Quantitative Precipitation Forecast
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000
FOUS30 KWBC 200040
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
739 PM EST SUN FEB 19 2017

...VALID 01Z MON FEB 20 2017 - 12Z MON FEB 20 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
60 W MMNL 15 WNW MMPG 15 ESE E29 DYS 15 NNE CSM 30 N WDG
25 E PNC 25 WNW OKM 30 SE DUA 10 ENE TYR 20 ESE UTS 25 WNW KGVX
25 SSE KBQX 40 SSE KBBF.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
160 WNW CEC 145 WSW OTH 70 W OTH 35 SSW OTH 30 ENE CEC
40 NE ACV 25 NW O54 10 N O54 25 ENE O54 30 NNE RDD 25 ENE RDD
35 ENE RBL 35 NE OVE 10 SE BLU 30 WSW TVL 50 S TVL 40 NNE MCE
35 NNE MOD 10 ESE SCK 30 SSW MOD 45 ESE SNS 20 SE PRB SMX
30 SW VBG 60 WSW VBG 85 SSW 87Q.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 N LUD 15 W MWL 35 WSW BWD 30 S ABI 40 WNW RPH FDR 15 W CHK
OUN 15 NE PVJ 1F0 15 N LUD.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 ESE PWG 15 WSW PSN 25 WNW CXO 5R5 20 WSW PKV 45 WSW VCT
20 SSE AUS 30 ESE PWG.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
55 W O87 40 NW O87 20 NNE O87 30 N UKI 25 NNE STS 10 SE SUU
15 ENE RHV 25 NE SNS 20 SE SNS 30 NNE 87Q 15 WSW PRB 25 WNW SBP
40 WSW 87Q 80 W 87Q 90 WSW MRY.


...SOUTHERN PLAINS...

AT 0030Z CONVECTION HAD SHOWN ITSELF CAPABLE OF TRAINING SOUTH TO
NORTH WITHIN DEEP LAYER SOUTHERLY FLOW...AFFECTING PARTS OF BOTH
TEXAS AND OKLAHOMA. THE GREATEST NEAR TERM CONCERN WILL BE CENTRAL
TEXAS AND WESTERN NORTH TEXAS. A WELL DEFINED SHORTWAVE EMBEDDED
ON THE EAST SIDE OF A LARGER SCALE TROUGH...WAS TRACKING A BIT
MORE TOWARD CENTRAL TEXAS THAN IN PREVIOUS FORECASTS...AS
EVIDENCED BY SATELLITE IMAGERY AND RAP FORECASTS...THE LATTER OF
WHICH THROUGH 06Z EXPANDS MID LEVEL ASCENT INTO THE WESTERN PART
OF THE HILL COUNTRY AND UP THROUGH THE BIG COUNTRY WEST OF FORT
WORTH. ADDITIONALLY...NARROWER BANDS OF CONVECTION OVER SOUTHWEST
AND CENTRAL OKLAHOMA WILL PRODUCE HEAVY RAINFALL. THE OKLAHOMA
MESONET AT WEATHERFORD MEASURED NEARLY AN INCH OF RAIN IN 30
MINUTES THROUGH 0020Z.

THUNDERSTORMS WERE OCCURRING WHERE THE LEADING EDGE OF LARGE SCALE
HEIGHT FALLS OVERLAPPED WITH AN INSTABILITY AXIS. THROUGH THE
EVENING / OVERNIGHT PERIOD GUIDANCE IS STRONGLY SUGGESTIVE OF TWO
AREAS OF MAXIMUM COVERAGE AND INTENSITY OF CONVECTIVE
RAINFALL...ONE BEING OVER SOUTH TEXAS...ESPECIALLY LATER IN THE
NIGHT...AND THE OTHER STRADDLING THE RED RIVER INTO SOUTHERN
OKLAHOMA. THE SECOND AREA IS PERHAPS BEING BETTER SUPPORTED BY
BROAD SCALE ASCENT NORTH OF A WARM FRONT AND NEAR THE INFLECTION
POINT IN THE UPPER LEVEL FLOW. THE HRRR INSISTS ON TAKING HEAVY
RAIN POTENTIAL EVEN FARTHER NORTH TOWARD SOUTHERN KANSAS...WHICH
WOULD SEEM TO OUTPACE THE ABILITY FOR INSTABILITY TO DEVELOP
NORTHWARD...BUT BASED ON OBSERVATIONAL TRENDS WE DID EXPAND THE
MARGINAL RISK AREA UP TOWARD THE STATE LINE. THE RISK OF SOME
FLASH FLOODING APPEARS ESPECIALLY FOCUSED THROUGH 06Z IN
CENTRAL/NORTH TEXAS UP TO CENTRAL OKLAHOMA...WITH A LOW CROSSING
ANGLE BETWEEN THE 0-6KM WIND AND FORWARD PROPAGATING CORFIDI
VECTORS...COUPLED WITH LIGHT BACKWARD PROPAGATING CORFIDI VECTORS.
PRECIPITABLE WATER VALUES OF 1.25 INCHES REPRESENTS 3 TO 4
STANDARD DEVIATIONS ON THE PLUS SIDE FOR MID FEBRUARY...AND LOW
LEVEL INFLOW WILL BE BETTER CONCENTRATED HERE COMPARED TO AREAS
FARTHER SOUTH...AT LEAST THROUGH THE FIRST HALF OF THE NIGHT.

