF THE FORECAST IS THE
POTENTIAL FOR GUSTY WINDS AND WARMER TEMPERATURES AS WE HEAD INTO
THURSDAY INTO FRIDAY.

THURSDAY-FRIDAY:
THE MODELS APPEAR TO BE IN FAIRLY GOOD AGREEMENT IN SHOWING AN
UPPER LEVEL WAVE MOVING THROUGH BRITISH COLUMBIA...SASKATCHEWAN
AND ALBERTA THURSDAY INTO FRIDAY. THIS WILL FAVOR OUR REGION IN A
MORE ZONAL FLOW REGIME WHICH MAY YIELD TO SOME ANOMALOUS 700MB
FLOW(~30-35KTS). IF THINGS REALLY MIX OUT ON THURSDAY WE COULD
END WITH A GOOD SHOT AT SEEING CRITICAL FIRE WEATHER CONDITIONS.
SEE THE FIRE WEATHER DISCUSSION BELOW. IN ADDITION...TEMPERATURES
COULD BE QUITE WARM ESPECIALLY IN AREAS EAST OF THE LARAMIE RANGE
WHERE DOWNSLOPE FLOW WILL AID. WE DID BUMP UP TEMPERATURES A
COUPLE OF DEGREES FROM THE BLENDS TO REFLECT THIS POTENTIAL. THE
WIND SPEEDS DO BACK OFF QUITE A BIT ON FRIDAY AS THE UPPER LEVEL
RIDGE TRIES TO MAKE A QUICK RETURN. AS A RESULT...TEMPERATURES MAY
BE A TAD COOLER WITH POSSIBLY SLIGHTLY HIGHER DEWPOINTS.

SATURDAY-MONDAY:
THE MODELS ARE IN PRETTY GOOD AGREEMENT IN SHOWING THE SOUTHWEST
FLOW DEVELOPING OVER OUR REGION WHICH MAY BRING BACK THE MONSOONAL
MOISTURE IN AREAS ALONG AND EAST OF THE LARAMIE RANGE. THE MAIN
QUESTION DURING THIS TIMEFRAME WILL BE THE POSITION OF THE UPPER
LEVEL TROF IN THE PACIFIC NORTHWEST. IF THE HEIGHT FALLS STAY FOCUSED
IN THE PACIFIC NORTHWEST THE MONSOONAL FETCH MAY NOT BE AS GREAT
WHICH MAY TEND TO SUPPRESS THE BULK OF THE MOISTURE ACROSS
COLORADO AND NEW MEXICO. HOWEVER...IF THE UPPER LEVEL TROF CAN
SHIFT A LITTLE FURTHER EAST WE MAY SEE A STRONGER FETCH OF
MONSOONAL MOISTURE INTO AREAS EAST OF THE LARAMIE RANGE. FOR
NOW...WE WILL PLAY THINGS CONSERVATIVE UNTIL THE PICTURE BECOMES A
BIT CLEARER.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 531 AM MDT TUE AUG 4 2015

LATEST WATER VAPOR LOOP WAS SHOWING THE CLOSED UPPER LEVEL LOW
SPINNING OVER NORTHWEST CARBON COUNTY AND GRADUALLY SHIFTING EAST.
THIS FEATURE IS PROGGED TO CONTINUE MOVING SLOWLY EAST TODAY.
AHEAD OF THIS WAVE...SOME SCATTERED THUNDERSTORMS MAY DEVELOP OVER
AREAS MAINLY NORTH OF INTERSTATE 80. ANY STORMS THAT DO DEVELOP
WILL BE SLOW MOVERS. ALONG AND SOUTH OF INTERSTATE 80 GUSTY WEST
WINDS ARE EXPECTED WITH GUSTS APPROACHING 35 KTS. OTHERWISE...MVFR
CONDITIONS ARE STILL POSSIBLE AT THE KRWL TAF SITE THROUGH MID
MORNING UNTIL THE WESTERLY FLOW INCREASES AND HELPS SCOUR OUT THE
LOW LEVEL MOISTURE.

&&

.FIRE WEATHER...
ISSUED AT 300 AM MDT TUE AUG 4 2015

WIDESPREAD WETTING RAINS EXPECTED TODAY AS A LOW PRESSURE SYSTEM
TRACKS ACROSS NORTHERN COLORADO. THIS WILL BE ESPECIALLY TRUE FOR
FIRE WEATHER ZONES NORTH AND EAST OF THE LARAMIE RANGE TODAY. BEST
CHANCES WILL BE 301...302 AND 311 WHERE HEAVY RAINS COULD OCCUR
THIS AFTERNOON. A DRIER DAY FOR WEDNESDAY AS THE LOW PRESSURE
SYSTEM TRACKS INTO EASTERN NEBRASKA. NEXT CHANCE FOR ELEVATED TO
CRITICAL FIRE WEATHER WILL BE WEDNESDAY NIGHT INTO THURSDAY AS LOW
PRESSURE TRACKS ACROSS NORTHERN MONTANA AND SOUTHERN ALBERTA
CANADA. THIS WILL CREATE STRONG WINDS ACROSS WYOMING WHERE AREAS
WEST OF THE LARAMIE RANGE COULD SEE WIND GUSTS IN EXCESS OF 40 MPH
AND AFTERNOON HUMIDITIES NEAR CRITICAL. GUSTY AFTERNOON WINDS AND
HUMIDITIES NEAR CRITICAL EACH DAY THROUGH FRIDAY.

&&

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

$$

SHORT TERM...GCC
LONG TERM...REC
AVIATION...REC
FIRE WEATHER...GCC



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