Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 200841
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
340 AM EST MON FEB 20 2017

...VALID 12Z MON FEB 20 2017 - 12Z TUE FEB 21 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 E KBBF 10 NE KBBF 10 SW PSX 25 SE 11R 30 S PSN 10 NNW 3T1
25 NNE PRX 35 NNE PRX 30 S RKR 20 N DEQ 20 SE DEQ 30 E OSA
35 ESE OSA 10 E GGG 25 SSE GGG 30 ESE OCH 20 W POE 15 SE ACP
15 E LFT PTN 15 N KEIR 20 ESE KVQT 20 ESE 3B6 35 SSE W60.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
140 W ACV 95 W CEC 70 NW CEC 40 SSW OTH 35 SSE OTH 15 W SXT
35 SSW SXT 30 ESE CEC 25 ESE ACV 20 WSW O54 15 ESE O54
20 NNW RDD 15 NNE RDD 10 ESE RDD 15 ENE RBL 30 NNE CIC 40 NE CIC
50 NE CIC 40 NNW BLU BLU 30 WSW TVL 60 ENE MOD 55 WNW MMH
35 WSW MMH 35 ENE FAT 35 NE VIS 15 NE PTV 10 NNW VIS FAT
15 ENE MAE 15 NE MCE 20 NNW MCE 15 SSW MOD 35 ENE WVI 30 E SNS
20 NE 87Q 15 S 87Q 75 SW 87Q 135 SW 87Q 195 WSW 87Q.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
145 WSW STS 110 SW UKI 85 SW UKI 65 SW UKI 30 SW UKI 10 ESE UKI
35 E UKI 15 NW VCB 15 NE VCB BAB 10 ESE CIC 25 NE CIC 35 ENE CIC
20 NW BLU BLU 30 ESE AUN 50 SSW TVL 50 NE MCE 35 NNE FAT
20 E FAT 20 ENE MAE 25 NE MAE 30 ENE MCE 35 NNE MCE 20 NE MOD
10 E SCK 20 ESE LVK SNS 20 N 87Q 15 N 87Q 20 WSW 87Q 55 SW 87Q
110 WSW 87Q 130 WSW 87Q.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 SSE KXIH 15 ENE KGVX 20 WNW KGVX 10 SW LBX 15 SSW IAH
10 ENE DWH 20 NE CXO 35 S LFK 25 SSW JAS 25 N BPT 15 ESE BPT
15 NW KVBS 15 SW KVBS.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
65 W SFO 35 SW STS STS 15 NW SUU 10 SW SAC MHR 10 NW AUN
15 ENE BAB 25 NNE OVE 30 E CIC 30 ENE OVE 20 WNW BLU 15 E AUN
35 SW TVL 50 NE MOD 40 NE MOD 30 NNE MOD 25 ENE SCK SCK 10 E LVK
15 SE LVK SNS 35 NNW 87Q 25 NW 87Q 30 WNW 87Q 40 W 87Q 70 W 87Q.


...N-CENTRAL CA...

