Scientific Forecaster Discussion
fxus63 kdvn 200431
Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
1031 PM CST Tue Nov 19 2019
issued at 1213 PM CST Tue Nov 19 2019
Extensive, slow moving cloud cover was found across the area this
morning. This cloud cover has essentially held temperatures down
across the area. Looking a loft, an 850 mb ridge axis was located
across eastern Nebraska. 850 mb flow led to near zero temperature
advection. As such, the clouds will be very slow to leave the
Short term...(this afternoon through wednesday)
issued at 1213 PM CST Tue Nov 19 2019
1. Dense fog looking more likely tonight, especially in areas
where the clouds have cleared today.
2. Warm air advection will bring temperatures slightly above normal on Wednesday.
Perfect set up for fog tonight across the area as weak surface
flow is intersected with 850 mb warm air advection flow and moisture. This will lead
to widespread fog across the area. Areas that have clear skies
today have a good chance for dense fog to develop across the area.
Since clouds may still clear out across the west from where they
are currently, decided to hold off on a dfa. One will likely be
needed later tonight across the area, but at this juncture, not
entirely sure where it will be needed.
Into tomorrow, after the fog Burns off, expect temperatures to
climb into the 40s and 50s across the area. This will be just
about average for highs.
Long term...(wednesday night through tuesday)
issued at 210 PM CST Tue Nov 19 2019
An active weather pattern will dominate the extended into week 2
forecast. This is supported by all deterministic model data in the
12z suite, as well as past runs. For our forecast, we will focus on
the 1st storm system, which will arrive Wednesday night.
A fast moving, synoptic storm system will sweep through the region
Wednesday night through Thursday. The track of this low pressure is
expected to move just northwest of the Highway 20 counties,
resulting in a forecast of all liquid precipitation for our area.
That track will allow for nearly all of the precipitation to fall in
the isentropic lift as the system arrives, which will largely occur
during the period from 9 PM Wednesday evening to 9 am Thursday
morning. A widespread rain is anticipated, with amounts generally
ranging from 0.25 to 1 inch. The highest totals synoptically will
favor locations northwest of our cwa, but with some possibility of
cape being entrained into the County Warning Area will allow for another maximum of
heavier totals in the thrust of strong moist warm air advection which will directly
cross through the County Warning Area. This difference in qpf is more of a
reflection of cape or lack there of, as the namnest, and other
mesoscale models bring mixed layer cape Thursday morning into a
short period of 200 to 500 j/kg, with the same time period
suggesting sfc-500mb bulk shear values in excess of 50 kts. Thus,
any updraft will rotate, but that is not a guarantee that we'll have
updrafts! Rather, an "if then" statement of if we can get storms to
briefly move through the the strongly forced low pressure passage,
we may see a low threat of both lightning, and with the rotation,
tornadoes. This threat remains low enough, that it will be only
mentioned in this afd for now.
Following Thursday morning's low passage and lingering Post frontal
light rains, we will be dry through Monday, as the next system
passes to the south of the region. The pattern of synoptic storms
will once again re-Load it's western deep trof for Monday into
Tuesday, with that trof entering the plains and forming another
strong synoptic low pressure. For now, models depict a wide open
Gulf, and slow progression east of this low pressure next week. That
will favor seasonally heavy rainfall in the region, and for some
western portion of the low's track, a possible snow event.
Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1015 PM CST Tue Nov 19 2019
Areas of fog are expected tonight, lasting into Wednesday
morning. Shallow dense fog has already developed at kdbq, which
should become more widespread and thicker later tonight. With the
fog increasing in coverage and severity, periods of LIFR are
possible -- the best chances at kdbq and kbrl. The fog will be
slow to dissipate Wednesday morning, especially at kdbq where it
could persist through 10-11 PM.