Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 291026
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
526 AM CDT Fri Mar 29 2024

.KEY MESSAGES...

- Elevated (High based) thunderstorms are expected tonight, with
hail possible with the strongest cells.

- Periods of rain likely Sunday and Sunday night with additional
elevated thunderstorms possible.

- Severe weather chances early next week remain low, but are tied to
the placement of the quasi-stationary frontal zone.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 242 AM CDT Fri Mar 29 2024

A stationary front has shifted south a bit early  this morning, and
is found in our southern CWA as of 2 AM. Near the front,
temperatures are holding near 50, while north of it is in the upper
20s to mid 30s. There remains a thin band of altocumulus clouds and
cirrus over the region, with WAA over top of this frontal zone.

Today, the front is forecast to shift north a bit, with mild
temperatures over nearly all of the CWA. Highs near 60 north will
transition to upper 60s along and south of I-80. The day should be
dry, as we wait for the LLJ strengthening tonight for our chances
for showers and thunderstorms.

Tonight, AC should again be spreading over the CWA early in the
evening, as the advection increases over the nearby frontal zone. A
wave approaching from the west is forecast to combine with a
strengthening LLJ to produce high based shower and thunderstorms
tonight. These are expected to initiate over eastern Iowa
during the 7 to 9 PM time frame, then progress east and increase
in coverage. While the timing is agreed on by models, the
widespread vs isolated nature of storms is quite varied. No
matter that, the initial updrafts should support hail up to
quarter size given the steep mid level lapse rates and modest
CAPE of 500-1000 J/KG forecast by CAMs tonight. Rainfall amounts
should be generally quite light, but where storms downdrafts
track, 0.25 to 0.5 are possible, there could be some training in
narrow swathes as well tonight, so a localized inch is
possible. SPC has introduced a marginal risk for severe hail in
our CWA tonight.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 242 AM CDT Fri Mar 29 2024

Saturday and Saturday night, the front is expected to drop well
south again, with highs in the 50s to lower 60s, and lows in the mid
30s to lower 40s. This should be a temporary dry period, until after
midnight, when warm advection begins to spread moisture northward
again.

There are two camps for the Sunday through Monday period in
deterministic models.  The northern camp, supported by 00z GFS,
suggests heavy precipitation of 1 to 2 inches, with rain, and
elevated thunderstorms, followed by a low passing by Monday night
that could bring some stronger storms nearby. SPC will be going with
a marginal risk for areas along and south of I-80 in the day 3
outlook.

The southern camp, supported by deterministic EC, is much farther
south, and has our CWA has a cold rain, focused mainly in the
southern CWA.

Ensemble mean solutions are a good blend of the two positions, with
mainly a rain event of 1 to 2 inches over the southeast 2/3rds of
the CWA.

No matter how these details shake out, this synoptic boundary/low
pressure will certainly bring another breezy to windy period. There
is low confidence regarding temperatures later in the extended as
NBM mean is in the 50s to lower 60s, but with a deep trof over the
Great Lakes in many solutions, it appears we could be around 10
degrees cooler.

ERVIN

&&

.AVIATION /12Z TAFS THROUGH 06Z SATURDAY/...
Issued at 524 AM CDT Fri Mar 29 2024

VFR weather will continue through early evening hours today,
with winds generally blowing from the southeast around 10 kts
through tonight, then south winds return, with some potential
for gusts over 20 kts by the end of the period. This transition
will be due to a warm front developing over the area, and with
that an increase in mid clouds today will be followed by a round
of high based showers and thunderstorms this evening,
developing first between 00-03z in Iowa, then spreading quickly
through Illinois by 06z, and decreasing after midnight. Some
brief heavy downpours and hail are possible within these storms.

Late in the period, some MVFR cigs are expected to move
southward into northeast Iowa affecting CID and DBQ.


&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...Ervin
LONG TERM...Ervin
AVIATION...Ervin


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