Quantitative Precipitation Forecast
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FOUS30 KWBC 190006
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
804 PM EDT THU AUG 18 2016

...VALID 01Z FRI AUG 19 2016 - 12Z FRI AUG 19 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 E MMCU 60 W MRF 10 SSW ODO 60 N DYS 30 S SPS 20 NE GLE
15 SE AQR 30 ESE MLC 20 S FYV FLP 30 SSE POF 20 NW MKL 30 N TUP
40 NNE JAN 25 S TVR 20 N AEX 35 N UTS 20 ESE ERV 60 SSW MMPG.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NNE CMY 10 ENE DKB 20 E VYS 25 SE MLI 15 NE IOW 20 WSW ALO
10 WNW SLB 15 S YKN 10 ENE ONL TIF 35 N OGA 25 ENE SNY 25 SW SNY
15 S IBM 30 SSW TOR 10 ESE AIA 60 SE IEN 35 W VTN 40 NW ICR
25 NW 9V9 15 NNE HON 20 WNW ATY 25 WSW VVV 10 SW GHW 15 WSW LXL
20 W JMR ROS 15 NNE OEO 20 NNE CMY.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 NNW CTD 25 W LND 25 E JAC 25 S LVM 35 N LVM 45 W LWT
15 NNE LWT 45 ESE LWT 35 SSW JDN 25 W MLS 60 SSW MLS 30 NE BYG
10 SE BYG 30 WSW BYG 15 NNE GEY 40 NNE COD 20 NNW COD 40 S COD
25 S WRL 30 SW IDV 25 NW TMH CPR PAT 30 NNW CTD.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 SSE OTG 25 SSW FSD 25 SE 9V9 25 E HON OVL 15 WSW LVN
30 NE AXA 20 SSE OTG.


19/0100 UTC UPDATE...
SOME REALIGNMENT OF THE MARGINAL RISK AREA WAS MADE WHILE
INTRODUCING A SLIGHT RISK FOR PORTIONS OF THE NRN PLAINS INTO SRN
MN/NW IA.  RECENT SATL AND RADAR IMAGERY HAS SHOWN A RAPID
INCREASE IN CONVECTION ACRS WRN/NRN NEBRASKA AND BEGINNING TO
EXPAND INTO SRN SD ALONG A SW/NE ORIENTED FRONTAL BNDRY EXTENDING
FROM WRN NEB INTO SE SD AND INTO SRN MN.  THESE STORMS WERE DVLPG
ALONG A RIBBON OF HIGH ML CAPES OF BETWEEN 3 TO 5 THSD J/KG
EXTENDING ALONG THE BNDRY FUELED BY STG INSOLATION FROM CLEAR
SKIES SOUTH OF THE FRONT THUR AFTN..AS WELL AS DECENT LOW LEVEL
CONVERGENCE ALONG THE BNDRY AND HEIGHT FALLS/UPR DIFFLUENCE AHEAD
OF IMPLUSE ACRS WRN SD/ND AND STGR ONE OVER SW WY.    RECENT
BLENDED PWS AND GPS DERIVED PWS INDICATED AN INCREASE IN PWS
BETWEEN 1.5 TO 1.75 FOCUSING JUST NORTH OF THE BNDRY FROM SRN/SE
SD INTO SRN MN.  RECENT HRRR PARALLEL RUNS CONTINUE TO SHOW A
RAPID EXPANSION OF STORMS ENEWD ALONG THE FRONT THIS EVENING
TOWARD HIER SFC DPS AND PWS WHICH WILL ALLOW FOR IMPROVED RAINFALL
RATES.  WITH DEEP LAYERED NEARLY PARALLEL FLOW ALONG THE FRONT AND
INCREASING RT ENTRANCE REGION FORCING DVLG OVER THE REGION
TONIGHT...POTNL FOR ORGANIZED TRAINING BANDS ARE PSBL.  CONSENSUS
OF RECENT HRRR AND HRRR PARALLEL RUNS WOULD SUGGEST POTNL FOR
LOCAL 2 TO 3"+ RAINS IN SEVERAL HOURS..ESPECIALLY ACRS THE SLIGHT
RISK AREA.  SEE MPD#578 VALID UNTIL 0515Z FOR FURTHER INFORMATION.

ELSEWHERE...ONLY SMALL REDUCTIONS TO MARGINAL RISK AREAS WERE MADE
WHERE EXCESSIVE RAIN THREAT APPEARS QUITE MINIMAL.  SULLIVAN
PREVIOUS DISCUSSION FOLLOWS...


...EASTERN PORTIONS OF THE NORTHERN PLAINS INTO THE UPPER MS
VALLEY...

