Time: 1032 AM Tue July 16, 2019 Forecaster: Alan Smith

Heavy Precipitation Outlook
Flash Flood Prediction Program

HOT WITH WIDELY SCATTERED AFTERNOON THUNDERSTORMS
-A stronger westerly flow aloft is developing across Colorado today, which will usher in some drier air to the District. Some morning clouds will give way to mostly sunny skies by early afternoon with temperatures heating up into the mid 90s on the plains.
-At the surface, dewpoints remain elevated in the low/mid 50s this morning. Some of this moisture will mix out with daytime heating and dewpoints are projected to fall into the low/mid 40s this afternoon. Overall, thunderstorm coverage should be less today compared to recent days, but an upper level trough is passing north of the area with the jet stream dipping into Northern Colorado, and this will support 1-2 rounds of widely scattered afternoon thunderstorms.
-Steering flow has increased which will result in faster storm motions today from west to east at 15-20mph, and as a result a lower threat for heavy rainfall. However, if a strong thunderstorm manages to develop then enough lingering moisture remains that brief heavy rainfall cannot be ruled out over an area. The best chance of storms outside of the foothills will be mid to late afternoon, with storm activity quickly diminishing after sunset with the loss of daytime heating.
STORM RAINFALL POTENTIAL AND DURATION: Typical weak to moderate thunderstorms will produce rainfall amounts of 0.05-0.3" in 10-30 minutes. A strong thunderstorm could produce rainfall of 0.3-0.8" in 10-30 minutes.

WORST CASE SCENARIO: Low level moisture does not mix out as expected and a strong thunderstorm or training of thunderstorm cells along a wind convergence boundary produces heavy rainfall of up to 1.8" in 60-90 minutes.

A LOOK AHEAD: A strong westerly flow aloft will scour out moisture across the District, resulting in a stretch of very hot and dry weather over the second half of the week. Wednesday will see a very low chance of isolated high-based thunderstorms, mainly over the foothills/Palmer Divide, while Thursday and Friday look dry District-wide. Highs will range from 95-100 on the plains all three days.

Location Prime Time 30-Minute Rainfall
and % Probability
Message
Potential
Plains      
Adams 300 PM TO 900 PM
0.1" (85%) to 0.3" (45%) to 0.8" (15%) LOW
Arapahoe 300 PM TO 900 PM
0.1" (90%) to 0.3" (50%) to 0.8" (15%) LOW
Boulder 300 PM TO 900 PM
0.1" (80%) to 0.3" (40%) to 0.8" (10%) LOW
Broomfield 300 PM TO 900 PM
0.1" (80%) to 0.3" (40%) to 0.8" (10%) LOW
Denver 300 PM TO 900 PM
0.1" (80%) to 0.3" (40%) to 0.8" (10%) LOW
Jefferson 300 PM TO 900 PM
0.1" (80%) to 0.3" (40%) to 0.8" (10%) LOW
Douglas 200 PM TO 900 PM
0.1" (90%) to 0.3" (50%) to 0.8" (15%) LOW
Foothills above 6500ft      
Boulder 100 PM TO 900 PM
0.1" (90%) to 0.3" (45%) to 0.8" (10%) LOW
Douglas 100 PM TO 900 PM
0.1" (90%) to 0.3" (50%) to 0.8" (15%) LOW
Jefferson 100 PM TO 900 PM
0.1" (90%) to 0.3" (45%) to 0.8" (10%) LOW
MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.