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fxus63 kdvn 162026 

Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
326 PM CDT Mon Sep 16 2019

..hydrology update...

issued at 256 PM CDT Mon Sep 16 2019

Dense fog burned off early this morning. In it's wake a mid-Summer
feel dominates, especially South/West of the Quad Cities where
pooling dew points in the 70s combined with above normal temps are
yielding heat index readings in the 90s across southeast Iowa,
northeast Missouri and west central Illinois. Areas North/East
of Quad Cities where the fog held on the longest mainly far
northeast Iowa into northern Illinois, more typical mid September
temperatures and slightly lower humidity levels prevail with
light easterly flow from Great Lakes ridging. The ridge axis will
not move all that much over the next 24 hours and as a result
not expecting much change in the overall sensible weather as well.


Short term...(this evening through tuesday)
issued at 256 PM CDT Mon Sep 16 2019

Some fog and low clouds are possible late tonight into Tuesday
mid morning, especially along and east of the Mississippi River
in closer proximity to the surface ridge axis and via some
advection potential from Lake Michigan. Winds are a bit stronger
tonight just above the surface and would support more stratus than
fog. Then add some high cloudiness albeit fairly opaque, and this
all adds to more uncertainty on the coverage and magnitude of the
fog tonight into Tuesday morning. For now have mainly patchy fog
mentioned and skies trending partly cloudy, and will just have
to monitor trends for any adjustments. Expect range in lows from
upper 50s northeast to upper 60s southwest.

Tuesday, will be fairly similar to today with any fog and low
clouds burning off in the morning. In it's wake mostly sunny
skies with a another mid-Summer feel southwest to typical September
feel northeast. Will have to keep tabs in our far southwest cwa for
stray weak diurnal convection late PM residing near weak low level
convergence axis and pooling moisture. For now the signal in some
of the cams is further South/West of our cwa.

Long term...(tuesday night through monday)
issued at 256 PM CDT Mon Sep 16 2019

Potential for heavy rainfall this weekend.

Tuesday night through friday: highly amplified pattern with a big
ridge in the east and deep trough in the west. This will keep our
area in the Summer-like weather with warm/humid conditions. Highs
will be in the 80s with lows well into the 60s to lower 70s.
Dewpoints will be on the muggy side around 70, quite high for mid
September. There will be chances for thunderstorms most favored
Wednesday night into Thursday as a weak disturbance arrives.

This weekend into early next week: this is when the active pattern
really sets in with periodic rounds of thunderstorms. Deep trough
will slowly makes it's way into the Midwest. This will pull copious
western Gulf moisture northward (along with Pacific moisture). This
will be a period to watch for heavy rain as an impressive 1.8 - 2.0"
precipitable water plume stems from the western Gulf into the upper Mississippi
Valley. Naefs is already showing integrated water vapor (iwv)
transport values around 2 Standard deviations above the mean for the
middle to end of September. While it is too soon to determine
rainfall amounts or locations of the heaviest rain, interests
especially along rivers should pay attention to later forecasts.
Also, too early to determine the severe potential. Highs will be in
the 70s to lower 80s with lows in the 60s to around 70.



Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 105 PM CDT Mon Sep 16 2019

Main focus is with fog and stratus potential again later tonight
into Tuesday am.

The greatest potential for fog and stratus again late tonight into
Tuesday am appears to be east of the terminals into northern Illinois
via Lake Michigan and being in closer proximity to the ridge axis and
near calm winds, and this is in agreement with general model
consensus. The terminals will be slightly further removed from the
ridge axis and have a bit more wind off the surface (around 10-20
kts at 500-1000ft agl per BUFKIT soundings), thus would support
more potential for stratus than fog. Direction in this layer is
forecast from south-southeast (130-160 degs) which is not the most favorable
direction (due east) for impacting terminals, but offers some
potential for stratus to impact dbq and mli should it develop far
enough southward off Lake Michigan toward central Illinois. Confidence is low
right now on this occurring and for now have just gone with MVFR
fog at the terminals while hinting also at the low cloud
possibility by including a scattered IFR stratus deck at the river


issued at 325 PM CDT Mon Sep 16 2019

We have raised Moline on the Rock River to moderate as the river
continues to rise, with additional contribution from the Green
River. Joslin continues to rise and is in moderate while como fell
below flood stage and the warning was cancelled.

On the Pecatonica River at Freeport the river will remain right
near moderate for the next several days.

The forecast calls for these rivers to fall below flood stage by
the weekend. However, an active weather pattern with periodic
showers and thunderstorms is expected later this week and into the
weekend. Additional heavy rainfall may cause the Pecatonica and
rock rivers to rise once again but it is too early to predict
rainfall amounts or where the heaviest rains may fall. Other
rivers across the area may also rise if repeated heavy rains occur.
Interests along rivers should pay attention to later forecasts.


Dvn watches/warnings/advisories...



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