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Big Cool Down On The Horizon

A decent cold front will move through central parts of the country late this week into the weekend. The sub-tropical ridge that has kept temperatures across the Southern Plains and Southeast above average recently will begin to move eastward as a trough moves in from the west. This will send a cold front south on Thursday and the front will continue its southward progression into the weekend. The front should move through Nebraska and into Kansas on Thursday into Friday, and through Oklahoma and northern Texas on Friday into Saturday. Tomorrow, along the cold front, a few severe thunderstorms look possible due to forecasted instability and shear values (see Fig. 1).

Fig. 1: Thunderstorm outlook map for Thursday

The front should stall across northern Texas and western parts of the Mississippi and Tennessee Valleys as it feels the influence of the ridge. This will keep temperatures warm for much of the Southeast outside of Arkansas, northern Louisiana, northwestern Mississippi and western Tennessee (cooler temperatures are in the forecast for other parts of the South/Southeast later in the extended period so keep reading for details on the cooler temperatures). Temperatures behind the cold front will be well below average for much of the Southern Plains and Midwest late this week and weekend (see Fig. 2 and 3).

Fig 2: Friday afternoon temperature anomalies

Fig 3: Saturday afternoon temperature anomalies

It should be noted, deep moisture will move into New Mexico, Texas and Oklahoma from Thursday into Saturday as the trough nears. This moisture will stream into this region from the Gulf of California where a Tropical Depression is located this afternoon. The increase in moisture will lead to increased rainfall, which may lead to flooding in parts of New Mexico, Texas and Oklahoma. Isolated areas in Texas and Oklahoma may see 2-6″ (see Fig. 4). The increase in precipitation and cloud-cover should keep afternoon temperatures below average even before the front moves through on Friday (see Fig. 2 and 3). High temperatures late this week into the weekend should be in the 60s and 70s for Oklahoma and 80s for most of Texas.

Fig. 4: Rainfall forecast through 7 days

Looking ahead to next week, a more amplified trough appears to usher in a reinforcing shot of cooler air. The cooler air will first be felt across the Northern Plains early next week, followed by the Southern Plains by mid-week, then eventually parts of the Southeast by late week into next weekend. Far Southeastern parts of the United States (Florida, eastern Georgia, South Carolina, and eastern North Carolina) may miss out on the coolest fall-like temperatures from this front but temperatures should still decrease. For other parts of the South, this will be the first significant cold front of the fall season. High temperatures will be well below average (see Fig. 5). It is too early to forecast high and lower temperatures with much confidence but right now it appears highs may be in the 60s and 70s with lows in the 40s and 50s behind this front. Locations further north will see temperatures much cooler than this.

Fig. 5: Temperature probabilities days 8 through 14