Quantitative Precipitation Forecast
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000
FOUS30 KWBC 300040
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
839 PM EDT FRI MAY 29 2015

...VALID 01Z SAT MAY 30 2015 - 12Z SAT MAY 30 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SSE JXN 10 NNE JYM OEB HAI 10 NE GYY 10 NNW IKK 15 WNW TIP
15 SE DEC 15 NE SLO 15 WNW HSB 15 SW PAH 10 ENE DYR 15 SE HKA
10 N OLV 20 E UTA 30 SSE UTA 10 NNW GLH 25 W GLH 20 SE BQP
15 N AEX DRI 25 S JAS 15 ENE CXO 30 E CLL 20 SSE TPL 10 WNW GRK
35 W BWD 40 NNW SJT 35 SE BPG 10 SW BPG 45 NNW MDD 40 NE HOB
55 NNE HOB 50 SSE CVN 30 ESE CVN 40 E CVN 35 NNW PVW 30 SSE AMA
45 S PPA 35 N CDS 25 NW LTS 30 E HBR 15 NW CHK 15 WNW CQB
30 E SWO 15 SSW BVO 10 W CFV 10 SSW CNU 40 E UKL 35 ENE LXT
25 WNW IRK 25 SSW OTM 10 NNW TNU 25 NE AMW MCW 10 WSW RST EAU
10 SSW PBH ARV IMT 20 ENE MCD 25 NW CWNL 10 ESE CYZE 15 WNW CWWX
20 SSW CXCY 15 SSE CWGD 25 NNE CTZR 10 WSW PHN PTK 10 SSE JXN.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
55 S F05 40 NW RPH 30 WNW GLE 15 SW 1F0 15 NW GYI 15 E GYI
25 NE TKI 15 E TKI HQZ 15 ESE JWY 15 NNW INJ 15 E SEP SEP
30 NNW 7F9 20 ENE ABI 15 N DYS 35 NNW DYS 55 NNE SWW 65 NE SNK
55 SSW F05 55 S F05.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 NNW HRO 35 N SGF JEF 30 W FAM UNO 25 SE FLP 30 E RUE
10 NE RUE 35 NW RUE 30 NNW HRO.



...SOUTHERN PLAINS TOWARD THE LOWER MS VALLEY...

THE MAIN FOCUS DURING THE FIRST PART OF THE PERIOD IS ACROSS THE
LOWER TO MID MS VALLEY...WHERE CONVECTION DEVELOPING OVER AR/MO
ALONG A LOW LEVEL SURFACE TROUGH HAS BEEN PRODUCING FLASH
FLOODING. THE CONVECTION DEVELOPED ON THE WESTERN EDGE OF A MLCAPE
AXIS. EAST OF THE AXIS...THE LOW LEVEL SOUTHERLY FLOW CONTINUES TO
FEED 2500 J/KG AIR INTO MO/AR. THE HIGH CAPE VALUES ARE RESULTING
IN SEVERE WEATHER ALONG WITH THE FLASH FLOODING...BUT AS THE LOW
LEVEL JET INCREASES ABOVE THE RELATIVELY STABLE SURFACE
INVERSION...THE COLUMN MOISTENS...AND THE MAIN CONVECTIVE MODE
SHIFTS FROM SEVERE WEATHER TO FLASH FLOODING.

THE 25 TO 35 KNOT LOW LEVEL INFLOW TRANSPORTS 1.75 INCH
PRECIPITABLE WATER VALUES INTO THE CONVECTIVE AXIS... WHICH FEEDS
CONVECTIVE LINES MOVING NORTH IN THE WAKE OF THE MCV. THE BROAD
UNIDIRECTIONAL FLOW SUPPORTS THIS TYPE OF CONVECTION MOVEMENT
THROUGH 30/06Z OVER WESTERN AND CENTRAL AR/MO. GIVEN THE DEEP
INSTABILITY AND RICH SUPPLY OF HIGH MOISTURE CONTENT AIR...THE
HIGHEST QPF AMOUNTS ARE EXPECTED ALONG THIS AXIS. WHILE THE ONE
AND THREE HOUR FLASH FLOOD VALUES REMAIN FAIRLY HIGH...THE
POTENTIAL FOR TRAINING SHOULD BE THE MAIN DRIVER OF FLASH
FLOODING. WITH THIS IN MIND...A MODERATE RISK IS INTRODUCED INTO
PORTIONS OF CENTRAL AR/MO...WHERE THE CONSENSUS OF THE HIGH
RESOLUTION GUIDANCE MODELS PLACE THE HIGHEST QPF IN THE NEAR TERM.
THE FOCUS FOR THE HIGHEST THREAT SHIFTS NORTHWARD THROUGH
30/12Z...AS THERE ARE A NUMBER OF BOUNDARIES FOR CONVERGENT FLOW
ACROSS MO DURING THIS TIME.

