941
FXUS65 KCYS 191735
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1135 AM MDT WED JUN 19 2019
UPDATE
ISSUED AT 1011 AM MDT WED JUN 19 2019
WILL CONTINUE TO MONITOR THE POTENTIAL FOR STRONG WIND GUSTS ALONG
I-80 BETWEEN RAWLINS AND LARAMIE THIS AFTERNOON. AS OF 10 AM,
WINDS HAVE INCREASED BETWEEN 20 TO 30 MPH IN A FEW AREAS NEAR ELK
MOUNTAIN AND ARLINGTON. NOT CONFIDENT ENOUGH FOR A WARNING QUITE
YET, MAINLY BECAUSE OF TO THE UNUSUAL PATTERN AND TYPICAL
FREQUENCY OF THESE TYPE OF EVENTS FOR THIS TIME OF THE YEAR.
OTHERWISE, A MARGINAL RISK OF STRONG TO SEVERE THUNDERSTORMS
STILL EXISTS TODAY ACROSS EAST CENTRAL WYOMING AND THE FAR
NORTHERN NEBRASKA PANHANDLE, MAINLY FOR NORTH OF A LINE FROM
JUST NORTH OF DOUGLAS WYOMING SOUTHEAST TOWARDS ALLIANCE NEBRASKA.
MAIN CONCERN IS STRONG GUSTY WINDS, BUT THUNDERSTORM COVERAGE
SHOULD BE PRETTY ISOLATED.
SHORT TERM
(TODAY THROUGH FRIDAY EVENING)
ISSUED AT 320 AM MDT WED JUN 19 2019
...HIGH WIND WATCH FOR ARLINGTON THIS AFTERNOON THROUGH THURSDAY
EVENING...
AN ACTIVE AND UNUSUAL PATTERN FOR THIS TIME OF YEAR IS SET TO
TAKE SHAPE ACROSS SOUTHEASTERN WYOMING AND THE ROCKY MOUNTAINS
LATER THIS AFTERNOON AND CONTINUE TO THE WEEKEND. ANOMALOUSLY
DEEP TROUGHING AND STRONG JET ENERGY WILL DEVELOP THIS MORNING
AND AFTERNOON ACROSS WESTERN WYOMING. STRONG WEST WINDS WILL
DEVELOP AS 700 AND 500 MB FLOW INCREASE AHEAD OF THE MAIN TROUGH.
DEEP SURFACE MIXING FROM THE DRYING WEST WIND AND RESIDUAL
ELEVATED UNSTABLE LAYERS WILL HELP TO TRANSPORT 35 TO 45 KTS OF
MOMENTUM TO THE SURFACE. LOW LEVEL PRESSURE GRADIENTS WILL ALSO
INCREASE THROUGH THE EVENING AND OVERNIGHT AS A DEEP LEE LOW
DEVELOPS OVER EASTERN WYOMING. LOW LEVEL WINDS IN GAP AREAS WILL
LIKELY ACCELERATE IN RESPONSE TO THE MIXING AND SUPPORTIVE LOW
LEVEL PRESSURE GRADIENTS. A HIGH WIND WATCH WAS ISSUED FOR
ARLINGTON TO ACCOUNT FOR THE THREAT OF STRONG WIND IMPACTS TO
TRAILERS AND RECREATION VEHICLES OUTSIDE THE NORMAL CLIMATOLOGICAL
TIMING.
A FEW SHOWERS AND POSSIBLY HIGH BASED THUNDERSTORMS MAY ALSO
DEVELOP IN THE AFTERNOON AND EVENING HOURS MAINLY OVER THE EASTERN
PLAINS WHERE RESIDUAL MOISTURE REMAINS THE HIGHEST. PSEUDO
DRYLINE/ SURFACE TROUGH WILL LIKELY INITIATE SCATTERED STORMS OVER
THE EASTERN PLAINS WITH THE POTENTIAL FOR DAMAGING WINDS THANKS
TO LARGE LOW LEVEL INVERTED V SIGNATURES. AGREE WITH SPC ON
MAINTAINING THE MARGINAL SEVERE PROBS THROUGH THE AFTERNOON.
STORMS WILL QUICKLY FADE WITH THE LOSS OF DAYTIME HEATING AND
LITTLE PRECIPITATION IS EXPECTED OVERNIGHT.
