Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

Home | 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 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
670
FXUS63 KDVN 202128
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
328 PM CST Tue Feb 20 2018


.SYNOPSIS...
Issued at 325 PM CST Tue Feb 20 2018

Latest sfc analysis was indicating occluding low acrs the U.P. of
MI, with main trailing cold front dropping down acrs north central
IL and then down toward the St Louis MO area. Seasonably impressive
long fetch moist conveyor of showers with some embedded thunder
stretching all the way from southern TX, to the heart of the GRT
LKS. Post-frontal northwest winds increasing to 15 to 20 KTS acrs
the western CWA, with some drier sfc DPT influx noted. This will
eventually lead to a wintry mix scenario again on the western flank
of lingering over-running precip band this evening. Then active
southwest flow will continue to make for a challenging fcst period
with precip system possible almost every other day into the
weekend.

&&

.SHORT TERM...(This Evening and Tonight)
ISSUED AT 325 PM CST Tue Feb 20 2018

Tonight...With post frontal cooling and drying LLVL fetch feeding
into the backside of the rather slow moving precip conveyor, feel
there will be another transition to freezing rain profiles as the
late afternoon and especially evening progress...especially along
and east of the MS RVR generally from far northeastern MO,
northeastward to the Princeton and Sterling IL areas. Toward the end
of the period, cold air may deepen enough for some sleet to mix in,
before the precip train pushes off to the east. Will issue a new
Winter Weather Advisory for primarily the freezing rain acrs the
southeastern third or more of the DVN CWA, with up to a tenth of an
inch of glaze possible. Will run it to 09z Wed morning for a buffer
end time , but several of the latest HiRes models wind it down
several hours before then. The rest of the CWA will have to watch
out for freezing up wet surfaces and puddles this evening, if the
increasing northwest winds don`t dry up the surfaces before then.
Flurries noted in the stratocu deck out acrs central into western IA
ATTM, and some of these may make it into the local area later this
evening. Will go with lows in the low 20s in the east, to the low
teens or around 10 in the northwest. These northwestern areas will
also have wind chills around or below zero toward 12z Wed morning.
..12..

.LONG TERM...(Wednesday through next Tuesday)
ISSUED AT 325 PM CST Tue Feb 20 2018

Forecast focus on active pattern through this weekend. This forecast
based heavily on the GFS, as the ECMWF was not available as of this
writing.

Wednesday...Mostly sunny but cold with highs in the mid 20s to lower
30s. Clouds should be on the increase during the afternoon
especially across our southern half of the cwa. This will be ahead
of the next upper level disturbance ejecting out the main western
trough.

Wednesday night and Thursday: Potential for a winter weather
advisory headline for our southern and western counties for a
combination of light snow and freezing rain. Forecast soundings
suggest the freezing rain may be confined to our southern cwa while
the snow would be in our north. During the afternoon, warmer air
coming northward would change everything over to rain. Lows will be
in the upper teens to mid 20s with afternoon highs in the 30s. As of
now, ice accumulations are expected to be less than a tenth of an
inch with snow amounts less than an inch.

Thursday night and Friday...Another upper level disturbance (and a
bit stronger) will push into the Midwest in the fast southwest flow.
This system will also have more moisture to work with. This also
looks to be a freezing rain event, especially in our northern half.
This too may need a winter weather advisory headline with ice
accumulations between one and two tenths of an inch possible. Warmer
air arriving by afternoon should change the freezing rain over to
rain. Lows will be in the 20s north to the 30s south with highs
pushing into the 40s.

Friday night through Sunday: A potent storm system will arrive as a
negatively-tilted trough pushes out of the southern Rockies and into
the Midwest during this time frame. The GFS takes a deepening
cyclone from the OK Panhandle 12z Sat (1006 mb) to eastern IA 06z
Sun (991 mb) to the eastern Great Lakes (980mb) later on Sunday.
This may start out as light snow but change to light moderate rain
(possibly heavy rain) and then back to snow as the system pushes off
to the northeast. This system bears watching especially if the ECMWF
is on board. Any additional rain would aggravate any existing
flooding at that time. Caution: this is low confidence at this time
without seeing what the 12z/20 ECMWF showed.

Haase

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
ISSUED AT 1140 AM CST Tue Feb 20 2018

More organized rain with embedded thunder shifting east of the
terminals, but secondary rain bands still to move up through at
least mid afternoon and affect all sites except maybe CID. Varying
MVFR to IFR Cigs and VSBYS through mid to late afternoon with the
lingering precip, with increasing west to northwest sfc winds of
10-15+ KTs. Some concern a strip of freezing rain, possibly mixed
with snow and sleet will occur on the western fringe of the
departing precip shield during the late afternoon and early
evening, especially at BRL and MLI. The freezing rain will look to
hang on longest at BRL possibly to 8-9 PM before shifting east of
the MS RVR. Brisk northwest winds overnight into Wed morning with
improving CIGS behind a frontal passage.   ..12..

&&

.HYDROLOGY...
Issued at 1116 AM CST Tue Feb 20 2018

Rainfall since yesterday was 1 to 2 inches across much of the cwa
with isolated 3 inch amounts in western IL. Additional 1/2 to 1
inch of rain is expected today. This amount of rain, falling on
frozen ground, has resulted in rapid rises on many rivers and streams.
There is high confidence in these river forecasts.

Details:

Rock River:

Major flooding is forecast at Moline, with moderate
at Joslin and minor at Como. The river will rise above flood
stage Wednesday morning.

La Moine/Green/Wapsipinicon River:

Moderate flooding is forecast at Colmar, Geneseo, and De Witt.

Maquoketa/English River:

Minor flooding is forecast at Maquoketa and Kalona.

Pecatonica River:

A flood watch has been issued for Freeport.

Areal flood warning is in effect for portions of northwest IL and
extreme eastern IA until 1015 am on Wednesday. Additional flooding
is possible.

Please see the flood warning and flood watch products for updated
forecasts.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flood Watch until 6 PM CST this evening for Clinton-Des Moines-
     Henry IA-Jackson-Lee-Louisa-Muscatine-Scott-Van Buren.

     Winter Weather Advisory until 3 AM CST Wednesday for Des Moines-
     Lee.

IL...Flood Watch until 6 PM CST this evening for Bureau-Carroll-
     Hancock-Henderson-Henry IL-Jo Daviess-McDonough-Mercer-
     Putnam-Rock Island-Stephenson-Warren-Whiteside.

     Winter Weather Advisory until 3 AM CST Wednesday for Bureau-
     Hancock-Henderson-Henry IL-McDonough-Mercer-Putnam-Warren-
     Whiteside.

MO...Flood Watch until 6 PM CST this evening for Clark-Scotland.

     Winter Weather Advisory until 3 AM CST Wednesday for Clark-
     Scotland.

&&

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...Haase
AVIATION...12
HYDROLOGY...Haase



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