970
FXUS65 KCYS 070443
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1043 PM MDT TUE JUN 6 2023
UPDATE
ISSUED AT 905 PM MDT TUE JUN 6 2023
RAINFALL THIS EVENING IS COMING TO AN END. WENT AHEAD AND EXPIRED
THE FLASH FLOOD WATCHES THAT WERE IN EFFECT FOR THE MULLEN BURN
SCAR AND UPPER NORTH PLATTE RIVER VALLEY. UPDATES HAVE BEEN SENT.
SHORT TERM
(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 345 PM MDT TUE JUN 6 2023
LATEST SATELLITE AND RADAR SHOWS NUMEROUS SHOWERS AND THUNDERSTORMS
DEVELOPING INITIALLY OVER THE HIGH TERRAIN OF THE SIERRA MADRE,
SNOWY, AND LARAMIE RANGES. DIURNAL CONVECTION WILL CONTINUE, BUT
LIMITED 0-6 KM SHEAR AROUND 10 KT WILL KEEP STORMS PULSEY AND SINGLE
CELLULAR. HOWEVER, SLOW STORM MOTIONS WILL POSE A RISK FOR POTENTIAL
FLOODING NEAR THE MULLEN BURN SCAR. WHILE NOT AS MOIST AS THE PAST
FEW DAYS WITH PWATS, FORECAST SOUNDINGS STILL SHOW FAIRLY GOOD
MOISTURE THROUGH THE COLUMN TODAY. FARTHER EAST, A BOUNDARY HAS BEEN
EVIDENT IN RADAR IMAGERY BETWEEN CHEYENNE AND LARAMIE AS A SUDO-
DRYLINE ALONG THE SOUTH LARAMIE RANGE. ENHANCED SURFACE VORTICITY
HAS BEEN NOTED WITH SURFACE SOUTHWESTERLIES TO THE EAST AND
WESTERLIES FARTHER WEST. SO FAR, A FEW FAILED ATTEMPTS AT DEEPER
CONVECTION HAVE BEEN MADE, BUT HI-RES GUIDANCE CONTINUES TO SUPPORT
FURTHER STORM DEVELOPMENT IN THE AREA LATER THIS AFTERNOON. ONE
CONCERN WILL BE THE POTENTIAL FOR LANDSPOUTS ALONG THIS BOUNDARY
WITH ANY UPDRAFTS THAT COULD STRETCH THIS VORTICITY IN TO THE
VERTICAL. LATEST SPC MESOANALYSIS HAS ALSO HIGHLIGHTED THIS AREA
WITH THE NON-SUPERCELL TORNADO PARAMETER. OTHERWISE, HEAVY RAIN,
SMALL HAIL, AND LIGHTNING WILL BE THE MAIN CONCERNS THROUGH THIS
EVENING.
THE ONGOING BLOCKING PATTERN CONTINUES WEDNESDAY WITH FAVORABLE
UPPER LEVEL DIVERGENCE FROM THE UPPER LEVEL LOW OVER THE SOUTHWEST
CONUS, ESPECIALLY ACROSS CARBON CO IN SOUTH-CENTRAL WY. STEEP MID-
LEVEL LAPSE RATES WILL SUPPORT STORM DEVELOPMENT ONCE AGAIN WITH
WIDESPREAD MLCAPE REACHING 500 J/KG. GREATER INSTABILITY WILL BE
PRESENT WHERE LOW-LEVEL MOISTURE CAN SNEAK IN. WEAK FLOW ALOFT WILL
ONCE AGAIN KEEP SHEAR LIMITED AND RESULT IN SLOW MOVING SINGLE CELL
CONVECTION, ESPECIALLY WITH INITIAL DEVELOPMENT OVER THE HIGHER
TERRAIN EARLY IN THE AFTERNOON BEFORE THE SHORTWAVE MOVES THROUGH.
