Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kdvn 131225 

Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
625 am CST Wed Nov 13 2019

..aviation update...

issued at 242 am CST Wed Nov 13 2019

Cold conditions continue across the region early Wednesday, with
increasing high clouds and southerly winds. 07z msas surface
analysis shows a strong 1033 surface high drifting over the Ohio
River valley and a surface low starting to develop on the Lee side
of the Colorado rockies. Pressure gradient between these two
systems has allowed south winds to gust up to 20 mph this
morning. Looking aloft, two notable shortwaves were observed on
GOES WV imagery moving over southern ND and central Wyoming. These will
bring our precipitation chances this afternoon and evening.

At 2 am, temperatures were in the teens over the County Warning Area. This is 15+
degrees below normal, but several degrees above record lows for
the 13th.


Short term...(today and tonight)
issued at 242 am CST Wed Nov 13 2019

Main forecast concerns focus on precipitation chances late this
morning through the evening with a clipper system and high
temperatures today.

Latest 00z models, National guidance, and cams have come in
weaker with the system today and thus I have lowered quantitative precipitation forecast/snow
totals. This event will be all snow across our area, as the Max
wet bulb aloft remains above 0c. Most, if not all areas along
Highway 30 and north will see less than 1 inch of snow. Expect
mixed precipitation to start over north central Iowa this morning
and quickly change over to snow as it approaches eastern Iowa.
Forecast soundings also suggest quite a bit of dry low level air
that will need to saturate first and there may be a delay with the
onset of snow until early afternoon. 07z rap low level
convergence fields and 800-850 fgen progs increase after 18z
across northeast IA, as the stronger mid level wave drops
southeast over Minnesota. This will be when most of our snowfall occurs
between noon and 6 PM. Stronger signal for heavier snow is near
our northern border or just north of our area today and our
precipitation should end by 10 PM for all areas.

South winds to increase this morning between 20 and 30 mph and
may lead to some blowing and drifting of already fallen snow in
open or rural areas. These winds will decrease by late
morning or early afternoon, as the pressure gradient relaxes.

Increasing cloud cover and the current snow pack will make for a
challenging temperature forecast today. Will go with below
freezing highs over snow covered areas, to the mid to upper 30s
elsewhere. A cold front will push through the region tonight, with
winds switching out of the northwest and lows dropping into the
upper teens to lower 20s.

Long term...(thursday through tuesday)
issued at 242 am CST Wed Nov 13 2019

A warmup is expected with mostly dry conditions. Upper level
pattern will become more zonal and even southwesterly, as a wave
dives south into Colorado and nm Saturday night. Models differ on timing
of any precipitation chances, but most of them largely agree on
Saturday night-Sunday and on Tuesday and thus slight chance pops
are forecast. Any precipitation is expected to be light, with
rain being the dominant precipitation type. The great news about
the long term will be temperatures increasing into the 40s and
even some 50s by early next week, which is where we should be for
highs for the middle of November. This will help get rid of much
if not all of the snow cover over the forecast area.


Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 615 am CST Wed Nov 13 2019

Gusty south winds up near 25 kts this morning will decrease and
veer to the west-southwest this afternoon. Minor drifting of snow is possible
in open areas before the winds subside, mainly at kcid and kdbq.

A narrow band of light snow will move through eastern Iowa this
afternoon into tonight. However, its exact placement is
uncertain. Kdbq has the best chance for a period of light snow and
MVFR/IFR visibilities, while kcid is on the edge. MVFR ceilings
are then possible through tonight, especially north of kbrl.


Dvn watches/warnings/advisories...


National Weather Service Glossary of Abbreviations