![National Oceanic and Atmospheric Administration](/build/images/header/noaa.d87e0251.png)
![National Weather Service](/build/images/header/nws.4e6585d8.png)
![United States Department of Commerce](/build/images/header/doc.b38ba91a.png)
Quantitative Precipitation Forecast
Issued by NWS
Issued by NWS
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
329 FOUS30 KWBC 160022 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 822 PM EDT Mon Jul 15 2024 Day 1 Valid 01Z Tue Jul 16 2024 - 12Z Tue Jul 16 2024 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR ACROSS PORTIONS OF NORTHERN ILLINOIS, INCLUDING THE CHICAGO METRO... ...Midwest into the Ohio Valley... ...0100Z Update... Few changes were made to the previous (special) ERO update, based on the latest observational trends along with recent HREF and HRRR guidance. MCS across IA-WI-IL continues to grow upscale, with cloud tops getting up to around -75C per the latest longwave IR loops. Plenty of instability in place out in front of the MCS...to the tune of 5000 J/Kg ML CAPEs downshear across northern to east- central IL and central IN. Given the current low-mid level shear profiles, expect the QLCS to remain progressive for a while, however the rapid refresh guidance (RAP and HRRR) continue to show increasing low level inflow with time overnight, while aligning nearly parallel to the mean 850-300 mb flow. This should allow for more upwind propagation by the time the activity reaches central IL and northeast MO. As a result, we did expand the Slight and Marginal Risk areas slightly southward across these areas, though the Moderate Risk area continues as was, due in large part because of recent heavy rainfall (antecedent saturated soils) while the northern portion of the QLCS is poised to cross the area this evening. Hurley ...Southwest... Monsoon moisture will fuel another day of afternoon showers and thunderstorms, with isolated flash flooding remaining a concern from southeastern Arizona and southwestern New Mexico into the Mogollon Rim. Models have been underplaying the convection development further to the west into southern California. Considering a somewhat decent signal with the SBCAPE fields off the recent CAMs and PWAT anomalies within the interior of SoCal and Southern NV, have expanded the MRGL risk and connected the separated risk areas to become a more uniform MRGL over the region. Pereira/Kleebauer Day 2 Valid 12Z Tue Jul 16 2024 - 12Z Wed Jul 17 2024 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF KANSAS THROUGH PORTIONS OF THE MID MISSISSIPPI AND OHIO VALLEYS... ...20z Update Summary... The previous SLGT risk was expanded west to include the rest of the southern half of Missouri all the back into the High Plains of Western Kansas. A high-end SLGT is forecast over the Ohio Valley with the primary area of focus located from Southeast MO across Southern IN/IL/OH and adjacent Northern Kentucky. MRGL risks over the Southwest and Northeast U.S were adjusted slightly based on the latest QPF and instability trends, along with some local collaboration with impacted WFOs. Kleebauer ...Central Plains to the Northeast... As a broad upper trough begins to amplify over the Great Lakes, the associated surface boundary and accompanying moisture pool will become a focus for showers and storms and the potential for heavy rainfall amounts. Southwesterly inflow into the front will support PWs climbing upwards of 2 inches from the mid Mississippi Valley eastward into the Ohio Valley. This is also where the guidance shows the best mid-to-upper level forcing, raising the potential for west-to-east training storms and heavy accumulations. Recent HREF neighborhood probabilities are officially in range of the full threat and are depicting some elevated signals for heavy rain totals positioned across much of the Ohio Valley within the corridor extending from Southern IL/IN all the way into Southern OH where the >3" probability is solidly within 40-70% across the entire aforementioned area of focus. The >5" probability was also on the higher side considering the setup with 25-40% probs nestled across Southern IL/IN into Northeast KY. This is likely due to the increased LLJ interaction with the front as it bisects the area and runs parallel to the boundary. Mean wind between 925-700mb is aligned out of the west-southwest with small mid-level perturbations ejecting eastward across the area. The combination of all these variables will create an environment conducive for thunderstorm development and training regime that would exacerbate the flood threat in any given area along and near the front. This area was solidly in the SLGT risk prior, but the area was extended a bit further south to account for a typical northern bias and likely southern surges of the front due to outflow generation from the convection nearby. Across the Central Plains, the front will progress south into KS by tomorrow afternoon while a shortwave out of the Rockies will dive southeastward around the eastern flank of a ridge west of the Continental Divide. The interaction between the front and the shortwave trough will allow for convective