Area Forecast Discussion
Issued by NWS Springfield, MO
Issued by NWS Springfield, MO
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923 FXUS63 KSGF 260532 AFDSGF Area Forecast Discussion National Weather Service Springfield MO 1232 AM CDT Thu Sep 26 2024 .KEY MESSAGES... - Pleasant weather expected today and tomorrow with near normal temperatures in the mid 70s and mostly sunny skies. Low chance (15%) of an isolated shower across the eastern Ozarks this afternoon. - Rain chances increase Thursday night into Friday due to the remnants of Hurricane Helene. The highest rain chances are Friday afternoon across south-central Missouri and the eastern Ozarks. - There remains a high degree of uncertainty regarding forecast rainfall totals this weekend. - Breezy conditions are likely Friday with gusts up to 30 mph. && .SHORT TERM /THROUGH FRIDAY/... Issued at 247 PM CDT Wed Sep 25 2024 An upper-level trough axis was situated over the Mississippi Valley this afternoon with a cutoff low sitting over eastern Missouri and southern Illinois. To the west, high amplitude ridging was set up over the Plains, with broad high pressure at the surface. Dry air and subsidence aloft will keep our area mostly dry today. Scattered cumulus have developed across the region this afternoon in response to modest surface heating and a shallow layer of mid-level moisture. Hi- res guidance suggests there may be just enough moisture and forcing from the upper-level low to spark a shower or two later this afternoon and evening across the eastern Ozarks, though most areas remain dry, and PoPs have been limited to 15-20%. Cool conditions return overnight with lows in the low to mid 50s. With light winds and strong enough radiational cooling, there could be some light ground/valley fog in the early morning hours, but widespread dense fog is not expected at this time. For Thursday, the upper-level low will slink down into northeastern Arkansas; otherwise, little will change with the synoptic pattern until Thursday night. Therefore, tomorrow`s sensible weather will be similar to today`s. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Issued at 247 PM CDT Wed Sep 25 2024 Rain Chances from Hurricane Helene: Helene has officially reached hurricane strength as of this morning. Model forecast tracks have remained fairly consistent and tightly clustered over the last 48 hours, making landfall somewhere along the Florida Big Bend/Panhandle Thursday evening and tracking to the NNW from there. Greater uncertainty is naturally introduced into the forecast with time, but the uncertainty is further increased by Helene`s apparent interaction with the aforementioned cutoff low over northeast Arkansas. Most guidance depicts some degree of Fujiwhara effect occurring, which would act to swing Helene`s remnants to the northwest as it passes through the Tennessee Valley. What exactly this means for precipitation in the Missouri Ozarks remains highly uncertain. The latest NBM PoPs increase Thursday night across southeast Missouri and spread to the northwest on Friday. The highest PoPs (50-60%) for our CWA remain across the eastern Ozarks and south-central Missouri during the day Friday, with lower chances (20-40%) lingering into Saturday and Sunday. Instability appears fairly minimal with this activity, so the lightning potential will be limited. Analysis of ensemble clusters reveals two distinct solutions. The majority of GEFS and ENS members more closely follow the NHC`s official forecast and bring Helene`s remnants farther west into the Mississippi Valley and potentially into eastern Missouri. This solution would bring more precipitation to our area. GEPS members, on the other hand, tend to favor a more easterly solution, which results in low precipitation totals for our area. Another variable to consider will be available moisture as dry antecedent air will have to be overcome by the tropical moisture return from Helene. A glance at forecast PWATs suggests a decent gradient in moisture from west to east across the forecast area, which will influence rainfall rates and totals. For what it`s worth, the extended reaches of the hi-res guidance tends to fall more in line with the GEFS and ENS, but they will become more reliable in the next 24 hours. These discrepancies-- among others-- produce high uncertainty in the rainfall forecast. This uncertainty is depicted well in the fairly large spread (2-4 inches) of 25th-75th percentile QPF differences in the NBM. It is entirely possible there will ultimately be a large rainfall gradient that sets up somewhere across our forecast area. Notably, the QPF signal from the Extreme forecast Index and Shift of Tails has decreased and shifted east slightly since yesterday. This decrease is consistent with the overall decrease in model QPF. Given the high uncertainty in the rainfall forecast, we will stick with probabilistic messaging for now. The latest NBM probabilities of rainfall totals from Thursday night through Sunday night are as follows: >1 inch: 0% (west) to 50% (east) >2 inches: 0% (west) to 40% (east) >3 inches: 0% (west) to 30% (east) Moderately Gusty Winds Friday & Saturday: Wind gusts will also have to be monitored with Helene`s remnants as they will also be affected by this system`s eventual track. We have nudged gusts closer to the NBM 75th percentile on Friday and Saturday (with gusts up to 30 mph) as the NBM tends to have a low bias in gustier setups. Seasonable to Slightly Cool Temperatures: Temperatures will stay seasonable or a bit below normal through the long term. NBM interquartile spreads remain moderately large (6-7 degrees) through the weekend owing in large part due to uncertainty with precipitation coverage. Beyond that, Helene`s remnants and the cutoff low are progged to eventually drift east early next week. Global models suggest the passage of a cold front will occur during this time period, which may keep seasonable temperatures over the region, at least for the time being. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1215 AM CDT Thu Sep 26 2024 VFR through the period with breezy northerly winds this afternoon for areas along and east of Highway 65. && .SGF WATCHES/WARNINGS/ADVISORIES... KS...None. MO...None. && $$ SHORT TERM...Didio LONG TERM...Didio AVIATION...Soria