Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 141535
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
935 AM MDT TUE APR 14 2015

.UPDATE...
ISSUED AT 921 AM MDT TUE APR 14 2015

ONLY MINOR ADJUSTMENTS TO THE GRIDS AT THIS TIME. BACKED OF THE
CLOUD COVER IN THE GRIDS A BIT THROUGH EARLY AFTERNOON...WITH
MINOR ADJUSTMENTS TO THE WINDS AROUND DENVER...OTHERWISE THE TREND
IN THE FORECAST LOOKS GOOD...DRY AND WINDY THIS AFTERNOON...
ESPECIALLY EAST OF THE URBAN CORRIDOR. ISOLATED TO SCATTERED HIGH
BASED SHOWERS/TSTMS STILL A POSSIBILITY IN THE HIGH COUNTRY LATE
THIS AFTERNOON.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 436 AM MDT TUE APR 14 2015

A VERY WARM AND BREEZY DAY IS EXPECTED ACROSS THE PLAINS. IN THE
MOUNTAINS...WARM SPRING-LIKE CONDITIONS WILL PREVAIL THROUGH LATE
IN THE AFTERNOON. A WEAK UPPER LEVEL RIDGE IS OVER THE STATE THIS
MORNING WITH WEAK WESTERLY FLOW ALOFT. THIS WILL TRANSITION TO
INCREASING SOUTHWESTERLY FLOW THIS AFTERNOON AS AN UPPER TROUGH
DIGS IN THE GREAT BASIN. THIS WILL ALSO INCREASE CLOUDINESS OVER
THE MOUNTAINS AS MOISTURE ALOFT APPROACHES. LATE IN THE AFTERNOON
AND THROUGH THE EVENING...ISOLATED SHOWERS WILL DEVELOP WHICH MAY
CONTAIN SOME THUNDER.

ACROSS THE PLAINS...A STRONG SOUTHWEST-NORTHEAST PRESSURE GRADIENT
WILL EXISTS ALL DAY AS A LEE TROUGH INTENSIFIES ALONG THE
FOOTHILLS AND A SURFACE HIGH REMAINS ANCHORED OVER WESTERN KANSAS.
PRESSURE GRADIENTS OF 12-16 MB BETWEEN KLAA AND KCYS WILL
CONTINUE INTO THIS EVENING. THIS WILL PRODUCE THE GUSTY SOUTHERLY
WINDS ACROSS THE PLAINS...MAINLY EAST OF A KDEN-KGXY LINE. AREAS
OF LINCOLN AND WASHINGTON COUNTIES...WHERE THE WINDS WILL BE
STRONGEST MAY SEE AREAS OF BLOWING DUST THROUGH MUCH OF THE
AFTERNOON. HIGH TEMPERATURES WILL CLIMB TO THE LOWER 70S AND
RELATIVE HUMIDITIES WILL BE DROPPING TO THE LOWER TEENS. THIS WILL
PRODUCE FIRE WEATHER CONCERNS...WHICH ARE FURTHER ADDRESSED IN THE
SECTION BELOW. WINDS ACROSS THE PLAINS SHOULD TAPER OFF DURING THE
EVENING AS THE WEATHER REMAINS DRY. THERE WILL BE A GRADUAL
INCREASE IN CLOUD COVER OVERNIGHT AS THE UPPER LEVEL SYSTEM OVER
THE WESTERN HALF OF THE STATE BEGINS SPREADING ITS INFLUENCE TO
THE EAST.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 436 AM MDT TUE APR 14 2015

ON WED AN UPPER LEVEL TROUGH WILL INTENSIFY OVER THE GREAT BASIN
WITH A CLOSED LOW LIKELY DEVELOPING NR THE FOUR CORNERS BY EARLY WED
EVENING. THE GFS IS THE ONLY MODEL WHICH DOES NOT HAVE IT THEIR
AS IT HAS OVER SCNTRL WY...HOWEVER SEVERAL OF THE GFS ENSEMBLE
MEMBERS HAVE IT NR THE FOUR CORNERS.

