Quantitative Precipitation Forecast
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000
FOUS30 KWBC 290101
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
900 PM EDT SUN AUG 28 2016

...VALID 01Z MON AUG 29 2016 - 12Z MON AUG 29 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 SW CYHD 35 SSW CWCH 25 E BFW 15 NNE PBH 20 NNW LUM OVL
25 NNE HON 40 SW ABR 50 ESE K7L2 20 NW KBAC 35 ESE DVL 25 W KD55
25 N CWEI.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
100 ESE BRO 45 ESE PIL 10 SE BKS 25 W VCT 10 NW DWH 10 W ACP
10 SSE ASD 40 NE KIPN.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
115 SSW MMCS 105 SSW MMCS 35 SW DMN 45 NNW SVC 50 NW TCS
55 NNE TCS 15 NNW SAF 30 SE ALS 45 ESE MYP 25 WSW AFF MNH
30 NE MNH 30 E DEN AKO 45 N ITR ITR 30 SSE ITR 55 ENE LAA
35 NNW EHA 20 N DUX 20 NW BGD 15 WSW PYX 40 SSW DDC 40 NE RSL
25 S BIE 15 ENE FNB 10 ENE STJ FOE 10 SW WLD 25 W F05 60 NNE SNK
45 W SJT 20 SW E29 25 SSE ECU 25 ESE MMPG 65 N MMMV.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
125 SW SRQ 65 SW SRQ 30 W SRQ 15 SW LAL 45 SE BOW 30 SSW MLB
75 E TTS.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 E HNB OLY 15 SSW PRG 10 SW IND 20 NE MIE 25 W MNN 15 NNW ZZV
BTP 15 ENE DUJ 25 SSW ELM 20 ESE SYR 35 SSW SLK 25 S CWBZ CWEW
20 N CYSC 30 E BML 15 W 1P1 40 N MSV 10 NE 2G4 40 WSW UNI
25 NNE FFT 30 E HNB.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
70 W KEY 65 NW KEY 25 W TMB 15 W FXE 30 WNW MYGF.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SE KOPM 15 SW NGP VCT 10 NNE SGR 20 NNE BPT 20 ESE 7R3
15 WNW KMDJ 25 SSW KGRY.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 ENE AXN 10 NW 8D3 30 ESE KBAC 10 SE CKN 20 W VWU 10 SE FOZ
AIT 15 ENE AXN.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 ENE RTN 25 SE PUB 30 NNE LHX 20 S LAA 15 E CAO 25 NE TCC
35 NW TCC 10 ENE RTN.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SSE INK 35 S CNM 15 NW GDP 25 E MMCS 15 S MMCS 40 WSW MMCS
25 WSW LRU 25 WSW HMN 25 SW SRR 20 SE SRR 20 SE ROW 25 WNW LBB
35 NW SNK 20 ESE MDD 25 SSE INK.


01Z UPDATE...

...MINNESOTA/WISCONSIN...

AFTER ADJUSTING NORTHWARD IN A 22Z UPDATE...WE HAVE STAYED THE
COURSE WITH THE 01Z UPDATE. THUNDERSTORMS WERE DEVELOPING ALONG
THE 850 MB WARM FRONT IN NORTHERN MINNESOTA AS OF 01Z...AND THE
CAP HAD BEGUN TO BREAK IN WESTERN MN WHERE MID LEVEL TROUGHING WAS
OVERLAPPING WITH THE SURFACE WARM FRONT. SEE MESOSCALE DISCUSSION
0614 FOR DETAILS.

THE GREATEST ODDS OF EXCEEDING FLASH FLOOD GUIDANCE ARE EXPECTED
WHERE THE PLAINS LOW LEVEL JET MOVES TO THE COOL SIDE OF A WARM
FRONT LATE THIS EVENING FROM FAR SOUTHEASTERN ND INTO WESTERN MN.
AREAL QPF IS EXPECTED TO FALL OUT SOMEWHAT LIKE THE 12Z SSEO MEAN
WHICH FACTORED INTO PLACEMENT OF THE SLIGHT RISK AREA. THIS PLACES
THE SLIGHT RISK AREA MORE SQUARELY OVER CENTRAL MN...ALTHOUGH THE
TWIN CITIES REMAIN IN MARGINAL RISK.

LOW LEVEL INCREASES TO 40+ KTS AT 850 HPA...AND LOCAL RAINFALL
AMOUNTS IN THE 3-5" RANGE ARE INDICATED BY THE MESOSCALE GUIDANCE.
MUCH OF THIS COULD FALL QUICKLY AS AVAILABLE MOISTURE SUPPORTS
HOURLY RAIN RATES TO AT LEAST 1.75" WERE CELLS MERGE/TRAIN.


...MIDWEST / OHIO VALLEY / MID ATLANTIC / NORTHEAST...

