Tough week for DEN forecasters

[Portastorm]

Interesting forecast discussion this morning from the Denver NWS office. Gives you a good idea on all of the things forecasters struggle with in difficult forecasts. This particular forecaster spells out many parameters to take into consideration. They have a tough job, especially this week!

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.LONG TERM...AS THE NEXT SYSTEM MOVES CLOSER TO THE FORECAST AREA
...MY CONFIDENCE WITH THE VARIED AND CONFLICTING MODELS IS
CONSIDERABLY LESS THAN THE PREVIOUS SHIFT. GRANTED...THE NAM HAS
COME AROUND FAIRLY CLOSE TO THE GFS SOLUTION THROUGH 72 HOURS
CONCERNING BOTH THE NORTH AND SOUTH CLOSED CENTERS ON THE 500 MB
HEIGHT FIELDS. BY 84 HOURS THE TWO DIVERGE SUCH THAT THE
PROBABILITY OF HEAVY SNOW COULD MERELY BE A DREAM. THEN THERE IS
THE 27.00Z ECMWF WHICH IS RELATIVELY CLOSE TO THE GFS THROUGH 96
HOURS. THE OTHER MODELS...CANADIAN...NOGAPS...UKMET SHOW THE UPPER
LOW IN VARIOUS LOCATIONS...SOME NOT CONDUCIVE TO PRODUCING A LARGE
SNOWFALL HERE.

I AM WONDERING ABOUT HOW FAR SOUTH THE CENTERS ARE
CONCERNING IDEAL LOCATION FOR A LARGE AMOUNT OF SNOW FOR THE
FORECAST AREA. ALSO WHAT AFFECT WILL THE NORTHERN CLOSED CENTER
HAVE ON THE OVERALL SYNOPTIC SCALE ENERGY AND THE LARGE SCALE FLOW?
WHAT HAPPENS WHEN THE CENTERS MERGE AND WHERE WILL THAT LOCATION
BE? DOES IT EVEN REALLY EVEN LOOK LIKE THAT? THE QG VERTICAL
VELOCITY FIELDS ON THE NAM AND GFS HAVE DECENT UPWARD MOTION FOR THE
FORECAST AREA THURSDAY...GETTING STRONGER UPWARD BY THURSDAY
NIGHT...DECREASING FRIDAY...BUT STILL UPWARD THROUGH MOST OF THE DAY
OVER AT LEAST THE EASTERN HALF OF OUR AREA. IN FACT THE GFS KEEPS
UPWARD MOTION OVER THE EASTERN PORTIONS OF THE FORECAST AREA FOR
MUCH OF THE WEEKEND.

BOTH MODELS BRING A SURGE OF UPSLOPE AND A
COLDER AIRMASS INTO THE FORECAST AREA THURSDAY MORNING. CROSS
SECTIONS OF MOISTURE AND QPF FIELDS OF THE NAM ARE WAY MORE
FAVORABLE FOR HEAVY SNOW PRODUCTION COMPARED TO THE GFS...ESPECIALLY
ON FRIDAY. BY FRIDAY NIGHT...THE GFS GETS BETTER...THE NAM DRIES
OUT SOME. THIS ALL HAVING TO DO WITH THE LOCATION OF THE UPPER
FEATURES. THERE IS ALSO THE TIMING ISSUE. WILL NEED TO BRING THE
PRECIPITATION/POPS IN SLOWER ON THURSDAY WITH BOTH MODELS IN MIND.
WILL NEED TO KEEP POPS GOING IN SOME AREAS WELL INTO THE WEEKEND
WITH THE GFS. FOR TEMPERATURES...THURSDAY`S HIGHS ARE 5-8 C COLDER
THAN WEDNESDAY`S. FRIDAY IS 4-6 C COLDER THAN THURSDAY. OF
NOTE...THIS SYSTEM IS NOT SHAPING UP AS A "NO-BRAINER" STORM LIKE
THE PREVIOUS ONE WAS...FORECAST-WISE. THE MODELS DID PRETTY WELL ON
THAT ONE. TIME WILL TELL ON THIS NEW ONE. ONE THING IS THAT THE
ANTI-CYCLONIC UPSLOPE IS MORE SIGNIFICANT WITH THIS STORM AND THE
COLDER AIRMASS MOVING IN IS MORE SIGNIFICANT TOO. TRY AS I MIGHT TO
WARN FOR THIS STORM ON THIS UPDATE...THERE ARE TO MANY ISSUES SO
WILL CONTINUE THE WATCH FOR NOW.