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
FXUS63 KDVN 242111

Area Forecast Discussion
National Weather Service Quad Cities IA IL
311 PM CST Sat Feb 24 2018

Issued at 310 PM CST Sat Feb 24 2018

An overcast sky and cold east breeze continued during the early
afternoon, with areas of light rain, drizzle and light fog.
Temperatures were mainly in the 35 to 40 degree range. A large
area of showers and embedded thunderstorms approached the area
from the south, but are only expected to brush far northeast
Missouri and west central Illinois through the late afternoon.


.SHORT TERM...(Tonight)
ISSUED AT 310 PM CST Sat Feb 24 2018

The main forecast issues in the short term period are
precipitation type and amounts tonight, and strong westerly winds.

In the near term, high res models have a good handle on the rain
shield to the south, and barely clip the southern counties through
late afternoon. The main period of precipitation will be from 5 pm
to 11 pm as rain spreads across the entire forecast area. Rainfall
amounts are not expected to be high enough to cause further river
flooding, but there may be some nuisance ponding. A few
thunderstorms may develop during the early evening, mainly along
and east of the Mississippi River. The favorable severe weather
parameters should remain well to the southeast, although an
isolated storm may generate some small hail. Cooling aloft should
be sufficient for a quick change over to all snow in the far
northwest, with any wet accumulations likely limited to less than
an inch. Precipitation should be all rain elsewhere across the
forecast area.

After midnight, a strong westerly wind will increase, with gusts
of 35 to 40 mph. Due to the wet nature of any snow, blowing snow
should not be an issue, although there may be some shallow
drifting in the far northwest counties. Am not expecting advisory
criteria winds at this time.

.LONG TERM...(Sunday through Saturday)
ISSUED AT 310 PM CST Sat Feb 24 2018

Sunday...Post frontal, drying day with lingering brisk west winds of
15 to 25 MPH decreasing late in the day. Mixing wind profiles,
combined with some late Feb insolation to help temps make it up well
into the 40s acrs most of the area. Overnight lows in the 20s, and
will have to watch developing light south to southwest llvl flow for
non-diurnal trends into Monday morning on backside of departing
sfc ridge.

Monday and Tuesday...The latest suite of 12z run medium range models
generally dig a closed upper low into a L/W Trof acrs the desert SW
and far northern Baja this period, while resultant broad
southwesterlies take shape from the deep southwestern plains to the
southern GRT LKS. Increasing southerly LLVL flow to make for two
seasonably mild days this stretch, with some upper 50s to low 60s
likely by Tuesday. A sfc boundary sagging down acrs the region and
becoming increasingly aligned and stalled under this flow, may act
as a moisture convergence agent by Tue night. Light precip may break
out in the vicinity of this feature, and depending on where it lays
out, occur in the local area. the 12z GFS and NAM suggest light rain
along this feature north of I80, with some possible precip type
issues popping up north of the boundary late that night if sfc/BL
temps can cool enough. Other precip fields may be advecting into the
southern CWA at that time as well but would remain all rain down
there. The 12z ECMWF is mainly dry through 12z Wed with the front
hanging up further to the northwest. May be some localized fog
issues as well around the front late Tue night.

Wednesday through next Saturday...Main feature of consequence this
mid to late week period, is that several medium range models roll
out east-northeastward the western upper trof, resulting in a
"bowling ball" of a llvl cyclone rolling east somewhere acrs the MS
RVR Valley. Much will depend on eventual phasing and handling of
this wave, but several models such as the 12z GFS and ECMWF are
unusually/unseasonably wet with this system. Potentially heavy rain
in or near the local fcst area(if the latest models are near to
being correct...a big "if") mainly from late Wednesday through
Thursday. On the western flank of this rather slow roller, strong
sfc winds and dynamical cooling may make for some dicey winter-type
conditions with wet snow accums in the west and northwestern fcst
anywhere form late Wed night into Thu, again if current model timing
and top-down cooling parameters unfold. The models will continue to
vary and be inconsistent with their phasing of this system, and will
have to look a upper jet trends around this potentail low pressure
system as well over the next several days. Can the sfc low really
deepen below 990 MB like the latest models indicate as it passes
eastward acrs the area? Temp trends on either side of the system
along with the potential QPF, still vary much up in the air and will
make just general trends for now of the latest solution indications.

Dry ridging both at the sfc and aloft should follow into the start
of next weekend in the wake of whatever storm system can(or cannot)
materialize during the midweek.   ..12..


.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
ISSUED AT 1134 AM CST Sat Feb 24 2018

Expect mainly drizzle, low stratus, and MVFR fog this afternoon.
Another round of precipitation will arrive this evening, with a
4-5 hour window from west to east. P-type at TAF sites is expected
to be predominately rain, although cannot rule out a brief mix at
KDBQ this evening. Surface winds will become strong and gusty from
the west overnight, in the wake of the exiting surface low, as
ceilings and visibilities improve through daybreak.


Issued at 1134 AM CST Sat Feb 24 2018

Rock River

Major flooding continues to affect Joslin and Moline along the Rock
River. Joslin has reached crest and has begun slowly falling over
the past few hours, with the current forecast taking it below major
flood stage by late Sunday afternoon. However, changes in river
levels are possible until ice completely breaks up.

Pecatonica River

A crest into major flooding is expected at Freeport early morning
Monday. Also, renewed rises on Yellow Creek are possible, so people
affected by the creek should remain alert.

Rainfall amounts up to 0.3 inches are expected tonight. This
additional rain is not expected to have a significant impact on
area rivers.




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