Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 282116
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
316 PM MDT SAT MAR 28 2015

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 245 PM MDT SAT MAR 28 2015

VERY WARM...DRY...AND WINDY. THAT IS THE WEATHER THIS AFTERNOON IN A
NUTSHELL. RED FLAG WARNINGS ARE ON TRACK EAST OF THE MOUNTAINS WITH
TEMPERATURES IN THE 70S YIELDING HUMIDITY VALUES IN THE LOWER TEENS
AND WIDESPREAD WIND GUSTS BETWEEN 30 AND 40 MPH...SLIGHTLY STRONGER
IN THE TYPICALLY WIND PRONE AREAS. WILL KEEP THAT HIGHLIGHT GOING AS
SCHEDULED. TEMPERATURES ARE SOME 25 DEGREES ABOVE NORMAL ACROSS THE
BOARD AS OF 20Z WITH MANY AREAS CLOSING IN ON RECORDS. KCYS REACHED
73 F A SHORT TIME AGO...ONE DEGREE SHY OF THE CURRENT RECORD. THINK
WE WILL SEE AT LEAST A COUPLE DEGREES OF WARMING INTO THE LATE AFTN
HOURS. NOT MUCH ELSE GOING ON IN THE NEAR TERM. WILL NEED TO WATCH
CONVERSE AND NIOBRARA COUNTIES FOR HIGH WINDS OVER THE NEXT COUPLE
OF HOURS AS WE ARE AT PEAK MIXING. HAVE SEEN SEVERAL GUSTS NEAR 50
MPH RECENTLY.

A FEW CONCERNS AS WE HEAD INTO THE EVENING AND OVERNIGHT. A STRONG
COLD FRONT WAS ANALYZED OVER FAR NORTHWEST WY LATE THIS AFTN WITH
EXCELLENT PRESSURE FALLS OBSERVED ACROSS THE STATE. GFS AND NAM BOTH
SHOW A CONSIDERABLE INCREASE IN LLVL PRESSURE GRADIENTS POST-FROPA
OVERNIGHT. THE LATEST RAP SHOWS A BROAD SWATH OF 45 TO 50 KT WINDS
BETWEEN H8-H7 AFTER 00Z OVER THE NORTHERN TIER OF ZONES. WHILE THIS
WILL GO BEYOND PEAK MIXING...WE DO EXPECT A FEW CONVECTIVE SHOWERS
WITH SLIGHTLY NEGATIVE LIFTED INDICES AND WEAK PVA IN ADVANCE OF AN
APPROACHING MID LEVEL SHORTWAVE. IN FACT...A FEW CUMULUS ARE ALREADY
STARTING TO POP UP ON VISIBLE SATELLITE. INVERTED-V THERMAL PROFILES
SUGGEST STRONG WIND GUSTS BENEATH SHOWERS...SO A STRAY 50 KT GUST IS
NOT ENTIRELY OUT OF THE QUESTION THIS EVENING. COVERAGE IS EXPECTED
TO BE MINIMAL GIVEN VERY MEAGER MOISTURE ALOFT. LLVL COLD ADVECTION
WILL KEEP LAPSE RATES STEEP OVERNIGHT...SO EXPECT WINDS TO ACTUALLY
STRENGTHEN OVER THE NORTHERN PANHANDLE AFTER MIDNIGHT. AM CONFIDENT
IN A FEW 40 TO 50 MPH WIND GUSTS...ESPECIALLY OVER HIGHER ELEVATIONS
ALONG THE PINE RIDGE. WENT AHEAD AND ISSUED A WIND ADVISORY FOR THE
NORTHERN HALF OF THE PANHANDLE.

MAIN SHORTWAVE OF INTEREST IS CURRENTLY OVER EASTERN ID INTO WESTERN
MT. THIS WILL SWEEP ACROSS THE CWA OVERNIGHT WITH PLENTY OF LOW AND
MID LEVEL COLD ADVECTION IN ITS WAKE. A FEW LIGHT SHOWERS WILL MOST
LIKELY LINGER WELL INTO THE NIGHT...BUT DO NOT EXPECT ANYTHING OF
SIGNIFICANCE. THE GFS SHOWS H7 TEMPS FALLING FROM AROUND +7 DEG C
THIS AFTERNOON TO -5 DEG C BY NOON SUNDAY ALONG THE I-80 CORRIDOR.
IT WILL BE CONSIDERABLY COOLER TOMORROW...BUT STILL A PLEASANT AFTN
WITH WIDESPREAD HIGHS IN THE 60S. LESS WIND TOO WITH THE H85 CAG-CPR
GRADIENT LESS THAN 10 METERS. TRANQUIL THROUGH THE REMAINDER OF THE
SHORT TERM WITH BROAD UPPER-LEVEL RIDGING AND DRY AIR ALOFT KEEPING
THINGS ON THE DRY SIDE. THIS SETS THE STAGE FOR A RETURN TO WARMTH
AS WE HEAD INTO THE EXTENDED.

