Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 142123 CCA

Area Forecast Discussion...corrected long term
National Weather Service Quad Cities IA IL
359 PM CDT Fri Oct 14 2016

Issued at 334 PM CDT Fri Oct 14 2016

Latest SFC analysis was indicating tightening south to southeasterly
pressure gradient up the plains and acrs the upper midwest. Low to
mid 60 sfc dpts noted upstream of the flow acrs OK and northeastern
TX. Solid stratocu deck from KS to central and eastern IA has eroded
some in areas for partly cloudy to mostly clear patches.
Aloft, vigorous vort max with associated baroclinic leaf was noted
acrs southeastern MO and up the OH RVR Valley, while broad scale low
amplitude southwesterlies occupied the western CONUS to the lee of
Pacific NW storm system.


.SHORT TERM...(This Evening through Saturday)
ISSUED AT 334 PM CDT Fri Oct 14 2016

Tonight...Main challenge tonight will be the cloud cover and if it
fills back in and engulfs the rest of the CWA into the early morning
hours. Several of the short range models and their RH progs suggest
that the stratocu will fill back in nocturnally and then continue to
slide eastward overnight and will play it that way.
Enough of a in-building southerly gradient to maintain sfc winds
overnight of 8-12 MPH or so especially under areas of cloud cover.
Will not put in any mention of drizzle or sprinkles overnight for
now with questions of adequate cloud thickness and saturation, but
there could be some acrs the far west and northwestern CWA late.
Will go with lows in the 50-55 degree range with the cooler readings
east of the MS RVR where clear skies linger the longest. With any
delay in cloud cover making it into the east, lows could dip into
the 40s in those areas. South winds will advect increasing sfc dpts
and warmer air itself, making for some non-diurnal temp trends late

Saturday...Current trends and fetch from the south should make for a
mostly cloudy, breezy and seasonably mild day. Feel the NAM and GFS
advecting mid to upper 60 dpts acrs the area overdone some, but
could see the upstream lower to mid 60 readings make it acrs
portions of the area by later afternoon. Cloud cover may make the
cooler of temp guidance(The MAV`s upper 60s to lower 70s) more in
line, but for now will go with a model blend which advertises more
in the way of low to mid 70s. If we were going to have full
sunshine, highs would range from the upper 70s to lower 80s. Will
keep the patchy drizzle or sprinkles in the west during the morning
and early afternoon with some thickening of the deck expected, but
the afternoon may be more in the way of sctrd light showers mainly
along and west of the MS RVR. MUCAPES may range from 600 to around a
1000 J/KG west of the MS RVR by late afternoon, but it may be more
the plume of elevated CAPES of 400-800 J/KG that support at least
some isolated thunderstorms rooted aloft in northeastern IA mainly
after 4 PM. Both llvl and deep layer shear will really be on the
increase from the west as well late in the day and may allow for a
stronger storm in the northwest toward sunset.   ..12..

.LONG TERM...(Saturday Night through Friday)
ISSUED AT 334 PM CDT Fri Oct 14 2016

Initial focus is with storms Saturday night and the potential for
severe weather. A strengthening 40-45+ kt low level jet ahead
of an approaching cold front along with increasingly diffluent
flow aloft with a shortwave passing through the Upper Midwest will
come together for showers and storms developing Saturday evening.
Strong shear with 0-6km of 30-35 kts and modest instability with
MLCAPE of 500-1000 J/kg support the potential for a few strong to
severe storms, especially west of the Mississippi River over
portions of northeast and east central Iowa where best overlap of
shear and instability is depicted. Main threat is large hail and
damaging winds, but can`t rule out an isolated tornado with
0-1km shear of 35-40 kts being depicted which is not too far off
from last Thursday, and with a bit more low level instability and
weak SBCIN. In addition heavy rainfall is likely with strongest
cells with precipitable water values around 1.5 inches, but fast
storm motion should limit amounts and preclude any potential for
flooding as it appears right now.

Sunday the cold front looks to pull up stationary over roughly
the northern half or so of the area, with weak ridging aloft.
The concern will be potential for low clouds and a bust on highs
(too warm) north of I-80, as BUFR soundings show decent inversion
with abundant low level moisture and given time of year could be
difficult to excavate clouds. I have started to trim back highs
a bit on Sunday along and north of Highway 30 (lower 70s), but they
could end up needing to be lowered further. Stayed near 80 south
where anticipate more sunshine.

Next week, the flow pattern will transition from southwest to fast
zonal flow. The week looks to begin on an unseasonably warm note
with highs well above normal (20-25+ degrees), with highs in the
upper 70s and lower to possibly a few mid 80s Monday with gusty
southerly winds. A cold front looks to pass Monday night into
early Tuesday and indications are not much chance of rain with
weak forcing. This front will gradually lower temperatures down
from the 70s on Tuesday back into the 60s Wednesday still
near to slightly above normal for mid October. The models really
diverge mid to late next week on timing and evolution of western
energy. General trends and signal support our next chance of rain
late Wednesday through Thursday. ECM is more progressive and keeps
bulk of energy and rain to our south and most of cwa on drier
side. GFS being slower and stronger allows more moisture
entrainment into evolving southwest to northeast baroclinic zone
for a wetter and cooler scenario late Wednesday through Thursday.
Blended forecast is not aggressive with pops and mild on
temperatures mid to late week, but overall confidence is low.


.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
ISSUED AT 1240 PM CDT Fri Oct 14 2016

Main challenge will be timing MVFR stratocu deck from the west at
the TAF sites, with CID and possibly BRL being the first to get
under the deck this afternoon, and DBQ/MLI tonight. South to
southeast sfc winds this afternoon gusting to 20 KTs where the sun
lasts the longest or on edge of incoming cloud deck. Some IFR
decks possible under brunt of the cloud deck overnight into early
Sat morning, with 4-6SM VSBY around sunrise. Winds overnight to
maintain from the south at 8-12 KTs. With southwesterly winds at
30+ KTs projected aloft at around 2000 FT AGL toward 12z Sat, not
that far off of LLVL wind shear set up. Low MVFR cloud deck
expected for much of Sat morning with southerly SFC winds picking
up to 10-20 KTs by late morning.     ..12..




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