MEANWHILE ANOTHER BIG QUESTION FOR WED IS THE TIMING OF A CDFNT INTO
NERN CO.  THE GEM AND ECMWF ARE SLOWER WITH THIS FEATURE AND HOLD
OFF PASSAGE UNTIL LATE AFTN OR EARLY EVENING WHILE THE GFS AND
NAM HAVE IT MOVING ACROSS BY 18Z AS SFC LOW PRES MOVES INTO OVER
SERN CO. FOR NOW WILL GO WITH A FASTER MOVEMENT AND KEEP HIGH
TEMPS OVER NERN CO SIMILAR TO PREVIOUS FCST. AS FAR AS PCPN
CHANCES NOT SURE HOW THINGS ARE GOING TO EVOLVE BY AFTN. THERE IS
SOME MID LVL ASCENT BY AFTN WITH INCREASING MOISTURE IN THE MTNS
ALONG WITH DECENT LAPSE RATES SO SHOULD SEE A GOOD CHC OF SHOWERS
AND A FEW TSTMS. OVER NERN CO IF FNT DOES MOVE ACROSS BY MIDDAY
THIS WOULD ALLOW FOR MOISTURE TO INCREASE BEHIND THE FNT WITH A
CHC OF SHOWERS AND POSSIBLY A FEW TSTMS AS WELL.

FOR WED NIGHT THRU THURSDAY SIGNIFICANT DIFFERENCES CONTINUE TO
BETWEEN THE GFS AND THE OTHER MODELS.  THE ECMWF AND GEM HAVE THE
UPPER LEVEL LOW DRIFTING SLIGHTLY SOUTHWARD INTO NWRN NEW MEXICO BY
LATE THU AFTN WHILE THE GFS HAS AN ELONGATED UPPER LEVEL LOW
STRETCHING FM SRN WYOMING INTO NWRN NEW MEXICO.  AT THIS POINT
BELIEVE THE ECMWF AND GEM ARE MORE REALISTIC WITH A MORE
CONSOLIDATED UPPER LEVEL LOW.  AT THE SFC LOW PRES WILL DEVELOP OVER
SWRN CO AS SFC HIGH PRES BUILDS INTO NRN CO ON THU.  AT THIS TIME AM
NOT REAL CONFIDENT ABOUT PCPN POTENTIAL OVER NRN CO WED NIGHT INTO
THU MORNING.  EVEN IF ONE FAVORS THE ECMWF AND GEM SOLUTIONS NEITHER
MODEL SHOWS MUCH MOISTURE OVER THE AREA WED NIGHT INTO THU MORNING
AS BEST MID LVL ASCENT STAYS MAINLY WEST AND SOUTHWEST OF THE
AREA. THUS WILL LEAVE MAINLY CHC POPS IN THE FCST DUE TO
UNCERTAINTY OF SITUATION.

MEANWHILE FM THU AFTN THRU THU NIGHT BOTH THE ECMWF AND GEM SHOW
INCREASING ENE LOW LVL FLOW DEVELOPING OVER NRN CO AS THE UPPER
LEVEL SYSTEM DEVELOPS A BROADER CIRCULATION OVER NWRN NEW MEXICO.
TRAJECTORIES SHOW THE POTENTIAL FOR SOME INFLUX OF DEEPER LOW LVL
MOISTURE INTO NRN CO FM THE EAST.  IN ADDITION SOME MID LVL ASCENT
WILL AFFECT THE AREA SO THIS COULD BRING A BETTER CHC OF HEAVIER
PCPN LATE THU AFTN THRU THU NIGHT IF THINGS COME TOGETHER RIGHT.
LATEST TEMP PROFILES ARE BORDERLINE FOR SNOW BLO 5500 FT SO PCPN
OVER THE PLAINS MAY STAY AS RAIN WITH SNOW CONFINED TO THE PALMER
DIVIDE AND PORTIONS OF THE URBAN CORRIDOR INTO THE FOOTHILLS.  ONCE
AGAIN OVERALL CONFIDENCE IS NOT HIGH AS TO HOW THINGS MAY DVLP THU
AFTN THRU THU NIGHT.

