427
FXUS65 KCYS 231134
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
534 AM MDT MON SEP 23 2019
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 338 AM MDT MON SEP 23 2019
MAIN HIGHLIGHT TODAY WILL THE NEAR-CRITICAL TO BRIEFLY CRITICAL
FIRE WEATHER HAZARD AND THE ABOVE NORMAL TEMPERATURES OF 5-9F
DEGREES.
SHORTWAVE H5 RIDGING IS OCCURRING FROM SOUTH-CENTRAL CANADA
SOUTHWARD ALONG THE ROCKIES AND FRONT RANGE THIS MORNING PER WATER
VAPOR AND RAP ANALYSIS. A NOTABLE SHORTWAVE TROUGH IS POSITIONED
ACROSS OR TO NV FARTHER WEST BUT WILL BE SHIFTING SOUTHEAST TO CA
AND AZ WITH MINIMAL IMPACTS TO WY/NE. THE SHORTWAVE RIDGING AND
RESULTANT SUBSIDENCE WILL AID DRY WEST WINDS AND ABOVE NORMAL
TEMPERATURES TODAY WITH LOTS OF SUN. AFTERNOON RELATIVE HUMIDITY
WILL FALL INTO THE 10-15 PERCENT RANGE ACROSS MUCH OF SOUTHEAST WY
AND WITH WIND GUSTS REACHING NEAR 25 MPH AT TIMES, NEAR-CRITICAL
TO BRIEFLY CRITICAL FIRE WEATHER CONDITIONS WILL OCCUR. SEE FIRE
WEATHER DISCUSSION BELOW FOR MORE DETAILS. OUTSIDE OF THE ELEVATED
FIRE WEATHER HAZARD, IT WILL BE A WARM AND PLEASANT DAY ACROSS
THE REGION WITH ABOVE NORMAL TEMPERATURES. A QUICK MOVING
SHORTWAVE TROUGH WILL PASS OVER WY LATE TONIGHT INTO TUESDAY WITH
NO SENSIBLE WEATHER IMPACTS GIVEN THE DRY AIR IN PLACE OTHER THEN
A FEW MORE MID- AND HIGH-LEVEL CLOUDS.
LONG TERM
(TUESDAY THROUGH SUNDAY)
ISSUED AT 338 AM MDT MON SEP 23 2019
CONTINUED WARM TUESDAY WITH A QUICK COOL OFF WEDNESDAY FOLLOWED BY
A WARMUP THURSDAY AND THEN A MUCH MORE ACTIVE PATTERN FOR THE LATE
WEEK AND WEEKEND INTO NEXT WEEK. PRECIPITATION CHANCES WILL BE LOW
UNTIL LATE THURSDAY INTO FRIDAY AND STAY ELEVATED THROUGH THE
UPCOMING WEEKEND AND EARLY NEXT WEEK. SOME WINTRY PRECIPITATION
COULD BE POSSIBLE LATE WEEKEND INTO EARLY NEXT WEEK FOR PORTIONS
OF THE HIGH TERRAIN IN SE WY.
A QUICK MOVING FRONT WILL BRUSH FAR NE WY AND THE NORTH NEBRASKA
PANHANDLE TUESDAY FOR A SLIGHT COOL OFF BUT MOST OF THE REGION
WILL SEE SIMILAR TEMPERATURES TOMORROW AS THEY DID TODAY WITH
READINGS PERHAPS 1-3F DEGREES COOLER. A BROAD, LOW-AMPLITUDE
LONGWAVE TROUGH WILL TAKE SHAPE OVER THE NORTHERN CONUS LATE
TUESDAY INTO WEDNESDAY AND WILL AID IN ANOTHER COLD FRONT PASSING
THROUGH WEDNESDAY THAT WILL DROP TEMPERATURES 10F DEGREES OR SO
TO MORE NORMAL VALUES FOR THIS TIME OF YEAR. HOWEVER, WAA WILL
LIKELY OCCUR THURSDAY WITH ABOVE NORMAL READINGS AGAIN. ALL THE
WHILE, PRECIPITATION CHANCES WILL REMAIN LOW DUE TO THE LACK OF
A DEEPER VERTICAL LIFT MECHANISM.
THE VERTICAL LIFT DYNAMICS WILL CHANGE BY LATE THURSDAY, LATE
WEEK, AND WEEKEND AS A STRONGER FRONT AND GREATER DIVERGENCE
ALOFT IS ADVERTISED PER GFS/ECMWF. PRECIPITATION SHOULD PRIMARILY
BE RAIN THROUGH THIS PERIOD UNTIL LATE WEEKEND WHEN A GREATER
AMPLIFIED STRONGER WESTERN CONUS TROUGH DEVELOPS OVER THE PACIFIC
NW AND SHIFTS TOWARDS THE INTER-MOUNTAIN WEST. WILL NEED TO KEEP
CLOSE WATCH ON SURFACE BOUNDARY TIMING VS. DEEPER LIFT TIMING FOR
HIGH PLAINS RAIN/STORMS AND HIGH TERRAIN SNOW SHOWERS A WEEK FROM
NOW. IT IS TOO FAR OUT TO SPECULATE ON IMPACTS OR SNOW AMOUNTS BUT
MULTI-MODEL GUIDANCE DOES SUGGEST WINTRY PRECIPITATION BEING
POSSIBLE IN THE MOUNTAINS.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 531 AM MDT MON SEP 23 2019
VFR CONDITIONS ACROSS ALL TERMINALS UNDER FEW TO SCT HIGH
AFTERNOON CEILINGS. WIND GUSTS FROM THE WEST TO 25 KTS ALONG AND
WEST OF THE LARAMIE RANGE BEGINNING AS EARLY AS 23/17Z,
DIMINISHING BY 24/02Z. OTHERWISE, WEST WINDS AROUND 10 KTS OR
LESS, BECOMING SOUTHERLY ACROSS THE PANHANDLE TERMINALS BY 23/23Z.
WINDS TURN WESTERLY ONCE AGAIN AROUND 24/06Z AHEAD OF A DRY NORTH
TO SOUTH MOVING FRONT.
FIRE WEATHER
ISSUED AT 338 AM MDT MON SEP 23 2019
NEAR-CRITICAL TO BRIEFLY CRITICAL FIRE WEATHER CONDITIONS ANTICIPATED
THIS AFTERNOON TO EARLY EVENING AND AGAIN TUESDAY. RELATIVE HUMIDITY
VALUES WILL FALL TO 10 TO 15 PERCENT WITH WIND GUSTS 18 TO 23 MPH AND
OCCASIONAL GUSTS TO 25 MPH POSSIBLE ACROSS THE HIGH TERRAIN AND HIGH
PLAINS OF WYOMING TODAY. MOST LIKELY ZONES OF GREATEST CHANCE FOR A RED
FLAG WARNING WOULD BE ZONES 302-303. SPATIAL COVERAGE OF MARGINAL WINDS
WILL PRECLUDE THE ISSUANCE OF A RED FLAG WARNING AT THIS TIME BUT THIS
WILL BE MONITORED CLOSELY THROUGH THE DAY. TUESDAY WILL HAVE HIGHER
WINDS BUT SLIGHTLY HIGHER HUMIDITY. WEDNESDAY WILL BE COOLER WITH
GREATER MOISTURE.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...JSA
LONG TERM...JSA
AVIATION...AB
FIRE WEATHER...JSA
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