HEAVY CONVECTIVE RAINS HAD PRODUCED RADAR ESTIMATES OF 2 TO 3
INCHES IN 1 TO 2 HOURS IN A FEW SPOTS INCLUDING AROUND PITTSBURGH
AND CINCINNATTI. OUTFLOWS AND BOUNDARY COLLISIONS HAD PROVEN TO BE
VERY EFFICIENT AT RELEASING MODERATE INSTABILITY AND TAPPING INTO
ABOVE AVERAGE PRECIPITABLE WATER VALUES IN A PSEUDO-ORGANIZED WAY.
STILL...WITH NIGHTFALL AND LESS THAN ENTHUSIASTIC SYNOPTIC
SUPPORT...WE WOULD EXPECT A DECREASE IN COVERAGE OF SMALL SCALE
HEAVY RAINFALL...AND HAVE MANTAINED LOWER PROBABILITIES...MARGINAL
RISK...GOING FORWARD.


...LOWER MS VALLEY & WESTERN GULF COAST...

WITH A SURFACE TROUGH AND MID LEVEL CIRCULATION POSITIONED NEAR
THE WESTERN GULF COAST...AND SURROUNDED BY PRECIPITABLE WATER
VALUES OF 2.0 TO 2.25 INCHES...HEAVY LOCAL RAINFALL WILL REMAIN
POSSIBLE. THE THUNDERSTORM ACTIVITY HAS SHOWN STRONG DIURNAL
TRENDS...WITH RELATIVELY QUICK MOVING SCATTERED DOWNPOURS
SPREADING INLAND DURING THE DAY...AND STEADIER HEAVY RAIN FALLING
ALONG THE IMMEDIATE COASTLINE OVERNIGHT. THE DAYTIME ACTIVITY MAY
CAUSE LOCAL PROBLEMS WITH RAPID RUNOFF IN PLACES THAT ARE PRONE TO
FLOODING. THE OVERNIGHT ACTIVITY HAS POTENTIAL TO PRODUCE GREATER
RAINFALL AMOUNTS...EXCEEDING 2 OR 3 INCHES PER SOME OF THE
MESOSCALE GUIDANCE...BUT SHOULD BE LIMITED TO THE COAST. THE
SLIGHT RISK OF EXCESSIVE RAINFALL IS TIED MAINLY TO THE OVERNIGHT
CONVECTION...AND WAS DRAWN TOWARD THE HI-RES MODEL CONSENSUS QPF.


...FLORIDA...

THERE IS SOME RISK OF EXCESSIVE RAINFALL AROUND TROPICAL
DEPRESSION NINE AS IT ATTEMPTS TO BECOME MORE ORGANIZED. WITH THE
TRACK BEING SOUTH OF THE KEYS...THE RISK OF HEAVY RAIN WOULD COME
INDIVIDUAL CELLS OR SMALL LINE SEGMENTS IN THE BANDS MOVING EAST
TO WEST AND AFFECTING A FEW LOCATIONS REPEATEDLY. IN THE
MEAN...AND OVER TIME...CONVERGENCE WILL BE MAXIMIZED OVER FAR
SOUTH FLORIDA AND THE KEYS...LEADING TO SOMEWHAT GREATER ODDS OF
REPEATED HEAVY DOWNPOURS THERE...AND HENCE A MAINTENANCE OF SLIGHT
RISK IN THE DAY 1 PERIOD. PREDICTED AREAL AVERAGE RAINFALL
INCREASES IN THE DAY 2 PERIOD...BEYOND 12Z MONDAY.


...SOUTHERN ROCKIES/CENTRAL AND SOUTHERN PLAINS...

THE UPPER LOW OVER NEW MEXICO IS PREDICTED TO BE SLOW TO EJECT
FROM THE MOUNTAINS...BUT WILL PROVIDE A FAVORABLE FLOW REGIME FOR
ORGANIZED CONVECTION THIS EVENING/OVERNIGHT OUT OVER THE PLAINS OF
EASTERN/SOUTHEASTERN NEW MEXICO AND WEST TEXAS. AT THE SAME TIME A
DIFLUENCE MAXIMUM LOCATED NORTHEAST OF THE LOW CENTER...IS
EXPECTED TO PERSIST OVER NORTHEAST NM INTO SOUTHEAST
COLORADO...WHILE LOWER LEVEL INFLOW INTO THIS REGION GRADUALLY
IMPROVES AFTER DARK. THE UPDATED OUTLOOK HIGHLIGHTS THESE AREAS
WITH SLIGHT RISK...BASED IN PART ON THE MODEL QPF SIGNALS THAT
ACCOMPANY THOSE AREAS...IN THE HRRR...NSSL WRF...AND NAM CONUS
NEST...IN PARTICULAR. MARGINAL RISK WAS EXPANDED A BIT TO CAPTURE
ESTABLISHED OUTFLOW BOUNDARIES AND INCREASING INFLOW OVER OTHER
PARTS OF THE HIGH PLAINS...WHILE THE OVERALL SIGNALS IN THIS
REGION ARE FOR SMALLER SCALE CONCERNS AND NO WELL DEFINED FOCUSED
AREAS OF EXCESSIVE RAIN EXCEPT PERHAPS THOSE MENTIONED WITHIN THE
SLIGHT RISK AREAS.

BURKE
$$




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