Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 011628
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1028 AM MDT FRI MAY 1 2015

.UPDATE...
ISSUED AT 1028 AM MDT FRI MAY 1 2015

WILL BE UPDATING THE FORECAST TO INCREASE THE THUNDERSTORMS TO THE
LIKELY CATEGORY ON THE PALMER DIVIDE AND EASTERN PLAINS DURING THE
AFTERNOON AND EVENING. SATELLITE PICTURES SHOW THAT THE STRATUS
ALONG THE FOOTHILLS IS THICKEST FROM THE NORTHWEST SIDE OF DENVER
TO THE WYOMING BORDER. THIS IS LEAVING THE PALMER DIVIDE IN NEARLY
FULL SUNSHINE. THE STRONGER HEATING OVER THE PALMER DIVIDE WILL
CAUSE THE AIRMASS TO DE-STABILIZE THERE FIRST. THE LATEST RUNS OF
THE HRRR AND RAP SHOW THE STRONGEST CONVECTION DEVELOPING OVER
DOUGLAS COUNTY BY SHORTLY AFTER 18Z. THE MORNING SOUNDING SHOWED A
PRECIPITABLE WATER OF .66 INCHES WHICH IS JUST SHORT OF THE RECORD
FOR MAY 1. SHOULD SEE A GOOD ROUND OF SHOWERS DEVELOP EARLY IN
THE AFTERNOON WHICH WILL DRIFT EASTWARD. THE OTHER MAIN AREA OF
PRECIPITATION IS EXPECTED TO DEVELOP OVER THE CHEYENNE RIDGE AFTER
ABOUT 21Z WHICH WILL MOVE OVER THE NORTHERN PLAINS ZONES THROUGH
THE EVENING. WITH CAPE VALUES IN THE 1000-1500 J/KG RANGE THIS
AFTERNOON...STORMS MAY GET STRONG ENOUGH TO PRODUCE SOME HAIL
CLOSE TO 1 INCH IN DIAMETER. OTHERWISE...THEY WILL PRODUCE BRIEF
HEAVY RAIN AND SOME GUSTY WINDS. MOST THUNDERSTORM ACTIVITY ALONG
THE FRONT RANGE SHOULD BE DONE BY EARLY EVENING...WITH THE FOCUS
OF CONVECTION THROUGH THE EVENING OUT ON THE NORTHEAST PLAINS.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 337 AM MDT FRI MAY 1 2015

MUCH OF THE SHOWERS HAVE DISSIPATED OVER THE NORTHEAST PLAINS WITH
JUST A FEW LIGHT SHOWERS EXITING WASHINGTON AND PARK COUNTIES.
STILL QUITE A BIT OF STRATUS AROUND AT VARIOUS LEVELS AND IS NOT
WIDESPREAD OR UNIFORM. NO FOG BEING REPORTED YET BUT STILL EXPECT
SOME PATCHY FOG STILL TO DEVELOP OVER LOW LYING AREAS AS SOME
T/TD SPREADS ARE ONLY 2-5 DEGREES.

COLORADO WILL BE UNDER A MODERATE WESTERLY FLOW ALOFT TODAY
FOLLOWING LAST NIGHTS DISTURBANCE WITH STILL SOME UPSTREAM
MOISTURE TO WORK WITH. MOST IMPRESSIVE IS THE INCREASE IN PW
VALUES OVER THE PAST 24 HOURS...WITH INCREASES OVER .40" OVER THE
FRONT RANGE WITH READINGS AROUND .75" FROM INTEGRATED PW FROM GPS.
SHOULD SEE ANOTHER ROUND OF AFTERNOON/EVENING THUNDERSTORMS TODAY
GIVEN AMPLE MOISTURE AS SURFACE DEWPOINTS SHOULD REMAIN IN THE
40S. THIS WILL RESULT IN SURFACE BASED CAPES FROM 800-1500J/KG.
THERE IS SOME INITIAL STABILITY WITH LOW LEVEL INVERSIONS AROUND
750MB THIS AM WHICH MODELS EVENTUALLY ERODE BY LATE AFTERNOON.
EXPECT HIGHER COVERAGE OF STORMS TODAY OVER FRONT RANGE FOOTHILLS
AND PALMER DIVIDE AND LOWER COVERAGE OVER THE FAR PLAINS AS HIGHER
STABILITY REMAINS. GIVEN CAPE VALUES AND THE INCREASE SHEAR ALOFT
COULD BE A FEW SEVERE STORMS WITH HAIL UP TO ONE INCH IN DIAMETER
AND DAMAGING WINDS. NOT MUCH HELP UPSTAIRS TODAY AS QG VERTICAL
VELOCITY FIELDS INDICATE A NEUTRAL TO SLIGHTLY SUBSIDENT AIRMASS.
STORMS SHOULD FOLLOW DIURNAL TRENDS WITH MOST STORMS ENDING BEFORE
MIDNIGHT.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 337 AM MDT FRI MAY 1 2015

