Mesoscale Precipitation Discussion 0654
NWS Weather Prediction Center College Park MD
1119 PM EDT Fri Jul 11 2025

Areas affected...Eastern Colorado...Western Kansas...Far Southwest
NEB...

Concerning...Heavy rainfall...Flash flooding possible

Valid 120320Z - 120830Z

SUMMARY...Chaotic, slow cell motions support large mergers and
repeating incidents within increasing moisture environment. 
Isolated to widely scattered incidents of flash flooding remain
possible with 2-3" totals in 1-3 hours.

DISCUSSION...Regional RADAR mosaic and Lightning detection
networks show a broad area of active and locally intensifying
thunderstorms across the High Plains of Colorado starting to
advance into W Nebraska and NW Kansas.   GOES-E WV shows a very
strong/sharpening longwave trof digging over the northern High
Plains with based of the trough providing deep layer DPVA along
and ahead of it, particularly along the southward pressing cold
front across central NEB into the NE corner of CO.  Deep layer
moisture had pooled along the boundary with Tds in the the mid-
50s and low 60s, though some pockets of drier surface air do
remain in the core of the area of concern.  Still solid heating
and return upslope easterly flow continue to maintain unstable air
with solid moisture flux.

A secondary cluster, shortwave over-topping the larger scale ridge
in the Four Corners is also helped to initiate convection that has
become a bit more linear south to north from Crowley to Washington
county and with a bit less mid-level forcing/focus; cells are
forward propagating into the remaining unstable air.

As such, thunderstorms have been slow moving from west to
southeast, but there are many outflow collisions and cell mergers.
 Given total moisture of 1.25-1.5" and confluent flux from
20-25kts at 850mb; rates of 1.5"/hr are becoming more common and
with mergers and broader slab ascent near these outflow
boundaries, rates can locally reach 2".  Duration is limited to
30-60 minutes, but there are opportunities for some upstream cells
(particularly along the cold front) to tap remaining weak
instability and track through areas affected earlier.  This may
result in 2-3" localized totals and in proximity to FFG values of
1-1.5"/hr and 1.5-2.5"/3hrs, random occuring widely scattered
incident or two of flash flooding remain possible into the core of
the overnight period. 

Gallina

ATTN...WFO...BOU...DDC...GLD...LBF...PUB...

ATTN...RFC...KRF...TUA...NWC...

LAT...LON   40930287 40930133 40420071 39810035 39070016
            38290007 37070051 37210241 38070372 39550368
            40840442