Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 162108
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
308 PM MDT THU APR 16 2015

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 257 PM MDT THU APR 16 2015

WATER VAPOR SATELLITE IMAGERY SHOWING THE UPPER LEVEL LOW
CENTERED OVER THE FOUR CORNERS AT THIS TIME WITH A SHORT WAVE
ROTATING AROUND IT OVER NORTH CENTRAL NEW MEXICO. THIS WAVE WILL
ROTATE NORTH OVER EASTERN COLORADO TONIGHT BRINGING WIDESPREAD
RAIN AND SNOW TO THE AREA.

IN ADDITION TO THE WAVE PASSING ACROSS THE AREA...UPSLOPE WINDS WILL
REMAIN STRONG AT 20 TO 40 KNOTS ALONG THE FRONT RANGE. EXPECT
MODERATE TO HEAVY SNOW THROUGH THE NIGHT WITH SNOWFALL RATES 1 TO 2
INCHES PER HOUR AT TIMES IN THE FOOTHILLS AND MOUNTAINS. LAPSE RATES
ARE ALSO STEEP...SO A FEW THUNDERSTORMS WILL BE POSSIBLE TONIGHT.
WILL MENTION A SLIGHT CHANCE IN THE FORECAST FOR THE FRONT RANGE AND
EASTERN PLAINS TONIGHT AND FRIDAY. MODELS GENERALLY SHOWING 1 TO 2
INCHES OF PRECIPITATION THROUGH FRIDAY MORNING WITH THIS SYSTEM...A
LITTLE MORE OVER LARIMER COUNTY. SO 1 TO 3 FEET LOOKS ON TRACK FOR
SNOWFALL AMOUNTS IN THE FOOTHILLS AND FRONT RANGE MOUNTAINS.

EXPECT A RAIN/SNOW MIX THIS EVENING BETWEEN 5000 TO 6000 FEET WITH
OCCASIONAL HEAVY SNOW UNDER THE STRONGEST SHOWERS. EASTERLY WINDS
AROUND THE LOW WILL CONTINUE TO PUMP MOISTURE INTO THE AREA ALONG
WITH WARMER AIR. THIS IS EXPECTED TO CHANGE SNOW TO RAIN ACROSS THE
DENVER AREA OVERNIGHT. BY FRIDAY MORNING...EXPECT RAIN FOR MOST
PLACES UNDER 6000 FEET. MAY SEE UP TO 6 INCHES OF SLUSHY SNOW PRIOR
TO CHANGING TO RAIN IN THE DENVER AREA OVERNIGHT...POSSIBLY A LITTLE
MORE NEAR THE FOOTHILLS AND PALMER DIVIDE. WILL ISSUE AN ADVISORY
FOR PARK COUNTY AND PALMER DIVIDE WHERE AN ADDITIONAL 4 TO 8 INCHES
WILL BE POSSIBLE.

ON FRIDAY...THE UPPER LEVEL LOW WILL LIFT INTO COLORADO. AT THE
SURFACE...A LOW WILL MOVE EAST ACROSS EASTERN COLORADO. TO THE NORTH
AND EAST OF THE SURFACE LOW...SURFACE BASED CAPES CLIMB TO AROUND
2000 J/KG BASED ON THE 18Z NAM. WITH STRONG SHEAR IN PLACE...THIS
WILL BE ENOUGH INSTABILITY FOR A CHANCE OF SEVERE
THUNDERSTORMS...MAIN THREATS WILL BE LARGE HAIL UP TO GOLF BALL SIZE
AND TORNADOS. RIGHT NOW APPEARS THE BEST CHANCE WILL BE FROM GREELEY
TO LIMON AND EASTWARD...THOUGH THIS WILL DEPEND ON WHERE THE LOW
TRACKS. FOR THE FOOTHILLS AND MOUNTAINS...STILL LOOKS LIKE IT WILL
STAY COLD ENOUGH FOR SNOW THROUGH THE DAY.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 257 PM MDT THU APR 16 2015

