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Forecast Discussion for Indianapolis, IN
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021 FXUS63 KIND 131130 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 630 AM EST Tue Jan 13 2026 .KEY MESSAGES... - Gusty winds between 30-40mph today and Wednesday. - Scattered rain showers tonight, changing to snow showers on Wednesday - Minor snowfall accumulations from a dusting to around 1 inch possible. - Well-below normal temperatures later this week into early next week && .SHORT TERM (Today and tonight)... Issued at 306 AM EST Tue Jan 13 2026 Strong ridge-building over the eastern Pacific will allow a trough to dig southward over the Midwest later today and tomorrow. Cyclogenesis associated with this trough is taking shape well to our north over central Canada. The resulting low then progresses eastward along a path north of the Great Lakes. Though far to our north, the system will drive a cold front southward with cold air advection reinforced by the digging trough. First, however, a period of strong warm air advection is anticipated as the MSLP gradient tightens ahead of the low. Gusty southwest winds between 30-40 mph will help pump temperatures into the 40s and low 50s today. Additionally, modest frontogenesis along the approaching front allows rain showers to develop after sunset. These rain showers should be light, and confined mainly across the southern half of our CWA. Once the aforementioned cold front arrives early Wednesday morning, temperatures begin to fall quickly despite it being daytime. In fact, high temperatures on Wednesday should occur before sunrise, with temps falling into the 20s during the afternoon. Any lingering rain showers should begin to change to snow Wednesday morning as well. Guidance shows low-level instability within the post-frontal environment, which should promote a scattered/cellular characteristic to the snow showers. Winds look to be out of the north, which will help maximize the fetch off Lake Michigan. A more coherent snow shower or snow band may develop which could extend southward enough to bring accumulating snow to parts of central Indiana. The best chance of this would be from Lafayette to the north suburbs of the Indy metro and points northeast. As much as an inch of snow is possible within this band. Elsewhere, a dusting is the most probable scenario. && .LONG TERM (Wednesday through Monday)... Issued at 306 AM EST Tue Jan 13 2026 A pattern shift is expected in the long range with a trend towards colder than average temperatures. As mentioned in the short term discussion, strong ridge-building is occurring over the eastern Pacific. Ensemble guidance show this ridge becoming a dominant feature while evolving into a classic Rex Block. Ridging over the West Coast then reinforces troughing over the Midwest and Eastern US. The developing blocking pattern then locks it in for at least a week. Global teleconnections support the developing pattern, with a positive Pacific North American Pattern (PNA) and an Arctic Oscillation (AO) quickly trending negative. A negative AO favors a highly amplified jet stream while the positive phase PNA favors ridging over the western US and troughing over the east. The combination of the two will help prolong deep troughing over the Midwest and eastern US. Troughing in turn promotes colder than average temperatures. Scaling down a bit, guidance is in good agreement showing a series of vort maxes diving southeast within the broad northwesterly flow on the eastern flank of the Pacific ridge. Each likely has an attendant cold front with a reinforcing shot of cold air. Though potent, these systems lack moisture. Given the cold air mass likely to be in place, snow is favored over rain this weekend onward. Guidance differs regarding the timing and stretch of each wave, so we`ll keep PoPs broad and prolonged through the weekend. Temperatures through the period, as alluded to above, look to be well-below normal...except Friday, where a shortwave ridge is modeled to pass through with a brief period of modest warm air advection. Guidance is in good agreement showing sub-freezing highs from Saturday to the end of the period. Sunday looks to be the coldest day, with highs in the teens/low 20s and lows in the single digits. Wind chills likely dip below zero for a good chunk of the weekend into early next week. Days 8-14...ensemble guidance is hinting at another pattern shift late next week where ridging shifts eastward and flattens somewhat. Such a pattern may allow for a trend towards warmer (but still below normal) temperatures and greater precipitation chances. An east-west oriented baroclinic zone may develop which will help determine the eventual storm track. Ensemble guidance tends to keep the AO strongly negative while allowing the PNA to trend negative as well, which adds weight to the potential pattern described above. However, ensemble guidance diverges considerably adding to forecast uncertainty. That said, take individual models runs / deterministic guidance with a grain of salt. && .AVIATION (12Z TAF Issuance)... Issued at 629 AM EST Tue Jan 13 2026 Impacts: - Winds gusts between 25-35kt today - Marginal LLWS this morning possible - Rain showers developing after 00z with MVFR ceilings possible - Snow showers after 10z Wednesday Discussion: Winds will be the primary impact to aviation today, with gusty southwesterly winds between 15-20kt gusting 25-35kt at times. The boundary layer may be stable enough this morning to promote a brief period of marginal low-level wind shear (30-40kt at 1500ft), mainly from 12z to 15z. Boundary layer mixing will then allow this to diminish and surface gustiness to increase. Mid/high-level clouds are streaming in from the northwest signaling the arrival of a weak storm system. Mid/high ceilings are expected to develop this morning and continue into the evening. By tonight, continued lowering may allow for a period of MVFR ceilings. Additionally, a period of rain showers is likely along and ahead of an approaching cold front, mainly from 04z onward. A transition to snow showers is expected after about 10z Wednesday, once the front moves through. Winds become northwesterly while increasing to between 10-15kt gusting to 20-25kt. Ceilings continue to drop becoming MVFR early Wednesday morning, continuing through the day. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Eckhoff LONG TERM...Eckhoff AVIATION...Eckhoff |
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