Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 151041
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
441 AM MDT WED APR 15 2015

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 441 AM MDT WED APR 15 2015

MOST OF THE PLAINS WILL SEE ANOTHER BREEZY DAY TODAY AS A SURFACE
LOW REMAINS OVER THE NORTHEAST QUARTER OF THE STATE. AT THE SAME
TIME...SOUTHWEST FLOW AT MID-LEVELS WILL BE INCREASING AS AN UPPER
LOW INTENSIFIES OVER WESTERN COLORADO AND MOVES INTO POSITION OVER
THE FOUR-CORNERS AREA. DYNAMIC FORCING ASSOCIATED WITH THE UPPER
LOW WILL PRODUCE SCATTERED SNOW SHOWERS OVER THE MOUNTAINS. THE
PLAINS WILL REMAIN DRY THROUGH LATE AFTERNOON DUE TO THE STRONG
DOWNSLOPING EFFECT OF THE SOUTHWEST WINDS ROTATING AROUND THE
DEVELOPING STORM SYSTEM. BY LATER THIS EVENING...A SURFACE COLD
FRONT WILL DROP DOWN THE FRONT RANGE FROM THE NORTH. THIS WILL
SWITCH THE WINDS TO A NORTHERLY DIRECTION AND BRING COOLING
TEMPERATURES. SHOWER ACTIVITY WILL ALSO SPREAD ONTO THE NORTHERN
PLAINS LATE IN THE AFTERNOON AND THEN FILL IN SOUTHWARD THROUGH
THE EVENING. TEMPERATURES SHOULD REMAIN WARM ENOUGH THROUGH THE
EVENING THAT PRECIPITATION ACROSS THE PLAINS REMAINS AS RAIN.
AFTER MIDNIGHT...THE AIRMASS WILL BECOME COOL ENOUGH FOR
PRECIPITATION TO CHANGE OVER TO SNOW. ALTHOUGH WITH LOW
TEMPERATURES ONLY AROUND THE FREEZING MARK...THE SNOW WILL HAVE A
HARD TIME ACCUMULATING. ADDITIONAL SNOW ACCUMULATIONS AT LOWER
ELEVATIONS IS NOT EXPECTED UNTIL LATER IN THE STORM CYCLE.
MOUNTAINS AREAS MAY PICK UP A FEW INCHES OF SNOWFALL
OVERNIGHT...BUT THE HEAVIEST PRECIPITATION IS NOT EXPECTED UNTIL
LATER IN THE STORM...IF IT REMAINS OVER THE STATE LONG ENOUGH.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 441 AM MDT WED APR 15 2015

OVERALL MODELS HAVE COME INTO BETTER AGREEMENT TONIGHT WITH AN UPPER
LEVEL LOW BEING CENTERED NR THE FOUR CORNERS AREA AT 12Z THU WHICH
WILL STAY NEARLY STATIONARY OR DRIFT SLOWLY SOUTH INTO NWRN NEW
MEXICO BY THU NIGHT.  BY THU AFTN INTO THU NIGHT A 700 MB LOW WILL
BECOME MORE ORGANIZED OVER SRN CO/NRN NM AS SFC HIGH PRES REMAINS
OVER WY WHILE SFC LOW PRES IS OVER NM.  THIS LEADS TO INCREASING ELY
LOW LVL FLOW ESPECIALLY THU NIGHT INTO FRI WHICH MAY ALLOW FOR
DEEPER LOW LVL MOISTURE TO ADVECT IN FM THE EAST.  MEANWHILE THERE
WILL BE MID LVL ASCENT AND FAVORABLE LAPSE RATES ACROSS THE AREA AS
WELL.  OVERALL THERE APPEARS TO BE AN INCREASING THREAT FOR HEAVY
WET SNOW THU NIGHT INTO FRI IN THE MTNS AND FOOTHILLS.  AT LOWER
ELEVATIONS BUFFER DATA SUGGEST SNOW LEVELS WILL BE GENERALLY ABOVE
5500 FEET WITH A RAIN/SNOW MIX BETWEEN 5000 AND 5500 FT.

ON FRI THE MODELS BEGIN TO DIVERGE WITH THE MOVEMENT OF THE UPPER
LEVEL LOW.  THE ECMWF AND TO SOME EXTENT THE GFS BEGIN TO LIFT A
SIGNIFICANT PIECE OF ENERGY INTO ERN CO WHICH ALLOWS FOR THE UPPER
LEVEL LOW TO MOVE ENE INTO SCNTRL OR SERN CO BY FRI AFTN.  MEANWHILE
THE GEM MODEL KEEPS THE MAIN UPPER LEVEL LOW BACK OVER SWRN CO/NWRN
NM THRU FRI AFTN.  AT THIS POINT NOT SURE WHICH SOLUTION IS THE BEST
HOWEVER WITH ELY UPSLOPE FLOW...MID LVL ASCENT AND DECENT LAPSE
RATES STILL IN PLACE SHOULD CONTINUE TO SEE PERIODS OF HEAVIER PCPN
THRU FRI AFTN ONE WOULD THINK.