A MAJOR PCPN EVENT THREAT REMAINS ON TAP. LATEST SATELLITE IMAGERY
AND MODELS STILL STRONGLY INDICATE THAT A STORM SYSTEM WILL TRACK
ENEWD TOWARD THE PAC NW WITH A TRIPLE POINT LOW STILL EXPECTED TO
REACH THE OREGON COAST BY MON MRNG. AHEAD/UNDERNEATH OF THIS
FEATURE...YET ANOTHER WELL DEFINED AND LONG FETCH ATMOSPHERIC
RIVER PLUME WITH ORIGINS WELL PAST HAWAII INTO THE
SUBTROPICALW-CENTRAL PACIFIC WILL BE DIRECTED WITH MAIN FOCUS INTO
THE CA COAST INVOF SFO BAY REGION INTO THE SANTA CRUZ MOUNTAINS
WITH INITIAL WARM FRONTAL BNDRY AS 85H WINDS INCREASE TO OVER
40KTS WITH PWS NEAR 1.25+ INCHES FOCUS INTO THE AREA MON MRNG.
AMSU MICOWAVE DATA OFFERS SOME EMBEDDED .3"/HR RATES THAT COULD
LATER DOUBLE INLAND AIDED BY TERRAIN LIFT. AS THE INITIAL WAVE
MOVES INLAND ACRS THE PAC NW MON MRNG...THE TRAILING COLD
FRONT/BAROCLINIC BNDRY IS EXPECTED TO HANG UP INVOF THE SFO BAY
REGION IN RESPONSE TO AN UPSTREAM DVLPG LOW PRES SYSTEM THAT IS
EXPECTED TO DEEPEN SEVERAL HUNDRED MILES OFF THE NRN CA COAST BY
LATE MON AFTN AND MAIN EFFECTS SLAM INLAND MONDAY NIGHT INTO TUE.
THE PROLONGED AND FOCUSED ATMOSPHERIC RIVER PLUME IS EXPECTED TO
LEAD TO VERY HEAVY RAINS OVER W/SW OR AND ESPECIALLY N-CENTRAL CA.
THIS INCLUDES A FOCUS FROM THE SFO BAY REGION EWD THROUGH THE
SACRAMENTO VALLEY INTO THE SIERRA RANGE WITH DEEP LAYERED SWLY
FLOW PROVIDING VERY FAVORABLE UPSLOPE COMPONENT TO THE SW FACING
MTN RANGE. DYNAMIC FORCING AND IMPRESSIVE MSTR PROFILES WILL BE
QUITE FAVORABLE IN SUPPORT FOR SOME OF THE HEAVIER RAINFALL TOTALS
SUGGESTED BY A CONSENSUS OF HI RES GUIDANCE HERE THAT SPOTS COULD
REACH UPWARDS OF 6-9" LIQUID LOCALLY THIS PERIOD OVER MOST FAVORED
TERRAIN. MAIN MODEL DIFFERENCES HAVE REVOLVED AROUND SMALL N/S
DIFFERENCES IN WHERE THE MAIN QPF AXIS WILL SET UP ACRS THE BAY
REGION...BUT SPREAD CONTINUES TO DECREASE APPROACHING THE EVENT.
THESE HEAVY RAINS WILL LEAD TO INCREASING RUNOFF ISSUES ACRS A
RATHER BROAD AREA OF CNTL/NRN CA GIVEN THE RECENT HEAVY RAINS.

...SE/ERN TX INTO SRN LA...

STRONG TO SEVERE CONVECION HAS ERUPTED OVER THE SRN PLAINS IN A
LOADED AIRMASS IN RESPONSE TO EJECTING SW UPR TROF INTERCEPTING
DEEPENING RETURN FLOW FROM FROM THE WRN GULF THROUGH THE SRN
PLAINS. THERE IS ALSO A MID LEVEL MOISTURE CONNECTION ALOFT FROM
THE SUBTROPICAL ERN PACIFIC EVIDENT IN LATEST BLENDED SATELLITE
LOOPS. WAVES INDUCED ALONG THE BANDED CONVECTION ARE FEEDING ON
THE DEEPENED MOISTURE AND INSTABILITY/UPPER DIFFLUENCE AND
ENAHNCED JET SUPPORT. SOME OF THIS WIDESPREAD ACTIVITY WILL LINGER
INTO MORNING IN A WEAKENING STATE AS THE AREA SHIFTS SLOWLY EWD AS
PER ADVENT OF STEADY HEIGHT FALLS AND CONVECTIVE GRADIENTS. EXPECT
WEAKENING ACTIVITY TOWARD THE UPPER TX COAST AND INCREASINGLY
OFFSHORE INTO LATER MON AS THE SRN PORTION OF UPR TROF UNDERGOES
TRANSITION TO A CLOSED LOW...BUT LINGERING SUPPORT AND MOISTURE
SHOULD COMBINE TO SUPPORT THE THREAT FOR HEAVY RAINFALL OVER ERN
TX/OK AND ESPECIALLY SERN TX INTO LA LATER MON WITH HEATING THAT
MAY PRODUCE SOME RUNOFF PROBLEMS WITH AMOUNTS UPWARDS OF 2-3"
POSSIBLE/SEVERAL HRS WITH TRAINING IN DEEP FLOW CONSIDERING STILL
ENHANCED PRECIPITABLE WATER VALUES. OPTED FOR A SLOWER PROGRESSION
THAN MOST OF THE MESO MODELS GIVEN THE CLOSING NATURE OF THE SRN
END OF THE MAIN MID-UPPER LEVEL TROUGH.

SCHICHTEL
$$




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