902
FXUS65 KCYS 111236
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
636 AM MDT WED SEP 11 2024
KEY MESSAGES
- SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS
AFTERNOON WITH LOCALLY HEAVY RAINFALL AND GUSTY WINDS
POSSIBLE.
- CRITICAL FIRE WEATHER CONDITIONS ARE EXPECTED FOR MOST OF THE
AREA ON THURSDAY WITH STRONG WINDS GUSTING 40 TO 50 MPH. FIRE
WEATHER WATCHES HAVE BEEN ISSUED.
SHORT TERM /THROUGH THURSDAY NIGHT/
ISSUED AT 400 AM MDT WED SEP 11 2024
A POTENT EARLY SEASON SHORTWAVE TROUGH CURRENTLY MOVING ONSHORE IN
THE PACIFIC NORTHWEST WILL BE THE MAIN PLAYER DRIVING A FAIRLY
DYNAMIC NEXT 48 HOURS OR SO OF WEATHER. AN INITIAL SHORTWAVE
DISTURBANCE/VORT-MAX IS ALREADY MOVING OUT AHEAD OF THE MAIN
PARENT TROUGH, CURRENTLY LOCATED OVER WESTERN WYOMING. SYNOPTIC
LIFT AHEAD OF THIS SYSTEM IS PRODUCING INCREASING CLOUD COVER
ACROSS WYOMING, WHICH IN TURN HAS LEAD TO A FAIRLY WARM START TO
OUR WEDNESDAY. CLOUD COVER WILL EXPAND EASTWARD THROUGH THE DAY
INTO WESTERN NEBRASKA, OVERALL LEADING TO TEMPERATURES SLIGHTLY
COOLER THAN THE LAST FEW DAYS. THIS INITIAL WAVE HAS ALSO
TAPPED INTO IMPROVED MID- LEVEL MOISTURE, AND IS HELPING TO
INCREASE COLUMN WATER VAPOR THROUGH THE DAY. AS A RESULT OF THE
HIGHER MOISTURE CONTENT, EXPECT MORE ACTIVE SHOWER AND
THUNDERSTORM ACTIVITY TODAY, WITH A MUCH BETTER CHANCE OF
RAINFALL REACHING THE GROUND. FORECAST SOUNDINGS FOR THE
AFTERNOON STILL SHOW A FAIRLY DRY BOUNDARY LAYER, BUT WITH
ENOUGH MOISTURE ALOFT THAT THE CLOUD MASS SHOULDN'T HAVE TROUBLE
REACHING THE GROUND. WHILE A FEW SHOWERS MAY BE AROUND LATER
THIS MORNING, THUNDERSTORM ACTIVITY SHOULD BEGIN BETWEEN ABOUT
NOON AND 2PM AND CONTINUE WELL INTO THE EVENING HOURS. MODEL
GUIDANCE HAS TRENDED A LITTLE BIT MORE DISORGANIZED WITH THE
MID-LEVEL FRONTAL BOUNDARY ALONG THE SHORTWAVE TROUGH AXIS THIS
PM, WHICH REDUCES THE PROBABILITY OF A MORE ORGANIZED LINEAR
SYSTEM. HOWEVER, A FEW HIRES MODELS STILL SHOW STORMS
LINEARIZING. OVERALL, LOOKING AT PRIMARILY A THREAT FOR STRONG
GUSTY WINDS AND ISOLATED HEAVY RAINFALL SINCE PARAMETERS REMAIN
MARGINAL FOR MORE ORGANIZED SEVERE THUNDERSTORMS.
AS THE PARENT TROUGH BARRELS ACROSS THE NORTHWEST TOWARDS CENTRAL
IDAHO BY THURSDAY MORNING, EXPECT THE DRY SLOT OF THE EXTRA-
TROPICAL CYCLONE TO POSITION ITSELF OVER OUR AREA. MID-LEVEL
MOISTURE WILL QUICKLY DEPART BETWEEN MIDNIGHT AND DAWN ON
THURSDAY. WYOMING PRECIPITABLE WATER VALUES AS LOW AS 0.25 TO
0.35" MAY SHOW UP BY MIDDAY THURSDAY. STRONG WINDS ALOFT
ROUNDING THE BASE OF THE TROUGH WILL MOVE OVER THE AREA. THE
POTENT TROUGH ALOFT WILL ALSO SUPPORT RAPID LEE CYCLOGENESIS
OVER NORTH CENTRAL WY/SOUTHEAST MT TONIGHT INTO THURSDAY. IN
FACT, THE NAEFS MEAN SHOWS SLP APPROACHING CLIMATOLOGICAL
MINIMUMS ACROSS MUCH OF THIS AREA. A SURFACE TROUGH TRAILING OUT
OF THE SURFACE LOW PRESSURE CENTER IS EXPECTED TO DEVELOP IN
CENTRAL WY BY EARLY MORNING, AND THEN GRADUALLY PROGRESS
EASTWARD ACROSS THE FORECAST AREA THROUGH THE DAY, REACHING THE
WY/NE BORDER BY MID AFTERNOON. EXPECT SOUTHERLY WINDS AHEAD OF
THIS BOUNDARY AND SOUTHWESTERLY WINDS BEHIND, ALONG WITH VERY
DRY AIR. STRONG MIXING SHOULD HELP GET THESE WINDS DOWN TO THE
SURFACE, AND MOST OF WY COULD BE LOOKING AT WIND GUSTS OF 40+
MPH. ALONG WITH CRITICAL AFTERNOON RH BEHIND THE BOUNDARY, THIS
WILL LEAD TO A FAIRLY CONCERNING FIRE WEATHER SETUP ACROSS THE
AREA. THERE IS SOME UNCERTAINTY ON HOW FAR AND HOW FAST THE DRY
AIR WILL PROGRESS EASTWARD, WHICH WILL IMPACT HOW MUCH OF THE NE
PANHANDLE SEES CRITICAL FIRE WEATHER CONDITIONS. FIRE WEATHER
WATCHES HAVE BEEN ISSUED FOR THE ENTIRE AREA FOR WHICH FUELS ARE
LISTED AS CRITICAL. THE LAST PIECE OF THE PUZZLE FOR THURSDAY'S
FORECAST WILL BE A NARROW THREAT FOR THUNDERSTORMS. WHILE MOST
OF THE AREA SHOULD BE IN THE DRY SLOT, MODELS SHOW A NARROW
TONGUE OF ELEVATED MOISTURE MOVING JUST HEAD OF THE SURFACE
TROUGH. STRONG ISENTROPIC LIFT IN THIS REGION MAY HELP SUPPORT
CONVECTION IN FAR EAST CENTRAL WY AND THE NORTHERN NEBRASKA
PANHANDLE THURSDAY AFTERNOON AND EVENING. HOWEVER, IT IS ALSO
POSSIBLE THIS FAVORABLE ASCENT REGION REMAINS JUST UP TO THE
NORTHEAST PRIMARILY IN SD. FOR NOW, HAVE SOME SLIGHT CHANCE TO
CHANCE POPS IN THE AREA, BUT WITH A FAIRLY DYNAMIC SETUP THANKS
TO THE STRONG UPPER LEVEL TROUGH, WE'LL NEED TO KEEP AN EYE ON
THIS FOR SOME LOCALLY STRONG TO SEVERE WINDS, IF THE STORMS CAN
DEVELOP.