THURSDAY WILL AGAIN BE WINDY FOR THE INTERIOR VALLEYS AND FOOT
HILLS AS THE MAIN BRUNT OF THE JET AND LEE LOW CONSOLIDATE OVER
THE REGION. THE REST OF THE AREA SHOULD REMAIN WARMER AND MOSTLY
DRY THROUGH THE DAY. THURSDAY AFTERNOON WILL LIKELY BE THE BEST
TIME FOR STRONG GUSTS TO REACH THE SURFACE WITH WELL ESTABLISHED
UPPER AIR SUPPORT AND DEEP MIXING FROM WARM TEMPERATURES.
THIS HIGH WIND SUPPORTIVE PATTERN WILL QUICKLY FADE THURSDAY
EVENING AS LIFT AND STEEP MID LEVEL LAPSE RATES FROM THE
APPROACHING TROUGH OVERSPREAD THE REGION. SHOWERS AND
THUNDERSTORMS WILL LIKELY DEVELOP THURSDAY EVENING AND CONTINUE
THROUGH FRIDAY MORNING AS THE LEE LOW MOVES TO THE EAST DRAGGING A
COLD FRONT SOUTH AND EAST ACROSS THE AREA. LOW LEVEL FLOW WILL
ADVECT DEEP MOISTURE BACK INTO THE REGION TRANSITIONING BACK TO A
WET AND STORMY PATTERN THROUGH THE WEEKEND. EXPECT COOLER
TEMPERATURES AND PRECIPITATION ON FRIDAY AS CONTINUED TROUGHING
AND MOISTURE RETURN SUPPORTS SHOWER AND THUNDERSTORM ACTIVITY.
LONG TERM
(SATURDAY THROUGH NEXT WEDNESDAY)
SUMMARY: MAIN FOCUS WILL BE ON SATURDAY AND SUNDAY TIME FRAME WITH
GREATER SHOWER AND THUNDERSTORM LIKELIHOOD WHILE EARLY TO MID NEXT
WEEK LOOKS DRIER AND WARMER. HAZARDS ON SATURDAY AND PERHAPS SUNDAY
COULD BE POCKETS OF HEAVY RAINFALL AND A FEW STRONG THUNDERSTORMS.
SUNDAY IS MORE CONDITIONAL AT THIS TIME DEPENDING ON PATTERN
EVOLUTION AND TIMING.
WEATHER DETAILS: QUITE ACTIVE PATTERN TO END THE WORK WEEK GOING
INTO THE WEEKEND WITH A LARGE-SCALE TROUGH OVER THE NORTHERN PLAINS
BACK ACROSS THE PACIFIC NORTHWEST PER MULTI-MODEL CONSENSUS. SEVERAL
VORTICITY MAXIMUMS AND EMBEDDED SHORTER WAVELENGTH TROUGHS WILL
ROTATE ABOUT THE PARENT TROUGH ACROSS WYOMING. AS A RESULT, A
FRONTAL BOUNDARY WILL SHIFT NEAR AND/OR BISECT SOUTHEAST WYOMING
LATE FRIDAY INTO SATURDAY AS THE FIRST SHORTWAVE TROUGHS PIVOTS
ACROSS NORTH-CENTRAL WYOMING. WITH BROAD SYNOPTIC LIFT AND
ISENTROPIC UPGLIDE OVER-TOP THE FRONTAL ZONE, SHOWERS WILL LIKELY
PERSIST FRIDAY NIGHT INTO EARLY SATURDAY MORNING. DEEPER H7-H5
SOUTHWEST FLOW WILL OCCUR BY SATURDAY, BRINGING THE FRONTAL BOUNDARY
NORTH AS A WARM FRONT WHILE ALSO ADVECTING HIGHER THETA-E AIR INTO
THE REGION. WITH GREATER THETA-E AIR COMES GREATER INSTABILITY AND
COVERAGE OF SHOWERS AND STORMS SHOULD INCREASE SATURDAY AFTERNOON
WITH ADDED DAYTIME HEATING. NOT OUT OF THE QUESTION THAT SOME STORMS
COULD BE STRONG AND ALSO HAVE HEAVY RAIN IN ISOLATED AREAS. IT
REMAINS TO EARLY TO PINPOINT MORE FAVORED AREAS OF THIS POSSIBLE
HEAVIER RAINFALL.
