Quantitative Precipitation Forecast
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686
FOUS30 KWBC 251839
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 PM EDT THU AUG 25 2016

...VALID 1838Z THU AUG 25 2016 - 12Z FRI AUG 26 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NE MLF 30 W 4HV 35 ESE BCE 35 SW PGA 15 SE 40G 50 W GCN
30 WNW SGU 70 WNW CDC 55 W MLF 20 NE MLF.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 SW KGVX 20 WSW KGVX 10 S IAH IAH 15 NW SHV 35 ESE MLC
20 SSE FSM 20 SSW LLQ 35 S HEZ 15 NNW NEW 40 NNE KMIS 30 NW KIKT.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
80 SW MRF 25 W MRF 60 S GDP 20 SSW GDP 20 NNW GDP 15 NE ALM
15 ESE 4MY 20 ESE 4SL 20 W E33 25 NE DRO 20 ESE CEZ 35 SSE CNY
15 W GJT 20 WSW EEO 15 NNE 20V 15 W LAR 10 SSE PUM BJC MNH
20 WNW PUB 35 NNW TAD 35 WNW CAO 10 E GUY 10 SE DDC 20 WSW BIE
30 SE LWD 10 SSE BRL 20 SSW ASW 35 SSW CXPT 15 NW HZY 25 SW ART
30 NW RUT ORE BAF 25 NNE MPO 20 SSE LBE 15 SSE VTA 25 SE AID
25 SSE AID 30 S TAZ 15 W TBN 10 N FSI 45 WNW SNK 30 N FST
35 SSE FST 55 SSW 6R6.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
50 SE CDJ 60 SSE OJC PWA 25 NNW LTS 35 SSE AMA 15 SW BGD
15 S GAG 20 WSW MHK 15 NNE MCI 50 SE CDJ.


18Z UPDATE...
ADJUSTED SLIGHT RISK AREA A BIT SOUTHWARD ACRS THE TX PANHANDLE
INTO OK/ERN KS/WRN MO GIVEN TREND OF LATEST HI RES GUIDANCE WHICH
HAVE COME SOUTH AS WELL DURING THE THUR OVERNIGHT PD.  THIS TREND
LOOKS REASONABLE GIVEN  LOCATION OF FRONTAL BNDRY AS OF 18Z AND
POOL OF GREATER THAN 1000 J/KG MLCAPES ALIGNING ALONG AND JUST
SOUTH OF THE FRONT.  STGR SFC HEATING SOUTH OF THE BNDRY HAS
ALLOWED CU FIELD TO EXPAND ALONG AND SOUTH OF THE FRONT FIRST
CELLS BEGINNING TO SHOW UP ACRS THE TX PANHANDLE AND WRN OK
SUPPORTING RECENT HRRR TRENDS.  SLIGHT STRENGHENING OF UPR WINDS
AHEAD OF WELLL DEIFNED UPR CIRC OVER SRN NM SHOULD ENCOURAGE
FURTHER EXPANSION OF STORMS ALONG AND JUST NORTH OF THE SFC FRONT
DURING THE REMAINDER OF THE AFTN AND ESPECIALLY TONIGHT.  INFLOW
INTO THE FRONT MAY BE BALANCED BY DEEPER LAYERED FLOW FOR A PERIOD
OVERNIGHT SUPPORTING A SLOW MOVING OR NEARLY STATIONARY BAND OF
STGR CONVECTION FROM THE TX PANHANDLE NEWD THRU WRN OK/SE KS AND
NRN MO..ALSO SUPPORTED BY DECENT RT ENTRANCE REGION JET. SULLIVAN
PREVIOUS DISCUSSION FOLLOWS

SOUTHERN PLAINS INTO THE MIDWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THE MAIN RAINFALL FOCUS ACROSS THE LOWER 48 STATES THIS PD WILL BE
ALONG SLOWLY PROGRESSIVE FRONTAL BNDRY WHERE A POOL OF DEEPER
MOISTURE LURED AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE WILL BE LURED WITH LOW LEVEL INFLOW IN THE 20-30 KTS RANGE
THURSDAY NIGHT.  THERE IS A MODERATELY STRONG CONSENSUS BETWEEN
THE GLOBAL AND MESOSCALE GUIDANCE ON A MORE FOCUSED HEAVY QPF AREA
DEVELOPING THURSDAY NIGHT IN SOUTHEAST KS INTO WESTERN MO AS A
SHORTWAVE PIVOTS THROUGH CO.  THIS SHOULD HELP INCREASE LOW LEVEL
JET WITH THE USUAL NOCTURNAL TIMING.  A FAVORABLY SLIGHTLY CURVED
UPPER JET MAXIMUM LIES TO THE NORTH. FAIRLY UNIDIRECTIONAL FLOW
COULD SUPPORT CELL TRAINING.  THE MESOSCALE (AND 00Z NAM) GUIDANCE
INDICATE THE POTENTIAL FOR LOCAL AMOUNTS IN THE 3-6" RANGE, WHICH
WOULD EXCEED FLASH FLOOD GUIDANCE VALUES ACROSS SOUTHEAST KS AND
WESTERN MO.  CONSIDERED A MODERATE RISK, BUT ENOUGH SPREAD EXISTED
IN THE GUIDANCE TO LEAD TO ENOUGH UNCERTAINTY TO MAINTAIN THE
PREVIOUS DAY 2 IDEA OF A SLIGHT RISK.