LOOKS TO BE ANOTHER DAY WHERE THE MULLEN BURN SCAR WILL NEED TO BE
MONITORED FOR POTENTIAL FLOODING WITH HI-RES GUIDANCE DEPICTING
NUMEROUS SHOWERS AND STORMS ACROSS CARBON AND ALBANY CO THROUGH THE
EARLY EVENING. FARTHER EAST, STORM COVERAGE WILL BE LIMITED WITH A
FEW ISOLATED STORMS POSSIBLE ALONG THE I-80 CORRIDOR EAST OF
CHEYENNE. AFTERNOON TEMPERATURES WEDNESDAY WILL BE FAIRLY SIMILAR TO
TODAY WITH HIGHS IN THE 70S TO LOW 80S.
LONG TERM
(THURSDAY THROUGH TUESDAY)
ISSUED AT 345 PM MDT TUE JUN 6 2023
THE LONG TERM FORECAST REMAINS LARGELY ON TRACK WITH UNSETTLED
WEATHER CONTINUING THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK.
THE SYNOPTIC WEATHER PATTERN WILL REMAIN MORE OR LESS FIXED THROUGH
MOST OF THIS FORECAST PERIOD. THE STUBBORN RIDGE TO OUR NORTHEAST
WILL MEANDER AROUND THE NORTHERN PLAINS TO SOUTHERN CANADIAN PRAIRIE
OVER THE NEXT WEEK, FORMING AN OMEGA BLOCK ALONG WITH THE PERSISTENT
CLOSED LOWS OVER THE CALIFORNIA COAST AND THE NORTHEAST CONUS. IN
BETWEEN, OUR AREA WILL BE LARGELY UNDER NEARLY VERTICALLY STACKED
SOUTHEASTERLY FLOW ON THE FRINGE OF THE PERSISTENT RIDGE. PICKING UP
ON THURSDAY, THE MOISTURE PLUME WILL SHIFT EASTWARD AS THE SLOW
MOVING CALIFORNIA CUTOFF LOW DRIFTS OUT WAY. A SUBTLE SHORTWAVE
LIFTING NORTHWARD AS IT ROTATES AROUND THE UPPER LEVEL TROUGH IS
LIKELY ON THURSDAY, WHICH MAY ENHANCE THE SOUTHEASTERLY FLOW ALOFT
MAINLY OVER OUR WESTERN COUNTIES. INCREASING MID-LEVEL MOISTURE OVER
THE HIGH PLAINS SHOULD ALLOW FOR A BIT MORE PRECIPITATION COVERAGE
TO THE EAST EVEN AS SIGNIFICANT DRYING LIKELY REDUCES COVERAGE OVER
CARBON COUNTY. THUS, HAVE POPS COMING UP SLIGHTLY MAINLY CENTERED
AROUND THE LARAMIE RANGE AND ITS VICINITY. TRIMMED BACK FROM THE NBM
SLIGHTLY, WHICH APPEARED A LITTLE AGGRESSIVE. THE SHORTWAVE
MENTIONED ABOVE WILL LIFT THE MOISTURE PLUME A LITTLE FURTHER NORTH
AND EAST FRIDAY, LEADING TO POPS EXPANDING TO A WIDER PORTION OF THE
AREA. OVERALL, THE SEVERE THREAT LOOKS LOW FOR THURSDAY AND FRIDAY
WITH VERY WEAK SHEAR IN PLACE. HOWEVER, LOCALLY HEAVY RAINFALL,
SMALL HAIL, AND GUSTY WINDS WILL CONTINUE TO BE POSSIBLE.
