Public Information Statement
Issued by NWS Great Falls, MT

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
NOUS45 KTFX 101538
PNSTFX
MTZ008>015-044>055-151800-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE GREAT FALLS MT
936 AM MDT WED AUG 10 2016

...RAINFALL INTENSITIES AND RAINFALL REPORTS AUGUST 9-10 2016 NORTH
CENTRAL MONTANA...

INTENSE RAINFALL RATES ACCOMPANIED THUNDERSTORMS (SOME SEVERE)
ACROSS CENTRAL AND NORTH-CENTRAL MONTANA TUESDAY AFTERNOON INTO
EARLY WEDNESDAY MORNING. OVER THREE INCHES OF RAIN WERE REPORTED IN A
24- HOUR PERIOD IN THE GREAT FALLS AREA. WINDS GUSTED TO 58 MPH AT
TWO LOCATIONS IN THE GREAT FALLS AREA AND AT THE HAVRE AIRPORT. GUSTS
REACHED 66 MPH SOUTHWEST OF RUDYARD AND NEAR WINIFRED. ADDITIONALLY
HAIL AS LARGE AS 1.25-INCHES FELL AROUND GREAT FALLS AND ROY.
ALTHOUGH SEVERE WEATHER IN THE FORM OF HAIL AND WINDS WERE REPORTED,
THESE STORMS WERE NOTABLE IN THEIR RAINFALL RATES. MOST OF THE RAIN
AMOUNTS IN THE GREAT FALLS AREA FELL IN A VERY SHORT PERIOD OF TIME.
RAINFALL RATES WERE IN THE 2.5 TO 3.5 INCHES PER HOUR RANGE AT
TIMES. THIS CAUSED SHORT-TERM FLOODING IN AREAS WITH THE GREATEST
RAINFALL AMOUNTS.

AT THE GREAT FALLS AIRPORT, THE RECORD AMOUNT OF RAIN IN A 24-HOUR
PERIOD IS 3.42-INCHES, SET IN MAY 1980. THE GREATEST 1-HOUR AMOUNT
IS 1.13 INCHES ON JUNE 20, 1991. ON AN HOURLY BASIS, AMOUNTS IN THE
GREAT FALLS ON TUESDAY EXCEEDED THIS AMOUNT.
FOR OTHER PERIODS, THE RECORD HIGHEST AMOUNT AT GREAT FALLS IN 30
MINUTES WAS 1.04-INCHES ON JULY 14, 2012. ON THIS DATE, 0.66 INCHES
FELL IN A 15 MINUTE PERIOD. THIS IS LIKELY THE LAST OCCURRENCE OF
RAINFALL RATES OF THE INTENSITY SEEN ON AUGUST 9 AT GREAT FALLS.

ON JUNE 20, 2003 AT HAVRE, RAINFALL WAS 0.59 INCHES IN 5 MINUTES AND
0.93 INCHES IN 10 MINUTES. IF SUSTAINED, THIS WOULD HAVE BEEN A RATE
OF 5.50-INCHES PER HOUR. RAIN RATES ON TUESDAY AFTERNOON WERE AROUND
1.2 INCHES PER HOUR AT HAVRE.

WHAT IS THE RETURN PERIOD OF THESE VALUES?
A PAPER PRESENTED AT AN AMERICAN METEOROLOGICAL SOCIEITY CONFERENCE
IN 1986 SHOWED THE FOLLOWING:

         AMOUNT OF PRECIPITATION IN PERIOD
 RETURN PD 2-YEAR                            100-YEAR
   5   10    15    30 (MIN)            5   10    15    30  (MINUTES)
0.39  0.58  0.69  0.85              0.37  0.56  0.69  0.87
(ARKEL AND RICHARDS (OFFICE OF HYDROLOGY, NWS, 1986)

THE NOAA PRECIPITATION FREQUENCY ATLAS DATA FOR RETURN PERIOD IN A 6-
HOUR PERIOD FOR MUCH OF NORTH CENTRAL MONTANA IS SUMMARIZED BELOW:

2-YEAR  5-YEAR  10-YEAR  25-YEAR  50-YEAR  100-YEAR
1.05    1.40     1.60     2.00     2.20     2.50

AMOUNT OF PRECIPITATION IN 24-HOUR PERIOD ENDING 6 AM AUGUST 10,
2016 FOLLOWS. THIS TABLE SHOWS ONLY AMOUNTS OF GREATER THAN 0.50".

