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fxus63 kdvn 181754 
afddvn

Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
1154 am CST Mon Nov 18 2019

..aviation update...

Synopsis...
issued at 312 am CST Mon Nov 18 2019

The upper level trough, weak surface cold front and associated light
rain that affected the region yesterday was over the western Great
Lakes early this morning leaving a weak ridge axis centered from MO
northward across eastern Iowa into se Minnesota. Temperatures were in the
lower to mid 30s with light northwest winds. Lingering low level
moisture immediately in the wake of the system was producing light
fog over northwest Illinois. Widespread stratus covered the entire
forecast area with satellite fog channel imagery showing the back
edge of this low cloud deck reaching from far southwest Scotland
County MO northwest through central Iowa. This was aligned with the
northwest flow aloft and has made very little eastward progress
overnight. The next upstream shortwave in the was seen on water
vapor imagery over eastern Mt, while a weaker impulse was over the
Central Plains. An associated trough/warm front stretched across
central South Dakota into northern NE, marked the leading edge of a transition
from readings in the 30s east to 40s to its west. As these features
progress southeast, they will bring another chance for at least
light precipitation across the forecast area later today and
overnight.

&&

Short term...(today and tonight)
issued at 312 am CST Mon Nov 18 2019

The main focus in the near term is the potential for light
precipitation with the weak clipper system tonight. Otherwise, there
are good indications that the cloud cover will remain in place,
providing little warming today and then holding temperatures above
freezing over most of the area overnight.

Lingering low level moisture, developing warm air advection above
the surface inversion, incoming mid and high level clouds and
overall weak surface wind fields support the low cloud cover hanging
strong today through tonight. The current back edge of the
clearing may temporarily reach into northwest MO and possibly a
portion of far southeast Iowa early this morning, but with the
incoming higher level clouds, the overall effect will be mostly
cloudy skies. A developing weak low level warm advection
southerly flow ahead of the approaching system and limited
insolation will be needed to allow temperatures to reach afternoon
highs ranging from the mid 30s over northwest Illinois to the mid
40s in southeast Iowa and northeast Missouri. Some high res
models suggest the weak impulse over the plains may bring light
rain into the far south by late afternoon, but there is little
model agreement or support for this and for now will keep pops
below slight chance this afternoon.

Tonight, the weak clipper system moves through with the best support
for precipitation with the Montana shortwave shown by the GFS, NAM and hi
res models possibly impacting east central Iowa into northwest Illinois
overnight. The European model (ecmwf) and Canadian models are in a slightly different
Camp, indicating a stronger, secondary vorticity maximum passing
through MO into southern IL, which would support precipitation
reaching further southward and possibly greater coverage. For now,
there is little to strongly support either scenario and will split
the difference with chance pops over most of the area for what
should be mainly be just a few hundredths of an inch of light rain
and possibly a brief mix of snow in the north. The lingering stratus
will hold temperatures in the 30s. This, along with light
precipitation and warm pavement temperatures, will provide little
threat for any snow or ice accumulations.

Long term...(tuesday through sunday)
issued at 312 am CST Mon Nov 18 2019

Key messages:

1) temperatures on a warming trend through Wednesday, cooler by the
weekend

2) several chances of precipitation, especially Wednesday night and
Thursday

Tuesday and Wednesday...

Cold front from the short term period will pass across the region
early Tuesday morning, taking any precipitation with it. Behind the
front, Tuesday should shape up to be a decent day overall with
clouds breaking by the afternoon. Almost immediately behind the
front, an 850 mb ridge will build over the eastern Great Plains and
Midwest, with a warmer air mass in Tow. Forecast soundings are
indicative of strengthening warm air advection in the column across the area
beginning Tuesday night.

The 850 mb ridge, southwest flow and warm air advection will continue into
Wednesday, and is expected to give US afternoon highs well above
average for a change. Currently have afternoon highs Wednesday
ranging from the upper 40s over northwest Illinois, to near 60 over
southeast Iowa, west central Illinois and northeast Missouri. Some
deterministic guidance such as the European model (ecmwf) and GFS actually show
warmer temperatures, so expect further change with this in the
coming forecast packages.

Wednesday night and Thursday...

Alas, with that warmth must come a chance for precipitation at some
point, and that is what we will see early Wednesday night and
Thursday. Latest guidance coming into much better agreement with a
surface low and attendant 500 mb shortwave passing over western or
central Iowa at that time, which firmly places our entire County Warning Area in the
warm sector. Rain showers, and potentially some thunder (guidance
hinting at some weak instability) will be prevalent in the warm
sector before a cold front arrives by early to mid afternoon
Thursday. The timing of this front will be key in determining our
overall chances of storms and our daytime highs, which both are
still low confidence at this point.

Thursday night on...

The weather will turn quiet with high pressure taking control
through the weekend. The European model (ecmwf) and CMC attempt to bring a system
through the mid-Mississippi River valley Saturday morning, but
confidence of this remaining in the forecast 7 days out is low and
pops remain at slight chance to chance for now. Temperatures will be
near to below average for the period.

&&

Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1139 am CST Mon Nov 18 2019

Expect MVFR to periods of IFR conditions to continue at all taf
sites into this evening ahead of a second storm system that will
move across the area this evening. This bring a round of light
rain to all taf sites overnight with generally MVFR ceilings and
visibilities. Low confidence that ceilings will go down to IFR
Tuesday morning at kcid and kdbq so I kept them IFR for now. A
cold front will move across the area after 10 UTC on Tuesday
brining precipitation to an end and turning the winds around to
the west behind the front.

&&

Dvn watches/warnings/advisories...
Iowa...none.
Illinois...none.
MO...none.
&&

$$

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