Dangerous Heat in the Central and Eastern U.S.; Critical Fire Weather in the Great Basin and Southwest

Dangerous, record-breaking heat will intensify across most of the central and eastern U.S this week. Heat indices will likely exceed 100 degrees. Heat is likely to continue across the eastern U.S. through the Independence Day holiday weekend. Critical fire weather conditions will continue Tuesday across portions of the Four Corners and Great Basin, as dry conditions and gusty winds persist. Read More >

Overview

Upper level high pressure set up across the region to end the month of June and lasted through the 4th of July holiday week. This resulted in high temperatures routinely reaching into the low to mid 90s across the Quad State region. Oppressive humidity levels were in place much of the time as well, with dewpoints up into the mid to upper 70s on a daily basis. We even had some dewpoint temperatures hit 80 degrees, which is considered extremely oppressive and uncomfortable. This resulted in daily heat index readings of 100 or above for 7 straight days. The most intense heat and humidity occurred on July 5th when high temperatures reached into the mid to upper 90s and heat index readings soared to between 110 and 115 across much of the region.

Graphics
Data Table
Upper Level Pattern

Graphics:

Observed Heat Index Readings Friday June 29th through Thursday July 5th, 2018

Photo of shelf cloud approaching NWS office at Paducah

Table:

The table below shows the maximum daily heat index readings observed at all airport locations (ASOS/AWOS) and Kentucky Mesonet stations across our 58 county forecast area. These are the most reliable and accurate stations across the region. The bottom row of the chart gives the highest daily heat index reading observed across the area from these 32 stations. The heat index is calculated from a combination of air temperatures and dewpoint temperatures or relative humidity.

Maximum Daily Heat Index Readings:

Location	State	Station Type	June 29	June 30	July 1	July 2	July 3	July 4	July 5
Cape Girardeau	MO	ASOS	102	103	105	105	102	102	107
Carbondale	IL	ASOS	106	105	105	102	102	103	109
Evansville	IN	ASOS	103	102	103	105	98	108	107
Paducah	KY	ASOS	102	106	103	106	102	110	114
Poplar Bluff	MO	ASOS	108	107	107	107	103	105	113
Cairo	IL	AWOS	100	105	108	105	103	106	110
Murray	KY	AWOS	100	100	105	105	103	107	111
3 WNW Fort Campbell North	KY	AWOS	97	98	102	101	99	108	105
3 WSW Owensboro	KY	AWOS	103	103	106	106	102	108	109
Mayfield	KY	AWOS	98	102	103	103	100	107	110
Henderson	KY	AWOS	103	102	106	102	102	109	114
Madisonville	KY	AWOS	105	102	107	105	106	112	113
Mt Vernon	IL	AWOS	105	109	105	100	108	109	107
Metropolis	IL	AWOS	102	105	106	107	105	107	112
Harrisburg	IL	AWOS	103	108	106	108	106	109	112
Fairfield	IL	AWOS	102	103	104	100	101	106	106
Carmi	IL	AWOS	106	106	108	111	106	111	113
Marion	IL	AWOS	105	107	106	106	105	105	110
1 ESE Princeton	KY	Mesonet	99	102	106	102	102	107	110
1 W Murray	KY	Mesonet	99	102	106	105	103	110	111
6 NNW Hopkinsville	KY	Mesonet	102	102	105	103	101	108	109
3 NE Marion	KY	Mesonet	103	102	105	104	104	106	111
1 ENE Hickman	KY	Mesonet	101	106	108	108	103	110	112
3 NNE Wingo	KY	Mesonet	102	106	108	107	103	110	112
4 ESE Henderson	KY	Mesonet	104	103	106	105	103	109	112
1 E Earlington	KY	Mesonet	103	102	106	108	103	109	111
4 NNE Benton	KY	Mesonet	98	102	106	103	101	109	111
5 NW Calhoun	KY	Mesonet	103	105	108	108	106	111	112
1 WSW Central City	KY	Mesonet	103	103	108	106	103	109	112
3 NE Trenton	KY	Mesonet	103	105	106	108	102	113	115
3 SW Cadiz	KY	Mesonet	99	102	106	103	103	107	113
1 ENE Breckinridge Center	KY	Mesonet	102	103	106	103	103	108	112
Daily Maximum:			108	109	108	111	108	113	115

Upper Level Pattern

The graphic below shows a 7 day loop of observed 500 mb heights, wind, and temperature. This shows the overall weather pattern approximately 20,000 feet above the surface. The higher heights are indicative of upper level ridging which was located over our region on June 29th. The center of this ridge axis became oriented across the northeast U.S. by July 1st and 2nd before migrating back westward toward the Ohio Valley region for July 4th and 5th. The shortwave trough affecting the upper Midwest on July 1st didn't bring our region any relief. Thus an extended period of heat and humidity set up for the 4th of July holiday week.

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Dangerous Heat in the Central and Eastern U.S.; Critical Fire Weather in the Great Basin and Southwest

Oppressive Heat and Humidity June 29 - July 5, 2018