557
FXUS65 KCYS 050430
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1030 PM MDT MON AUG 4 2025
KEY MESSAGES
- THERE IS A SLIGHT RISK (LEVEL 2 OF 5) FOR SEVERE WEATHER FOR
MONDAY ACROSS WESTERN NEBRASKA. ALL MODES OF SEVERE WEATHER
ARE POSSIBLE: LARGE HAIL, DAMAGING WINDS, AND AN ISOLATED
TORNADO OR TWO.
- RED FLAG WARNINGS AND THROUGH FRIDAY DUE TO VERY LOW RELATIVE
HUMIDITIES ALONGSIDE POOR OVERNIGHT RECOVERY AND GUSTY WINDS.
- HOT AND DRY CONDITIONS REMAIN ON TRACK, WITH THURSDAY BEING
THE WARMEST DAY OF THE WEEK.
SHORT TERM /THROUGH TUESDAY NIGHT/
ISSUED AT 311 PM MDT MON AUG 4 2025
A SEVERE THUNDERSTORM WATCH IS OUT THIS AFTERNOON FOR GOSHEN
COUNTY AND THE NEBRASKA PANHANDLE THROUGH THIS EVENING FOR LARGE
HAIL AND STRONG WIND GUSTS. MESOANALYSIS INDICATES A FAVORABLE
ENVIRONMENT FOR THUNDERSTORM DEVELOPMENT WITH 1000-2000 J/KG OF
MUCAPE ALONGSIDE BULK SHEAR VALUES OF UP TO 40-45 KNOTS. THIS
ENVIRONMENT SHOULD SUPPORT A FEW THUNDERSTORMS THROUGH THE
EVENING, WITH SOME HIGH RES MODELS INDICATING A DEVELOPING SMALL
LINE THAT WILL MOVE INTO THE NEBRASKA PANHANDLE THIS EVENING,
WHICH WOULD SUPPORT A STRONGER RISK OF SEVERE WIND GUSTS. THE
OTHER STORY IN REGARDS TO THE WEATHER IS HOT, DRY, AND BREEZY,
WITH CRITICAL FIRE WEATHER CONDITIONS ONGOING ACROSS CARBON AND
ALBANY COUNTIES. WITH MOISTURE CONTINUING TO BE SPARSE
OVERNIGHT AND THROUGH THE REST OF THE WEEK, RED FLAG WARNINGS
HAVE BEEN ISSUED FOR OUR WESTERNMOST FIRE WEATHER ZONES THROUGH
FRIDAY TO ACCOUNT FOR THIS MULTI-DAY EVENT.
AND MOVING INTO TUESDAY, OUR RED FLAG ENVIRONMENT SPREADS
NORTHEASTWARDS, WITH PORTIONS OF CONVERSE, NIOBRARA, PLATTE, AND
GOSHEN COUNTIES INCLUDED STARTING TOMORROW AS WINDS PICK UP
ACROSS THESE AREAS ALONGSIDE THE POOR RELATIVE HUMIDITY VALUES.
THE NORTHERNMOST FIRE WEATHER ZONES WILL BE ALLOWED TO EXPIRE
TUESDAY EVENING AS CONDITIONS ON WEDNESDAY LOOK NOTABLY IMPROVED
COMPARED TO TOMORROW. BUT THAT WILL LIKELY CHANGE FOR THURSDAY
AND FRIDAY AS MODEL DATA SUGGESTS WE'LL SEE ANOTHER UPTICK IN
WINDS ALONGSIDE LOW RH VALUES. FOR MORE INFORMATION ON THIS
PORTION OF THE FORECAST, SEE THE LONG TERM DISCUSSION. FOR
THUNDERSTORMS, THE BEST PARAMETERS HAVE SHIFTED JUST
NORTHEASTWARDS OUTSIDE OF OUR REGION, KEEPING US JUST OUTSIDE OF
A MARGINAL RISK FOR SEVERE WEATHER. A THUNDERSTORM OR TWO CAN'T
BE RULED OUT INTO THE NEBRASKA PANHANDLE TOMORROW EVENING, BUT
ALMOST ALL HIGH RESOLUTION GUIDANCE HAS REMOVED OUR CHANCES OF
SEEING THUNDER TOMORROW, LEADING TO POPS BEING REMOVED FROM THE
FORECAST AT THIS TIME. OUR DRYING TREND WON'T HELP THUNDERSTORM
CHANCES EITHER, AND WITH THE DRYING COMES WARMING. THE HOTTEST
TEMPERATURES SHOULD STILL LIE IN THE LONG TERM PERIOD, BUT
TOMORROW AFTERNOON EXPECT PORTIONS OF GOSHEN COUNTY AND THE
NEBRASKA PANHANDLE TO ALREADY BE APPROACHING TRIPLE DIGITS.
LONG TERM /WEDNESDAY THROUGH MONDAY/
ISSUED AT 311 PM MDT MON AUG 4 2025
WEDNESDAY THROUGH MOST OF FRIDAY WILL BE CHARACTERIZED BY DRY,
HOT CONDITIONS. A STOUT HIGH PRESSURE SYSTEM ANCHORED OVER THE
DESERT SOUTHWEST WILL PROMOTE MID-/UPPER-LEVEL RIDGING AND
RESULTING SUBSIDENCE ACROSS THE COUNTY WARNING AREA (CWA).