FURTHER SOUTHWEST...A MODERATE RISK REMAINS IN PLACE OVER NORTH
CENTRAL TX WHICH WAS HIT HARD BY ORGANIZED CONVECTION THU
NIGHT/FRI MORNING. ACTIVITY DEVELOPED ACROSS THE TERRAIN OF
EASTERN NM...AND THIS ACTIVITY BECOMES THE FOCUS FOR ADDITIONAL
CONVECTIVE DEVELOPMENT AS IT TRACKS INTO NORTH TX. ADDITIONAL
HEIGHT FALLS EXPECTED...IN THE WAKE OF THE MCV...PUSH EAST
SOUTHEASTWARD ACROSS NORTH TO NORTH CENTRAL TX TONIGHT INTO SAT.
THIS WILL ENHANCE UVVS ALONG AND AHEAD OF THE SOUTHWARD MOVING
COLD FRONT OVER THE SOUTHERN PLAINS... SUPPORTING POTENTIAL FOR
ADDITIONAL ORGANIZED CONVECTION OVER NORTH AND NORTH CENTRAL TX
OVERNIGHT...INTO SOUTHEAST TX DURING SAT. THERE IS A GOOD SIGNAL
IN THE LATEST MODEL GUIDANCE FOR ORGANIZED ACTIVITY.
HOWEVER...THERE ARE STILL DIFFERENCES WITH THE
DETAILS...ESPECIALLY HOW QUICKLY THE CONVECTION PUSHES DOWNSTREAM
AND AT WHAT AXIS THE MAX PRECIP OCCURS.  WITH NOT A HIGH LEVEL OF
CONFIDENCE WITH RESPECT TO THE AXIS...WPC WENT WITH SOMEWHAT OF A
COMPROMISE BETWEEN THE FARTHER NORTH AXES OF THE CMC GEM AND NAM
CONEST AND THE FARTHER SOUTH HI RES ARW AND 1200 UTC ECMWF...BUT
DID TREND FASTER TO MOVE CONVECTION DOWNSTREAM GIVEN THE MODEL
BIAS TO BE TOO SLOW. THERE MAY BE A PERIOD OF TRAINING OF CELLS IN
A WEST TO EAST DIRECTION ALONG AND SOUTH OF THE FRONT OVERNIGHT
INTO SAT ACROSS NORTH TO NORTH CENTRAL TX.  WITH RECENT HEAVY
RAINS LOWERING FFG VALUES....ADDITIONAL RUNOFF PROBLEMS
LIKELY...ESPECIALLY IF THE HEAVY RAINS GET BACK INTO THE
DALLAS-FORT WORTH AREA HIT HARD IN ACTIVITY THU NIGHT.


...UPPER MS VALLEY/GREAT LAKES...

00Z SOUNDINGS FROM KGRB AND KDTX SHOWED SBCAPE VALUES BETWEEN 1500
AND 2000 J/KG AHEAD OF A SURFACE FRONT CROSSING THE GREAT LAKES
DURING THE EVENING. LOW LEVEL CONVERGENCE AND UPPER LEVEL
DIFFLUENCE BETWEEN THE SHORT WAVE OVER WESTERN ONTARIO AND RIDGING
OVER THE MIDWEST CONTINUES TO SUPPORT CONVECTIVE DEVELOPMENT...AND
MOISTURE AND INSTABILITY SHOULD BECOME FOCUSED IN LINES AHEAD OF
THE FRONT. THE 1.60 INCH PRECIPITABLE WATER AIR (WHICH IS TWO
STANDARD DEVIATIONS ABOVE THE MEAN) SUPPORTS THE POTENTIAL FOR
HIGH RAINFALL RATES...AND CONVECTION IN LINES SUPPORTS THE
POTENTIAL FOR TRAINING.

FURTHER WEST INTO EASTERN IA AND SOUTHERN WI...00Z SOUNDINGS SHOW
MUCH LESS IN THE WAY OF INSTABILITY...ON THE AXIS OF THE
PRECIPITABLE WATER GRADIENT. THE THREAT FOR FLASH FLOODING SHOULD
LESSEN WITH TIME AS THE FOCUS ALONG THE FRONT MOVES EAST.


ORAVEC/HAYES


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