Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 202035
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
235 PM MDT SUN JUL 20 2014

.SHORT TERM...(TONIGHT THROUGH TUESDAY NIGHT)
ISSUED AT 232 PM MDT SUN JUL 20 2014

VERY HOT AND DRY CONDITIONS PREVAIL ACROSS THE CWA THIS AFTN. FIRE
WEATHER IS THE MAIN CONCERN AS SFC OBSERVATIONS SHOW RH VALUES WELL
BELOW 15 PERCENT ACROSS MUCH OF SOUTHEAST WY. STRONG HEATING YIELDED
ANOTHER DAY OF GOOD MIXING SO GUSTS TO 35 MPH ARE COMMON. MORE CLOUD
COVER OVER SARATOGA HAS KEPT WINDS A LITTLE LOWER OUT THERE...BUT IT
IS VERY DRY AND RIPE FOR FIRE GROWTH SO THE RED FLAG IS GOOD. LARGE
SCALE RIDGING BUILDS NORTH ON MON WITH CONTINUED WESTERLY DOWNSLOPE
WINDS IN THE LLVLS. WOULD EXPECT DEWPOINTS TO DROP SEVERAL DEGREES
BELOW MOS ON MON AFTN AS WELL WITH GUSTY WINDS. WITH HIGH CONFIDENCE
THAT RED FLAG WILL BE ACHIEVED AGAIN...EXTENDED THE RED FLAG WARNING
THROUGH 02Z TUE FOR FWZ 301-302-306.

NOT MANY OTHER CONCERNS THROUGH MIDWEEK. WATER VAPOR SATELLITE SHOWS
A STRONG UPPER LOW LIFTING NORTH ACROSS THE GREAT BASIN...WITH GOOD
MOISTURE ADVECTION IN THE MIDLVLS ACROSS WESTERN CO. WITH WESTERLY
WINDS IN PLACE OVER THE PLAINS...AFTN AND EVE PCPN CHANCES WILL BE
RESTRICTED TO AREAS ALONG AND WEST OF THE LARAMIE RANGE...POSSIBLY
AS FAR EAST AS CHEYENNE. A COUPLE OF WEAK DISTURBANCES WILL LIFT
ACROSS CENTRAL AND EASTERN WY LATER TONIGHT. THETA-E ADVECTION AHEAD
OF THESE FEATURES SUGGESTS NOCTURNAL SHOWERS OUT WEST. NOTHING TOO
CONCERNING WITH VERY LITTLE ELEVATED INSTABILITY AFTER 03Z. THE BEST
MOISTURE IN THE 700-300 MILLIBAR LAYER PER THE GFS AND ECMWF SHIFTS
WELL TO THE NORTH OF THE CWA AND MON AND TUE...KEEPING THINGS ON THE
DRY SIDE. A BUILDING UPPER RIDGE KEEPS H7 TEMPS IN THE MID TO UPPER
TEENS C AND 1000-500 HPA THICKNESSES ABOVE 582 DM. STILL LOOKS VERY
HOT...ESPECIALLY EAST. SOME LOCATIONS IN THE PANHANDLE WILL LIKELY
REACH THE CENTURY MARK ON MON AS WAS THE CASE TODAY WITH 102 AT SNY
AS OF 2 PM. A FEW DEGREES COOLER ON TUE AS SFC WINDS SHIFT BACK TO
THE SOUTHEAST.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 232 PM MDT SUN JUL 20 2014