.LONG TERM...(TUESDAY THROUGH FRIDAY)
ISSUED AT 245 PM MDT SAT MAR 28 2015

CRITICAL FIRE WEATHER CONDITIONS WILL DOMINATE THE WEATHER
HEADLINES ON TUES AND WED. THE MODELS SHOW A SHORTWAVE RIDGE
OVERHEAD ON TUES WITH 700MB TEMPS AROUND 5C. TEMPS WILL BE WELL
ABOVE NORMAL WITH WIDESPREAD 70S TO THE EAST OF THE LARAMIE
RANGE...WHICH WILL CAUSE MIN RH VALUES TO DROP TO 10-15 PERCENT.
COULD SEE A FEW GUSTS TO 20-25 KTS...HOWEVER THE LACK OF
WIDESPREAD HIGHER WINDSPEEDS WILL BE THE MAIN LIMITING FACTOR FOR
RED FLAG WARNINGS ON TUES. A POTENT SHORTWAVE WILL MOVE ACROSS
MONTANA ON WED...AND THIS WILL RESULT SOME COOLING BEHIND A WEAK
COLD FRONT. DESPITE THE COOLING...RH VALUES WILL FALL TO AROUND 15
PERCENT WITH A VERY DRY AIRMASS...AND WINDS WILL BE QUITE A BIT
STRONGER (GUSTS TO 30-35 KTS). THUS...WED IS SHAPING UP TO BE A
MORE CRITICAL FIRE WEATHER DAY.

ATTENTION ON THURS AND FRI THEN SHIFTS TO A STORM SYSTEM THAT
COULD BRING WIDESPREAD MODERATE PRECIP AMOUNTS TO THE CWA. BOTH
THE GFS AND ECMWF INDICATE AN UPPER TROUGH AMPLIFYING INTO
NEVADA/UTAH ON THURS THEN MOVING ACROSS COLORADO ON FRI. THERE IS
SOME PRETTY GOOD DEEP LAYER UPWARD MOTION FROM THURS AFTN INTO FRI
MORNING...WITH QPF AMOUNTS OF 0.25-0.75 INCHES OFF THE GFS AND
ECMWF. OF COURSE THERE ARE LOCATION DIFFERENCES...WITH THE ECMWF
TARGETING AREAS NEAR THE COLORADO BORDER WHEREAS THE GFS IS
FURTHER NORTH.  TEMPS BEHIND THE FRONT WOULD BE COLD ENOUGH TO
SUPPORT SNOW EVEN ACROSS THE NEBRASKA PANHANDLE. DID INCREASE POPS
INTO THE 20-40 PERCENT RANGE. MUCH COOLER TEMPS WOULD BE IN STORE
FOR FRI. APRIL HAS THE POTENTIAL TO START OUT WET AFTER A VERY
DRY MARCH.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1140 AM MDT SAT MAR 28 2015

VFR CONDITIONS THROUGH THE TAF PERIOD. IT WILL BE BREEZY TO WINDY
ACROSS THE REGION THROUGH THE AFTERNOON. WEST WIND GUSTS TO 30-35
KTS ARE EXPECTED ACROSS SOUTHEAST WY WITH 20-25 KTS OVER THE
NEBRASKA PANHANDLE. A COLD FRONT WILL PASS OVER THE SITES THIS
EVENING AND EARLY TONIGHT WITH WINDS BECOMING NORTHWEST TO THE
EAST OF THE LARAMIE RANGE. GUSTS TO 25-30 KTS WILL BE POSSIBLE
THROUGH SUN MORNING BEHIND THE FRONT.

&&

.FIRE WEATHER...
ISSUED AT 245 PM MDT SAT MAR 28 2015

A RED FLAG WARNING REMAINS IN EFFECT EAST OF THE MOUNTAINS UNTIL 8PM
THIS EVENING. CRITICAL FIRE WEATHER CONDITIONS ARE OCCURRING WITH
WIDESPREAD HUMIDITY VALUES BELOW 15 PERCENT AND WIND GUSTS BETWEEN
30 AND 50 MPH. A COLD FRONT WILL MOVE ACROSS THE AREA TONIGHT...WITH
A FEW SHOWERS DEVELOPING IN THE EVENING AND OVERNIGHT. GUSTY/ERRATIC
WINDS ARE LIKELY UNDER THIS ACTIVITY...ALONG WITH THE POSSIBILITY OF
A FEW LIGHTNING STRIKES THROUGH EARLY EVENING. LOW HUMIDITIES LIKELY
ONCE AGAIN FOR SUNDAY AFTERNOON...BUT WINDS WILL NOT BE AS STRONG AS
TODAY. AS SUCH...CRITICAL FIRE WEATHER CONDITIONS ARE NOT
EXPECTED.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING FOR WYZ301-310.

NE...RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING FOR NEZ311>313.

     WIND ADVISORY FROM 9 PM THIS EVENING TO 6 AM MDT SUNDAY FOR
     NEZ002-003-095-096.

&&

$$

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


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