Areal Flood Warning 14, NWS St. Louis, MO

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
646 AM CDT Mon May 1 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 325 AM CDT Mon May 1 2017

Upper level low has moved into northwest MO with the surface low
just ahead of it in southwest IA. Still getting areas or bands of
light rain or showers rotating around the low, particularly
across parts of IA and northwest MO. The upper level low and
associated surface low will move northeastward through IA and WI
today. Will continue to get scattered light showers or areas of
light rain today, mainly across northeast and central MO and west
central IL, north and west of STL. The QPF from this rain should
be quite low, not enough to aggravate the current flooding from
weekend heavy rains. Any precipitation should shift northeast of
our forecast area by this evening as the low continues to move
further northeast of the region. With plenty of low level clouds
today to hinder solar insolation coupled with cold 850 mb
temperatures around zero degrees C over the forecast area will see
cool high temperatures, around 15 degrees below normal for the
first of May. There will also be relatively strong and gusty winds
today due to the tight surface pressure gradient on the backside
of the deepening surface low. Cool conditions will continue
tonight as the low level clouds advect northeast of the forecast
area and the surface winds gradually weaken.

GKS

.LONG TERM...  (Tuesday through Sunday)
Issued at 325 AM CDT Mon May 1 2017

After a dry day on Tuesday, precipitation chances will increase
again on Tuesday night in response to an approaching disturbance.
This feature will dive southeastward and develop into a mature
low pressure system by Wednesday night. The surface low initially
develops south and southeast of the CWA before the entire system
lifts northeastward, a placement which would keep the most
unstable air out of the CWA and limit the available instability.
Therefore, widespread rain is expected with this system rather
than widespread thunderstorms. Although any additional rainfall
will undoubtedly exacerbate ongoing river and areal flooding
across the region, the lack of convective downpours will lessen
the additional impacts. Most of the rain with this system is
expected to fall on Wednesday, Wednesday night, and Thursday,
although some showers may linger into Thursday night and early
Friday morning. An additional 1-1.75" of rain is currently
forecast for the Wed-Thu period.

By midday Friday, the low pressure system will have moved far
enough away from the region for most areas to remain dry through
early Saturday morning. At that time, a separate vorticity maxima
will dive down the back side of a trough and could bring a few
showers to the northern or northeastern CWA, primarily over west
central or southwest Illinois. An upper ridge over the western
CONUS will begin to shift eastward, eventually reaching MO/IL
towards the end of next weekend and early next week.

High temperatures will be 5-15 degrees cooler than average across
the area between Tuesday and Friday. Overnight lows will
generally be in the 40s this week.

Kanofsky

&&

.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 630 AM CDT Mon May 1 2017

Low pressure over IA will move northeastward into the Great Lakes
region later today. Areas of light rain will move through COU and
UIN today. MVFR cigs in western and central MO will advect into
UIN and the St Louis metro area later this morning. Strong and
gusty southwest winds will veer around to a westerly direction by
late this afternoon or early this evening, then weaken tonight.
The MVFR cigs will clear out this evening.

SPECIFICS FOR KSTL: Low pressure over IA will move northeastward
into the Great Lakes region later today. Could see a few sprinkles
today. MVFR cigs in western and central MO will advect into STL
later this morning. Strong and gusty southwest winds will veer
around to a westerly direction by early this evening, then weaken
tonight. The MVFR cigs will clear out this evening.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

WFO LSX

Hazardous Weather Outlook
National Weather Service Saint Louis MO
522 AM CDT Mon May 1 2017

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-020000-
Greene IL-Macoupin IL-Montgomery IL-Bond IL-Fayette IL-Clinton IL-
Marion IL-Washington IL-Randolph IL-Adams IL-Brown IL-Pike IL-
Calhoun IL-Jersey IL-Madison IL-Saint Clair IL-Monroe IL-Knox MO-
Lewis MO-Shelby MO-Marion MO-Monroe MO-Ralls MO-Pike MO-Boone MO-
Audrain MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO-
Lincoln MO-Gasconade MO-Warren MO-Saint Charles MO-Franklin MO-
Saint Louis MO-Saint Louis City MO-Jefferson MO-Crawford MO-
Washington MO-Saint Francois MO-Sainte Genevieve MO-Iron MO-
Madison MO-Reynolds MO-
522 AM CDT Mon May 1 2017

This hazardous weather outlook is for portions of eastern and
central Missouri as well as west central and southwest Illinois.

.DAY ONE...Today and Tonight

Flooding is ongoing on many area rivers. Some river basins where
major and possibly record river flooding is forecast include the
Cuivre, Big, Bourbeuse, Gasconade, Meramec, Illinois, and
Kaskaskia.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Flooding is ongoing on many area rivers. Some river basins where
major and possibly record river flooding is forecast include the
Cuivre, Big, Bourbeuse, Gasconade, Meramec, Illinois, and
Kaskaskia.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated through tonight.

Kanofsky

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