Quantitative Precipitation Forecast
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
000
FOUS30 KWBC 191501
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1100 AM EDT Sat May 19 2018

Valid 15Z Sat May 19 2018 - 12Z Sun May 20 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SE HXD 15 NNE NBC 20 NE OGB 25 NW UDG 20 ENE EQY 10 SSE JQF
10 W UZA GRD 20 NW 27A 20 SSW 1A5 10 S OQT 10 S K8A3 15 E GLW
40 SSW FFT 30 SSE LUK 20 WNW MNN 15 S CXPT 25 N HZY 20 ESE ERI
20 WNW IDI 30 SW OKV RMN DMH 25 NNW RDG 35 E BGM 45 WSW SCH
25 NE MSV 10 W MGJ 20 WNW HPN TEB BLM 20 S PHL 10 WSW MIV
15 NNE GED 10 NW OXB 10 NNW WAL 25 E FYJ 15 SW SFQ 15 ENE EWN
35 SW MRH.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
60 SSE HST 35 ESE MTH MTH 20 W APF SPG 15 SW OCF LEE 10 E GIF
40 SE BOW 30 WSW VRB 30 NE COF 60 ENE COF.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 S BIE 30 SE HDE 25 NNE GLD 20 ESE LIC 15 ESE APA 15 WSW FNL
25 SSE BRX 20 ENE TOR 20 SSE AIA 15 WNW LBF 15 NE SUX 25 SSW CCY
10 ENE MRJ RFD 25 E MLI 15 NW IJX 30 NNW SLO MVN 10 NE CGI
30 E FLP 25 SW JSV 20 SW MWL 20 W ERV 30 SSW UVA 30 WSW MMPG
45 W DRT 10 SE MAF 20 W LBB 30 SSE AMA 25 WNW PNC 30 SSE MHK
35 S BIE.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
CHK 30 SSE DUC 20 W 1F9 15 E ABI 15 SE SNK 45 N SNK 20 SSW CDS
15 SSW CSM CHK.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 S TRI 15 SSW MKJ 15 NNW BLF 20 SSE 48I 20 SSE EKN 20 W SHD
20 ENE ROA 15 NNW INT 10 S SVH 10 SSE GSP 10 NNW CEU 25 W AVL
25 S TRI.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SE HST 30 S HST 15 SW HST 25 WNW OPF 30 WNW PBI 15 NW SUA
15 ENE FPR 30 NE SUA.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 SW UIN 40 W SUS 35 ESE VIH 25 ESE TBN 40 SSW AIZ 55 N JLN
15 NE UKL 20 NNW TOP 25 SSW AFK 10 N CBF ADU 10 NW TNU
15 NNW AWG 45 SW UIN.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 S CHS 10 SSW CHS 30 N CHS 15 ESE UDG TTA 10 WNW LHZ RWI
15 SSW OAJ 20 E SUT.


1500 Update...

No changes made to the previous day 1 ERO, based on the current
observational/mesoanalysis trends, recent high-res CAM output, and
the latest FFG from the RFCs/soil moisture and streamflow analysis
from the National Water Model.

Hurley


...OH Valley into the Mid Atlantic...

Will be another wet day across much of the east, although the
pattern will finally begin to progress today. The broad mid/upper
level trough will finally begin pushing off to the northeast,
which will push increased moisture into the northeast and push the
Mid Atlantic front north as well. Thus anticipate showers will
overspread the northeast with time, and generally become less
focused over the Mid Atlantic. Given weak to no instability, not
anticipating rainfall rates will be all that high today from the
northern Mid Atlantic into the Northeast, and thus a Marginal risk
should suffice from the eastern Mid Atlantic into southern NY to
account for the locally heavier amounts forecast.

The shortwave that has only slowly been progressing east across
the MS Valley into the OH valley over the last few days will pick
up a bit more speed off to the northeast today. Anticipate another
day of ample instability and moisture ahead of this wave and
trough axis for more scattered to widespread diurnally driven
convection. Main focus will be across the OH Valley into the
western Mid Atlantic. Mean flow is greater today, thus anticipate
storms will be more progressive than we have seen the past few
days. Thus in general would expect rainfall magnitudes to be
lower, although with continued high PWATs, briefly intense rates
are still likely. Normally this setup would probably not be too
much of a flash flood threat, however where recent rainfall is
saturating soils and lowering FFG, this rain may cause additional
flash flood concerns. Biggest threat appears to be across portions
of southeast WV south into northwest NC, where some signal this
convection today could briefly hang up and/or repeat near the
terrain resulting in localized heavier amounts. Given antecedent
rainfall here, and the possibility of intense rates with this
activity, additional flash flooding is possible...and will carry a
Slight risk here.