UPPER HIGH LOCATED OVR COLORADO WILL BE FLATTENED AS UPPER LOW PLOWS
INTO THE PACNW ON WED...THRU THE NRN ROCKIES THU...AND INTO THE NRN
PLAINS FRI-SUN. MONSOONAL MOISTURE ROTATING AROUND THE BACK SIDE OF
THE UPPER HIGH WILL COMBINE WITH COOLING MID-LEVEL TEMPS AND LLVL
MOISTURE ADVECTION TO PRODUCE AFTERNOON THUNDERSTORM CHANCES FOR
BOTH WED AND THU. LLVL CONVERGENCE ALONG A LEE-SIDE PRESSURE TROUGH
ALONG WITH THE TERRAIN WILL BE SUFFICIENT FOR CONVECTIVE INITIATION.
BEST CHANCES WILL BE FOR LOCATIONS ALONG AND EAST OF THE LARAMIE
RANGE WED AND THU. INSTABILITY PARAMETERS ALONG WITH DEEP LAYER
SHEAR VALUES SUGGESTS A FEW THUNDERSTORMS MAY BECOME STRONG TO
LOCALLY SEVERE WED AFTERNOON/EVENING...ESPECIALLY NR THE WY/NE
STATELINE AND THE WRN NEBRASKA PANHANDLE. INSTABILITY LOOKS WEAKER
ON THURSDAY...SO EXPECT ONLY GARDEN VARIETY THUNDERSTORM CHANCES. A
COOL FROPA ALONG WITH NW FLOW WILL ENSUE FRI-SUN. ALTHOUGH DID KEEP
SOME SMALL CONVECTIVE CHANCES GOING FRIDAY MAINLY OVR LARAMIE COUNTY
AS POST-FRONTAL UPSLOPE MAY BE JUST ENOUGH TO KICK OFF A FEW SHOWERS
OR WK THUNDERSTORMS. THE AIR MASS WILL TURN COOLER AND LESS UNSTABLE
SAT-SUN. THIS WILL YIELD DRIER CONDITIONS AND HIGH TEMPERATURES THAT
WILL COOL BACK INTO THE 80S AT ALL LOCALES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY MORNING)
ISSUED AT 232 PM MDT SUN JUL 20 2014

ANOTHER QUIET AVIATION PERIOD SHAPING UP AS VFR CONDITIONS WILL
CONTINUE AT TAF SITES. THERE IS A SOME MONSOONAL MOISTURE THAT
WILL ROTATE NORTHEAST INTO SOUTHEAST WYOMING THIS AFTERNOON AND
MAY PRODUCE A FEW WEAK SHOWERS. FOR NOW...IT LOOKS LIKE KRWL WOULD
HAVE THE BEST OPPORTUNITY TO SEE THIS ACTIVITY...SO HAVE KEPT THE
VCSH GOING THERE. OTHERWISE...JUST SEE SOME INCREASING MID-LEVEL
CLOUDINESS THRU THE AFTERNOON. WINDS AND ANY CONVECTION THAT IS
ABLE TO DEVELOP WILL DECREASE BY AROUND SUNSET.

&&

.FIRE WEATHER...
ISSUED AT 232 PM MDT SUN JUL 20 2014

CRITICAL FIRE WEATHER CONDITIONS FOR FWZ 301-302-306 THROUGH 8 PM
THIS EVENING. RELATIVE HUMIDITIES OF 10 TO 15 PERCENT COMBINED WITH
WIND GUSTS TO 35 MPH WILL CREATE RAPID FIRE GROWTH POTENTIAL. THESE
CONDITIONS WILL IMPROVE OVERNIGHT...BUT WILL RETURN AGAIN ON MONDAY
AFTER 11 AM. A RED FLAG WARNING IS IN EFFECT THROUGH MONDAY EVENING
FOR THIS PROLONGED EVENT. AFTN AND EVE SHOWERS AND STORMS WILL BE
VERY ISOLATED...MAINLY ALONG AND WEST OF THE LARAMIE RANGE OVER THE
NEXT FEW DAYS. THUNDERSTORM ACTIVITY IS EXPECTED TO INCREASE TOWARD
THE MIDDLE OF THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING UNTIL 8 PM MDT MONDAY FOR WYZ301-302-306.

NE...NONE.
&&

$$

SHORT TERM...HAMMER
LONG TERM...HAHN
AVIATION...HAHN
FIRE WEATHER...HAMMER






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