LONG TERM /FRIDAY THROUGH TUESDAY/
ISSUED AT 400 AM MDT WED SEP 11 2024
THE UPPER-LEVEL PATTERN IS EXPECTED TO REMAIN SOMEWHAT ACTIVE IN
THE EXTENDED FORECAST PERIOD W/ GENERAL LONG-WAVE TROUGHING MOST
LIKELY PERSISTING THROUGH EARLY TO MID NEXT WEEK. THE POST-FROPA
COOL DOWN ON FRIDAY WILL BE SHORT LIVED W/ A SLIGHT TREND TOWARD
WARMER TEMPERATURES OVER THE WEEKEND AS THE THERMAL RIDGE BEGINS
TO BUILD BACK INTO THE REGION. HIGHLY ACTIVE QUASI-ZONAL MID AND
UPPER-LEVEL FLOW COULD HELP HOLD TEMPERATURES BACK SLIGHTLY, BUT
DAYTIME HIGHS MAY STILL REACH THE UPPER 80S TO NEAR 90 DEG F FOR
THE WESTERN NE PANHANDLE ON SUNDAY. THE NEXT SUBSTANTIAL SHOT OF
COOLER AIR SHOULD ARRIVE ON TUESDAY AS THE NEXT TROUGH DIGS INTO
THE GREAT BASIN. DESPITE THE VERY ACTIVE PATTERN ALOFT, PROFILES
REMAIN VERY DRY AND ANY CHANCES FOR CONVECTION SHOULD BE MINIMAL
UNTIL LATE IN THE FORECAST PERIOD AHEAD OF THE NEXT LARGER SCALE
DISTURBANCE ALOFT.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 632 AM MDT WED SEP 11 2024
IN GENERAL, VFR PREVAILS. SCATTERED HIGH-BASED SHOWERS AND A FEW
THUNDERSTORMS ARE EXPECTED THIS AFTERNOON, ROUGHLY BETWEEN 18Z &
03Z. GUSTY & ERRATIC SURFACE WINDS WILL BE THE PRIMARY HAZARD TO
AVIATION INTERESTS. WIND GUSTS UP TO 40 KNOTS MAY BE POSSIBLE AT
KCDR LATER THIS AFTERNOON THROUGH THE EVENING W/ A STRENGTHENING
LOW-LEVEL JET.
FIRE WEATHER
ISSUED AT 400 AM MDT WED SEP 11 2024
ELEVATED FIRE WEATHER CONDITIONS ARE EXPECTED THIS AFTERNOON.
SOUTHERLY WINDS GUSTING 25 TO 30 MPH WITH MIN RH BETWEEN 15 AND 20%
WILL BE PRESENT IN THE NEBRASKA PANHANDLE, PORTIONS OF EAST CENTRAL
WY, AND IN CARBON COUNTY VALLEYS. ADDITIONALLY, AFTERNOON CONVECTIVE
ACTIVITY MAY BRING LIGHTNING AND GUSTY WINDS. SOME WETTING RAINFALL
WILL BE POSSIBLE, BUT THE COVERAGE OF WETTING RAINS MAY NOT BE VERY
HIGH.
WIDESPREAD CRITICAL FIRE WEATHER CONDITIONS ARE INCREASINGLY LIKELY
FOR THURSDAY. STRONG SOUTHWEST TO SOUTH WINDS AND MIN RH BETWEEN 10
AND 15% FOR ALL SE WYOMING VALLEYS AND FAR WESTERN NEBRASKA WILL
LEAD FAVORABLE CONDITIONS FOR RAPID FIRE SPREAD. WINDS COULD GUST AS
HIGH AS 40 TO 50 MPH. FIRE WEATHER WATCHES HAVE BEEN ISSUED FOR MOST
OF THE AREA FOR 12PM TO 8PM THURSDAY.
CYS WATCHES/WARNINGS/ADVISORIES
WY...FIRE WEATHER WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY
EVENING FOR WYZ417>423-425-427>433.
NE...FIRE WEATHER WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY
EVENING FOR NEZ435>437.
SHORT TERM...MN
LONG TERM...CLH
AVIATION...CLH
FIRE WEATHER...MN
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