...Eastern Carolinas...

Will need to continue to monitor portions of eastern SC and NC
through the day for the potential of an axis of heavier rainfall.
An axis of near 2" PWATs is expected to focus across this area for
an extended period of time, with at least weakly convergent flow
in the lower levels. Also appears like one or more weak shortwaves
will push north in the southerly flow, locally enhancing lift and
low level moisture transport. Not expecting convection to be too
organized, and instability is not all that great. However, the
persistent convergence axis, higher PWATs and mean flow does
support the potential for a period of south to north moving repeat
cells capable of producing briefly heavy rates. The 0z HREF shows
moderate to high probabilities of exceeding 3" across portions of
the area, and so think the setup suggests at least a localized
flash flood threat. Will maintain continuity and have a Slight
risk to account for this risk.


...Florida...

Another wet day across Florida as well. PWATs and 850 mb moisture
transport should both be higher today than previous days,
potentially resulting in a wetter overall day. Activity should
initially focus along the west coast sea breeze boundary, before
potentially shifting to the east coast overnight. Most of the 0z
high res guidance is quiet wet over eastern FL with this overnight
activity. The potential is certainly there for these heavier
totals given the increased southeasterly flow, strong convergence
signature and near climatological record PWATs. Appears like the
high res models are hinting at a subtle wave riding north,
interacting with these favorable parameters and producing a period
of south to north training. Tough to say for sure if this will
materialize, but certainly something to watch, as given wet
antecedent conditions, a greater flood threat could exist. With
the above environmental parameters in place, 0z HREF probabilities
of locally exceeding 5" in the moderate to high category, and wet
antecedent conditions, will go with a Slight risk across the
southeast Florida coast. Lower confidence with this risk area, but
the conditional risk appears high enough to warrant it at this
time and will monitor trends through the day.


...Central Plains into the Mid MS Valley...

Another active convective day expected across the area. By this
afternoon the surface setup should feature a cold front extending
from the Southern Plains into the Mid and Upper MS Valley, and a
dryline across western TX. The mid/upper levels will remain
broadly divergent and generally uncapped. Thus by afternoon will
see an uptick in convection along both these boundaries. PWAT
values will remain high enough to support heavy rains. Thus any
flash flood threat will come down to if and where convection is
able to train and or repeat for a period. The general consensus is
that the first area to convect will be along the front across
OK/KS this afternoon. This activity should move northeast along
the front for a period, but then should advect eastward into the
very unstable airmass forecast over MO. The orientation of
propagation vectors relative to the instability gradient does
support the potential for a period of west to east training of
convection across this area. Also, should see storms form further
northeast along the front from southeast NE into southern IA. Some
training along this front is also possible. Overall confidence is
low with exactly where the better convective training threat ends
up...with outflows from this mornings activity potentially playing
a role. Would lean towards the better threat probably being
somewhere over MO, given the placement of the stronger 850 mb
moisture transport, higher instability pool, and the potential for
this mornings convection establishing an effective boundary
further south. However southeast NE into southern IA is certainly
in play as well, likely being closer to the best mid/upper forcing
and having a slow moving cold front to potentially train along.
Thus opted to just go with a broader Slight risk to encompass both
potential areas.


...Southern Plains...

Higher confidence in what evolves over TX/OK...with widespread
development appearing likely along/east of the dryline. Would
appear like there is a window of potential training near the
intersection of the cold front and dryline from north central TX
into southern OK. This is depicted by a good amount of the 0z high
res guidance, and given the orientation of the fronts at play and
increasing 850 mb moisture transport, it seems plausible.
Eventually would anticipate any complex to become more progressive
off to the south into the instability pool. Will issue a Slight
risk to account for this flash flood potential. Further south
along the dryline it is less favorable for training. However could
see some backbuilding into the dryline for a period, which could
produce localized flash flood issues, and thus will go with a
Marginal risk there.

Chenard



$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.