Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 230915
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
315 AM MDT THU APR 23 2015

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 304 AM MDT THU APR 23 2015

THE WEAK UPPER LEVEL RIDGE OVER NORTHEASTERN COLORADO THIS MORNING
WILL SHIFT EAST OF THE REGION BY THE AFTERNOON. THE FLOW ALOFT
WILL BE MORE WEST SOUTHWESTERLY WITH SOME WEAK MID LEVEL QG ASCENT
DEVELOPING IN THE AFTERNOON. IN THE MOUNTAINS...PLENTY OF MID
LEVEL MOISTURE ADVECTING IN FROM THE SOUTHWEST. COVERAGE IN THE
MOUNTAINS...IN THE SCATTERED CATEGORY. OVER NORTHEASTERN
COLORADO...THE MDLS MAINTAIN A WEAK SURFACE TROUGH OVER THE
PLAINS. THE MDLS KEEP THE LOWER LEVELS FAIRLY DRY THIS AFTN WITH
DEWPOINTS IN THE LOWER TO MID 30S ALONG THE URBAN CORRIDOR. THIS
WILL RESULT IN MAINLY HIGH BASED THUNDERSTORMS WHICH WILL PRODUCE
GUSTY OUTFLOW WINDS TO 45 MPH AND JUST SOME BRIEF LIGHT RAINFALL.
NAM12 SOUNDINGS THIS AFTERNOON YIELD CAPES AROUND 800 J/KG. COULD
SEE A DENVER CYCLONE DEVELOP...BUT IT DOES NOT LOOK LIKE IT WILL
BE A VERY INTENSE ONE. FURTHER EAST...THE MDLS HAVE SOME BETTER
LOW LEVEL MOISTURE TO WORK WITH IN THE AFTERNOON WITH DEWPOINTS IN
THE LOWER 40S. BEST CHANCE FOR STRONG...POTENTIALLY
SEVERE...STORMS WILL BE EAST OF A LINE FROM NEW RAYMER TO FORT
MORGAN TO LIMON. FORECAST CAPES IN THIS REGION IN THE 1200-1500
J/KG RANGE LATE THIS AFTERNOON. THE BEST WINDOW FOR THE STORMS
WILL BE FROM AROUND 22Z TO 03Z...WITH DECREASING COVERAGE
THEREAFTER. TEMPERATURES THIS AFTN WILL BE SIMILAR TO YESTERDAY.
MAIN THREAT FROM ANY SEVERE STORMS COULD BE HAIL TO ONE INCH AND
WIND GUSTS IN EXCESS OF 60 MPH.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 304 AM MDT THU APR 23 2015

AN UPPER LEVEL TROUGH OVER THE FOUR CORNER 12Z FRIDAY MORNING WILL
MOVE INTO KANSAS BY FRIDAY EVENING. A SURFACE TROUGH WILL BE OVER
EASTERN COLORADO WHICH WILL PRODUCE A WESTERLY FLOW ACROSS THE
STATE. THIS SHOULD LIMIT THE AMOUNT OF PRECIPITATION WITH THIS
SYSTEM. AIRMASS WILL BE SLIGHTLY UNSTABLE FRIDAY WITH CAPES UP TO
500 J/KG. WILL KEEP SHOWERS AND THUNDERSTORMS IN THE FORECAST FOR
FRIDAY. THE BEST CHANCE WILL BE OVER THE MOUNTAINS WHERE OROGRAPHIC
LIFT WILL HELP AND ALSO OVER THE PLAINS WHERE MOISTURE WILL BE THE
BEST. SUBSIDENCE BEHIND THE TROUGH AND A SHORT WAVE RIDGE MOVING
OVER THE STATE SHOULD KEEP THE AREA DRY FRIDAY NIGHT AND SATURDAY
MORNING.

THE RIDGE WILL BE PUSHED EAST OF THE STATE BY 00Z SUNDAY AS A LARGE
UPPER LEVEL TROUGH DIGS OVER THE WESTERN U.S. FLOW ALOFT WILL BECOME
SOUTHWESTERLY AND MOISTURE WILL INCREASE. SCATTERED SHOWERS AND
THUNDERSTORMS ARE EXPECTED TO FORM SATURDAY AFTERNOON OVER THE
HIGHER TERRAIN AND THEN SPREAD EASTWARD DURING THE LATE AFTERNOON
AND EVENING.

BY 12Z SUNDAY...MODELS SHOWING THE PACIFIC TROUGH CLOSING OFF JUST
EAST OF LAS VEGAS. OVERALL...MODEL AGREEMENT NOT TOO BAD WITH THIS
SYSTEM. GENERAL CONSENSUS IS THAT THIS SYSTEM WILL MOVE ACROSS
ARIZONA AND NEW MEXICO SUNDAY AND SUNDAY NIGHT...EVENTUALLY ENTERING
NORTHERN TEXAS SOMETIME MONDAY. FOR NORTHEAST COLORADO...BEST CHANCE
FOR PRECIPITATION WILL BE SUNDAY AND SUNDAY NIGHT WHEN THE BEST LIFT
WILL BE OVER THE STATE. WILL CONTINUE TO TREND POPS A LITTLE HIGHER
DURING THIS PERIOD. WEAK UPSLOPE AND INSTABILITY WILL KEEP THE
CHANCE FOR SHOWERS GOING MONDAY AND MONDAY EVENING.

ON TUESDAY...MOST MODELS INDICATE A NORTHERLY FLOW WILL PREVAIL
BEHIND THE EXITING SYSTEM. SOME DIFFERENCES AMONG THE MODELS FOR
TUESDAY AND WEDNESDAY. THE LATEST GFS SHOWS A WAVE DIVING SOUTH OUT
OF CANADA AND ACROSS THE CENTRAL PLAINS TUESDAY/WEDNESDAY. THE ECMWF
IS FARTHER EAST WITH THIS SYSTEM AND HAS AN UPPER LEVEL RIDGE
ARRIVING SOONER THEN THE GFS AND GEM. WILL KEEP THE FORECAST DRY FOR
NOW TUESDAY AND WEDNESDAY WITH TEMPERATURES SLOWLY REBOUNDING AS THE
RIDGE BUILDS OVER THE REGION.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 304 AM MDT THU APR 23 2015

EXPECT VFR CONDITIONS WILL CONTINUE OVER THE NEXT 24 HOURS. SWLY
SFC WINDS THIS MORNING MAY BECOME MORE ESELY AFTER 15Z...THEN BACK
TO SOUTHWESTERLY THIS AFTERNOON ONCE OUTFLOW FROM THE DEVELOPING
THUNDERSTORMS OVER THE FOOTHILLS SHIFTS EASTWARD...AFTER 20Z.
EXPECT ISOLATED TO SCATTERED SHOWERS/TSTMS THIS AFTERNOON...
MAINLY HIGH BASED AROUND DENVER. MAIN CONCERN WILL BE GUSTY
OUTFLOW WINDS TO 45 MPH. BETTER LOW LEVEL MOISTURE WILL BE EAST OF
DENVER. IF ANY ILS RESTRICTIONS OCCUR IT SHOULD BE BRIEF AND IN
THE VICINITY OF THE THUNDERSTORMS. THE SURFACE TROUGH IS EXPECTED
TO SHIFT EAST FRIDAY MORNING ALLOWING FOR PRIMARILY WEST/NORTHWEST
SFC WINDS AFTER 12Z FRIDAY.
&&

.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...COOPER
LONG TERM...MEIER
AVIATION...COOPER



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