Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 240425

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1125 PM CDT MON MAY 23 2016


Issued at 330 PM CDT Mon May 23 2016

Another warm and dry day across eastern Iowa, western Illinois,
and northeastern Missouri. Winds have increased out of the south,
but the plume of 60s dewpoints remains off to the west with little
eastward advection taking place. Locally, sfc dewpoints are in
the 40s which has allowed temps to spike into the low to mid 80s,
and has continued the dry trend.


ISSUED AT 330 PM CDT Mon May 23 2016

This Evening and Tonight...dry air beneath weakening low to mid
level ridge will preclude widespread showers and thunderstorms.
For most of the forecast area, have up to 30% PoPs overnight as
better chances are for areas to stay dry. 850mb transport vectors
are forecast to be oriented more to the north than the east which
increases confidence of the mainly dry scenario.

The exception, based on proximity to deep moisture plume with
PWATS over 1 inch and on consistent hi-res model runs, is across
the NW section of the DVN CWA where showers and a few embedded
storms are more likely late tonight. Strong storms are not

Tuesday...Mid to upper level cloud debris should hold temps down
compared to Monday. Rising dewpoints into the lower to middle 60s
also support slightly cooler temps in the upper 70s/lower 80s.

Thunderstorm potential: Chances for convection are tricky because
absence of a formidable shortwave or low-level jet and associated
ascent should prevent anything but isolated or sct pockets of
showers and storms. In other words, I think dry periods will be
the rule across the CWA, and for areas that receive showers or
storms it should only be for brief periods. PWATS are forecast to
rise above 1.25 inches, increasing the potential for brief
moderate or heavy downpours from storms that form.

Although instability will be much higher than Monday - MUCAPE at
or above 1500-2000 J/kg - the threat for severe weather is low
with 0-6 km bulk shear below 30 kts. Uttech

.LONG TERM...(Tuesday NIGHT THROUGH next Monday)
ISSUED AT 330 PM CDT Mon May 23 2016

Tuesday night and Wednesday...Besides some lingering diurnal precip
activity of sctrd to even isolated in nature in the west and north
of I80 through mid evening...the 12z run ECMWF,ARW and NAM now
suggest a mainly dry Tue night as main forcing zones continue acrs
the central/northern plains, as well as MO and up the OH RVR Valley.
Western GRT LKS sfc and upper ridging still having it`s effect. This
while the aggressive 12z GFS spreads an MCS generated in western and
central IA acrs the areas the night progresses. MCS forcing tool and
lingering ridge to the east deflecting more optimum moisture
profiles to the west, makes one think the ECMWF is on to something
and will start to trend back POPs especially 00z-06z Wed. A low
potential for portion of a decaying MCS or storm clusters will make
it into the northwestern quarter of the DVN CWA out of
Northwestern/north central IA before dawn Wed morning. But most of
the american model/GFS and national guidance QPF progs may be too
high this far east for Tue night. Mild lows in the 60s.

Northern plains troffiness and southwesterlies to the south of it
aimed at the MO RVR Valley will look to keep these areas
convectively active on Wed. Some signs that the ridging just off to
the east to migrate eastward enough to allow better llvl moisture
return finally into our area of well as southwesterlies
spilling acrs the mid and upper MS RVR Valley may allow for isolated
to sctrd thunderstorm development to occur acrs portions of the area
by Wed afternoon. If temps can warm into the low 80s with sfc Dpts
of at least low to mid 60s, the local area could have SBCAPES of
1500 to 2500 J/kg by mid afternoon giving any lasting afternoon
storm some pop. But a more widespread shower/storm potential may
occur Wed night. The same MCS forcing tool, as well as llvl THTA-
feed and convergence fields to lee of an embedded wave in the
southwesterlies suggest storm clusters or even an MCS-type system
may develop Wed evening acrs central into northeastern IA, then
propagate east southeast acrs much of the CWA into early The
morning. Besides a marginal severe weather threat, PWAT`s of 1.3 to
1.4 inches suggest Wed night may be the first good soaker for the
area if the Tue night storms don`t materialize. A few swaths equal
to or even higher than the above mentioned Precipital Water possible
by Thu morning.

Thursday and Friday...Southwesterlies overhead and a more easterly
adjustment of the warm moist conveyor feed up off the Gulf will look
to make this end of week period convectively active and wet. If Thu
remains mainly dry after what ever convective debris lingers out of
Wed night-early Thu AM clears off, there will be heating potential
of low to mid 80s along with sfc Dpts at least in the upper 60s if
not around 70 for SBCAPEs of 3k-4k J/KG by late Thu afternoon. Fcst
soundings suggest marginal deep shear that day though, along with a
CAP that may limit Thu afternoon convection until later that night.
Thus if nothing takes off Thu afternoon, the stage could be set for
a substantial storm complex to feed on the thermodynamic fuel that
has built up locally all afternoon for Thu night. Friday may be
similar...with Thu night convective debris having a impact on Fri
depending on where it lays out and how long it lingers. Fri evening
and overnight will then look to be more active than earlier in the
day Friday. Another round of locally heavy rain possible Fri night
as well that may start to compound on rains from earlier in the
week. Will keep above normal temps going at weeks end and into the

Saturday through next Monday...Taking an ensemble approach to the
latest medium range model runs, a wave ejecting out in
southwesterlies maintaining aloft will make for another stormy day
Sat, but after that feature passes we may be in for a reprieve for
Sunday. Nocturnal storms may then return later Sunday night, and
linger into portions of the Holiday Monday.     ..12..


ISSUED AT 1119 PM CDT Mon May 23 2016

VFR conditions to generally VFR conditions to prevail the next 24+ hours.
Clouds will slowly increase tonight with any bases aoa 4k agl as a plume
of moisture from the gulf arrives late overnight into Tuesday. Isolated
to scattered coverage of showers and storms will slowly arrive at the
terminals from west to east after 24/09z and last through Tuesday morning.
Coverage at this time warrants tempo late overnight into mid Tuesday
AM. Then removed vicinity wording afterwards due to poor confidence
and coverage issues. Possible another chance of showers and storms may
redevelop Tuesday evening. The strongest showers and storms may reduce
visibility briefly to mvfr conditions this morning.


.DVN Watches/Warnings/Advisories...



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