Quantitative Precipitation Forecast
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FOUS30 KWBC 281447
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
946 AM EST TUE FEB 28 2017

...VALID 15Z TUE FEB 28 2017 - 12Z WED MAR 01 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 W SAD 30 ESE CGZ 10 NNE CGZ 35 NE FFZ 35 WSW SOW 25 S SOW
45 SSE SOW 55 NNE SAD 60 NNW SVC 45 NW SVC 25 NE SAD 45 W SAD.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NW DUJ 20 E EKN 20 ESE JKL 15 N GEV 1A5 15 SSE CBM
35 SSW GLH 30 N ELD 15 NNW RUE 20 S CPS 15 S MQB 10 SE IIB
10 WNW RQB 20 SW CYKF 20 NW DUJ.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 ESE FWC 20 WSW HAO 10 NNE UNI 15 NW CRW 10 N JKL 30 WSW HOP
25 NW BYH 35 WNW POF 10 ESE FWC.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 E PWK LAN DTW 15 ENE DFI 25 NE TIP 20 ESE C75 25 E PWK.


...MIDDLE AND LOWER MISSISSIPPI VALLEY / TENNESSEE AND OHIO
VALLEYS / LOWER GREAT LAKES...

1500 UTC UPDATE...

MADE A FEW MINOR TWEAKS TO THE PREVIOUS DAY 1 ERO...MAINLY TO
EXPAND THE MARGINAL RISK S-SE TO ACROSS THE LOWER MS VLY AND INTO
THE LOWER TN VALLEY. THIS IS BASED ON CURRENT TRENDS WITH THE
OBSERVATIONAL DATA (ESPECIALLY COMPOSITE RADAR IMAGERY)...WITH
SOUTHWESTERLY 850 MB FLOW OF 40-50 KTS AND RESULTANT ANOMALOUS
MOISTURE TRANSPORT (+3 STANDARD DEVIATIONS ABOVE NORMAL) FEEDING
INTO THE CONVECTION ACROSS NORTHERN MS/AL AND SOUTHERN TN.
DELINEATING BETWEEN THE "MARGINAL" AND "SLIGHT" AREAS REMAINS THE
MOST CHALLENGING ASPECT WITH THIS CURRENT OUTLOOK. TO THAT
END...HAVE CONTINUED TO UTILIZE A MULTI-FACETED APPROACH IN
OUTLINING THE SLIGHT RISK AREAS... INCLUDING WHERE HIGHEST
MULTI-MODEL DETERMINISTIC QPF (PARTICULARLY WITH HIGH-RES CAM
GUIDANCE) OVERLAP THE LOWER 1 AND 3 HOURLY FLASH FLOOD GUIDANCE
ALONG WITH AREAS NOT HIGHLIGHTED IN THE DROUGHT MONITOR.

HURLEY


PREVIOUS DISCUSSION BELOW...


IN A PATTERN LOOKING MORE LIKE APRIL THAN FEBRUARY...WITH RECORD
WARMTH AND PLENTIFUL COVERAGE OF 1.00-1.25 INCH PRECIPITABLE WATER
OVER THE EASTERN U.S...THE NOW ESTABLISHED FULL LATITUDE TROUGH IN
THE WEST WILL SWING INTO A NEUTRAL TILT BY WEDNESDAY MORNING OVER
THE PLAINS...SPURRING AN OUTBREAK OF CONVECTIVE PRECIPITATION FROM
THE MISSOURI / MISSISSIPPI VALLEYS EASTWARD. SYNOPTIC FORCING IS
STRONG ENOUGH THAT MESOSCALE INFLUENCES WILL NOT ENTIRELY
DOMINATE...SO THERE IS A FAIR AMOUNT OF AGREEMENT TO THE QPF
PATTERN FROM MULTIPLE MODELS.

WITH SUCH A DEEP TROUGH THERE WILL BE MULTIPLE CORRIDORS OF
ENHANCED LOW LEVEL AND UPPER LEVEL JET STRENGTH...LEADING TO
RELATIVELY GREATER FOCUS TO THE PRECIPITATION PATTERN ALONG
CERTAIN WSW-ENE ORIENTED SWATHS. ONE SUCH FOCUS IS LIKELY TO
AFFECT NORTHERN ILLINOIS ACROSS PARTS OF IN/MI...WHILE ANOTHER IS
LIKELY TO AFFECT MO/AR ACROSS THROUGH MUCH OF KY...AND ADJACENT
SOUTHERN IN/OH. THIS LATTER SWATH WILL SEE BROADER INFLOW AND
GREATER INSTABILITY WITHIN THAT INFLOW...BUT THE NORTHERN SWATH
WILL SEE CELL MOTIONS ORIENTED A BIT MORE PARALLEL TO THE MEAN
WIND...WHICH ENHANCES THE POTENTIAL FOR TRAINING. THERE HAS BEEN A
HEAVY RAIN SIGNAL ALONG BOTH OF THESE SWATHS
DATING BACK A FEW DAYS IN THE MODELS.

HEAVY LOCAL RAIN RATES WILL BE POSSIBLE THROUGHOUT THE EASTERN
U.S. AS FAR EAST AS THE SPINE OF THE APPALACHIANS. COVERAGE WILL
LIKELY INCREASE...HOWEVER...WITH EASTWARD EXTENT...CULMINATING IN
A PRONOUNCED HEAVY RAIN THREAT ALONG THE OHIO RIVER AND INCLUDING
MUCH OF KENTUCKY THIS EVENING/OVERNIGHT...AS STRONG MOISTURE FLUX
ANOMALIES DEVELOP...WITH POTENTIAL FOR REDEVELOPMENT AND TRAINING
ALONG THE FLANKS OF VARIOUS CONVECTIVE OUTFLOWS.


...ARIZONA / NEW MEXICO...

PERSISTENT RAIN RATES OF A FEW TENTHS OF AN INCH EVERY 6 HOURS
WILL CONTINUE THROUGH MIDDAY FROM THE MOGOLLON RIM INTO THE GILA
MOUNTAINS AND EXTENDING INTO FAR SOUTHWEST NEW MEXICO. ADDITIONAL
RAINFALL TOTALS OF UP TO ONE INCH ARE POSSIBLE BELOW THE SNOW
LINE...AND MAY CAUSE A FEW RUNOFF ISSUES. ANTECEDENT STREAM FLOWS
WERE ALREADY NEAR OR ABOVE NORMAL IN SOME CASES PER THE NATIONAL
WATER MODEL.

BURKE
$$





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