FARTHER SOUTH...THE INITIAL CONVECTION RUNNING OFF THE HIGH
TERRAIN OF THE SIERRA MADRE INTO FAR SOUTH TX MAY STRUGGLE TO
PRODUCE FLOOD CONCERNS DUE TO VEERING LOW LEVEL FLOW AND GREATER
EVAPORATIVE POTENTIAL / COLD POOL GENERATION. LATER IN THE
NIGHT...HOWEVER...DEEP LAYER FORCING AND LOW LEVEL INFLOW ARE
FORECAST TO COME BETTER INTO PHASE TOWARD SOUTHEAST TEXAS. WHERE
THIS OCCURS HAS JOSTLED AROUND IN THE HRRR...BUT GENERALLY HAS
BEEN TRENDING A BIT FARTHER INLAND FROM THE COAST NORTH OF
VICTORIA...WHICH WOULD BE CONSISTENT WITH THE SHARP SHORTWAVE
COMING OUT A LITTLE FARTHER NORTH/WEST.

IN BOTH OF THE SLIGHT RISK AREAS DEEPENING MOISTURE/INSTABILITY
AND POTENTIAL FOR SOME CELL TRAINING COULD SUPPORT SOME LOCAL 2-3"
RAINS OVER 1 TO 3 HOURS...WITH AN ASSOCIATED RISK OF FLASH
FLOODING.


...CALIFORNIA AND FAR SOUTHWEST OREGON...

REFER TO MESOSCALE PRECIPITATION DISCUSSION 0058 FOR THIS REGION.

THE ONSET OF THE NEXT POTENT EASTERN PACIFIC STORM IS EXPECTED
TONIGHT...INITIALLY DRIVEN BY DEEP WARM ADVECTION...AND THEN
STEADY AND STRENGTHENING SOUTHWESTERLY DEEP LAYER FLOW DIRECTED
INTO CENTRAL AND NORTHERN CALIFORNIA AND FAR SOUTHWEST OREGON. PER
THE ESRL ATMOSPHERIC RIVER DETECTION TOOL MODELED OFF THE
GFS...EXPECT ATMOSPHERIC RIVER CONDITIONS TO BE MET AFTER 06Z
TONIGHT ALONG A LONG STRETCH OF CALIFORNIA COASTLINE...WITH THE
CENTRAL CORRIDOR OF RICH MOISTURE CUTTING ACROSS SAN FRANCISCO
TOWARD THE SACRAMENTO VALLEY AND INTO THE SIERRAS. PRECIPITATION
WATER ANOMALIES WILL INCREASE UPWARDS TO 2-3 STANDARD DEVIATIONS
FROM NORMAL...AND HOURLY AND THREE-HOURLY RAIN RATES WILL LOCALLY
CLIMB ABOVE 0.50 INCHES AND 1.25 INCHES RESPECTIVELY. FOR MANY OF
THESE AREAS PRECIPITATION OVER THE PAST THREE MONTHS...NOV 17 -
FEB 17...RANKS IN THE TOP 5 ON RECORD...AND IS THE WETTEST SUCH
PERIOD AT SACRAMENTO PER THE REGIONAL CLIMATE CENTER PERSPECTIVES
TOOL. AS SUCH...THE INCOMING HEAVY RAIN IS LIKELY TO PRODUCE
FLOODING AND FLASH FLOODING...BEGINNING LATE TONIGHT...BUT
INCREASING ON MONDAY.

BURKE
$$





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