Severe Thunderstorm Warning 222, NWS Cheyenne, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
630 PM MDT TUE AUG 6 2013

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)

ISSUED AT 252 PM MDT TUE AUG 6 2013

CURRENT REGIONAL RADAR MOSAIC OVER WYOMING SHOWS ISOLATED RAIN
SHOWERS AND A FEW LIGHTNING STRIKES OVER THE MOUNTAINS AND
ADJACENT VALLEYS AND HIGH PLAINS TO AROUND CHEYENNE AND WHEATLAND.
ACTIVITY IS MUCH WEAKER COMPARED TO YESTERDAY...AT LEAST SO FAR
THIS AFTERNOON. BELIEVE DRIER AIR NEAR THE TOP OF THE BOUNDARY
LAYER IS PREVENTING DEEP CONVECTION FROM INITIATING THIS
AFTERNOON. FOR TONIGHT...CURRENT WATER VAPOR SATELLITE LOOP
SHOWS A POTENT UPPER LEVEL DISTURBANCE MOVING NORTHWARD ACROSS
ARIZONA AND INTO UTAH. THIS TRACK OF THIS DISTURBANCE WILL PLAY A
SIGNIFICANT ROLE IN AMOUNT AND COVERAGE OF PRECIPITATION OVER THE
NEXT FEW DAYS. JET ENERGY ALOFT AND A WEAK LLVL JET ACROSS THE
HIGH PLAINS WILL PUSH OVER THE AREA TONIGHT AND WEDNESDAY. WENT
WITH HIGHER POP TONIGHT COMPARED TO THIS AFTERNOON DUE TO MODELS
INDICATE DECENT 250 TO 300 MB DIVERGENCE AND THE POTENTIAL FOR
ELEVATED CONVECTION NEARLY ALL NIGHT AND INTO WEDNESDAY MORNING.
THIS WILL SET UP A TRICKY FORECAST FOR WEDNESDAY.

ALL MODELS SHOW THE POTENT UPPER LEVEL DISTURBANCE...MOVING
SLOWLY NORTHEAST AROUND THE PERIPHERY OF THE UPPER LEVEL HIGH NEAR
THE GULF COAST. AS ALREADY STATED...HAVE TO TRACK THIS FEATURE
CAREFULLY OVER THE NEXT 24 HOURS WITH SUBTROPICAL MOISTURE IN
PLACE AND A FRONTAL BOUNDARY STALLED OVER THE LARAMIE RANGE.
PREVIOUS MODEL RUNS WERE TRACKING THIS DISTURBANCE FAR ENOUGH
SOUTH SO THAT MOST LOCATIONS ONLY RECEIVED LIGHT TO MODERATE
RAINFALL AMOUNTS. THE NEW 12Z MODEL RUNS NOW SHOW THIS DISTURBANCE
TRENDING FURTHER NORTH WITH LOCATIONS ALONG I80 EAST OF THE
LARAMIE RANGE RECEIVING RESPECTABLE RAINFALL AMOUNTS IN SHOWERS
AND TSTORMS THROUGH WEDNESDAY NIGHT. CONTINUED TO INCREASE POP
BETWEEN 40 TO 60 PERCENT NEAR THE COLORADO BORDER AND INCREASE QPF
AMOUNTS AS WELL. THE UPPER LEVEL DISTURBANCE WILL LINGER AROUND
THE HIGH PLAINS OF COLORADO FOR THURSDAY...AND WITH AMPLE
INSTABILITY AND MOISTURE...CAN NOT RULE OUT WIDELY SCATTERED OR
SCATTERED SHOWERS/TSTORMS THROUGH THURSDAY EVENING AS WELL.

.LONG TERM...(FRIDAY THROUGH TUESDAY)

ISSUED AT 300 PM MDT TUE AUG 6 2013

NEW 12Z ECMWF RUN...WHICH THE LONG TERM IS MAINLY BASED ON...LIFTS
SOME ENERGY NORTH OUT OF COLORADO DURING THE DAY FRIDAY. NAM
SHOWING SOMETHING SIMILAR...BUT NOT QUITE AS HEALTHY ON
QPF AS THE ECMWF IS SHOWING. WENT AHEAD AND RAISED POPS FOR FRIDAY
WITH HIGH CHANCE POPS EAST OF THE LARAMIE RANGE AND LIKELY POPS IN
THE MOUNTAINS OUT WEST. STORM MOTIONS FOR FRIDAY FROM NAM
SOUNDINGS PRETTY SLOW...GENERALLY UNDER 10KTS...SO DO THINK SOME
HEAVY RAINFALL IS POSSIBLE.

SHORTWAVE LIFTS NORTH OF THE CWFA BY SATURDAY 18Z WITH SOME DRIER
AIR TO THE SOUTHWEST. STILL SHOULD SEE 20 TO 30 PERCENT CHANCES
FOR AFTERNOON SHOWERS AND THUNDERSTORMS WITH HIGHEST CHANCES IN
THE MOUNTAINS.

