Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 120902
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
402 AM CDT Thu Oct 12 2017

.SYNOPSIS...
Issued at 402 AM CDT Thu Oct 12 2017

Moisture trapped below the inversion was keeping low clouds
blanketing the forecast area early this morning. Areas of drizzle
and light fog were being observed across the area as warm air
advection was increasing on southwest winds at 850 mb, just above
the saturated low level airmass shown in the KDVN 00z sounding.
Moisture and clouds were keeping temperatures in the lower to mid
50s, having cooled only a few degrees from Wednesday`s cool
afternoon highs.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 402 AM CDT Thu Oct 12 2017

Low clouds are likely to hang on through much of today, slowly
clearing from southwest to northeast, where overcast skies could
hang on well into the evening. Light winds are expected to keep at
least some easterly component through the day as they gradually
veer to more southerly following the eastward shift of weak high
pressure. With the deep moisture in place, increasing warm
advection southwest flow aloft, and the current back edge of the
stratus way out in western IA and western MO, confidence in this
clearing trend is low. Have thus lowered highs to a range from the
upper 50s north to mid 60s in the far southwest, where there is
the greatest potential for afternoon sunshine.

Tonight, low clouds may linger over the far northeast, while
higher cloud cover is likely to increase ahead of the next system
moving into the plains. This along with light southerly winds
will limit cooling and lead to another night with lows in the
lower to mid 50s.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 402 AM CDT Thu Oct 12 2017

Friday

A sfc warm front will develop across the southern forecast area
during the morning. Temps will range from the mid 60s far north to
the upper 70s far south. The majority of the CWA will be either
along or north of the front and will have NE or ENE sfc winds
through the day with mostly cloudy skies.

Thunderstorm and Rain Potential:

Elevated scattered showers and isolated thunderstorms are likely
across the N/NW forecast area during the afternoon along a zone of
elevated frontogenesis and WAA (~925-850mb).

For the evening and overnight, chances for showers and thunderstorms
increase over the CWA with likely PoPs extending south and including
counties along I-80. However, the highest PoPs of 70-80% remain
roughly north of highway 30.

A weak low pressure wave may ride along the low-level baroclinic
zone overnight, enhancing thunderstorm coverage in the process.
There is potential for localized heavy rainfall in a narrow SW to NE
oriented band. Forecast environmental parameters -- high PWATs and
sufficient MUCAPE (up to ~1000 J/kg) and deep layer shear -
- are supportive of heavy rainfall rates and hail in the strongest
storms.

Saturday through Sunday morning

Active weather pattern for the first half of the weekend. The
primary concerns are:

1) Threat for severe weather Saturday afternoon into Saturday night.
The Storm Prediction Center has a slight risk over the SW third of
the CWA and a marginal risk elsewhere. While it`s still several days
away, all severe weather hazardous are possible with the strongest
storms.

2) Heavy rainfall rates from thunderstorms which may lead to
localized flash flooding. The Weather Prediction Center has a slight
risk for excessive rainfall across the entire CWA.

3) Storm total rainfall from Friday through Saturday night of 1 to 3
inches (with localized higher amounts) will likely lead to rises on
area rivers. Across E Iowa/NW Illinois, NAEFS progged PWATs (near
2") and integrated WV transport values (up to 1000 kg/ms) are
approximately 3-4 standard deviations above the mean for the middle
of October. PWATs of this magnitude only occur once every 5-10 years
during this time of year.

Sunday Afternoon through Wednesday

Conditions should be drying out Sunday afternoon and evening as the
system moves to the east. After a cool start in the upper 30s and
lower 40s Monday morning, expect seasonable temps in the 60s for the
afternoon. Slightly above normal temps in the mid to upper 60s are
forecast for Tuesday and Wednesday. Uttech

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday Night)
ISSUED AT 1146 PM CDT Wed Oct 11 2017

Cloudy skies with mostly IFR/LIFR conditions with isolated very
light drizzle are possible until mid morning with light east to
southeast winds. The patchy light nature of the drizzle have left
out of the TAF attm. Light fog for with low ceilings to prevail
with mainly visibilities of 1 to 4 miles. VFR conditions to
develop with clearing by mid to late day with winds becoming
southerly through Thursday evening.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...Sheets
SHORT TERM...Sheets
LONG TERM...Uttech
AVIATION...Nichols



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