MESOSCALE PRECIPITATION DISCUSSION 0851
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
827 PM EDT SUN OCT 01 2017

AREAS AFFECTED...CENTRAL NEBRASKA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 020027Z - 020527Z

SUMMARY...THUNDERSTORMS INITIATING OVER CENTRAL NEBRASKA JUST
AHEAD OF A COLD FRONT MAY TRAIN AND PRODUCE A CORRIDOR OF HEAVY
RAINFALL AND LOCALIZED FLASH FLOODING THIS EVENING.

DISCUSSION...AS OF 00Z A CONTINUOUS LINE OF THUNDERSTORMS HAD
DEVELOPED JUST AHEAD OF A COLD FRONT...PERHAPS ALONG A PRE-FRONTAL
TROUGH...FROM NEAR NORTH PLATTE NE TO NEAR ONIELL NE. RADAR
RAINFALL ESTIMATES MAY BE A BIT HAIL CONTAMINATED GIVEN THE
NUMEROUS REPORTS OF HAIL WITH THESE STORMS. HOWEVER...A MESONET
SITE NEAR TAYLOR NE IN LOUP COUNTY DID RECENTLY MEASURE ABOUT 0.6
INCHES OF RAIN IN 20 MINUTES...SO SOME 1-2 INCH PER HOUR RAIN
RATES SEEM ACHIEVABLE WITH TRAINING STORMS THIS EVENING.

SEVERAL FACTORS MAY LIMIT THE FLASH FLOOD THREAT. FIRST...PORTIONS
OF THE OUTLINED DISCUSSION AREA ARE IN OR NEAR THE NEBRASKA SAND
HILLS WHICH ARE HYDROLOGICALLY LESS FAVORABLE FOR FLASH FLOODING.
SECOND...THE HRRR INDICATES VERY LOW SOIL SATURATION PERCENTAGES
IN THE AREA SUGGESTING THAT THE SOIL MAY BE ABLE TO ABSORB SOME
RAIN BEFORE RUNOFF BEGINS IN EARNEST. THIRD...THE DEEPER MOISTURE
EXISTS FURTHER TO THE EAST WITH CIRA LAYER PRECIPITABLE WATER
PRODUCTS INDICATING THE AXIS OF DEEPER MOISTURE SITUATED CLOSER TO
THE NE-IA BORDER. THIS MAY REDUCE PRECIPITATION EFFICIENCY ACROSS
CENTRAL NEBRASKA.

NEVERTHELESS...THE AFOREMENTIONED BAND OF CONVECTION IS ORIENTED
ROUGHLY PARALLEL TO THE MEAN FLOW AND THIS IS EXPECTED TO CONTINUE
FOR ANOTHER FEW HOURS BEFORE THE MEAN FLOW BEGINS TO VEER AS THE
LEAD SHORTWAVE KICKS NORTH OF THE AREA. WITH A WELL-ESTABLISHED
BAND OF THUNDERSTORM ACTIVITY...THIS MAY ENABLE PERSISTENT HEAVY
RAINFALL AT SOME LOCATIONS FOR 2-3 HOURS AND THE POTENTIAL FOR A
FEW INCHES OF RAIN IN A SHORT PERIOD OF TIME AND LOCALIZED FLASH
FLOODING. THE RAP SUGGESTS THIS MAY FOCUS FURTHER TO THE SOUTHEAST
LATER IN THE EVENING...AS THE NOSE OF THE LOW-LEVEL JET FOCUSES
NEAR OR JUST SOUTH OF I-80 IN SOUTH-CENTRAL NEBRASKA.

LAMERS

ATTN...WFO...FSD...GID...GLD...LBF...OAX...

ATTN...RFC...MBRFC...

LAT...LON   43569783 43179762 42439753 41569810 40919811
            40069905 40020011 40110076 40340107 41030118
            41610047 41999992 42449931 43029869