DRIEST DAY LOOKS TO BE SUNDAY AS THE FRONT THAT ALMOST CONTINUALLY
LAYS ALONG THE LARAMIE RANGE PUSHES EAST INTO THE
PANHANDLE...ALLOWING DRIER AIR TO FILTER IN ACROSS MUCH OF
SOUTHEAST WYOMING. WITH RESIDUAL MOISTURE...DO THINK IT WILL
RECYCLE DURING THE AFTERNOON TO GIVE US A LOW CHANCE FOR AFTERNOON
SHOWERS. THESE SHOULD END FAIRLY QUICKLY THOUGH AFTER SUNSET.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY AFTERNOON)
ISSUED AT 630 PM MDT TUE AUG 6 2013

ISOLATED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO BE THE
PRIMARY IMPACT AT TERMINALS THRU AT LEAST 03Z. MAY EVEN SEE SOME
SHOWER ACTIVITY LINGER INTO THE REMAINDER OF THE OVERNIGHT HOURS
AS WELL. MAY SEE SOME BRIEF MVFR/IFR CIGS AND VISIBILITIES WITHIN
THIS ACTIVITY. AFTER CONDITIONS RETURN TO VFR LATER TONIGHT...CAN
EXPECT ANOTHER ROUND OF SHOWER AND THUNDERSTORM ACTIVITY AFTER 18Z
ON THURSDAY.

&&

.FIRE WEATHER...
ISSUED AT 152 PM MDT TUE AUG 6 2013

FIRE WEATHER CONCERNS WILL BE MINIMAL THIS WEEK AND MAINLY
CONFINED TO PORTIONS OF CARBON COUNTY. DAYTIME RELATIVE HUMIDITY
VALUES WILL LOWER INTO THE TEENS OVER LOWER ELEVATIONS OF CARBON
COUNTY WITH WESTERLY WINDS AROUND 15 TO 20 KNOTS. WINDS MAY GUST
AS HIGH AS 25 KNOTS IN A FEW LOCATIONS ACROSS CARBON COUNTY THIS
AFTERNOON...BUT DO NOT EXPECTED WIDESPREAD CRITICAL CONDITIONS TO
DEVELOP. OTHERWISE...SUBTROPICAL MOISTURE WILL REMAIN IN PLACE
RESULTING IN HIGH HUMIDITIES ALONG AND EAST OF THE LARAMIE RANGE
INCLUDING WESTERN NEBRASKA...IN ADDITION TO ISOLATED TO SCATTERED
SHOWERS EXPECTED THROUGH MUCH OF THE WEEK.

&&

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

SHORT TERM...TJT
LONG TERM...CLAYCOMB
AVIATION...HAHN
FIRE WEATHER...TJT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHEYENNE WY
432 AM MDT TUE AUG 6 2013

NEZ002-003-019>021-054-055-095-096-WYZ101>119-071045-
DAWES-BOX BUTTE-SCOTTS BLUFF-BANNER-MORRILL-KIMBALL-CHEYENNE-
NORTH SIOUX-SOUTH SIOUX-CONVERSE COUNTY LOWER ELEVATIONS-
NIOBRARA COUNTY-NORTH LARAMIE RANGE-
FERRIS/SEMINOE/SHIRLEY MOUNTAINS-SHIRLEY BASIN-
CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE COUNTY-
EAST PLATTE COUNTY-GOSHEN COUNTY-CENTRAL CARBON COUNTY-
NORTH SNOWY RANGE FOOTHILLS-SOUTHWEST CARBON COUNTY-
SIERRA MADRE RANGE-UPPER NORTH PLATTE RIVER BASIN-SNOWY RANGE-
LARAMIE VALLEY-SOUTH LARAMIE RANGE-SOUTH LARAMIE RANGE FOOTHILLS-
CENTRAL LARAMIE COUNTY-EAST LARAMIE COUNTY-
432 AM MDT TUE AUG 6 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA
PANHANDLE...EAST CENTRAL WYOMING...SOUTH CENTRAL WYOMING AND
SOUTHEAST WYOMING.

.DAY ONE...TODAY AND TONIGHT

THERE IS A CHANCE FOR SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND
INTO TONIGHT OVER SOUTHEAST WYOMING AND THE NEBRASKA PANHANDLE.
THUNDERSTORMS ARE NOT EXPECTED TO BE SEVERE.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

CHANCES FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH THE
WEEK AND INTO THE WEEKEND.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT.

&&

THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND
CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT...
HTTP://WEATHER.GOV/CHEYENNE

LIEBL

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHEYENNE WY
602 PM MDT TUE AUG 6 2013

NEZ096-WYZ108-070030-
GOSHEN COUNTY WY-SOUTH SIOUX NE-
602 PM MDT TUE AUG 6 2013

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN SIOUX AND EASTERN GOSHEN
COUNTIES UNTIL 630 PM MDT...

AT 558 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 11 MILES NORTHEAST OF LINGLE...OR 12 MILES NORTH
OF TORRINGTON...MOVING EAST AT 20 MPH.

HAIL UP TO THE SIZE OF NICKELS AND WIND GUSTS UP TO 50 MPH ARE
EXPECTED WITH THIS STORM.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...
MAINLY RURAL AREAS OF EASTERN GOSHEN AND WESTERN SIOUX COUNTIES.

&&

LAT...LON 4242 10395 4219 10385 4213 10426 4228 10432
TIME...MOT...LOC 0003Z 249DEG 17KT 4225 10415

MAZUR

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHEYENNE WY
620 PM MDT TUE AUG 6 2013

NEZ096-070045-
SOUTH SIOUX NE-
620 PM MDT TUE AUG 6 2013

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN SIOUX COUNTY UNTIL
645 PM MDT...

AT 615 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 6 MILES SOUTH OF WATSON RANCH...OR 19 MILES NORTH
OF SCOTTSBLUFF...MOVING EAST AT 15 MPH.

HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 50 MPH ARE
EXPECTED WITH THIS STORM.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...
MAINLY RURAL AREAS OF SOUTHEASTERN SIOUX COUNTY.

&&

LAT...LON 4222 10346 4203 10350 4209 10377 4222 10375
TIME...MOT...LOC 0021Z 277DEG 13KT 4214 10366

MAZUR

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