MID-RANGE MODELS DIVERGE ON SUNDAY WITH GFS MUCH SLOWER ON TROUGH
MOVEMENT WHILE ECMWF MORE PROGRESSIVE BUT HAS SLOWED VS. THE
PREVIOUS 18/12Z RUN. LATEST OPERATIONAL GFS REMAINS QUITE BULLISH ON
MORE RAIN/STORM CHANCES SUNDAY BUT WILL TEMPER THESE DOWN UNTIL
GREATER MID-RANGE AGREEMENT OCCURS.
FOR EARLY TO MID NEXT WEEK - WARMER AND OVERALL DRIER CONDITIONS
LOOK TO SET UP WITH SHORTWAVE RIDGING OCCURRING OVER THE CENTRAL
ROCKIES. WHILE SOME AFTERNOON HIGH TERRAIN SHOWERS/STORMS COULD BE
POSSIBLE, COVERAGE COMPARED TO THE CURRENT STRETCH OF WET WEATHER
SHOULD BE REDUCED BY A GOOD FACTOR.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1132 AM MDT WED JUN 19 2019
CONTINUED STRONG WINDS AND ISOLATED SHOWERS AND THUNDERSTORMS
POSSIBLE LATER THIS AFTERNOON INTO THE EARLY EVENING. BASED OFF
THE LATEST HRRR STRONGEST POTENTIAL WILL BE ON THE NORTHERN
COUNTIES WITH KCDR SEEING MORE OF THE THUNDERSTORM ACTIVITY THOUGH
LINGERING STORMS MAY PASS NEAR FROM KCYS EASTWARD. MVFR CONDITIONS
AT THE TERMINAL MAY BE POSSIBLE WITH ANY STORMS OVER EACH SITE. MODELS
ARE ALSO TRENDING TO STRONGER WIND FIELD ALOFT PARTICULARLY AT
KLAR TO INTRODUCE OVERNIGHT LLWS THERE.
FIRE WEATHER
ISSUED AT 320 AM MDT WED JUN 19 2019
FIRE WEATHER CONCERNS REMAIN LOW THANKS TO THE VERY WET AND COOL
PATTERN OF LATE. INCREASING WINDS AND DECREASING RH WILL FAVOR
MARGINAL ELEVATED FIRE WEATHER CONDITIONS ACROSS THE WEST TODAY
AND THURSDAY BUT FUELS REMAIN WET AND FIRE WEATHER IS UNLIKELY TO
BE CRITICAL. ADDITIONAL MOISTURE WILL RETURN FOR THE WEEKEND
ENDING ANY THREAT.
HYDROLOGY
ISSUED AT 320 AM MDT WED JUN 19 2019
FLOOD WARNING FOR THE NORTH PLATTE AT SARATOGA REMAINS. THE NEXT
UPDATE IS EXPECTED BY 10 AM THIS MORNING. 3 AM HYDROGRAPHS SHOW A
CONTINUED STEADY RISE ABOVE ELEVATED BASE FLOWS AT THE SITE.
RIVER STAGE IS EXPECTED TO CONTINUE ABOVE 8 FEET TODAY WITH
EXPECTED CREST IN MINOR FLOOD STAGE AT 8.5 FEET WITHIN THE NEXT 20
TO 24 HOURS. LITTLE CHANGE IS EXPECTED TODAY WITH LOW CHANCES FOR
PRECIPITATION INTO THE BASIN. WARMER TEMPERATURES AND STRONG
WINDS COULD SLIGHTLY INCREASE EVAPORATION AND LIMIT SNOW MELT RUN
OFF TODAY SLOWING THE RISE. HOWEVER, THE FORECAST REMAINS ON
TRACK AND MINOR FLOODING IS POSSIBLE. WET WEATHER RETURNS THIS
WEEKEND AND COULD INCREASE FLOWS.
CYS WATCHES/WARNINGS/ADVISORIES
WY...HIGH WIND WATCH FROM 3 PM MDT THIS AFTERNOON THROUGH THURSDAY
EVENING FOR WYZ110.
NE...NONE.
UPDATE...TJT
SHORT TERM...ALYONS
LONG TERM...JSA
AVIATION...WM
FIRE WEATHER...ALYONS
HYDROLOGY...ALYONS
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