FOUS30 KWBC 260829
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Sat Apr 26 2025

Day 1
Valid 12Z Sat Apr 26 2025 - 12Z Sun Apr 27 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTH AND NORTHWEST TEXAS INTO SOUTHERN OKLAHOMA...

...Summary...
Based on the latest observational and guidance trends, have
expanded the Slight Risk from yesterday's Day 2 ERO a little 
farther west-southwest to include a bit more of the Rolling Plains
in Northwest Texas. Otherwise, more minor adjustments were made to
the surrounding Marginal Risk area.

...Southern Plains...
MCS and resultant MCV currently traversing the Texas Panhandle 
early this morning will gradually track ENE along the quasi-
stationary surface frontal boundary across much of the TX-OK Red 
River Valley today. By late morning, the weakening LLJ will allow
the MCS to diminish, while later in the day (afternoon) a narrow broken
line of convection develops farther upstream along the dryline 
across Northwest TX during peak heating. This second area of
convection is expected to take on a more ESE trek during the
afternoon and evening, thus the southwest 'bulge' to both the
Slight and Marginal Risk areas across the Rolling Plains and (for
the Marginal Risk) into northern portions of the Hill Country. 
Overnight, the surface stationary front will eventually lift 
northeast as a warm front Saturday night, taking the more 
organized/widespread convection with it. 

As with yesterday's Day 2 ERO, the Day 1 Slight Risk area was
adjusted to capture areas where 1-2+ in/hr rainfall rate probabilities
from the HREF/RRFS ensembles are highest, while also overlapping
areas where heavy rainfall has fallen over the past couple of days
(wetter antecedent interviews). 

Hurley


Day 2
Valid 12Z Sun Apr 27 2025 - 12Z Mon Apr 28 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE NORTHERN HIGH PLAINS INTO THE UPPER MISSISSIPPI VALLEY...

Mid-upper trough across the southern Great Basin early Sunday will
lift across the central Rockies by 12Z Monday. This in-turn will 
nudge the upper ridge axis east of the Northern Plains and Upper MS
Valley late Sunday-Sunday night, with a quick onset of upper level
divergence in its wake. Along with the more favorable dynamical 
forcing (upper divergence and deep-layer ascent), deepening 
southerly flow will tap the western Gulf and lead to an uptick in 
low-mid layer moisture transport, with TPW values climbing to 1.3+ 
inches. Deep-layer instability meanwhile will also be ramping up, 
to the tune of 1000-2000+ J/Kg MUCAPE per the 00Z models. To some 
degree, the latest models indicate MCS development along the 
western periphery of the upper ridge, tracking east to eventually 
southeast along the 850-300 mb thickness. For the most part, the
forward-propagating Corfidi vectors would support a rather 
progressive area of any organized convection that can grow 
upscale, though much will depend on the strength of the LLJ. For 
now, have maintained a fairly broad Marginal Risk area given the 
potential of intense short-term (sub-3hr) rainfall rates.

Hurley


Day 3
Valid 12Z Mon Apr 28 2025 - 12Z Tue Apr 29 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE NORTHERN PLAINS INTO THE UPPER MIDWEST...

Mid-level circulation will open into a shortwave trough across the
northern Plains and Upper Midwest on Monday-Monday night. Ample
pre-frontal low-mid layer moisture transport and PW values climbing
to 1.5-1.75" will make for a favorable thermodynamic profile, 
along with deep-layer instability as MUCAPEs peak between 
2,000-3,000 J/Kg (even ~1,000 J/Kg wrapping westward into the 
TROWAL zone). The biggest concern during this period will be with 
cell training, especially late Monday-Monday night across the Upper
Midwest with the strengthening LLJ and weakening downwind Corfidi 
Vectors. For now, guidance spread with the heavier QPF is still 
rather high (not well consolidated to support a Slight Risk at 
this point). However, per the GFS/ECMWF and especially the GEM- 
Regional, localized totals of 3-5+ inches within 12 hours would 
appear likely in this setup.

Hurley

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