initiation across the Southeast CO Front Range over into Southwestern KS where the best instability and deep layered moisture will be co-located. Guidance has ramped up the coverage and expected intensity of the thunderstorm development in-of the above area with correlating higher probabilities in both the 3" (40-70%) and 5" (25-35%) neighborhood probs with rainfall rates projected between 2-3"/hr in the strongest cells. There was enough of a signal and agreement within the deterministic and ensemble QPF distribution to upgrade that area with a SLGT and link with the threat further east. Pereira/Kleebauer ...Southwest... Greater coverage of isolated to scattered diurnal convection is expected as the upper high currently in place weakens. This will allow more showers and storms to develop further to the north, extending the threat for isolated flash flooding across a greater portion of northern Arizona and New Mexico. Isolated flash flood threat will be plausible within the complex terrain of any of the highlighted regions within the risk, as well as targeted areas of focus in the copious amounts of burn scars present within northern and central NM and AZ. Pereira/Kleebauer Day 3 Valid 12Z Wed Jul 17 2024 - 12Z Thu Jul 18 2024 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF COLORADO AND NEW MEXICO, THE LOWER MISSISSIPPI VALLEY, AND THE CENTRAL APPALACHIANS... ...20Z Update Summary... Previous SLGT risk across Colorado and New Mexico was adjusted to encompass some higher threat areas within south-central NM and to account for recent QPF trends within the ensemble bias corrected output. A SLGT risk was introduced across portions of the Lower Mississippi Valley, as well as portions of the Central Appalachians. More information included in the respective sub-headings below.... Kleebauer ...Southwest to the Central and Southern Rockies... A Slight Risk was introduced from south-central Colorado to central New Mexico, where moist upslope flow will support increasing coverage of showers and storms and locally heavy amounts. This will raise the potential for flash flooding, especially across vulnerable areas. Guidance indicates a notable increase in low level moisture transport, raising PW anomalies to 1.5 standard deviations above normal across central New Mexico. This moisture along with weak flow aloft and daytime heating, is expected to support slow-moving storms capable of producing heavy rainfall rates. Vulnerable areas, including burn scars, urbanized areas, and areas of complex terrain will be most susceptible to flash flooding. Elsewhere, the potential for diurnal convection producing at least isolated concerns for heavy rainfall and flash flooding will continue to expand across the Southwest. Pereira ...Lower Mississippi Valley... Frontal progression will slow considerably by mid-week with the front bisecting parts of the Southern Plains, extending east through the Lower Mississippi and Tennessee Valleys. The upstream wave from the prior period over the Central Plains will nose eastward through the front half of the period with sights on the Lower Mississippi Valley by the second half of Wednesday. The coupled shortwave approach, diurnal destabilization, and boundary layer convergence will initiate a round of scattered to widespread heavy thunderstorms in-of Eastern OK through AR into Western TN. The signal for significant rainfall in those areas has grown within the ensemble QPF and probability fields with the conservative NBM even depicting 2-3" of QPF at range. NAEFS standardized anomaly output indicates a broad area of +1 to +2 deviations above normal PWATs with an areal average of 2+" PWATs located within proximity of the front across the Ozarks into much of Western TN. There was enough consensus in the expected synoptic evolution of the pattern to add a SLGT risk over the above region with an adjustment possible within the neighboring confines of the outlined area. ...Central Appalachians... Approaching cold front will slowly meander into the western flank of the Appalachians by Wednesday afternoon with pooling moisture anchored within proxy of the front. To the north, upper jet max across Ontario will be strengthening through the period with much of the Central Mid Atlantic and Ohio Valley focused under the right entrance region (RER) of the jet. This large scale ascent pattern will help initiate more scattered to widespread convective coverage across the area with a mesoscale focus in-line with the terrain located over WV down into Eastern KY. The convective regime within an above normal moist environment characterized by PWATs exceeding +2 standard deviations over the terrain will likely cause some flash flood concerns, some potentially significant if the pattern unfolds verbatim. The signal for >1" QPF has grown over the past succession of model output which is lending credence to the threat. There was enough signal to warrant the upgrade to a SLGT risk located over the terrain, specially the Central Appalachians from far Southwest PA down through WV and parts of Eastern KY. Kleebauer Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt