Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 240929
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
329 AM MDT FRI JUL 24 2015

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 330 AM MDT FRI JUL 24 2015

VIRTUALLY NO CHANGE IN THE LARGE SCALE FLOW WITH A STATIONARY
UPPER RIDGE OVER THE SOUTH CENTRAL CONUS FLANKED BY TROUGHS
NEAR THE WEST AND EAST COASTS. SHORTWAVES EMBEDDED IN THE
FLOW ROUNDING THE RIDGE TRIGGERED ACTIVE CONVECTIVE CLUSTERS
FROM THE EAST CENTRAL PLAINS TO THE UPPER MIDWEST AS WELL AS
THE SOUTHEAST CONUS. A DRY SLOT WAS EVIDENT ON WATER VAPOR LOOP
FROM SOUTHERN CA NORTHEAST ACROSS SOUTHERN WY AND NORTHERN WY
INTO WESTERN NE...WITH THE MONSOON MOISTURE PLUME DIVERTED
SOUTH OVER THE FOUR CORNERS. THE SURFACE ANALYSIS SHOWED A WEAK
FRONT OR WIND SHIFT BOUNDARY FROM NORTHEAST WY INTO NORTHWEST
NE SLOWLY DRIFTING SOUTH. REGIONAL SKIES WERE FAIR WITH LIGHT
WINDS. TEMPERATURES RANGED FROM 49 AT LARAMIE TO 72 AT BORDEAUX.

THE LATEST SHORT RANGE MODELS REFLECT LITTLE OVERALL CHANGE WITH
THE UPPER RIDGE PARKED OVER SOUTH CENTRAL CONUS...KEEPING THE
SUBTROPICAL MOISTURE CONFINED WELL TO THE SOUTH AND DRY AIR ALOFT
IN PLACE THROUGH THE WEEKEND. SEVERAL SHORTWAVES EMANATING
FROM THE NORTHWEST CONUS TROUGH WILL RIDE OVER THE RIDGE THROUGH
THE NORTHERN PLAINS. THE WEAK SURFACE BOUNDARY WILL EVENTUALLY
STALL NEAR THE LARAMIE RANGE TODAY THEN SHIFT EAST OF THE CWA
SATURDAY. EAST TO SOUTHEAST WINDS OVER THE PLAINS TODAY WILL VEER
AROUND TO THE SOUTHWEST TOMORROW. THE MODELS ARE SHOWING A
SHORTWAVE MOVING THROUGH THE HIGH PLAINS SUNDAY. THIS WAVE MAY
AID IN ISOLATED AFTERNOON TSTORM DEVELOPMENT OVER THE FAR EASTERN
COUNTIES...MAINLY EAST OF A HARRISON TO KIMBALL NE LINE. THE
UNSEASONABLE WARMTH WILL CONTINUE THROUGH THE SHORT TERM AS 700 MB
TEMPERATURES PEAK NEAR 15C EACH AFTERNOON. EXPECT DAILY HIGH
TEMPERATURES IN THE 80S AND 90S LOWER ELEVATIONS WITH 60S AND 70S
MOUNTAINS AND HIGH VALLEYS. LOW TEMPERATURES WILL RANGE FROM THE
50S TO LOW 60S LOWER ELEVATIONS TO THE 40S MOUNTAINS AND HIGH
VALLEYS. THERE WILL BE A SUFFICIENT LOW LEVEL PRESSURE GRADIENT
IN PLACE OVER SOUTHEAST WY WITH BREEZY SOUTHWEST WINDS DEVELOPING
EACH AFTERNOON WEST OF THE LARAMIE RANGE.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 250 AM MDT FRI JUL 24 2015

THE MODELS ARE IN GOOD AGREEMENT AT SHOWING AN UNSEASONABLY STRONG
UPPER TROUGH MOVING ACROSS THE NORTHERN ROCKIES ON MONDAY WITH
STRONG SOUTHWESTERLY FLOW ALOFT OVER WYOMING. SOUTHWEST WINDS WILL
INCREASE DURING THE DAY WITH GUSTS TO 30 TO 35 KT POSSIBLE ALONG
AND WEST OF THE LARAMIE RANGE. MAIN CONCERN WILL BE WIDESPREAD
CRITICAL FIRE WEATHER CONDITIONS ACROSS SOUTHEAST WY AS RH VALUES
FALL TO 10 TO 15 PERCENT AND COMBINE WITH THE BREEZY WINDS. HAVE
SLIGHT CHANCE POPS ON MONDAY EVENING OVER THE NEBRASKA PANHANDLE
WITH CONVERGENCE ALONG THE SFC TROUGH. A COLD FRONTAL PASSAGE
TUESDAY MORNING WILL BRING AN END TO THE VERY WARM CONDITIONS WITH
TEMPS DROPPING 10 TO 15 DEGREES. DRY WESTERLY MID LEVEL FLOW WILL
BE IN PLACE FROM TUESDAY THROUGH THURSDAY WITH PW VALUES MOSTLY
BELOW 0.5 INCH. COULD SEE AN ISOLATED AFTN/EVENING TSTM ALONG THE
COLORADO BORDER TUESDAY AND WEDNESDAY AS BETTER MOISTURE RESIDES
OVER NORTHEAST COLORADO...HOWEVER MUCH IF NOT ALL OF THE CWA WILL
REMAIN STORM FREE. MIN RH VALUES WILL DROP TO 15 TO 20 PERCENT
EACH AFTN (TUESDAY TO THURSDAY) WEST OF THE LARAMIE RANGE...BUT
WITH WEAKER WIND SPEEDS DO NOT EXPECT CRITICAL FIRE WEATHER
CONDITIONS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY NIGHT)
ISSUED AT 250 AM MDT FRI JUL 24 2015

VFR CONDITIONS FORECAST THROUGH THE TAF PERIOD. SOUTHWEST WINDS
WILL INCREASE BY LATE MORNING WEST OF THE LARAMIE RANGE. GUSTS TO
20 TO 25 KT WILL BE COMMON AT LAR AND RWL THROUGH THE AFTERNOON.
THE WINDS WILL DIMINISH AFTER AROUND 01Z. NO AFTERNOON THUNDERSTORMS
ARE EXPECTED.

&&

.FIRE WEATHER...
ISSUED AT 235 AM MDT FRI JUL 24 2015

THE WARM...DRY AND BREEZY WEATHER PATTERN WILL CONTINUE THROUGH
THE WEEKEND. AFTERNOON HIGH TEMPERATURES WILL RISE INTO THE 80S
AND 90S WITH AFTERNOON HUMIDITIES FALLING INTO THE TEENS PERCENT.
SOUTHWEST WINDS WILL GUST TO AROUND 25 MPH WEST OF THE LARAMIE
RANGE...CREATING NEAR CRITICAL FIRE WEATHER CONDIITONS. CRITICAL
FIRE WEATHER CONDITIONS WILL BE POSSIBLE FOR MUCH OF SOUTHEAST
WYOMING MONDAY AS WINDS INCREASE.

&&

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

$$

SHORT TERM...MAJ
LONG TERM...ZF
AVIATION...ZF
FIRE WEATHER...MAJ



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