SOUTHERN GREAT LAKES/NY/PA
~~~~~~~~~~~~~~~~~~~~~~~~~~
A CONTINUATION OF THE ONGOING CONVECTIVE COMPLEX IS EXPECTED TO
MOVE EASTWARD ALONG AND JUST SOUTH OF THE SOUTHERN FRINGES OF THE
GREAT LAKES BEFORE BRIEFLY WEAKENING DURING THE MORNING HOURS.
PRECIPITABLE WATER VALUES OF 1.75"+ ALONG WITH SUFFICIENT
LOW-LEVEL INFLOW AND BUILDING INSTABILITY DUE TO DAYTIME HEATING
DURING THE LATE MORNING/AFTERNOON AND OUTFLOW BOUNDARIES WITH
OVERNIGHT/MORNING ACTIVITY SHOULD REFIRE CONVECTION FROM SOUTHEAST
MI/NORTHERN OH INTO NORTHERN PA AND SOUTHERN NY.  THE EXACT AXIS
OF THE HIGHEST AMOUNTS IN THIS REGION REMAINS IN QUESTION.  LOCAL
AMOUNTS IN THE 2-4" RANGE ARE INDICATED BY THE MESOSCALE GUIDANCE
IN THIS AREA, WHICH COULD EXCEED THE LOCAL FLASH FLOOD GUIDANCE
VALUES OVER A SEVERAL COUNTY AREA AROUND NORTHERN OH, SUGGESTING A
SLIGHT RISK.  UNCERTAINTY IN PLACEMENT OF THE QPF AXIS KEPT THIS
AREA IN THE MARGINAL RISK CATEGORY.


ROCKIES/GREAT BASIN/SOUTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
AN UPPER TROUGH AMPLIFYING ACROSS THE NORTHERN AND CENTRAL ROCKIES
WILL PROVIDE COOLING ALOFT, WHILE EMBEDDED WEAKER IMPULSES
INTERACTING WITH AVERAGE AMOUNTS OF MOISTURE FOR LATE AUGUST WILL
SUPPORT WIDESPREAD SCATTERED CONVECTION ACROSS MUCH OF THE
ROCKIES, GREAT BASIN, AND SOUTHWEST.  SOME LOCALLY ENHANCED
AMOUNTS WILL BE POSSIBLE ACROSS EASTERN CO DUE TO A MODEST UPSLOPE
COMPONENT.  THE MESOSCALE GUIDANCE INDICATES LOCAL AMOUNTS IN THE
2-3" RANGE ARE POSSIBLE, WHICH COULD EXCEED THE RELATIVELY LOW
FLASH FLOOD GUIDANCE VALUES IN CO AND CAUSE ROCK/MUD SLIDES IN
DESERT LOCATIONS.  SINCE ONLY A FEW SPOTS ARE EXPECTED TO SEE THIS
SORT OF RAIN, CONTINUED THE MARGINAL RISKS PREVIOUSLY SEEN IN THE
DAY 2 EXCESSIVE RAINFALL FORECAST.


LOUISIANA/ARKANSAS
~~~~~~~~~~~~~~~~~~
AN AXIS OF ABOVE AVERAGE PW VALUES MOVING WEST ALONG SOUTHERN
PERIPHERY OF SUBTROPICAL RIDGE -- ASSOCIATED WITH A DYING RELIC OF
A FRONTAL ZONE -- WILL MOVE INTO THE CENTRAL AND WESTERN GULF
COAST LEADING TO AN EXPANSION OF MAINLY DIURNAL THUNDERSTORMS.
THE MESOSCALE GUIDANCE SHOWS LOCAL AMOUNTS IN THE 2-4" RANGE,
WHICH WOULD CAUSE PROBLEMS IN ANY RIVER BASINS STILL EXPERIENCING
FLOODING FROM THE RAINS OF A COUPLE WEEKS AGO ACROSS SOUTHERN LA.
THIS INDICATES A SLIGHT RISK COULD BE WARRANTED.  HOWEVER, FLASH
FLOOD GUIDANCE VALUES HAVE NEARLY RECOVERED IN THE INTERIM AND THE
GUIDANCE INDICATE A RANDOM SMATTERING OF HIGHER AMOUNTS, DUE TO
THE PULSE THUNDERSTORM ENVIRONMENT EXPECTED.  MAINTAINED THE
MARGINAL RISK DUE TO THE LACK OF ORGANIZATION EXPECTED IN THIS
CONVECTIVE REGIME.

ROTH
$$





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