THE FIRST PART OF THE LONG TERM FORECAST HINGES OF THE LOCATION AND
MOVEMENT OF THE 500 MB UPPER LEVEL LOW PRESSURE SYSTEM. THE MODELS
ARE IN PRETTY GOOD AGREEMENT...HOWEVER JUST A SLIGHT DEVIATION IN
THE UPPER LOW TRACK WOULD AFFECT PRECIPITATION AND SNOWFALL AMOUNTS
ACROSS NORTH CENTRAL AND NORTHEASTERN COLORADO. THE ECMWF HAS BEEN
VERY CONSISTENT AND HAS THE 500 MB LOW CENTERED JUST WEST OF
COLORADO SPRINGS AT 00Z SATURDAY. THE GFS AND NAM MODELS HAVE THE
CENTER NEAR CANON CITY WHICH IS APPROXIMATELY 75 SOUTH OF THE
PREVIOUS TWO RUNS. THESE MODELS THEN TRACK THE LOW TO NEAR DENVER BY
12Z SATURDAY MORNING. AS THE LOW MOVES NORTH DENVER SHOULD SEE A
DECREASE IN PRECIPITATION...HOWEVER THE MOUNTAINS AND FOOTHILLS NEAR
THE WYOMING BORDER COULD STILL BE UNDER THE GUN AS WRAP AROUND
PRECIP WRAPS INTO THE REGION FROM THE NORTH. THE 15Z RUC JUST CAME
IN AND SHOWS THE UPPER LOW TAKING A MORE SOUTHERLY TRACK ACROSS
SOUTHERN COLORADO. THIS TRACK COULD PROLONG THE PRECIP EVENT BUT FOR
NOW WILL GO WITH THE CONSENSUS OF THE GFS...ECMWF AND NAM.
PRECIPITATION CHANCES DECREASE SATURDAY NIGHT INTO SUNDAY AS THE
UPPER LOW WEAKENS AND MOVES INTO THE CENTRAL PLAINS STATES AND A
NORTHWEST FLOW ALOFT DEVELOPS OVER THE STATE.

UNSETTLED WEATHER WILL CONTINUE ACROSS NORTH CENTRAL AND
NORTHEASTERN COLORADO THROUGH MONDAY AS RESIDUAL MOISTURE COMBINES
WITH INSTABILITY DUE TO DAYTIME HEATING. A WEAK SURGE IN THE
NORTHWEST FLOW COULD ENHANCE PRECIPITATION CHANCES.  WARMER AND
DRIER WEATHER WILL RETURN TO THE REGION ON TUESDAY AS UPPER LEVEL
HIGH PRESSURE BUILDS OVER THE ROCKY MOUNTAIN REGION.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z FRIDAY LATE AFTERNOON)
ISSUED AT 257 PM MDT THU APR 16 2015

RAIN AND SNOW WILL CONTINUE THROUGH THE EVENING AND EVENTUALLY TURN
TO RAIN BY FRIDAY MORNING. VISIBILITY WILL FALL TO A QUARTER MILE AT
TIMES IN THE HEAVIER SNOW. CEILINGS WILL BE UNDER 1000 FEET AND ONLY
OCCASIONAL BE HIGHER THAN THAT. NORTHERLY WINDS WILL PREVAIL AT
SPEEDS LESS THAN 20 KNOTS. SNOW ACCUMULATION AT KDEN IS EXPECTED TO
STAY BELOW 3 INCHES...WITH UP TO 6 INCHES POSSIBLE AT KAPA AND KBJC.
IN ADDITION TO THE RAIN/SNOW...ISOLATED THUNDERSTORMS ARE EXPECTED
TO FORM...MAINLY THIS EVENING THEN AGAIN FRIDAY AFTERNOON.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM MDT
FRIDAY FOR COZ037-041.

WINTER STORM WARNING UNTIL 6 AM MDT SATURDAY FOR COZ033>036.

&&

$$

SHORT TERM...MEIER
LONG TERM...JK
AVIATION...MEIER


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