EXPECT THE UPPER RIDGE TO REMAIN ALOFT ON SATURDAY. AT THE
SURFACE...A TROUGH DIGGING ALONG THE EASTERN CO PLAINS WILL HELP
MIX OUT THE POST FRONTAL STABLE AIRMASS FOR MUCH WARMER
TEMPERATURES. SHOWERS AND STORMS ARE NOT EXPECTED TO FORM UNTIL
THE AFTERNOON WITH SOME DECENT CAPE OVER THE FAR EASTERN PLAINS.
COULD SEE SOME STRONGER STORMS IN THE LATE AFTERNOON AND EARLY
EVENING OUT THAT WAY.

ANOTHER COLD FRONT IS PROGGED TO PUSH DOWN THE PLAINS SUNDAY
COMBINED WITH MOISTURE ADVECTING UP FROM NEAR BAJA. LOOK FOR
COOLER TEMPERATURES AND AN INCREASE IN SHOWER AND STORM COVERAGE.
AN UPPER LOW WILL DIG DOWN OVER SRN CALIFORNIA/BAJA SUNDAY NIGHT.

THIS UPPER LOW WILL PUSH EAST EARLY MONDAY THEN GET PICKED UP AND
BROUGHT NORTHEAST OVER THE STATE AS A LARGER LOW OVER THE PACIFIC
NORTHWEST MOVES ONSHORE TUESDAY. UPSLOPE FLOW FROM SUNDAY NIGHT IS
EXPECTED TO CONTINUE THROUGH TUESDAY AFTERNOON AS THE UPPER LOW
APPROACHES. THIS WILL BRING A VERY GOOD CHANCE FOR RAIN SHOWERS
AND THUNDERSTORMS TO THE AREA MONDAY THROUGH TUESDAY AFTERNOON.
HAVE PUT POPS IN THE HIGH CHANCE CATEGORY...WITH THE FAR EASTERN
PLAINS SEEING LIKELY POPS ON TUESDAY AFTERNOON. THEN AS THE UPPER
LOW PUSHES NORTHEAST OF THE AREA AND A SURFACE LOW FORMS OVER THE
EASTERN COLORADO PLAINS...CHANCES WILL START DECREASING FROM THE
SOUTH BUT WILL STILL SEE SHOWERS AROUND THROUGH WEDNESDAY. SYSTEM
WILL BE QUITE WARM WITH SNOW LEVELS REMAINING AROUND 10KFT.

PAST WEDNESDAY REMAINS AN UNCLEAR FORECAST...AS MODELS CONTINUE
TO STRUGGLE WITH THE EVOLUTION AND TRACK OF THE PACNW UPPER LOW.
MODELS HAD BEEN SEEMING TO TAKE A MORE SOUTHERLY TRACK...UNTIL THE
00Z EC CAME IN PUSHING IT BACK FARTHER NOR TH. HOWEVER...EITHER
WAY...MOISTURE WILL CONTINUE TO BE PRESENT WEDNEDAY INTO
THURSDAY...THE MODEL DIFFERENCES WILL MAINLY AFFECT TEMPERATURES.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z SATURDAY MORNING)
ISSUED AT 1028 AM MDT FRI MAY 1 2015

WILL MENTION THE BEST TIME FOR THUNDERSTORMS ACROSS THE DENVER
AREA AIRPORTS FROM 3 PM THROUGH ABOUT 7 PM. OVERNIGHT...THINGS
SHOULD CLEAR OUT NICELY WITH DECENT DRAINAGE WINDS WHICH SHOULD
KEEP FOG OR STRATUS FROM DEVELOPING. NO OTHER AVIATION IMPACTS ARE
EXPECTED AFTER THE ROUND OF AFTERNOON THUNDERSTORMS.

&&

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

$$

UPDATE...DANKERS
SHORT TERM...ENTREKIN
LONG TERM...KRIEDERMAN
AVIATION...DANKERS


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