BY FRI NIGHT INTO SAT THE GEM MODEL BEGINS TO MOVE MAIN UPPER LEVEL
EASTWARD ACROSS NRN NEW MEXICO WITH SOME TYPE OF NRN EXTENSION OVER
ERN CO BY SAT AFTN.  MEANWHILE THE GFS AND ECMWF SHOW THE MAIN UPPER
EVENTUALLY BECOMING MORE ELONGATED FM ERN CO INTO NERN NM AS WELL.
THE SREF MEAN SOLUTION STILL HAS A MORE CONSOLIDATED UPPER LEVEL LOW
ALONG THE SRN CO/NRN NM BORDER AREA THRU 18Z SAT.  OVERALL SHOULD
CONTINUE TO SEE SOME PCPN THRU FRI NIGHT HOWEVER CONFIDENCE IN SAT
FCST IS RATHER LOW AT THIS POINT.  IF THE SYSTEM STAYS MORE
CONSOLIDATED LIKE THE SREF SHOWS AND STAYS OVER SRN CO/NRN NM THEN
PCPN COULD LINGER WELL INTO SAT.

AT THIS TIME THERE IS AN INCREASING THREAT FOR A DECENT SPRING
STORM FM THU NIGHT THRU FRI NIGHT SO WILL ISSUE A WATCH FOR THE
MTNS AND FOOTHILLS. SNOW LEVELS FRI NIGHT INTO SAT ARE STILL NOT
CERTAIN AT LOWER ELEVATIONS SO WILL KEEP A RAIN SNOW MIX BETWEEN
5000 TO 5500 FT WITH RAIN BELOW 5000 FT. ITS POSSIBLE THE FAR WRN
AND SRN SUBURBS IN THE 5500-6000 FT RANGE COULD RECEIVE SOME
HEAVIER SNOWFALL BUT CONFIDENCE IS NOT HIGH ENOUGH AT THIS TIME TO
ISSUE A WATCH. QPF AMOUNTS FM THE MODELS GENERALLY AVERAGE FM 1 TO
2 INCHES OF WATER FOR THE EVENT HOWEVER SOME AREAS COULD RECEIVE
UP TO 3 INCHES OF WATER.

BY SAT NIGHT INTO SUN THE UPPER LEVEL LOW SHOULD MOVE EAST OF THE
AREA HOWEVER AS IT DOES SO A DISTURBANCE IN NW FLOW ALOFT MAY AFFECT
THE AREA ON SUN AS ANOTHER PUSH OF COOLER AIR MOVES INTO NERN CO.
CROSS-SECTIONS SHOW DECEN MOISTURE AND SOME MID LVL ASCENT WITH THIS
FEATURE SO COULD SEE ANOTHER ROUND OF PCPN MAINLY ON SUN.  TEMP
PROFILE SHOWS AIRMASS WOULD BE COLD ENOUGH FOR SNOW AT LOWER
ELEVATIONS SUN MORNING.

FOR SUN NIGHT INTO MON ANOTHER DISTURBANCE IN NWLY FLOW ALOFT MAY
AFFECT THE AREA ALONG WITH ANOTHER FNT.  THUS COULD SEE ANOTHER CHC
OF PCPN MAINLY SUN NIGHT INTO MON MORNING.  ON TUE NWLY FLOW ALOFT
WILL REMAIN OVER THE AREA.  THE GFS SHOWS ANOTHER DISTURBANCE AND
FNT AFFECTING NRN CO BRINGING ANOTHER CHC OF PCPN WHILE THE ECMWF
DOES NOT. FOR NOW WILL JUST KEEP IN LOW POPS.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 441 AM MDT WED APR 15 2015

WINDS ARE EXPECTED TO BE THE MAIN PROBLEM TODAY AS INCREASING
SOUTHWEST FLOW ALOFT SHOULD PRODUCE GUSTY WINDS AT TIMES THROUGH
THE LATE AFTERNOON. BY EVENING...A COLD FRONT DROPPING OUT OF
WYOMING WILL BRING A GUSTY WIND SHIFT TO THE NORTH OR NORTHWEST.
LATER TONIGHT RAIN SHOWERS ARE EXPECTED TO DEVELOP AS THE UPSLOPE
LOW LEVEL WINDS WILL COMBINE WITH DYNAMIC FORCING FROM THE UPPER
LEVEL DISTURBANCE SETTING UP OVER THE STATE. COOLING OF THE
AIRMASS THROUGH THE EVENING WILL ALLOW RAIN SHOWERS TO BEGIN
CHANGING OVER TO SNOW AFTER 06Z. ONLY MINOR SNOW ACCUMULATIONS ON
GRASSY SURFACES ARE EXPECTED THROUGH SUNRISE THURSDAY MORNING.

&&

.FIRE WEATHER...
ISSUED AT 441 AM MDT WED APR 15 2015

INCREASING SOUTHWEST WINDS ARE EXPECTED AGAIN BY THIS AFTERNOON
ACROSS THE PALMER DIVIDE REGION AND SOUTHERN LINCOLN COUNTY. WARM
ENOUGH TEMPERATURES AND LOW ENOUGH DEW POINTS ARE ALSO EXPECTED
WHICH MAY PRODUCE ANOTHER AFTERNOON OF FIRE WEATHER CONCERNS. WILL
ISSUE A RED FLAG WARNING FOR ZONE 47 TO HIGHLIGHT THE THREAT OF
DANGEROUS FIRE BEHAVIOR FOR ANOTHER DAY. THE REMAINDER OF
NORTHEAST COLORADO IS EXPECTED TO BE SOME 10 TO 15 DEGREES COOLER
TODAY THAN YESTERDAY...SO FIRE DANGERS ARE NOT EXPECTED TO BE AS
HIGH.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM 11 AM THIS MORNING TO 8 PM MDT THIS
EVENING FOR COZ247.

WINTER STORM WATCH FROM THURSDAY EVENING THROUGH LATE FRIDAY
NIGHT FOR COZ033>036.

&&

$$

SHORT TERM...DANKERS
LONG TERM...RPK
AVIATION...DANKERS
FIRE WEATHER...DANKERS


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