LOCATION            AMOUNT    COUNTY          PROVIDER
                   (INCHES)
GREAT FALLS 5.6SW     3.12    CASCADE         MESONET
GREAT FALLS 16TH S    2.26    CASCADE         COOP
GREAT FALLS WEST HL   2.20    CASCADE         MESONET
GREAT FALLS DWNTWN    2.25    CASCADE         MESONET
GREAT FALLS CMR       1.63    CASCADE         DAVISNET
CARTER 0.6S           1.50    CHOUTEAU        DAVISNET
BLACK EAGLE           1.45    CASCADE         DAVISNET
RUDYARD 20S           1.44    CHOUTEAU        DAVISNET
DARKHORSE LAKE        1.40    BEAVERHEAD      SNOTEL
LAKEVIEW RIDGE        1.40    BEAVERHEAD      SNOTEL
ROCKER PEAK           1.40    JEFFERSON       SNOTEL
HAVRE MUD LAKE        1.33    HILL            DAVISNET
GREAT FALLS 4S        1.27    CASCADE         PUBLIC
FLOWEREE              1.25    CHOUTEAU        COCORAHS
PIKE CREEK            1.20    GLACIER         SNOTEL
HAVRE ST JOE          1.14    HILL            MESONET
DIVIDE                1.10    MADISON         SNOTEL
GREAT FALLS FLOOD RD  1.04    CASCADE         HADS
GREAT FALLS NWS       1.00    CASCADE         NWS
CHESTER               0.99    LIBERTY         MESONET
ULM 8S                0.94    CASCADE         MESONET
CHOTEAU 6.7SW         0.87    TETON           MESONET
GALATA 16SSW          0.86    LIBERTY         COOP
HAVRE 1S              0.85    HILL            MESONET
VIRGELLE              0.85    CHOUTEAU        HADS
BYNYM PERKINS         0.83    TETON           MESONET
CHESTER COTTONWOOD    0.81    LIBERTY         MESONET
GREAT FALLS AIRPORT   0.78    CASCADE         ASOS
ULM 1S                0.77    CASCADE         AGRIMET
HAVRE AIRPORT         0.74    HILL            ASOS
BIG SANDY 13WNW       0.73    CHOUTEAU        MESONET
GIBSON RESERVOIR      0.73    LEWIS AND CLARK HADS
MALMSTROM AFB         0.72    CASCADE         AWOS
RUDYARD 19S           0.69    CHOUTEAU        COOP
HAVRE 2.1WSW          0.67    HILL            DAVISNET
HINGHAM               0.67    HILL            DAVISNET
ILIAD 4W              0.67    CHOUTEAU        DAVISNET
OILMONT 10NE          0.66    TOOLE           DAVISNET
PENDROY RICE RIDGE    0.66    PONDERA         MESONET
RUDYARD 13SW          0.66    LIBERTY         DAVISNET
GOAT HAUNT            0.63    GLACIER         DCP
LITTLE BULLWHACKER    0.63    BLAINE          RAWS
HAVRE 10SW            0.60    HILL            DAVISNET
MANY GLACIER          0.60    GLACIER         SNOTEL
WALDRON               0.60    PONDERA         SNOTEL
HELENA 1SE            0.57    LEWIS AND CLARK MESONET
CUT BANK 10SSW        0.56    GLACIER         DAVISNET
CHINOOK               0.55    BLAINE          COOP
FORT ASSINNIBOINE     0.54    HILL            SCAN
ST MARY               0.53    GLACIER         RAWS
FLOWEREE W            0.50    CHOUTEAU        MESONET

THESE DATA ARE PRELIMANARY AND HAVE NOT UNDERGONE FINAL QC BY NCEI.
THEREFORE THESE DATA ARE SUBJECT TO REVISION. FINAL AND CERTIFIED
CLIMATE DATA CAN BE ACCESSED AT THE NATIONAL CENTERS FOR
ENVIRONMENTAL DATA AT HTTP://WWW.NCEI.NOAA.GOV

$$
&&

NNNN



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