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 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FOUS30 KWBC 050100
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
900 PM EDT SAT JUL 04 2015

...VALID 01Z SUN JUL 05 2015 - 12Z SUN JUL 05 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 NW POE 10 SW SLR 10 ENE DUA 30 SE MLC 35 WSW M89 10 W BQP
TVR 20 NE JAN 30 NW TCL 20 WSW DCU 45 N MSL 20 E CKV 20 ESE GLW
1A6 45 NNW AVL 25 WNW CEU 10 NNW LGC 20 N GZH 30 NW MOB 10 S BTR
35 E CWF 30 NW POE.


...NORTHEAST TEXAS THROUGH THE SOUTHEAST STATES AND INTO EASTERN
TENNESSEE...

AFTERNOON MCS ACTIVITY HAD WET THE GROUND OVER MUCH OF NORTHERN
LOUISIANA AND CENTRAL/SOUTHERN MS/AL. BY LATE EVENING CONVECTION
WAS RACING INTO MORE STABLE AIR OVER GEORGIA...BUT OTHER
CONVECTION HAD BEEN SUSTAINED BACK OVER SOUTHEAST OKLAHOMA AND
ALONG THE TX/LA BORDER...WITHIN A REGION OF PERSISTENT 850-700 MB
CONFLUENCE AND ADVECTION OF MOISTURE / THETA-E. THE ZONE WITH WET
ANTECEDENT CONDITIONS WILL BE ESPECIALLY PRONE TO RAPID RUNOFF
SHOULD NEW ORGANIZED CONVECTION OCCUR. THIS APPEARS MOST PROBABLY
ALONG THE AFORE-MENTIONED GRADIENTS IN OK/TX/LA....BUT PERHAPS
ALSO AFFECTING SOUTHWEST ARKANSAS AND/OR ADVECTING TOWARD MS BY
MORNING. THIS WHOLE REGION SITS WITHIN A CHANNEL OF ENHANCED 700
MB FLOW AT THE BASE OF THE EASTERN U.S. LARGE SCALE TROUGH. MODEL
SIGNAL FOR HEAVY RAIN OVERNIGHT IS SPOTTY WITHIN THIS REGION...BUT
THE ODDS OF HEAVY RAINFALL MAY INCREASE LATE IN THE NIGHT AS
850-700 MB SOUTHWESTERLY FLOW IS FURTHER ENHANCED ON THE BACK SIDE
OF A PASSING SHORTWAVE OVER THE LOWER MS VALLEY.

FARTHER NORTH AND EAST...EARLY MORNING CONVECTION HAD STABILIZED A
ZONE RUNNING ACROSS NORTHERN MS/AL/GA AND FAR SOUTHERN TN. IT IS
UNLIKELY THAT SIGNIFICANT SURFACE BASED OR NEAR-SURFACE BASED
INSTABILITY WILL DEVELOP IN THOSE AREAS...BUT MID LEVEL HEIGHT
FALLS WILL TRACK IN THAT DIRECTION...WITH A WELL DEFINED 600 MB
LOW FORECAST OVER NASHVILLE BY SUNDAY MORNING. AHEAD OF THIS
FEATURE...EFFICIENT CONVECTIVE CELLS...ROOTED AT MID LEVELS...HAD
ALREADY BROKEN OUT OVER TENNESSEE AS OF 01Z. RESIDENCE OF HEAVY
RAINFALL OVER A PARTICULAR LOCATION IS NOT LIKELY TO LAST MORE
THAN ABOUT AN HOUR...GIVEN A LACK OF INFLOW...BUT FLASH FLOOD
GUIDANCE VALUES ARE LOW IN THIS REGION...ESPECIALLY ACROSS EASTERN
TENNESSEE. MODELS HAVE SHOWN A CONSISTENT SIGNAL FOR MODERATE
RAINFALL...WHICH WAS ALREADY EVIDENCED BY THE LATE EVENING
ACTIVITY IN CENTRAL TN.

...ARIZONA AND NEW MEXICO...

MONSOON STYLE CONVECTION IN NORTHERN AZ AND FAR WESTERN NM MAY
MAINTAIN MODERATE INTENSITY THROUGH ABOUT 03 TO 04Z WITHIN AN AREA
OF MIXED LAYER CAPE VALUES THAT WERE STILL RUNNING BETWEEN
500-1000 J/KG PER THE SPC MESO-ANALYSIS AT 00Z. THE VALUES OF
MODEL CAPE AND SIMULATED REFLECTIVITY DROP OFF SHARPLY LATER
SATURDAY EVENING. FARTHER SOUTH...SOME HEAVIER DOWNPOURS MAY
ADVECT UP INTO FAR SOUTHERN AZ LATE IN THE EVENING/OVERNIGHT AS A
SMALL INVERTED TROUGH LIFTS OUT OF MEXICO PER THE RAP AND NAM/GFS.
IN ALL CASES...THE RISK OF EXCESSIVE RAINFALL WAS ISOLATED...WITH
ODDS LESS THAN 5 PERCENT OF EXCEEDING FLASH FLOOD GUIDANCE AT ANY
GIVEN POINT.

...NORTH DAKOTA AND MINNESOTA...

SYNOPTIC FEATURES...INCLUDING DIFLUENT UPPER LEVEL FLOW IN ADVANCE
OF A MEDIUM WAVELENGTH TROUGH...WILL OVERLAP FAVORABLY WITH
INSTABILITY AND LOW LEVEL INFLOW TO SUPPORT CONVECTION WELL INTO
THE NIGHT ACROSS ND AND NORTHERN MN. THE PRE-CONVECTIVE
ENVIRONMENT WILL BE CHARACTERIZED BY A BROAD RIBBON OF
PRECIPITABLE WATER VALUES AROUND 1.25 INCHES...INCREASING ABOVE
THAT MARK WHERE MOISTURE IS POOLED NEAR THE APPROACHING
THUNDERSTORMS LATER TONIGHT. THE RAP FORECASTS MOST UNSTABLE CAPE
VALUES TO REMAIN PRETTY RESPECTABLE...AT GREATER THAN 1500 J/KG
EVEN AT 06Z...AS A 30 KNOT LOW LEVEL JET KEEPS THE LOWER
ATMOSPHERE MIXED. INDIVIDUAL CELLS AND LINE SEGMENTS SHOULD BE
PROGRESSIVE...BUT THERE IS POTENTIAL FOR SOME BACKWARD PROPAGATION
INTO THE LOW LEVEL INFLOW...AND BROAD SCALE LIFT MAY ALLOW FOR A
PERIOD OF REDEVELOPMENT ALONG OUTFLOWS AND SOME TRAINING TO BOOST
RAINFALL TOTALS. THE HIGH RESOLUTION MODELS HAVE A SIMILAR SIGNAL
TO ONE ANOTHER...PRODUCING LOCAL RAINFALL AMOUNTS ABOVE 2 INCHES
OVERNIGHT IN MAINLY NORTHEAST ND AND NORTHWEST MN. THIS SUGGESTS
RATES COULD EXCEED THE 1 OR 3 HOUR FLASH FLOOD GUIDANCE IN THAT
REGION.

BURKE/PEREIRA
$$




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