Quantitative Precipitation Forecast
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
000
FOUS30 KWBC 151432
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1032 AM EDT SUN OCT 15 2017

...VALID 15Z SUN OCT 15 2017 - 12Z MON OCT 16 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...



...CHANGES TO THE EXCESSIVE RAINFALL OUTLOOK DEFINITION AND
THRESHOLD PROBABILITIES...

NOTE TO USERS...ON FRIDAY OCTOBER 14TH WPC IMPLEMENTED CHANGES TO
THE EXCESSIVE RAINFALL OUTLOOK. THE DEFINITION OF THIS PRODUCT
CHANGES FROM A POINT PROBABILITY TO A NEIGHBORHOOD PROBABILITY. BY
CAPTURING MORE AREA AROUND A POINT...THE PROBABILITIES ASSOCIATED
WITH EACH RESPECTIVE CATEGORY WILL NECESSARILY INCREASE. SEE THE
GRAPHIC LEGEND FOR THE NEW PROBABILITIES. THE PRODUCT WILL LOOK
AND BEHAVE THE SAME AS IT ALWAYS HAS...BUT STUDIES SHOW THAT THE
RISK CONTOURS WPC DRAWS ARE BETTER CALIBRATED TO THE NEW
DEFINITION AND HIGHER ASSOCIATED PROBABILITIES. THESE CHANGES
BETTER ALIGN THE EXCESSIVE RAINFALL OUTLOOK WITH OTHER OUTLOOKS
FROM NATIONAL CENTERS...AND THE PRODUCT IS NOW DEFINED AS THE
PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE WITHIN 40
KM OR 25 MILES...OF A POINT.


...OUTLOOK FOR 15Z SUNDAY TO 12Z MONDAY...

THE PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE IS LESS
THAN 5 PERCENT.

THE ONLY AREA OF SOME CONCERN IS ALONG THE CENTRAL GULF COAST. A
SMALL PLUME OF ENHANCED COLUMN MOISTURE WAS DRIFTING ONSHORE FROM
SOUTHEAST LOUISIANA TO SOUTHERN MISSISSIPPI AND ALABAMA. SPOTTY
CONVECTION WITH HEAVY LOCAL RAIN IS EXPECTED THIS AFTERNOON AND
EVENING. INCREASING UPPER DIFLUENCE IN THE LARGE SCALE
PATTERN...ESPECIALLY THIS EVENING...COULD MAKE FOR MORE PRODUCTIVE
UPDRAFTS. AT LOW LEVELS...HOWEVER...INFLOW WILL BE VERY WEAK AND
INCONSISTENT...AND WITH DEEP LAYER SHEAR LESS THAN 20 KNOTS CELL
STRUCTURES SHOULD STRUGGLE TO SHOW ANY ORGANIZATION. BRIEF INTENSE
RAIN RATES ARE POSSIBLE...BUT GIVEN HIGH FLASH FLOOD GUIDANCE
VALUES THE NEIGHBORHOOD PROBABILITY OF EXCEEDANCE IS LESS THAN 5
PERCENT.

BURKE

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.