932
FXUS65 KCYS 130946
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
346 AM MDT TUE AUG 13 2013
.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 300 AM MDT TUE AUG 13 2013
CURRENTLY...LOOKING AT MOSAIC RADAR...OUR CWFA IS PRETTY MUCH ECHO
FREE WITH A LINE OF THUNDERSTORMS PUSHING SOUTHEAST IN CENTRAL
NEBRASKA AT 1 AM THIS MORNING. FRONTAL BOUNDARY STILL LAYS UP
ALONG THE LARAMIE RANGE THIS MORNING...EXTENDING NORTHWEST INTO
CENTRAL MONTANA. TO OUR NORTH...A COMPLEX OF THUNDERSTORMS LAYS ACROSS
EASTERN MONTANA JUST EAST OF THE FRONT.
IT REMAINS TO BE SEEN WHAT THAT LINE OF THUNDERSTORMS OVER
NEBRASKA WILL DO TO OUR LOW LEVEL MOISTURE. IT HAS CAUSED WINDS TO
BECOME MORE SOUTHWESTERLY AND THEREFORE A LITTLE DRIER IN THE
PANHANDLE SO FAR. LATEST 11U-3.9U SATELLITE IMAGERY HAS YET TO
SHOW THE ANTICIPATED STRATUS DEVELOPING YET.
THE MORNING SHOULD START OFF DRY WITH INCREASING SHOWERS AND
THUNDERSTORMS DEVELOPING BY NOON. LATEST HRRR COMPOSITE
REFLECTIVITY FORECAST HAS SHOWERS DEVELOPING OVER THE MOUNTAINS TO
THE WEST OF CHEYENNE BY 17Z AND REALLY INCREASING IN COVERAGE
AFTER 19Z. THIS CORRESPONDS WELL WITH THE 00Z ECMWF FORECAST FOR
THE UPPER VORT MAX TO MOVE THROUGH THE UPPER RIDGE THIS AFTERNOON.
FORECAST STORM MOTIONS THIS AFTERNOON ON THE NAM SOUNDINGS SHOW
STORMS TO BE ALMOST STATIONARY. SOME LOCATIONS ARE GOING TO SEE
SOME HEAVY RAINFALL...LIKELY LEADING TO SOME FLASH FLOODING.
CONFIDENCE NO HIGH ON WHERE THESE THUNDERSTORMS ARE GOING TO
DEVELOP...SO WILL HOLD OFF ON ANY WATCHES. BUT DO EXPECT US TO BE
ISSUING FLASH FLOOD WARNINGS FOR SOME AREAS TODAY.
UPPER VORT MAX STAYS WITH US THROUGH THE OVERNIGHT HOURS
TONIGHT...FINALLY EXITING SOUTHEAST WEDNESDAY AFTERNOON. DID KEEP
FAIRLY HIGH POPS GOING TONIGHT THROUGH AT LEAST MIDNIGHT...THEN
PICKING UP AGAIN WEDNESDAY AFTERNOON WITH DAYTIME HEATING.
PATTERN CHANGE THEN BEGINS WEDNESDAY NIGHT INTO THURSDAY AS THE
ECMWF BUILDS THE UPPER LEVEL RIDGE. WITH THE BUILDING RIDGE...THE
DRIER AIR OVER UTAH AND SOUTHERN COLORADO WILL FILTER INTO THE
AREA DURING THE DAY THURSDAY.
.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 242 AM MDT TUE AUG 13 2013
ALL LONG RANGE MODELS IN AGREEMENT...SHOWING A BREAK IN THE
PERSISTENT MOIST WEATHER PATTERN ACROSS THE FORECAST AREA LATE
THIS WEEK. A DRYING TREND WILL CONTINUE THROUGH SATURDAY WITH
WARMER TEMPERATURES IN THE 80S AND LOW 90S EXPECTED. THE WARMEST
DAY WILL LIKELY BE SATURDAY AS THE RIDGE AXIS SHIFTS EASTWARD INTO
THE PLAINS...WITH HIGHS IN THE MID 80S TO MID 90S
EXPECTED...WARMEST ACROSS THE LOWER ELEVATIONS BELOW 5000 FEET.
KEPT POP BELOW 10 PERCENT WITH LIMITED CLOUD COVER. KEPT
TEMPERATURES A FEW DEGREES BELOW MOS FOR NOW...SINCE IT IS UNCLEAR
HOW THE CURRENT SOIL MOISTURE WILL IMPACT TEMPERATURES AND
HUMIDITY. WITH LIGHT WINDS EXPECTED...DO NOT BELIEVE THE NEAR
SURFACE MOISTURE WILL BE ADVECTED EASTWARD AS THAT QUICK.
PRECIPITATION CHANCES WILL RETURN TO THE AREA BY LATE SUNDAY AND
INTO MONDAY OF NEXT WEEK AS A FAST MOVING PACIFIC TROUGH PUSHES
ACROSS THE NORTHERN AND CENTRAL ROCKIES. SOME COOLER AIR WILL PUSH
INTO THE REGION AS WELL WITH HIGH TEMPERATURES 5 TO 10 DEGREES
COOLER COMPARED TO FRIDAY/SATURDAY. INCREASED POP BETWEEN 20 TO 40
PERCENT FOR SHOWERS AND TSTORMS SUNDAY AND MONDAY.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 944 PM MDT MON AUG 12 2013
THROUGH 07Z...ISOLATED SHOWERS EAST OF A DOUGLAS TO CHEYENNE LINE.
FROM 10Z TO 16Z...AREAS OF LOW CLOUDS AND FOG AT NEBRASKA
AERODROMES WITH LOCALIZED IFR AND MVFR...VFR ELSEWHERE. AFTER 20Z
TUESDAY...SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS
PRODUCING LOCALIZED MVFR.
&&
.FIRE WEATHER...
ISSUED AT 300 AM MDT TUE AUG 13 2013
CURRENT THINKING IS THAT FIRE WEATHER CONCERNS WILL BE MINOR TODAY
AND WEDNESDAY AS MONSOONAL MOISTURE OVER WYOMING WILL CREATE
WIDESPREAD WETTING RAINS FOR MOST LOCATIONS. DRIER AIR BEGINS TO
MOVE INTO THE AREA WEDNESDAY NIGHT INTO THURSDAY. AFTERNOON
HUMIDITIES FORECAST TO BE IN THE SINGLE DIGITS ACROSS CARBON
COUNTY THURSDAY AFTERNOON. WINDS ARE EXPECTED TO REMAIN FAIRLY
LIGHT THOUGH AND SHOULD PRECLUDE ANY FIRE WEATHER CONCERNS.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM...CLAYCOMB
LONG TERM...TJT
AVIATION...TJT
FIRE WEATHER...CLAYCOMB