BELOW-AVERAGE PWAT VALUES WILL PREVAIL DURING THIS TIME FRAME,
AND WHEN COMBINED WITH LARGE-SCALE SUBSIDENCE, THE POTENTIAL FOR
RAIN EACH DAY IS QUITE LOW (AROUND 15% OR LESS). THIS SYNOPTIC
SETUP WILL SUPPORT HIGH TEMPERATURES IN THE MID-90S TO LOWER
100S EAST OF THE LARAMIE RANGE, AND UPPER 80S TO LOWER 90S WEST.
RELATIVE HUMIDITY IS PROGGED TO DROP AS LOW AS 5% TO 15% ACROSS
PORTIONS OF THE CWA, ESPECIALLY ACROSS THE WESTERN FIRE ZONES.
ADDITIONALLY, WINDS MAY GUST TO 20-30 KTS ACROSS THE WESTERN
FIRE ZONES. AS SUCH, A RED FLAG WARNING REMAINS IN EFFECT ACROSS
ALL OF CARBON COUNTY, ALL ALBANY COUNTY, AND THE FAR WESTERN
PORTION OF LARAMIE COUNTY -- WITH THE ADDITION OF A PORTION OF
PLATTE COUNTY AND SOUTHERN CONVERSE COUNTY -- FROM TUESDAY
EVENING THROUGH FRIDAY EVENING.
AN MID-/UPPER-LEVEL SHORTWAVE TROUGH IS PROGGED TO PUSH THROUGH THE
PACIFIC NORTHWEST ON THURSDAY, THEN SHIFT EASTWARD ACROSS THE
NORTHERN GREAT PLAINS ON FRIDAY. FAVORABLE MID-/UPPER-LEVEL DYNAMICS
WITH THE PASSING TROUGH AND EMBEDDED DISTURBANCES -- COUPLED WITH
ATTENDANT MOISTURE -- WILL SUPPORT THE POTENTIAL FOR SHOWERS AND
THUNDERSTORMS ACROSS A PORTION OF THE CWA ON FRIDAY EVENING AND
OVERNIGHT. THE PEAK WINDOW FOR SHOWERS AND STORMS WITH THIS SYSTEM
MAY SHIFT 6-12 HOURS EARLIER OR LATER IN SUBSEQUENT FORECAST
PACKAGES, AS THE TIMING OF THE TROUGH PASSAGE VARIES BETWEEN THE
GLOBAL MODELS. SPECIFICALLY, THE GFS PUSHES THE TROUGH EAST OF THE
CWA FASTER THAN THE ECMWF, WITH THE LATTER DEVELOPING A MORE LARGE-
SCALE, PERSISTENT TROUGHING PATTERN OVER NORTHERN GREAT PLAINS.
WHILE THE GFS TRANSITIONS THE MID-/UPPER-LEVEL PATTERN TO
NORTHWESTERLY FLOW BY SATURDAY EVENING, IT BRINGS A DISTURBANCE
SOUTHEASTWARD OUT OF IDAHO ON SUNDAY AND SKIRTS IT BY THE CWA. BOTH
MODEL SOLUTIONS SUPPORT THE INCLUSION OF 20% TO 40% POPS ON SATURDAY
AND SUNDAY. ANY DISTURBANCES THAT TRAVERSE THE FLOW IN BOTH MODEL
OUTCOMES COULD AID IN ORGANIZATION/INTENSIFICATION OF CONVECTION,
BUT FOR NOW, THE PROBABILITY FOR WIDESPREAD SEVERE WEATHER IS
LOW.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 1022 PM MDT MON AUG 4 2025
WEST FLOW ALOFT WILL PREVAIL.
WYOMING TAFS...SCATTERED TO BROKEN CLOUDS FROM 5000 TO
15000 FEET WILL OCCUR. AREAS OF SMOKE WILL PERSIST AT LARAMIE
UNTIL 10Z, REDUCING VISIBILITIES TO 4 MILES. WINDS WILL GUST TO
23 KNOTS AT CHEYENNE UNTIL 08Z, AND TO 25 KNOTS AT RAWLINS AND
LARAMIE FROM 15Z TO 01Z.
NEBRASKA TAFS...SCATTERED TO BROKEN CLOUDS FROM 10000 TO
12000 FEET WILL PREVAIL. CEILINGS NEAR 1500 FEET WILL OCCUR
FROM 08Z TO 14Z. THUNDERSTORMS WILL BE IN THE VICINITY OF
CHADRON UNTIL 08Z. WINDS WILL GUST TO 25 KNOTS AT SCOTTSBLUFF
UNTIL 09Z, TO 25 KNOTS AT SIDNEY UNTIL 14Z, TO 35 KNOTS AT
CHADRON UNTIL 19Z AND TO 30 KNOTS AT ALLIANCE UNTIL 01Z.
CYS WATCHES/WARNINGS/ADVISORIES
WY...RED FLAG WARNING FROM NOON TO 6 PM MDT TUESDAY FOR WYZ417-418.
RED FLAG WARNING FROM NOON TUESDAY TO 6 PM MDT FRIDAY FOR
WYZ419>421-427>429.
RED FLAG WARNING UNTIL 6 PM MDT FRIDAY FOR WYZ422>426.
NE...NONE.
SHORT TERM...CG
LONG TERM...KM
AVIATION...RUBIN
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