Quantitative Precipitation Forecast
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227
FOUS30 KWBC 240046
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
745 PM EST Fri Feb 23 2018

VALID 01Z Sat Feb 24 2018 - 12Z Sat Feb 24 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 SSE HEZ 20 E BQP 15 NE M89 15 SSW DEQ 10 SW GVT NFW
10 NW 1F9 25 NE DUC 10 SW CQB 10 W CFV 25 SSW SZL 35 WSW PPQ
10 NE DNV 30 E MIE 10 WNW SDF 25 ESE FTK 40 NW JKL 15 E PKB
10 W CBE 20 NNW HSP 15 NW 1A6 20 WNW CHA 30 NNE NMM 15 SE KDLP
10 W 9F2 25 WNW MSY 20 SSE HEZ.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 NNW GCM 45 NNE JLN 10 NE JEF 10 E STL FAM 20 SE UNO
40 NE RUE 25 SE FSM 35 N PRX GYI 10 SSW ADH 15 NNW GCM.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 SSE UTA 10 W MKL 15 E CKV 40 SSW GLW 25 NE MSL 30 ENE TUP
30 NE JAN 35 SSW GWO 35 SSE UTA.


0100z Update:

No significant changes were made to the previous issuance.

2200z Special Update:

Adjustments to the previous issuance are based on the latest runs
of the HRRR, HREFMEAN along with recent satellite and radar
trends.  The general consensus of the hi-res guidance shows
ongoing convection across the Red River in central Oklahoma
lifting to the northeast this afternoon and evening -- remaining
further to the north and west of areas impacted by the heaviest
rainfall.  Therefore, removed the moderate risk that was
previously across southeast Oklahoma into north-central Arkansas.
Shifted the previous slight risk further to the northwest across
eastern Oklahoma, western Arkansas and southern Missouri.  Several
hi-res guidance members show locally heavy amounts on the order of
1-2 inches within this region during the evening and overnight
hours.  Again, expect these amounts to fall across areas where
soils are relatively less saturated and pose less of a
flash-flooding threat.

Included a separate slight risk further to the south across
northern Mississippi into western and Middle Tennessee.  Some of
the guidance show convection developing along an axis of southerly
inflow producing some moderate to locally heavy amounts.  Flash
guidance are relatively lower across this region -- suggesting
flash flooding may become a concern across areas where heavy
amounts do materialize.

Further east, removed much of the marginal to slight risk that
extended into the upper Ohio valley.  Model consensus shows that
the heavy rainfall threat has momentarily subsided across the
region.

Pereira

...Previous Discussion...


Northeast TX/southeast OK---Arkansas---southeast MO---western TN
into the OH Valley

A very broad slight and moderate risk areas were maintained for
the upcoming day 1 period for yet another round of widespread
heavy to excessive rainfall amounts from northeast TX/southeast
OK---across much of Arkansas---southern MO and into the OH valley.
 The current training precipitation from SW to northeastern AR
into western TN may continue into the beginning of the upcoming
day 1 period.  However---the model consensus is then for
precipitation to begin to focus farther to the
northwest---initially from north central TX into southeast OK as
the low level southerly flow re-focuses across this area Friday
morning ahead of northeastward moving height falls embedded in the
southwest flow across the southern plains.  This developing
activity expected to then shift downstream into central to
northern AR---southern MO and into the OH valley. An overall very
favorable pattern will continue for widespread heavy to excessive
precip totals with an axis of much above average pw values---2 to
3+ standard deviations above the mean along and north of the
surface frontal boundary slowly moving northward day 1 across
these areas.  There are some typical model differences with the
latitude of the heaviest precip totals---with WPC leaning toward
the farther south solutions of the hi res arw--nssl wrf---HREF
mean.  This will support the heaviest rainfall and excessive
rainfall potential from northeast TX/southeast OK---central to
northern AR into the OH/MS river confluence area.  No significant
changes were made to the previous outlook for this period.

Oravec

$$





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