EARLY MORNING CONVECTION WAS ALREADY ACTIVE AHEAD OF THE FRONT
PUSHING EASTWARD INTO THE NORTHERN PLAINS. UPPER DIFLUENCE
EXPECTED TO REMAIN WELL DEFINED WITHIN AN AXIS OF ABOVE AVERAGE PW
VALUES OVER MINNESOTA AND THE EASTERN DAKOTAS...WHILE SURFACE LOW
PRESSURE TRACKS ALONG THE ADVANCING FRONT TOWARD SOUTHWEST
MINNESOTA BY EVENING. WHILE THIS WEATHER SYSTEM IS EXPECTED TO
REMAIN PROGRESSIVE...THERE MAY BE A PERIODS OF TRAINING CELLS NEAR
AND AHEAD OF THE SURFACE LOW...WITH THUNDERSTORM INTENSITY AND
FLASH FLOOD POTENTIAL TENDING TO MAXIMIZE WITH THE DIURNAL CYCLE
THIS EVENING. HI-RES GUIDANCE SHOWS FAIRLY GOOD AGREEMENT IN THE
QPF SIGNAL OVER THIS REGION...GENERALLY DEPICTING A NARROW AXIS 1
TO 2 INCHES OF RAIN WITH EMBEDDED 3 TO 4 INCH TOTALS...WHICH SEEMS
TO TELL AN ACCURATE STORY. MOISTURE FLUX FROM THE NAM/GFS SHOW A
PROGRESSIVE SYSTEM...WITH FORCING MOVING DOWN A PSEUDO WARM FRONT
TOWARD NORTHERN IOWA AND ILLINOIS OVERNIGHT. GIVEN MID RANGE FLASH
FLOOD GUIDANCE VALUES...WE WILL MAINTAIN A MARGINAL RISK OF
EXCESSIVE RAINFALL...WHILE IT IS LIKELY THAT A FEW SMALL SCALE
LOCATIONS WILL SEE CELL MERGERS / TRAINING AND SOME ELEVATED RISK
OF FLASH FLOODING.


...NORTHERN ROCKIES INTO THE NORTHERN HIGH PLAINS...

STRENGTHENING UPPER DIFFLUENCE ASSOCIATED WITH THE AFOREMENTIONED
AMPLIFYING TROF AND STRENGTHENING POST FRONTAL UPSLOPE FLOW ACROSS
THE CENTRAL AND NORTHERN HIGH PLAINS INTO THE NORTHERN ROCKIES
WILL SUPPORT INCREASING PRECIPITATION COVERAGE...ESPECIALLY LATE
AFTERNOON INTO THURSDAY NIGHT/EARLY HOURS OF FRIDAY MORNING. MODEL
CONSENSUS IS FOR AN ORGANIZED AREA OF MODERATE TO HEAVY PRECIP
TOTALS STRETCHING FROM CENTRAL AND SOUTH CENTRAL MONTANA TOWARD
SOUTHEAST WYOMING. MOISTURE POOLING ALONG AND NORTH OF THE SURFACE
BOUNDARY WILL BOOST PRECIPITABLE WATER VALUES...ESPECIALLY OVER
SOUTHERN WYOMING INTO ADJACENT WESTERN NEBRASKA...WHERE THE MODELS
SUGGEST A FEW SPOTS OF HEAVIER RAINFALL PERHAPS EXCEEDING 1.5 OR
2.0 INCHES LOCALLY. THE MARGINAL RISK AREA WAS EXPANDED SOUTH AND
EASTWARD IN THE 15Z UPDATE.


...PORTIONS OF THE SOUTHERN PLAINS INTO THE LOWER MS VALLEY...

NO SIGNIFICANT MOVEMENT EXPECTED TO THE AXIS OF ABOVE AVERAGE PW
VALUES CURRENTLY STRETCHING FROM CENTRAL TO EASTERN TX INTO THE
LOWER MS VALLEY.  ADDITIONAL WIDESPREAD SCATTERED CONVECTION IS
LIKELY ACROSS THESE AREAS...OWING TO A COMBINATION OF SUFFICIENT
HEATING/INSTABILITY AND LOCALLY ENHANCED SYNOPTIC ASCENT WITH
SHORTWAVES RIDING ON THE NORTHWEST SIDE OF THE UPPER RIDGE AND
ALONG THE SOUTHERN EDGE OF THE WESTERLIES. HEAVIER BOUTS OF RAIN
WILL TEND TO OCCUR ON SMALLER SCALES WHICH LOWERS CONFIDENCE.
GENERALLY SPEAKING...HEAVIER CONCENTRATIONS OF RAIN MAY OCCUR NEAR
MESOSCALE CONVECTIVE VORTICES IN ARKANSAS AND IN SOUTHWEST
TEXAS...WHILE ANTECEDENT CONDITIONS AND THE PROSPECT OF SCATTERED
HEAVY DOWNPOURS CAUSES US TO MAINTAIN A BROAD MARGINAL RISK
EXTENDING DOWN THROUGH CENTRAL/SOUTHEAST TEXAS AND MUCH OF
LOUISIANA.

BURKE/ORAVEC
$$





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