Excessive Heat Warning 1, NWS St. Louis, MO

Area Forecast Discussion
National Weather Service Saint Louis MO
353 AM CDT Fri Jun 15 2018

.SHORT TERM...  (Through Late Tonight)
Issued at 353 AM CDT Fri Jun 15 2018

Isolated SHRA/TSRA had developed early this morning near an
elevated warm frontal boundary which was draped across central IL.
These cells were slowly drifting southward into southwest IL and
should continue to percolate into the mid-morning hours.

An upper ridge will remain across the region today and tonight. At
the surface, a low pressure center was located across the northern
plains early this morning, and a warm front extended southeastward
from the surface low through MN/IA/IL and into KY/TN. The warm front
is expected to quickly lift northeastward this morning, and a
hot/humid air mass will then spread across the region. Isolated
SHRA/TSRA will be possible across most of the area during peak
heating.

Attention then turns to the hot/humid conditions for today. With air
temperatures in the low/mid 90s and dew points in the 70s, peak heat
index values of around 100-105 degrees are expected across most of
the area today. The warmest values (near 105) are expected in and
near the St. Louis metropolitan area. Hot/humid conditions will
persist for the next few days (see the long term forecast discussion
below). Due to the duration of these oppressively hot/humid
conditions, the Heat Advisory in the St. Louis metropolitan area has
been upgraded to an Excessive Heat Warning and a separate Heat
Advisory has been issued for all but the southern section of the
CWA.

Kanofsky

.LONG TERM...  (Saturday through Thursday)
Issued at 353 AM CDT Fri Jun 15 2018

This period can be summarized with dangerous heat and humidity
ongoing thru Monday with minimal chances for rain, with a slightly
cooler period from Tuesday on with higher chances for rain.

The first significant wave of dangerous heat and humidity is
expected to be ongoing on Saturday and continue into at least Monday
now.  An upper level RIDGE will be overhead at the start of the
period and is expected to dominate our region into Monday, with the
latest model solutions strengthening the position of the RIDGE into
early next week.  This will correspond to any frontal boundaries
remaining well to our north with a steady south to southwest flow at
the surface.  Daytime max temperatures are expected to be in the mid
to upper 90s, with the highest temperatures expected in the typical
heat island of the Saint Louis metro area and with the hottest days
on Saturday and Sunday where the upper RIDGE will be most dominant.
Dewpoints in the lower 70s for much of the region will yield max
heat index values around 105F each day in the Saint Louis metro
area, tapering to around 100F for other areas.  Based on this, the
Heat Advisory for the Saint Louis metro area has been extended in
time to early Monday evening for at least 4 days of 105+ daily
peak heat index values, with an expansion to much of the rest of the
forecast area for Friday thru Monday based on at least 4 days of
100+ daily peak heat index values.  This places all but the eastern
Ozarks of southeast MO in a Heat Advisory, and upgrades the STL
metro area counties into an Excessive Heat Warning.

There is an increasing trend where the upper RIDGE may continue to
hang on deeper into next week and keep the cold front locked up to
our north.

As it stands now, the RIDGE is still expected to weaken--just a day
later on Tuesday--which should allow the surface cold front to our
north to edge into our area, increasing rain chances and dropping
max temps into the upper 80s and lower 90s, which is still slightly
above average.  This trend looks to continue to the end of the
forecast period.

TES

&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1232 AM CDT Fri Jun 15 2018

Mainly dry and VFR conditions are expected during the period. Only
exceptions will be late Friday afternoon and early evening when
isolated thunderstorms may develop across eastern Missouri and
southwest Illinois which may affect the St. Louis area terminals.
Confidence is too low to include in the terminal at this time,
but any thunderstorm could bring brief MVFR or IFR ceilings and
visibilities. Otherwise, winds will be mainly out of the south
during the period.

SPECIFICS FOR KSTL:

Mainly dry and VFR conditions are expected the next 30 hours with
south winds. There is a slight chance of thunderstorms late Friday
afternoon and evening, but confidence is too low to include in
the terminal at this time. Any thunderstorm could bring brief
MVFR or IFR ceilings and visibilities.

Britt

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory from noon today to 8 PM CDT Monday for Audrain MO-
     Boone MO-Callaway MO-Cole MO-Franklin MO-Gasconade MO-Knox
     MO-Lewis MO-Lincoln MO-Marion MO-Moniteau MO-Monroe MO-
     Montgomery MO-Osage MO-Pike MO-Ralls MO-Shelby MO-Warren MO.

     Excessive Heat Warning from noon today to 8 PM CDT Monday for
     Jefferson MO-Saint Charles MO-Saint Louis City MO-Saint
     Louis MO.

IL...Heat Advisory from noon today to 8 PM CDT Monday for Adams IL-
     Bond IL-Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-
     Jersey IL-Macoupin IL-Marion IL-Montgomery IL-Pike IL-
     Washington IL.

     Excessive Heat Warning from noon today to 8 PM CDT Monday for
     Madison IL-Monroe IL-Saint Clair IL.

&&

WFO LSX

Hazardous Weather Outlook
National Weather Service Saint Louis MO
423 PM CDT Thu Jun 14 2018

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-151145-
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-
423 PM CDT Thu Jun 14 2018

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

.DAY ONE...Tonight

Strong to locally severe thunderstorms remain possible through
early this evening. Main threats will be locally damaging winds to
60 mph and large hail to the size of quarters.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

A dangerous combination of heat and humidity is expected to begin
Friday afternoon for portions of the area and continue through at
least Sunday, and possibly into Monday. Peak heat index values
will range from 100 to 106 each afternoon and early evening. The
highest values will occur in the Saint Louis metro area, where a
Heat Advisory has been issued from Friday afternoon through early
Sunday evening. See the Heat Advisory product for additional
details.

The chance for non-severe thunderstorms will continue over parts
of the area on Friday, then resume again for Monday, Tuesday, and
Wednesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is possible through early this evening.

Deitsch

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE ST LOUIS MO
955 PM CDT THU JUN 14 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0200 PM     TSTM WND DMG     QUINCY                  39.93N 91.39W
06/14/2018                   ADAMS              IL   PUBLIC

            CORRECTS PREVIOUS TSTM WND DMG REPORT FROM
            QUINCY. LARGE TREE DOWN ON OR NEAR A HOUSE
            AT THE CORNER OF SOUTH 24TH STREET AND
            PAYSON ROAD. TIME IS ESTIMATED.

&&

BRITT

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
1043 PM CDT THU JUN 14 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0621 PM     TSTM WND DMG     2 SE HOUSE SPRINGS      38.40N 90.54W
06/14/2018                   JEFFERSON          MO   BROADCAST MEDIA

            LARGE TREE, PARTIALLY ROTTEN AT BASE,
            SNAPPED OFF AND FELL ONTO A MOBILE HOME
            CAUSING CONSIDERABLE DAMAGE. NO ONE WAS HOME
            AT THE TIME.

&&

MAB