HEADING INTO THE WEEKEND, THE MAJOR FORECAST CHALLENGE WILL BE HOW
FAR WEST THE INFLUENCE OF THE EASTERN CUTOFF LOW WILL EXTEND. MODELS
HAVE TRENDED MORE TOWARDS A SOLUTION THAT BRINGS A SHORTWAVE AROUND
THE FAR WESTERN FRINGE OF A NEW CUTOFF LOW DROPPING INTO THE GREAT
LAKES REGION THIS WEEKEND. THIS COULD BRING A BACKDOOR FRONT THROUGH
UNDERNEATH THE STILL PERSISTENT RIDGE TO OUR NORTH. THE MOISTURE
PLUME ALOFT IS ALSO LIKELY TO PUSH BACK TO THE SOUTHWEST. GEFS MEAN
PW AT SCOTTSBLUFF PEAK AT 00Z SUNDAY NEAR 1.0", WHICH EVEN HIGHER
VALUES OFF TO THE NORTHEAST INCLUDING CHADRON. FORECAST SOUNDINGS
HAVE THE SKINNY CAPE LOOK OF A HEAVY RAINFALL POTENTIAL OVER THE
HIGH PLAINS STARTING SATURDAY AFTERNOON. HAVE FAIRLY WIDESPREAD HIGH
POPS SATURDAY, BUT AGAIN TONED BACK FROM THE NBM A TAD TO KEEP MOST
AREAS IN THE "LIKELY" CATEGORY JUST TO UNCERTAINTY STEMMING FROM A 4-
DAY LEAD TIME. ON SUNDAY, MODELS HAVE TRENDED A BIT COOLER ON THE
BACKSIDE OF THIS SHORTWAVE. 700-MB TEMPERATURES PER THE GEFS MEAN
DROP TO +4C AT CHADRON, AND A GOOD NUMBER OF MODELS GET CLOSE TO
+2C. MOST MODELS HAVE INSTABILITY DECREASING SIGNIFICANTLY ON
SUNDAY, BUT WE MAY SEE SOME FAIRLY WIDESPREAD STRATIFORM RAINFALL
DEVELOP WITH MOIST UPSLOPE FLOW AND SOME MODEST ISENTROPIC LIFT OVER
THE AREA. THE NORTHEASTERN BOUNDARY OF THE MOISTURE PLUME IS LIKELY
TO BE FAIRLY SHARP, WHICH INTRODUCES SOME UNCERTAINTY MAINLY IN THE
NORTHERN PANHANDLE. LOOKS LIKE A COOL AND FAIRLY WET DAY SUNDAY WITH
ON AND OFF SHOWERS LIKELY ESPECIALLY CLOSER TO THE MOUNTAINS.
WE THEN FLIP BACK TO THE INFLUENCE OF THE WESTERN CUTOFF LOW INTO
EARLY NEXT WEEK AS IT DRIFTS BACK TO THE NORTHEAST PER MODEL
FORECASTS ON MONDAY AND TUESDAY. TEMPERATURES SHOULD WARM SOMEWHAT
ON MONDAY AND MORESO ON TUESDAY. WHILE ENSEMBLE MOISTURE VALUES
DECREASE SLIGHTLY FROM THE WEEKEND, THEY REMAIN LARGELY ABOVE NORMAL
SUPPORTING ADDITIONAL ROUNDS OF AFTERNOON CONVECTION ACROSS THE
AREA. ENSEMBLES HAVE NOW COME INTO MUCH BETTER AGREEMENT IN BREAKING
DOWN THE OMEGA BLOCK AND RETURNING WESTERLY FLOW TO THE AREA BY THE
MIDDLE OF NEXT WEEK. THE MOISTURE COULD BE A LITTLE SLOWER TO
DEPART, BUT SOME FORM OF A PATTERN CHANGE DOES NOW APPEAR LIKELY.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1043 PM MDT TUE JUN 6 2023
VFR CONDITIONS EXPECTED TO PERSIST THROUGH OVERNIGHT HOURS FOR ALL
SOUTHEAST WYOMING AND WESTERN NEBRASKA TAF TERMINALS, WITH THE
EXCEPTION OF KAIA. DUE TO CLEAR SKIES AND LIGHT UPSLOPE WINDS
OVERNIGHT, SIMILAR CONDITIONS TO LAST NIGHT, OPTED TO ADD FG INTO
THE TAF FOR KAIA FROM 09Z TO 13Z. TOMORROW'S FORECAST IS VERY
SIMILAR TO TODAY'S WITH ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS IN PORTIONS OF SOUTHEAST WYOMING, MAINLY ALONG AND
WEST OF THE LARAMIE RANGE BETWEEN 18Z AND 03Z.
FIRE WEATHER
ISSUED AT 345 PM MDT TUE JUN 6 2023
NO FIRE WEATHER CONCERNS WITH WIDESPREAD PRECIPITATION CHANCES
CONTINUING WITH THE ONGOING PATTERN ACROSS SOUTHEAST WYOMING AND
WESTERN NEBRASKA.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
UPDATE...GCC
SHORT TERM...MB
LONG TERM...MN
AVIATION...LK
FIRE WEATHER...MB
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