Quantitative Precipitation Forecast
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000
FOUS30 KWBC 192212
QPFERD

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

...VALID 2211Z SUN FEB 19 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
50 E MMMY 50 S MMNL 10 WSW COT 25 W ERV 45 N ABI 15 SSW LTS
15 SSE JWG SWO 25 W RVS 20 N AQR 10 NNW GVT 25 W TYR 35 SSE PSN
IAH 25 NW KGVX 25 SSE KBQX 40 SSE KBBF.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
120 WSW OTH 80 W OTH 55 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 25 SW TVL 45 S TVL 45 NE MOD 25 ENE SCK
10 E SCK 15 WSW MOD 35 SW MCE 25 NW PRB 20 E SBP SMX 30 W VBG
60 SW 87Q.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 W 3T5 10 SW CLL 20 ESE CLL 25 W SGR PSX KRP RBO 30 N ALI
30 ESE SSF 20 W 3T5.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 N LUD RPH 40 NW RPH 10 SE FDR 20 WSW CHK OUN 15 NE PVJ 1F0
10 N LUD.

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 30 NNE STS 20 SW VCB
15 NW SUU SUU CCR LVK 20 ENE RHV 25 ESE RHV 20 E WVI 10 N MRY
50 W WVI 65 WSW SFO.


SPECIAL 22Z UPDATE...

...SOUTHERN PLAINS...

AT 2145Z SCATTERED THUNDERSTORMS WERE INITIATING OVER CENTRAL
TEXAS AND WESTERN NORTH TEXAS 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 AHEAD OF A STRONG SHORTWAVE
EVIDENT IN SATELLITE IMAGERY...AND THE OTHER STRADDLING THE RED
RIVER INTO SOUTHERN OKLAHOMA...WITH THAT AREA PERHAPS BEING BETTER
SUPPORTED BY BROAD SCALE ASCENT NORTH OF A WARM FRONT AND NEAR THE
INFLECTION POINT IN THE UPPER LEVEL FLOW. WITH 12Z GUIDANCE
TRENDING TOWARD HEAVIER SWATHS OF RAIN NEAR THE RED RIVER AND INTO
SOUTHERN OKLAHOMA...WE ARE EXPANDING THE MARGINAL RISK OF
EXCESSIVE RAINFALL INTO THIS AREA. ADDITIONALLY...THERE APPEARS TO
BE A HIGH LIKELIHOOD OF SOME TRAINING AND BACKWARD PROPAGATION IN
THE NEAR TERM...THROUGH 06Z...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. THEREFORE...WE EMBEDDED
A SMALL SLIGHT RISK AREA FOR NORTH TX / SOUTHERN OK.

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. LATER IN THE
NIGHT...HOWEVER...DEEP LAYER FORCING AND LOW LEVEL INFLOW ARE
FORECAST TO COME BETTER INTO PHASE TOWARD SOUTHEAST TEXAS...WHERE
WE MAINTAIN A SMALL SLIGHT RISK AREA...COINCIDENT WITH AN AREA OF
WETTER ANTECEDENT CONDITIONS.

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...

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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