ON FRI THE BROAD UPPER LEVEL CIRCULATION CONTINUES TO BE CENTERED
SOMEWHERE OVER NRN OR CNTRL NEW MEXICO BASED ON THE ECMWF/GEM
WHILE THE GFS HAS AN ELONGATED LOW FM NERN CO INTO SERN NEW
MEXICO. ONCE AGAIN FAVOR THE ECMWF/GEM SOLUTIONS AT THIS POINT.
MEANWHILE DESPITE THE UPPER LEVEL CIRCULATION BE RATHER FAR SOUTH
BOTH THE ECMWF AND GEM STILL SHOW A FETCH OF DEEPER LOW LVL
MOISTURE IN ENE FLOW THRU FRI AFTN OVER NERN CO WITH STILL SOME
POTENTIAL FOR HEAVIER PCPN FM THE FOOTHILLS ACROSS THE PLAINS.
EVEN THE GFS SHOWS A SIMILAR PTRN IN THE LOW LEVELS. LATEST SREF
PLUME DATA MEAN HAS 10 TO 12 INCHES OF SNOW ALONG THE FRONT RANGE
URBAN CORRIDOR FM LATE THU AFTN THRU FRI AFTN. ONCE AGAIN WITH SO
MUCH UNCERTAINTY WILL KEEP POPS ON THE CHC SIDE FOR NOW. SNOW
LEVELS MAY STAY AOA 5500 FEET BASED ON CURRENT TEMP PROFILES.

BY SAT THE GFS HAS AN UPPER LEVEL LOW OVER CENTRAL OKLAHOMA WHILE
THE GEM HAS IT OVER THE TX PANHANDLE.  MEANWHILE THE ECMWF MOVES THE
UPPER LEVEL LOW INTO SERN COLORADO.  THUS THERE IS NO AGREEMENT AS
TO WHERE THIS SYSTEM MAY END UP. THE GEM AND GFS SOLUTIONS WOULD
KEEP THE PCPN THREAT EAST AND SE OF THE AREA WHILE THE ECMWF
SOLUTION WOULD CONTINUE THE THREAT OF PCPN THRU THE DAY ON SAT
ESPECIALLY OVER NERN CO. FOR NOW WILL JUST KEEP LOW POPS IN THE
FCST. BY SUN THE UPPER LEVEL SYSTEM SHOULD MOVE EAST OF THE AREA
AS NWLY FLOW ALOFT DEVELOPS. THERE IS A WK UPPER LEVEL TROUGH
EMBEDDED IN THE FLOW WHICH MAY AFFECT THE AREA ON SUN ALONG WITH
ANOTHER CDFNT. THUS COULD SEE ANOTHER CHC OF PCPN ALONG WITH
COOLER TEMPS.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z WEDNESDAY MORNING)
ISSUED AT 921 AM MDT TUE APR 14 2015

WEAK WESTERLY WIND COMPONENT THIS MORNING STILL EXPECTED TO SHIFT
TO SELY LATE THIS MORNING AROUND 17Z THEN PICK UP IN THE AFTN AT
KDEN AND KAPA...WINDS AT KBJC MAY BECOME WNWLY THIS AFTN AS THE
DENVER CYCLONE SETS UP. OVERALL VFR CONDITIONS THROUGH THE
PERIOD...COULD SEE BRIEF BKN CIGS IN THE 080-100KFT AGL TOWARD
00Z WITH THE FORMATION OF ISOLATED HIGH BASED CONVECTION. MAYBE
SOME OUTFLOW PRODUCING BRIEF VRB WIND GUSTS TO 30-35 KTS AT TIME
ASSOCIATED WITH VIRGA IN THE AREA.

&&

.FIRE WEATHER...
ISSUED AT 436 AM MDT TUE APR 14 2015

WINDY CONDITIONS...WARM TEMPERATURES AND A LACK OF RECENT
PRECIPITATION THAT HAS DELAYED TO SPRING GREEN-UP WILL ALL COMBINE
TO PRODUCE A VOLATILE FIRE WEATHER SITUATION TODAY. THE RED FLAG
WARNING FOR MOST OF THE PLAINS WILL GO INTO EFFECT AT 11 AM AND
CONTINUE THROUGH 8 PM. RELATIVE HUMIDITIES COULD DROP TO THE 10-15
PERCENT RANGE ACROSS MOST OF NORTHEAST COLORADO FOR MUCH OF THE
AFTERNOON. SOUTHERLY WIND GUSTS IN LINCOLN AND WASHINGTON
COUNTIES COULD BE AS HIGH AS 40 MPH. AND TEMPERATURES WILL BE IN
THE LOWER TO MID 70S THROUGH MUCH OF THE AFTERNOON.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING FOR COZ241-242-
244>251.

&&

$$

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



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